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<span id="1038">1038</span>
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<span id="1055">1055</span>
</pre><pre class="rust">
<span class="kw">use</span> <span class="ident">std::collections::HashSet</span>;
<span class="kw">use</span> <span class="ident">std::fmt</span>;

<span class="kw">use</span> <span class="ident">anyhow</span>::{<span class="ident">Context</span>, <span class="prelude-ty">Result</span>};
<span class="kw">use</span> <span class="ident">geo::prelude::ClosestPoint</span>;
<span class="kw">use</span> <span class="ident">serde</span>::{<span class="ident">Deserialize</span>, <span class="ident">Serialize</span>};

<span class="kw">use</span> <span class="kw">crate</span>::{
    <span class="ident">Angle</span>, <span class="ident">Bounds</span>, <span class="ident">Distance</span>, <span class="ident">GPSBounds</span>, <span class="ident">HashablePt2D</span>, <span class="ident">InfiniteLine</span>, <span class="ident">Line</span>, <span class="ident">Polygon</span>, <span class="ident">Pt2D</span>, <span class="ident">Ring</span>,
    <span class="ident">EPSILON_DIST</span>,
};

<span class="comment">// TODO How to tune this?</span>
<span class="kw">const</span> <span class="ident">MITER_THRESHOLD</span>: <span class="ident">f64</span> <span class="op">=</span> <span class="number">500.0</span>;

<span class="comment">// TODO There used to be a second style that just has extra little hooks going out</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">ArrowCap</span> {
    <span class="ident">Triangle</span>,
}

<span class="comment">// TODO Document and enforce invariants:</span>
<span class="comment">// - at least two points</span>
<span class="comment">// - no duplicate points, whether adjacent or loops</span>
<span class="comment">// - no &quot;useless&quot; intermediate points with the same angle</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>, <span class="ident">PartialEq</span>, <span class="ident">Serialize</span>, <span class="ident">Deserialize</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">PolyLine</span> {
    <span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>,
    <span class="comment">// TODO Note that caching length doesn&#39;t improve profiling results (by running</span>
    <span class="comment">// small_spawn_completes test in release mode). May not be worth doing this.</span>
    <span class="ident">length</span>: <span class="ident">Distance</span>,
}

<span class="kw">impl</span> <span class="ident">PolyLine</span> {
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">&lt;</span> <span class="number">2</span> {
            <span class="macro">bail!</span>(<span class="string">&quot;Need at least two points for a PolyLine&quot;</span>);
        }
        <span class="kw">let</span> <span class="ident">length</span> <span class="op">=</span> <span class="ident">pts</span>.<span class="ident">windows</span>(<span class="number">2</span>).<span class="ident">fold</span>(<span class="ident">Distance::ZERO</span>, <span class="op">|</span><span class="ident">so_far</span>, <span class="ident">pair</span><span class="op">|</span> {
            <span class="ident">so_far</span> <span class="op">+</span> <span class="ident">pair</span>[<span class="number">0</span>].<span class="ident">dist_to</span>(<span class="ident">pair</span>[<span class="number">1</span>])
        });

        <span class="kw">if</span> <span class="ident">pts</span>.<span class="ident">windows</span>(<span class="number">2</span>).<span class="ident">any</span>(<span class="op">|</span><span class="ident">pair</span><span class="op">|</span> <span class="ident">pair</span>[<span class="number">0</span>] <span class="op">=</span><span class="op">=</span> <span class="ident">pair</span>[<span class="number">1</span>]) {
            <span class="macro">bail!</span>(
                <span class="string">&quot;PL with total length {} and {} pts has ~dupe adjacent pts&quot;</span>,
                <span class="ident">length</span>,
                <span class="ident">pts</span>.<span class="ident">len</span>(),
            );
        }

        <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">PolyLine</span> { <span class="ident">pts</span>, <span class="ident">length</span> };

        <span class="comment">// Can&#39;t have duplicates! If the polyline ever crosses back on itself, all sorts of things</span>
        <span class="comment">// are broken.</span>
        <span class="kw">let</span> (<span class="kw">_</span>, <span class="ident">dupes</span>) <span class="op">=</span> <span class="ident">to_set</span>(<span class="ident">result</span>.<span class="ident">points</span>());
        <span class="kw">if</span> <span class="op">!</span><span class="ident">dupes</span>.<span class="ident">is_empty</span>() {
            <span class="macro">bail!</span>(
                <span class="string">&quot;PL with total length {} and {} pts has dupe non-adjacent pts&quot;</span>,
                <span class="ident">result</span>.<span class="ident">length</span>,
                <span class="ident">result</span>.<span class="ident">pts</span>.<span class="ident">len</span>(),
            );
        }

        <span class="prelude-val">Ok</span>(<span class="ident">result</span>)
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">must_new</span>(<span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="ident">PolyLine::new</span>(<span class="ident">pts</span>).<span class="ident">unwrap</span>()
    }

    <span class="doccomment">/// Doesn&#39;t check for duplicates. Use at your own risk.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">unchecked_new</span>(<span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="macro">assert!</span>(<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">&gt;</span><span class="op">=</span> <span class="number">2</span>);
        <span class="kw">let</span> <span class="ident">length</span> <span class="op">=</span> <span class="ident">pts</span>.<span class="ident">windows</span>(<span class="number">2</span>).<span class="ident">fold</span>(<span class="ident">Distance::ZERO</span>, <span class="op">|</span><span class="ident">so_far</span>, <span class="ident">pair</span><span class="op">|</span> {
            <span class="ident">so_far</span> <span class="op">+</span> <span class="ident">pair</span>[<span class="number">0</span>].<span class="ident">dist_to</span>(<span class="ident">pair</span>[<span class="number">1</span>])
        });

        <span class="ident">PolyLine</span> { <span class="ident">pts</span>, <span class="ident">length</span> }
    }

    <span class="doccomment">/// First dedupes adjacent points</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">deduping_new</span>(<span class="kw-2">mut</span> <span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="ident">pts</span>.<span class="ident">dedup</span>();
        <span class="ident">PolyLine::new</span>(<span class="ident">pts</span>)
    }

    <span class="comment">// TODO Unused and experimental. Deduplicates and removes redundant inner points.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">angle_collapsing_new</span>(<span class="ident">input</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
        <span class="kw">for</span> <span class="ident">pt</span> <span class="kw">in</span> <span class="ident">input</span> {
            <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="ident">pts</span>.<span class="ident">len</span>();

            <span class="comment">// Also dedupe</span>
            <span class="kw">if</span> <span class="ident">len</span> <span class="op">&gt;</span> <span class="number">0</span> <span class="op">&amp;&amp;</span> <span class="ident">pts</span>[<span class="ident">len</span> <span class="op">-</span> <span class="number">1</span>] <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
                <span class="kw">continue</span>;
            }

            <span class="kw">if</span> <span class="ident">len</span> <span class="op">&gt;</span><span class="op">=</span> <span class="number">2</span>
                <span class="op">&amp;&amp;</span> <span class="ident">pts</span>[<span class="ident">len</span> <span class="op">-</span> <span class="number">2</span>]
                    .<span class="ident">angle_to</span>(<span class="ident">pts</span>[<span class="ident">len</span> <span class="op">-</span> <span class="number">1</span>])
                    .<span class="ident">approx_eq</span>(<span class="ident">pts</span>[<span class="ident">len</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">angle_to</span>(<span class="ident">pt</span>), <span class="number">0.1</span>)
            {
                <span class="ident">pts</span>.<span class="ident">pop</span>();
            }
            <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pt</span>);
        }

        <span class="ident">PolyLine::new</span>(<span class="ident">pts</span>)
    }

    <span class="doccomment">/// Like make_polygons, but make sure the points actually form a ring.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_thick_ring</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Ring</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">side1</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="ident">width</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">side2</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="op">-</span><span class="ident">width</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="ident">side2</span>.<span class="ident">reverse</span>();
        <span class="ident">side1</span>.<span class="ident">extend</span>(<span class="ident">side2</span>);
        <span class="ident">side1</span>.<span class="ident">push</span>(<span class="ident">side1</span>[<span class="number">0</span>]);
        <span class="ident">side1</span>.<span class="ident">dedup</span>();
        <span class="ident">Ring::must_new</span>(<span class="ident">side1</span>)
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_thick_boundary</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">self_width</span>: <span class="ident">Distance</span>,
        <span class="ident">boundary_width</span>: <span class="ident">Distance</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="ident">self_width</span> <span class="op">&lt;</span><span class="op">=</span> <span class="ident">boundary_width</span> <span class="op">|</span><span class="op">|</span> <span class="self">self</span>.<span class="ident">length</span>() <span class="op">&lt;</span><span class="op">=</span> <span class="ident">boundary_width</span> <span class="op">+</span> <span class="ident">EPSILON_DIST</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }
        <span class="comment">// TODO exact_slice() used to work fine here, but the SUMO montlake map triggers a problem</span>
        <span class="comment">// there</span>
        <span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">maybe_exact_slice</span>(<span class="ident">boundary_width</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="self">self</span>.<span class="ident">length</span>() <span class="op">-</span> <span class="ident">boundary_width</span> <span class="op">/</span> <span class="number">2.0</span>)
            .<span class="ident">ok</span>()<span class="question-mark">?</span>;
        <span class="prelude-val">Some</span>(
            <span class="ident">slice</span>
                .<span class="ident">to_thick_ring</span>(<span class="ident">self_width</span> <span class="op">-</span> <span class="ident">boundary_width</span>)
                .<span class="ident">to_outline</span>(<span class="ident">boundary_width</span>),
        )
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">reversed</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();
        <span class="ident">pts</span>.<span class="ident">reverse</span>();
        <span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>)
    }

    <span class="doccomment">/// Glue together two polylines in order. The last point of `self` must be the same as the</span>
    <span class="doccomment">/// first point of `other`. This method handles removing unnecessary intermediate points if the</span>
    <span class="doccomment">/// extension happens to be at the same angle as the last line segment of `self`.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">extend</span>(<span class="self">self</span>, <span class="ident">other</span>: <span class="ident">PolyLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">other</span>.<span class="ident">pts</span>[<span class="number">0</span>] {
            <span class="macro">bail!</span>(<span class="string">&quot;can&#39;t extend PL; last and first points don&#39;t match&quot;</span>);
        }

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">self_pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">other_pts</span> <span class="op">=</span> <span class="ident">other</span>.<span class="ident">pts</span>;

        <span class="kw">loop</span> {
            <span class="kw">let</span> (<span class="ident">pl1</span>, <span class="kw">_</span>) <span class="op">=</span> <span class="ident">to_set</span>(<span class="kw-2">&amp;</span><span class="ident">self_pts</span>);
            <span class="kw">let</span> (<span class="ident">pl2</span>, <span class="kw">_</span>) <span class="op">=</span> <span class="ident">to_set</span>(<span class="kw-2">&amp;</span><span class="ident">other_pts</span>[<span class="number">1</span>..]);

            <span class="kw">if</span> <span class="ident">pl1</span>.<span class="ident">intersection</span>(<span class="kw-2">&amp;</span><span class="ident">pl2</span>).<span class="ident">next</span>().<span class="ident">is_some</span>() {
                <span class="comment">// Happens on some walking turns. Just clip out the loop. Start searching from the</span>
                <span class="comment">// end of &#39;other&#39;.</span>
                <span class="comment">// TODO Measure the length of the thing being clipped out, to be sure this isn&#39;t</span>
                <span class="comment">// running amok.</span>
                <span class="kw">for</span> (<span class="ident">other_rev_idx</span>, <span class="ident">pt</span>) <span class="kw">in</span> <span class="ident">other_pts</span>.<span class="ident">iter</span>().<span class="ident">rev</span>().<span class="ident">enumerate</span>() {
                    <span class="kw">if</span> <span class="ident">pl1</span>.<span class="ident">contains</span>(<span class="kw-2">&amp;</span><span class="ident">pt</span>.<span class="ident">to_hashable</span>()) {
                        <span class="kw">while</span> <span class="ident">self_pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">pt</span> {
                            <span class="ident">self_pts</span>.<span class="ident">pop</span>();
                        }
                        <span class="ident">other_pts</span> <span class="op">=</span> <span class="ident">other_pts</span>[<span class="ident">other_pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span> <span class="op">-</span> <span class="ident">other_rev_idx</span>..].<span class="ident">to_vec</span>();
                        <span class="kw">break</span>;
                    }
                }
                <span class="comment">// Sanity check</span>
                <span class="macro">assert_eq!</span>(<span class="kw-2">*</span><span class="ident">self_pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>(), <span class="ident">other_pts</span>[<span class="number">0</span>]);
            } <span class="kw">else</span> {
                <span class="kw">break</span>;
            }
        }

        <span class="comment">// There&#39;s an exciting edge case: the next point to add is on self&#39;s last line.</span>
        <span class="kw">if</span> <span class="ident">other_pts</span>.<span class="ident">len</span>() <span class="op">&gt;</span><span class="op">=</span> <span class="number">2</span> {
            <span class="kw">let</span> <span class="ident">same_line</span> <span class="op">=</span> <span class="ident">self_pts</span>[<span class="ident">self_pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">2</span>]
                .<span class="ident">angle_to</span>(<span class="ident">self_pts</span>[<span class="ident">self_pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>])
                .<span class="ident">approx_eq</span>(<span class="ident">other_pts</span>[<span class="number">0</span>].<span class="ident">angle_to</span>(<span class="ident">other_pts</span>[<span class="number">1</span>]), <span class="number">0.1</span>);
            <span class="kw">if</span> <span class="ident">same_line</span> {
                <span class="ident">self_pts</span>.<span class="ident">pop</span>();
            }
        }
        <span class="ident">self_pts</span>.<span class="ident">extend</span>(<span class="ident">other_pts</span>.<span class="ident">iter</span>().<span class="ident">skip</span>(<span class="number">1</span>));
        <span class="ident">PolyLine::new</span>(<span class="ident">self_pts</span>)
    }

    <span class="doccomment">/// Like `extend`, but panics on failure.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">must_extend</span>(<span class="self">self</span>, <span class="ident">other</span>: <span class="ident">PolyLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">extend</span>(<span class="ident">other</span>).<span class="ident">unwrap</span>()
    }

    <span class="doccomment">/// Extends `self` by a single point. If the new point is close enough to the last, dedupes.</span>
    <span class="doccomment">/// Doesn&#39;t clean up any intermediate points.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">optionally_push</span>(<span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">into_points</span>();
        <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pt</span>);
        <span class="ident">PolyLine::deduping_new</span>(<span class="ident">pts</span>).<span class="ident">unwrap</span>()
    }

    <span class="doccomment">/// Like `extend`, but handles the last and first point not matching by inserting that point.</span>
    <span class="doccomment">/// Doesn&#39;t clean up any intermediate points.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">force_extend</span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">other</span>: <span class="ident">PolyLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">other</span>.<span class="ident">pts</span>[<span class="number">0</span>] {
            <span class="comment">// TODO Blindly... what if we need to do the angle collapsing?</span>
            <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">other</span>.<span class="ident">pts</span>[<span class="number">0</span>]);
        }
        <span class="self">self</span>.<span class="ident">extend</span>(<span class="ident">other</span>)
    }

    <span class="doccomment">/// One or both args might be empty.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">append</span>(<span class="ident">first</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>, <span class="ident">second</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="ident">second</span>.<span class="ident">is_empty</span>() {
            <span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">first</span>);
        }
        <span class="kw">if</span> <span class="ident">first</span>.<span class="ident">is_empty</span>() {
            <span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">second</span>);
        }

        <span class="prelude-val">Ok</span>(<span class="ident">PolyLine::new</span>(<span class="ident">first</span>)<span class="question-mark">?</span>
            .<span class="ident">extend</span>(<span class="ident">PolyLine::new</span>(<span class="ident">second</span>)<span class="question-mark">?</span>)<span class="question-mark">?</span>
            .<span class="ident">into_points</span>())
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">points</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="kw-2">&amp;</span><span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> {
        <span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">pts</span>
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_points</span>(<span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> {
        <span class="self">self</span>.<span class="ident">pts</span>
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">lines</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="kw">impl</span> <span class="ident">Iterator</span><span class="op">&lt;</span><span class="ident">Item</span> <span class="op">=</span> <span class="ident">Line</span><span class="op">&gt;</span> <span class="op">+</span> <span class="lifetime">&#39;_</span> {
        <span class="self">self</span>.<span class="ident">pts</span>
            .<span class="ident">windows</span>(<span class="number">2</span>)
            .<span class="ident">map</span>(<span class="op">|</span><span class="ident">pair</span><span class="op">|</span> <span class="ident">Line::must_new</span>(<span class="ident">pair</span>[<span class="number">0</span>], <span class="ident">pair</span>[<span class="number">1</span>]))
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">length</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Distance</span> {
        <span class="self">self</span>.<span class="ident">length</span>
    }

    <span class="doccomment">/// Returns the excess distance left over from the end</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">slice</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">start</span>: <span class="ident">Distance</span>, <span class="ident">end</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(<span class="ident">PolyLine</span>, <span class="ident">Distance</span>)<span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="ident">start</span> <span class="op">&gt;</span> <span class="ident">end</span> <span class="op">|</span><span class="op">|</span> <span class="ident">start</span> <span class="op">&lt;</span> <span class="ident">Distance::ZERO</span> <span class="op">|</span><span class="op">|</span> <span class="ident">end</span> <span class="op">&lt;</span> <span class="ident">Distance::ZERO</span> {
            <span class="macro">bail!</span>(<span class="string">&quot;Can&#39;t get a polyline slice [{}, {}]&quot;</span>, <span class="ident">start</span>, <span class="ident">end</span>);
        }
        <span class="kw">if</span> <span class="ident">start</span> <span class="op">&gt;</span> <span class="self">self</span>.<span class="ident">length</span>() {
            <span class="macro">bail!</span>(
                <span class="string">&quot;Can&#39;t get a polyline slice [{}, {}] on something of length {}&quot;</span>,
                <span class="ident">start</span>,
                <span class="ident">end</span>,
                <span class="self">self</span>.<span class="ident">length</span>()
            );
        }
        <span class="kw">if</span> <span class="ident">end</span> <span class="op">-</span> <span class="ident">start</span> <span class="op">&lt;</span> <span class="ident">EPSILON_DIST</span> {
            <span class="macro">bail!</span>(
                <span class="string">&quot;Can&#39;t get a polyline slice [{}, {}] -- too small&quot;</span>,
                <span class="ident">start</span>,
                <span class="ident">end</span>
            );
        }

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist_so_far</span> <span class="op">=</span> <span class="ident">Distance::ZERO</span>;

        <span class="kw">for</span> <span class="ident">line</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>() {
            <span class="kw">let</span> <span class="ident">length</span> <span class="op">=</span> <span class="ident">line</span>.<span class="ident">length</span>();

            <span class="comment">// Does this line contain the first point of the slice?</span>
            <span class="kw">if</span> <span class="ident">result</span>.<span class="ident">is_empty</span>() <span class="op">&amp;&amp;</span> <span class="ident">dist_so_far</span> <span class="op">+</span> <span class="ident">length</span> <span class="op">&gt;</span><span class="op">=</span> <span class="ident">start</span> {
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">line</span>.<span class="ident">must_dist_along</span>(<span class="ident">start</span> <span class="op">-</span> <span class="ident">dist_so_far</span>));
            }

            <span class="comment">// Does this line contain the last point of the slice?</span>
            <span class="kw">if</span> <span class="ident">dist_so_far</span> <span class="op">+</span> <span class="ident">length</span> <span class="op">&gt;</span><span class="op">=</span> <span class="ident">end</span> {
                <span class="kw">let</span> <span class="ident">last_pt</span> <span class="op">=</span> <span class="ident">line</span>.<span class="ident">must_dist_along</span>(<span class="ident">end</span> <span class="op">-</span> <span class="ident">dist_so_far</span>);
                <span class="kw">if</span> <span class="kw-2">*</span><span class="ident">result</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">last_pt</span> {
                    <span class="ident">result</span>.<span class="ident">pop</span>();
                }
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">last_pt</span>);
                <span class="kw">if</span> <span class="ident">result</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
                    <span class="comment">// TODO Understand what happened here.</span>
                    <span class="macro">bail!</span>(<span class="string">&quot;slice({}, {}) on {} did something weird&quot;</span>, <span class="ident">start</span>, <span class="ident">end</span>, <span class="self">self</span>);
                }
                <span class="kw">return</span> <span class="prelude-val">Ok</span>((<span class="ident">PolyLine::new</span>(<span class="ident">result</span>)<span class="question-mark">?</span>, <span class="ident">Distance::ZERO</span>));
            }

            <span class="comment">// If we&#39;re in the middle, just collect the endpoint. But not if it&#39;s too close to the</span>
            <span class="comment">// previous point (namely, the start, which could be somewhere far along a line)</span>
            <span class="kw">if</span> <span class="op">!</span><span class="ident">result</span>.<span class="ident">is_empty</span>() <span class="op">&amp;&amp;</span> <span class="kw-2">*</span><span class="ident">result</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">line</span>.<span class="ident">pt2</span>() {
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">line</span>.<span class="ident">pt2</span>());
            }

            <span class="ident">dist_so_far</span> <span class="op">+</span><span class="op">=</span> <span class="ident">length</span>;
        }

        <span class="kw">if</span> <span class="ident">result</span>.<span class="ident">is_empty</span>() {
            <span class="macro">bail!</span>(
                <span class="string">&quot;Slice [{}, {}] has a start too big for polyline of length {}&quot;</span>,
                <span class="ident">start</span>,
                <span class="ident">end</span>,
                <span class="self">self</span>.<span class="ident">length</span>()
            );
        }
        <span class="kw">if</span> <span class="ident">result</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
            <span class="macro">bail!</span>(
                <span class="string">&quot;Slice [{}, {}] on {} wound up a single point&quot;</span>,
                <span class="ident">start</span>,
                <span class="ident">end</span>,
                <span class="self">self</span>
            );
        }

        <span class="prelude-val">Ok</span>((<span class="ident">PolyLine::new</span>(<span class="ident">result</span>)<span class="question-mark">?</span>, <span class="ident">end</span> <span class="op">-</span> <span class="ident">dist_so_far</span>))
    }

    <span class="doccomment">/// No excess leftover distance allowed.</span>
    <span class="comment">// TODO Lot of callers of this. Make safer later.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">exact_slice</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">start</span>: <span class="ident">Distance</span>, <span class="ident">end</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">maybe_exact_slice</span>(<span class="ident">start</span>, <span class="ident">end</span>).<span class="ident">unwrap</span>()
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">maybe_exact_slice</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">start</span>: <span class="ident">Distance</span>, <span class="ident">end</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">let</span> (<span class="ident">pl</span>, <span class="ident">leftover</span>) <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">slice</span>(<span class="ident">start</span>, <span class="ident">end</span>)
            .<span class="ident">with_context</span>(<span class="op">|</span><span class="op">|</span> <span class="macro">format!</span>(<span class="string">&quot;exact_slice({}, {}) yielded empty slice&quot;</span>, <span class="ident">start</span>, <span class="ident">end</span>))<span class="question-mark">?</span>;
        <span class="kw">if</span> <span class="ident">leftover</span> <span class="op">&gt;</span> <span class="ident">EPSILON_DIST</span> {
            <span class="macro">bail!</span>(
                <span class="string">&quot;exact_slice({}, {}) on a PL of length {} yielded leftover distance of {}&quot;</span>,
                <span class="ident">start</span>,
                <span class="ident">end</span>,
                <span class="self">self</span>.<span class="ident">length</span>(),
                <span class="ident">leftover</span>
            );
        }
        <span class="prelude-val">Ok</span>(<span class="ident">pl</span>)
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">first_half</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="ident">Distance::ZERO</span>, <span class="self">self</span>.<span class="ident">length</span>() <span class="op">/</span> <span class="number">2.0</span>)
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">second_half</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="self">self</span>.<span class="ident">length</span>() <span class="op">/</span> <span class="number">2.0</span>, <span class="self">self</span>.<span class="ident">length</span>())
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">dist_along</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">dist_along</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="ident">dist_along</span> <span class="op">&lt;</span> <span class="ident">Distance::ZERO</span> {
            <span class="macro">bail!</span>(<span class="string">&quot;dist_along {} is negative&quot;</span>, <span class="ident">dist_along</span>);
        }
        <span class="kw">if</span> <span class="ident">dist_along</span> <span class="op">&gt;</span> <span class="self">self</span>.<span class="ident">length</span>() {
            <span class="macro">bail!</span>(<span class="string">&quot;dist_along {} is longer than {}&quot;</span>, <span class="ident">dist_along</span>, <span class="self">self</span>.<span class="ident">length</span>());
        }
        <span class="kw">if</span> <span class="ident">dist_along</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">length</span>() {
            <span class="kw">return</span> <span class="prelude-val">Ok</span>((<span class="self">self</span>.<span class="ident">last_pt</span>(), <span class="self">self</span>.<span class="ident">last_line</span>().<span class="ident">angle</span>()));
        }

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist_left</span> <span class="op">=</span> <span class="ident">dist_along</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">length_remeasured</span> <span class="op">=</span> <span class="ident">Distance::ZERO</span>;
        <span class="kw">for</span> (<span class="ident">idx</span>, <span class="ident">l</span>) <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>().<span class="ident">enumerate</span>() {
            <span class="kw">let</span> <span class="ident">length</span> <span class="op">=</span> <span class="ident">l</span>.<span class="ident">length</span>();
            <span class="ident">length_remeasured</span> <span class="op">+</span><span class="op">=</span> <span class="ident">length</span>;
            <span class="kw">let</span> <span class="ident">epsilon</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">idx</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">2</span> {
                <span class="ident">EPSILON_DIST</span>
            } <span class="kw">else</span> {
                <span class="ident">Distance::ZERO</span>
            };
            <span class="kw">if</span> <span class="ident">dist_left</span> <span class="op">&lt;</span><span class="op">=</span> <span class="ident">length</span> <span class="op">+</span> <span class="ident">epsilon</span> {
                <span class="kw">return</span> <span class="prelude-val">Ok</span>((<span class="ident">l</span>.<span class="ident">must_dist_along</span>(<span class="ident">dist_left</span>), <span class="ident">l</span>.<span class="ident">angle</span>()));
            }
            <span class="ident">dist_left</span> <span class="op">-</span><span class="op">=</span> <span class="ident">length</span>;
        }
        <span class="comment">// Leaving this panic, because I haven&#39;t seen this in ages, and something is seriously</span>
        <span class="comment">// wrong if we get here</span>
        <span class="macro">panic!</span>(
            <span class="string">&quot;PolyLine dist_along of {} broke on length {} (recalculated length {}): {}&quot;</span>,
            <span class="ident">dist_along</span>,
            <span class="self">self</span>.<span class="ident">length</span>(),
            <span class="ident">length_remeasured</span>,
            <span class="self">self</span>
        );
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">must_dist_along</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">dist_along</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> (<span class="ident">Pt2D</span>, <span class="ident">Angle</span>) {
        <span class="self">self</span>.<span class="ident">dist_along</span>(<span class="ident">dist_along</span>).<span class="ident">unwrap</span>()
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">middle</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Pt2D</span> {
        <span class="comment">// If this fails, must be some super tiny line. Just return the first point in that case.</span>
        <span class="kw">match</span> <span class="self">self</span>.<span class="ident">dist_along</span>(<span class="self">self</span>.<span class="ident">length</span>() <span class="op">/</span> <span class="number">2.0</span>) {
            <span class="prelude-val">Ok</span>((<span class="ident">pt</span>, <span class="kw">_</span>)) <span class="op">=</span><span class="op">&gt;</span> <span class="ident">pt</span>,
            <span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">&gt;</span> {
                <span class="macro">println!</span>(
                    <span class="string">&quot;Guessing middle of PL with length {}: {}&quot;</span>,
                    <span class="self">self</span>.<span class="ident">length</span>(),
                    <span class="ident">err</span>
                );
                <span class="self">self</span>.<span class="ident">first_pt</span>()
            }
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">first_pt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Pt2D</span> {
        <span class="self">self</span>.<span class="ident">pts</span>[<span class="number">0</span>]
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">last_pt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Pt2D</span> {
        <span class="kw-2">*</span><span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>()
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">first_line</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Line</span> {
        <span class="ident">Line::must_new</span>(<span class="self">self</span>.<span class="ident">pts</span>[<span class="number">0</span>], <span class="self">self</span>.<span class="ident">pts</span>[<span class="number">1</span>])
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">last_line</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Line</span> {
        <span class="ident">Line::must_new</span>(<span class="self">self</span>.<span class="ident">pts</span>[<span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">2</span>], <span class="self">self</span>.<span class="ident">pts</span>[<span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span>])
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">shift_right</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="self">self</span>.<span class="ident">shift_with_corrections</span>(<span class="ident">width</span>)
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">must_shift_right</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">shift_right</span>(<span class="ident">width</span>).<span class="ident">unwrap</span>()
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">shift_left</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="self">self</span>.<span class="ident">shift_with_corrections</span>(<span class="op">-</span><span class="ident">width</span>)
    }
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">must_shift_left</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="self">self</span>.<span class="ident">shift_left</span>(<span class="ident">width</span>).<span class="ident">unwrap</span>()
    }

    <span class="doccomment">/// Perpendicularly shifts the polyline to the right if positive or left if negative.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">shift_either_direction</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="self">self</span>.<span class="ident">shift_with_corrections</span>(<span class="ident">width</span>)
    }

    <span class="comment">// Things to remember about shifting polylines:</span>
    <span class="comment">// - the length before and after probably don&#39;t match up</span>
    <span class="comment">// - the number of points may not match</span>
    <span class="kw">fn</span> <span class="ident">shift_with_corrections</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">raw</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="ident">width</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">PolyLine::deduping_new</span>(<span class="ident">raw</span>)<span class="question-mark">?</span>;
        <span class="kw">if</span> <span class="ident">result</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() {
            <span class="ident">fix_angles</span>(<span class="self">self</span>, <span class="ident">result</span>)
        } <span class="kw">else</span> {
            <span class="prelude-val">Ok</span>(<span class="ident">result</span>)
        }
    }

    <span class="kw">fn</span> <span class="ident">shift_with_sharp_angles</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>, <span class="ident">miter_threshold</span>: <span class="ident">f64</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">2</span> {
            <span class="kw">let</span> <span class="ident">l</span> <span class="op">=</span> <span class="ident">Line::must_new</span>(<span class="self">self</span>.<span class="ident">pts</span>[<span class="number">0</span>], <span class="self">self</span>.<span class="ident">pts</span>[<span class="number">1</span>]).<span class="ident">shift_either_direction</span>(<span class="ident">width</span>);
            <span class="kw">return</span> <span class="macro">vec!</span>[<span class="ident">l</span>.<span class="ident">pt1</span>(), <span class="ident">l</span>.<span class="ident">pt2</span>()];
        }

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pt3_idx</span> <span class="op">=</span> <span class="number">2</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pt1_raw</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>[<span class="number">0</span>];
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pt2_raw</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>[<span class="number">1</span>];

        <span class="kw">loop</span> {
            <span class="kw">let</span> <span class="ident">pt3_raw</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>[<span class="ident">pt3_idx</span>];

            <span class="kw">let</span> <span class="ident">l1</span> <span class="op">=</span> <span class="ident">Line::must_new</span>(<span class="ident">pt1_raw</span>, <span class="ident">pt2_raw</span>).<span class="ident">shift_either_direction</span>(<span class="ident">width</span>);
            <span class="kw">let</span> <span class="ident">l2</span> <span class="op">=</span> <span class="ident">Line::must_new</span>(<span class="ident">pt2_raw</span>, <span class="ident">pt3_raw</span>).<span class="ident">shift_either_direction</span>(<span class="ident">width</span>);

            <span class="kw">if</span> <span class="ident">pt3_idx</span> <span class="op">=</span><span class="op">=</span> <span class="number">2</span> {
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">l1</span>.<span class="ident">pt1</span>());
            }

            <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">pt2_shift</span>) <span class="op">=</span> <span class="ident">l1</span>.<span class="ident">infinite</span>().<span class="ident">intersection</span>(<span class="kw-2">&amp;</span><span class="ident">l2</span>.<span class="ident">infinite</span>()) {
                <span class="comment">// Miter caps sometimes explode out to infinity. Hackily work around this.</span>
                <span class="kw">let</span> <span class="ident">dist_away</span> <span class="op">=</span> <span class="ident">l1</span>.<span class="ident">pt1</span>().<span class="ident">raw_dist_to</span>(<span class="ident">pt2_shift</span>);
                <span class="kw">if</span> <span class="ident">dist_away</span> <span class="op">&lt;</span> <span class="ident">miter_threshold</span> {
                    <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">pt2_shift</span>);
                } <span class="kw">else</span> {
                    <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">l1</span>.<span class="ident">pt2</span>());
                }
            } <span class="kw">else</span> {
                <span class="comment">// When the lines are perfectly parallel, it means pt2_shift_1st == pt2_shift_2nd</span>
                <span class="comment">// and the original geometry is redundant.</span>
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">l1</span>.<span class="ident">pt2</span>());
            }
            <span class="kw">if</span> <span class="ident">pt3_idx</span> <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">-</span> <span class="number">1</span> {
                <span class="ident">result</span>.<span class="ident">push</span>(<span class="ident">l2</span>.<span class="ident">pt2</span>());
                <span class="kw">break</span>;
            }

            <span class="ident">pt1_raw</span> <span class="op">=</span> <span class="ident">pt2_raw</span>;
            <span class="ident">pt2_raw</span> <span class="op">=</span> <span class="ident">pt3_raw</span>;
            <span class="ident">pt3_idx</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
        }

        <span class="macro">assert!</span>(<span class="ident">result</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>());
        <span class="ident">result</span>
    }

    <span class="doccomment">/// The resulting polygon is manually triangulated and may not have a valid outer Ring (but it</span>
    <span class="doccomment">/// usually does).</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_polygons</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Polygon</span> {
        <span class="comment">// TODO How to tune this?</span>
        <span class="self">self</span>.<span class="ident">make_polygons_with_miter_threshold</span>(<span class="ident">width</span>, <span class="ident">MITER_THRESHOLD</span>)
    }

    <span class="doccomment">/// The resulting polygon is manually triangulated and may not have a valid outer Ring (but it</span>
    <span class="doccomment">/// usually does).</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_polygons_with_miter_threshold</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">width</span>: <span class="ident">Distance</span>,
        <span class="ident">miter_threshold</span>: <span class="ident">f64</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Polygon</span> {
        <span class="comment">// TODO Don&#39;t use the angle corrections yet -- they seem to do weird things.</span>
        <span class="kw">let</span> <span class="ident">side1</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="ident">width</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">miter_threshold</span>);
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">side2</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="op">-</span><span class="ident">width</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">miter_threshold</span>);
        <span class="macro">assert_eq!</span>(<span class="ident">side1</span>.<span class="ident">len</span>(), <span class="ident">side2</span>.<span class="ident">len</span>());

        <span class="comment">// Order the points so that they form a ring. No deduplication yet, though.</span>
        <span class="kw">let</span> <span class="ident">len</span> <span class="op">=</span> <span class="number">2</span> <span class="op">*</span> <span class="ident">side1</span>.<span class="ident">len</span>();
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">points</span> <span class="op">=</span> <span class="ident">side1</span>;
        <span class="ident">side2</span>.<span class="ident">reverse</span>();
        <span class="ident">points</span>.<span class="ident">extend</span>(<span class="ident">side2</span>);
        <span class="ident">points</span>.<span class="ident">push</span>(<span class="ident">points</span>[<span class="number">0</span>]);
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">indices</span> <span class="op">=</span> <span class="ident">Vec::new</span>();

        <span class="comment">// Walk along the first side, making two triangles each step. This is easy to understand</span>
        <span class="comment">// with a simple diagram, which I should eventually draw in ASCII art here.</span>
        <span class="kw">for</span> <span class="ident">high_idx</span> <span class="kw">in</span> <span class="number">1</span>..<span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() {
            <span class="ident">indices</span>.<span class="ident">extend</span>(<span class="macro">vec!</span>[<span class="ident">high_idx</span>, <span class="ident">high_idx</span> <span class="op">-</span> <span class="number">1</span>, <span class="ident">len</span> <span class="op">-</span> <span class="ident">high_idx</span>]);
            <span class="ident">indices</span>.<span class="ident">extend</span>(<span class="macro">vec!</span>[<span class="ident">len</span> <span class="op">-</span> <span class="ident">high_idx</span>, <span class="ident">len</span> <span class="op">-</span> <span class="ident">high_idx</span> <span class="op">-</span> <span class="number">1</span>, <span class="ident">high_idx</span>]);
        }
        <span class="ident">Polygon::precomputed</span>(<span class="ident">points</span>, <span class="ident">indices</span>)
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">exact_dashed_polygons</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">width</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_len</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_separation</span>: <span class="ident">Distance</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">polygons</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> <span class="op">=</span> <span class="ident">Vec::new</span>();

        <span class="kw">let</span> <span class="ident">total_length</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">length</span>();

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">start</span> <span class="op">=</span> <span class="ident">Distance::ZERO</span>;
        <span class="kw">loop</span> {
            <span class="kw">if</span> <span class="ident">start</span> <span class="op">+</span> <span class="ident">dash_len</span> <span class="op">&gt;</span><span class="op">=</span> <span class="ident">total_length</span> {
                <span class="kw">break</span>;
            }

            <span class="ident">polygons</span>.<span class="ident">push</span>(
                <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="ident">start</span>, <span class="ident">start</span> <span class="op">+</span> <span class="ident">dash_len</span>)
                    .<span class="ident">make_polygons</span>(<span class="ident">width</span>),
            );
            <span class="ident">start</span> <span class="op">+</span><span class="op">=</span> <span class="ident">dash_len</span> <span class="op">+</span> <span class="ident">dash_separation</span>;
        }

        <span class="ident">polygons</span>
    }

    <span class="doccomment">/// Don&#39;t draw the dashes too close to the ends.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">dashed_lines</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">width</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_len</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_separation</span>: <span class="ident">Distance</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">length</span>() <span class="op">&lt;</span><span class="op">=</span> <span class="ident">dash_separation</span> <span class="op">*</span> <span class="number">2.0</span> <span class="op">+</span> <span class="ident">EPSILON_DIST</span> {
            <span class="kw">return</span> <span class="macro">vec!</span>[<span class="self">self</span>.<span class="ident">make_polygons</span>(<span class="ident">width</span>)];
        }
        <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="ident">dash_separation</span>, <span class="self">self</span>.<span class="ident">length</span>() <span class="op">-</span> <span class="ident">dash_separation</span>)
            .<span class="ident">exact_dashed_polygons</span>(<span class="ident">width</span>, <span class="ident">dash_len</span>, <span class="ident">dash_separation</span>)
    }

    <span class="doccomment">/// Fail if the length is too short.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">maybe_make_arrow</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">thickness</span>: <span class="ident">Distance</span>, <span class="ident">cap</span>: <span class="ident">ArrowCap</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">head_size</span> <span class="op">=</span> <span class="ident">thickness</span> <span class="op">*</span> <span class="number">2.0</span>;
        <span class="kw">let</span> <span class="ident">triangle_height</span> <span class="op">=</span> <span class="ident">head_size</span> <span class="op">/</span> <span class="number">2.0_f64</span>.<span class="ident">sqrt</span>();

        <span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">maybe_exact_slice</span>(<span class="ident">Distance::ZERO</span>, <span class="self">self</span>.<span class="ident">length</span>() <span class="op">-</span> <span class="ident">triangle_height</span>)
            .<span class="ident">ok</span>()<span class="question-mark">?</span>;

        <span class="kw">let</span> <span class="ident">angle</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">last_pt</span>().<span class="ident">angle_to</span>(<span class="self">self</span>.<span class="ident">last_pt</span>());
        <span class="kw">let</span> <span class="ident">corner1</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">last_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="op">-</span><span class="number">135.0</span>));
        <span class="kw">let</span> <span class="ident">corner2</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">last_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="number">135.0</span>));

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="ident">thickness</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="kw">match</span> <span class="ident">cap</span> {
            <span class="ident">ArrowCap::Triangle</span> <span class="op">=</span><span class="op">&gt;</span> {
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner2</span>);
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="self">self</span>.<span class="ident">last_pt</span>());
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner1</span>);
            }
        }
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">side2</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="op">-</span><span class="ident">thickness</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="ident">side2</span>.<span class="ident">reverse</span>();
        <span class="ident">pts</span>.<span class="ident">extend</span>(<span class="ident">side2</span>);
        <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pts</span>[<span class="number">0</span>]);
        <span class="ident">pts</span>.<span class="ident">dedup</span>();
        <span class="prelude-val">Some</span>(<span class="ident">Ring::must_new</span>(<span class="ident">pts</span>).<span class="ident">into_polygon</span>())
    }

    <span class="doccomment">/// If the length is too short, just give up and make the thick line</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_arrow</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">thickness</span>: <span class="ident">Distance</span>, <span class="ident">cap</span>: <span class="ident">ArrowCap</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Polygon</span> {
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">p</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">maybe_make_arrow</span>(<span class="ident">thickness</span>, <span class="ident">cap</span>) {
            <span class="ident">p</span>
        } <span class="kw">else</span> {
            <span class="comment">// Just give up and make the thick line.</span>
            <span class="self">self</span>.<span class="ident">make_polygons</span>(<span class="ident">thickness</span>)
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">make_double_arrow</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">thickness</span>: <span class="ident">Distance</span>, <span class="ident">cap</span>: <span class="ident">ArrowCap</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Polygon</span> {
        <span class="kw">let</span> <span class="ident">head_size</span> <span class="op">=</span> <span class="ident">thickness</span> <span class="op">*</span> <span class="number">2.0</span>;
        <span class="kw">let</span> <span class="ident">triangle_height</span> <span class="op">=</span> <span class="ident">head_size</span> <span class="op">/</span> <span class="number">2.0_f64</span>.<span class="ident">sqrt</span>();

        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">length</span>() <span class="op">&lt;</span> <span class="ident">triangle_height</span> <span class="op">*</span> <span class="number">2.0</span> <span class="op">+</span> <span class="ident">EPSILON_DIST</span> {
            <span class="comment">// Just give up and make the thick line.</span>
            <span class="kw">return</span> <span class="self">self</span>.<span class="ident">make_polygons</span>(<span class="ident">thickness</span>);
        }
        <span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="ident">triangle_height</span>, <span class="self">self</span>.<span class="ident">length</span>() <span class="op">-</span> <span class="ident">triangle_height</span>);

        <span class="kw">let</span> <span class="ident">angle</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">last_pt</span>().<span class="ident">angle_to</span>(<span class="self">self</span>.<span class="ident">last_pt</span>());
        <span class="kw">let</span> <span class="ident">corner1</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">last_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="op">-</span><span class="number">135.0</span>));
        <span class="kw">let</span> <span class="ident">corner2</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">last_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="number">135.0</span>));

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="ident">thickness</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="kw">match</span> <span class="ident">cap</span> {
            <span class="ident">ArrowCap::Triangle</span> <span class="op">=</span><span class="op">&gt;</span> {
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner2</span>);
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="self">self</span>.<span class="ident">last_pt</span>());
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner1</span>);
            }
        }
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">side2</span> <span class="op">=</span> <span class="ident">slice</span>.<span class="ident">shift_with_sharp_angles</span>(<span class="op">-</span><span class="ident">thickness</span> <span class="op">/</span> <span class="number">2.0</span>, <span class="ident">MITER_THRESHOLD</span>);
        <span class="ident">side2</span>.<span class="ident">reverse</span>();
        <span class="ident">pts</span>.<span class="ident">extend</span>(<span class="ident">side2</span>);

        <span class="kw">let</span> <span class="ident">angle</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">first_pt</span>().<span class="ident">angle_to</span>(<span class="ident">slice</span>.<span class="ident">first_pt</span>());
        <span class="kw">let</span> <span class="ident">corner3</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">first_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="op">-</span><span class="number">45.0</span>));
        <span class="kw">let</span> <span class="ident">corner4</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">first_pt</span>()
            .<span class="ident">project_away</span>(<span class="ident">head_size</span>, <span class="ident">angle</span>.<span class="ident">rotate_degs</span>(<span class="number">45.0</span>));
        <span class="kw">match</span> <span class="ident">cap</span> {
            <span class="ident">ArrowCap::Triangle</span> <span class="op">=</span><span class="op">&gt;</span> {
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner3</span>);
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="self">self</span>.<span class="ident">first_pt</span>());
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">corner4</span>);
            }
        }

        <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pts</span>[<span class="number">0</span>]);
        <span class="ident">pts</span>.<span class="ident">dedup</span>();
        <span class="ident">Ring::must_new</span>(<span class="ident">pts</span>).<span class="ident">into_polygon</span>()
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">dashed_arrow</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">width</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_len</span>: <span class="ident">Distance</span>,
        <span class="ident">dash_separation</span>: <span class="ident">Distance</span>,
        <span class="ident">cap</span>: <span class="ident">ArrowCap</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">Polygon</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">polygons</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">exact_dashed_polygons</span>(<span class="ident">width</span>, <span class="ident">dash_len</span>, <span class="ident">dash_separation</span>);
        <span class="comment">// And a cap on the arrow. In case the last line is long, trim it to be the dash</span>
        <span class="comment">// length.</span>
        <span class="kw">let</span> <span class="ident">last_line</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">last_line</span>();
        <span class="kw">let</span> <span class="ident">last_len</span> <span class="op">=</span> <span class="ident">last_line</span>.<span class="ident">length</span>();
        <span class="kw">let</span> <span class="ident">arrow_line</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">last_len</span> <span class="op">&lt;</span><span class="op">=</span> <span class="ident">dash_len</span> {
            <span class="ident">last_line</span>
        } <span class="kw">else</span> {
            <span class="ident">Line::must_new</span>(
                <span class="ident">last_line</span>.<span class="ident">must_dist_along</span>(<span class="ident">last_len</span> <span class="op">-</span> <span class="ident">dash_len</span>),
                <span class="ident">last_line</span>.<span class="ident">pt2</span>(),
            )
        };
        <span class="ident">polygons</span>.<span class="ident">push</span>(<span class="ident">arrow_line</span>.<span class="ident">to_polyline</span>().<span class="ident">make_arrow</span>(<span class="ident">width</span>, <span class="ident">cap</span>));
        <span class="ident">polygons</span>
    }

    <span class="doccomment">/// Also return the angle of the line where the hit was found</span>
    <span class="comment">// TODO Also return distance along self of the hit</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">intersection</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&amp;</span><span class="ident">PolyLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> {
        <span class="macro">assert_ne!</span>(<span class="self">self</span>, <span class="ident">other</span>);

        <span class="comment">// There could be several collisions. Pick the &quot;first&quot; from self&#39;s perspective.</span>
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">closest_intersection</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">closest_intersection_distance</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">Distance</span><span class="op">&gt;</span> <span class="op">=</span> <span class="prelude-val">None</span>;

        <span class="kw">for</span> <span class="ident">l1</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>() {
            <span class="kw">for</span> <span class="ident">l2</span> <span class="kw">in</span> <span class="ident">other</span>.<span class="ident">lines</span>() {
                <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">pt</span>) <span class="op">=</span> <span class="ident">l1</span>.<span class="ident">intersection</span>(<span class="kw-2">&amp;</span><span class="ident">l2</span>) {
                    <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">new_distance</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">get_slice_ending_at</span>(<span class="ident">pt</span>).<span class="ident">map</span>(<span class="op">|</span><span class="ident">pl</span><span class="op">|</span> <span class="ident">pl</span>.<span class="ident">length</span>()) {
                        <span class="kw">match</span> <span class="ident">closest_intersection_distance</span> {
                            <span class="prelude-val">None</span> <span class="op">=</span><span class="op">&gt;</span> {
                                <span class="ident">closest_intersection</span> <span class="op">=</span> <span class="prelude-val">Some</span>((<span class="ident">pt</span>, <span class="ident">l1</span>.<span class="ident">angle</span>()));
                                <span class="ident">closest_intersection_distance</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">new_distance</span>);
                            }
                            <span class="prelude-val">Some</span>(<span class="ident">existing_distance</span>) <span class="kw">if</span> <span class="ident">existing_distance</span> <span class="op">&gt;</span> <span class="ident">new_distance</span> <span class="op">=</span><span class="op">&gt;</span> {
                                <span class="ident">closest_intersection</span> <span class="op">=</span> <span class="prelude-val">Some</span>((<span class="ident">pt</span>, <span class="ident">l1</span>.<span class="ident">angle</span>()));
                                <span class="ident">closest_intersection_distance</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">new_distance</span>);
                            }
                            <span class="kw">_</span> <span class="op">=</span><span class="op">&gt;</span> {}
                        }
                    }
                }
            }
        }

        <span class="comment">// TODO Why is any of this necessary? Found a test case at the intersection geometry for</span>
        <span class="comment">// https://www.openstreetmap.org/node/274088813 where this made a huge difference!</span>
        <span class="kw">if</span> <span class="ident">closest_intersection</span>.<span class="ident">is_none</span>() <span class="op">&amp;&amp;</span> <span class="self">self</span>.<span class="ident">last_pt</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">other</span>.<span class="ident">last_pt</span>() {
            <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="self">self</span>.<span class="ident">last_pt</span>(), <span class="self">self</span>.<span class="ident">last_line</span>().<span class="ident">angle</span>()));
        }

        <span class="ident">closest_intersection</span>
    }

    <span class="comment">// TODO Also distance along</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">intersection_infinite</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">other</span>: <span class="kw-2">&amp;</span><span class="ident">InfiniteLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">Pt2D</span><span class="op">&gt;</span> {
        <span class="kw">for</span> <span class="ident">l</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>() {
            <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">hit</span>) <span class="op">=</span> <span class="ident">l</span>.<span class="ident">intersection_infinite</span>(<span class="ident">other</span>) {
                <span class="kw">return</span> <span class="prelude-val">Some</span>(<span class="ident">hit</span>);
            }
        }
        <span class="prelude-val">None</span>
    }

    <span class="doccomment">/// Panics if the pt is not on the polyline. Returns None if the point is the first point</span>
    <span class="doccomment">/// (meaning the slice is empty).</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_slice_ending_at</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">first_pt</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }

        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">idx</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lines</span>().<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">l</span>.<span class="ident">contains_pt</span>(<span class="ident">pt</span>)) {
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();
            <span class="ident">pts</span>.<span class="ident">truncate</span>(<span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>);
            <span class="comment">// Make sure the last line isn&#39;t too tiny</span>
            <span class="kw">if</span> <span class="kw-2">*</span><span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
                <span class="ident">pts</span>.<span class="ident">pop</span>();
            }
            <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pt</span>);
            <span class="kw">if</span> <span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
                <span class="kw">return</span> <span class="prelude-val">None</span>;
            }
            <span class="prelude-val">Some</span>(<span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>))
        } <span class="kw">else</span> {
            <span class="macro">panic!</span>(<span class="string">&quot;Can&#39;t get_slice_ending_at: {} doesn&#39;t contain {}&quot;</span>, <span class="self">self</span>, <span class="ident">pt</span>);
        }
    }

    <span class="doccomment">/// Returns None if the point is the last point.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_slice_starting_at</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">last_pt</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }

        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">idx</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lines</span>().<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">l</span>.<span class="ident">contains_pt</span>(<span class="ident">pt</span>)) {
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();
            <span class="ident">pts</span> <span class="op">=</span> <span class="ident">pts</span>.<span class="ident">split_off</span>(<span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>);
            <span class="kw">if</span> <span class="ident">pt</span> <span class="op">!</span><span class="op">=</span> <span class="ident">pts</span>[<span class="number">0</span>] {
                <span class="ident">pts</span>.<span class="ident">insert</span>(<span class="number">0</span>, <span class="ident">pt</span>);
            }
            <span class="prelude-val">Some</span>(<span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>))
        } <span class="kw">else</span> {
            <span class="macro">panic!</span>(
                <span class="string">&quot;Can&#39;t get_slice_starting_at: {} doesn&#39;t contain {}&quot;</span>,
                <span class="self">self</span>, <span class="ident">pt</span>
            );
        }
    }

    <span class="doccomment">/// Same as get_slice_ending_at, but returns None if the point isn&#39;t on the polyline.</span>
    <span class="comment">// TODO Switch everything to this, after better understanding why this is happening at all.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">safe_get_slice_ending_at</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">first_pt</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }

        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">idx</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lines</span>().<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">l</span>.<span class="ident">contains_pt</span>(<span class="ident">pt</span>)) {
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();
            <span class="ident">pts</span>.<span class="ident">truncate</span>(<span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>);
            <span class="comment">// Make sure the last line isn&#39;t too tiny</span>
            <span class="kw">if</span> <span class="kw-2">*</span><span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
                <span class="ident">pts</span>.<span class="ident">pop</span>();
            }
            <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">pt</span>);
            <span class="kw">if</span> <span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
                <span class="kw">return</span> <span class="prelude-val">None</span>;
            }
            <span class="prelude-val">Some</span>(<span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>))
        } <span class="kw">else</span> {
            <span class="prelude-val">None</span>
        }
    }

    <span class="doccomment">/// Same as get_slice_starting_at, but returns None if the point isn&#39;t on the polyline.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">safe_get_slice_starting_at</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">last_pt</span>() <span class="op">=</span><span class="op">=</span> <span class="ident">pt</span> {
            <span class="kw">return</span> <span class="prelude-val">None</span>;
        }

        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">idx</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">lines</span>().<span class="ident">position</span>(<span class="op">|</span><span class="ident">l</span><span class="op">|</span> <span class="ident">l</span>.<span class="ident">contains_pt</span>(<span class="ident">pt</span>)) {
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();
            <span class="ident">pts</span> <span class="op">=</span> <span class="ident">pts</span>.<span class="ident">split_off</span>(<span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>);
            <span class="kw">if</span> <span class="ident">pt</span> <span class="op">!</span><span class="op">=</span> <span class="ident">pts</span>[<span class="number">0</span>] {
                <span class="ident">pts</span>.<span class="ident">insert</span>(<span class="number">0</span>, <span class="ident">pt</span>);
            }
            <span class="prelude-val">Some</span>(<span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>))
        } <span class="kw">else</span> {
            <span class="prelude-val">None</span>
        }
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">dist_along_of_point</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Option</span><span class="op">&lt;</span>(<span class="ident">Distance</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist_along</span> <span class="op">=</span> <span class="ident">Distance::ZERO</span>;
        <span class="kw">for</span> <span class="ident">l</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>() {
            <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">dist</span>) <span class="op">=</span> <span class="ident">l</span>.<span class="ident">dist_along_of_point</span>(<span class="ident">pt</span>) {
                <span class="kw">return</span> <span class="prelude-val">Some</span>((<span class="ident">dist_along</span> <span class="op">+</span> <span class="ident">dist</span>, <span class="ident">l</span>.<span class="ident">angle</span>()));
            } <span class="kw">else</span> {
                <span class="ident">dist_along</span> <span class="op">+</span><span class="op">=</span> <span class="ident">l</span>.<span class="ident">length</span>();
            }
        }
        <span class="prelude-val">None</span>
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">trim_to_endpts</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">pt1</span>: <span class="ident">Pt2D</span>, <span class="ident">pt2</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="macro">assert!</span>(<span class="ident">pt1</span> <span class="op">!</span><span class="op">=</span> <span class="ident">pt2</span>);
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist1</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">dist_along_of_point</span>(<span class="ident">pt1</span>).<span class="ident">unwrap</span>().<span class="number">0</span>;
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist2</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">dist_along_of_point</span>(<span class="ident">pt2</span>).<span class="ident">unwrap</span>().<span class="number">0</span>;
        <span class="kw">if</span> <span class="ident">dist1</span> <span class="op">&gt;</span> <span class="ident">dist2</span> {
            <span class="ident">std::mem::swap</span>(<span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">dist1</span>, <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">dist2</span>);
        }
        <span class="self">self</span>.<span class="ident">exact_slice</span>(<span class="ident">dist1</span>, <span class="ident">dist2</span>)
    }

    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_bounds</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Bounds</span> {
        <span class="ident">Bounds::from</span>(<span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">pts</span>)
    }

    <span class="doccomment">/// If the current line is at least this long, return it. Otherwise, extend the end of it,</span>
    <span class="doccomment">/// following the angle of the last line.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">extend_to_length</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">min_len</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="kw">let</span> <span class="ident">need_len</span> <span class="op">=</span> <span class="ident">min_len</span> <span class="op">-</span> <span class="self">self</span>.<span class="ident">length</span>();
        <span class="kw">if</span> <span class="ident">need_len</span> <span class="op">&lt;</span><span class="op">=</span> <span class="ident">Distance::ZERO</span> {
            <span class="kw">return</span> <span class="self">self</span>.<span class="ident">clone</span>();
        }
        <span class="kw">let</span> <span class="ident">line</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">last_line</span>();
        <span class="comment">// We might be extending a very tiny amount</span>
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Ok</span>(<span class="ident">extension</span>) <span class="op">=</span> <span class="ident">PolyLine::new</span>(<span class="macro">vec!</span>[
            <span class="ident">line</span>.<span class="ident">pt2</span>(),
            <span class="ident">line</span>.<span class="ident">pt2</span>().<span class="ident">project_away</span>(<span class="ident">need_len</span>, <span class="ident">line</span>.<span class="ident">angle</span>()),
        ]) {
            <span class="self">self</span>.<span class="ident">clone</span>().<span class="ident">must_extend</span>(<span class="ident">extension</span>)
        } <span class="kw">else</span> {
            <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">clone</span>().<span class="ident">into_points</span>();
            <span class="ident">pts</span>.<span class="ident">pop</span>();
            <span class="ident">pts</span>.<span class="ident">push</span>(<span class="ident">line</span>.<span class="ident">pt2</span>().<span class="ident">project_away</span>(<span class="ident">need_len</span>, <span class="ident">line</span>.<span class="ident">angle</span>()));
            <span class="ident">PolyLine::must_new</span>(<span class="ident">pts</span>)
        }
    }

    <span class="doccomment">/// Produces a GeoJSON linestring, optionally mapping the world-space points back to GPS.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">to_geojson</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">gps</span>: <span class="prelude-ty">Option</span><span class="op">&lt;</span><span class="kw-2">&amp;</span><span class="ident">GPSBounds</span><span class="op">&gt;</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">geojson::Geometry</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
        <span class="kw">if</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">gps</span>) <span class="op">=</span> <span class="ident">gps</span> {
            <span class="kw">for</span> <span class="ident">pt</span> <span class="kw">in</span> <span class="ident">gps</span>.<span class="ident">convert_back</span>(<span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">pts</span>) {
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="macro">vec!</span>[<span class="ident">pt</span>.<span class="ident">x</span>(), <span class="ident">pt</span>.<span class="ident">y</span>()]);
            }
        } <span class="kw">else</span> {
            <span class="kw">for</span> <span class="ident">pt</span> <span class="kw">in</span> <span class="kw-2">&amp;</span><span class="self">self</span>.<span class="ident">pts</span> {
                <span class="ident">pts</span>.<span class="ident">push</span>(<span class="macro">vec!</span>[<span class="ident">pt</span>.<span class="ident">x</span>(), <span class="ident">pt</span>.<span class="ident">y</span>()]);
            }
        }
        <span class="ident">geojson::Geometry::new</span>(<span class="ident">geojson::Value::LineString</span>(<span class="ident">pts</span>))
    }

    <span class="doccomment">/// Returns the point on the polyline closest to the query.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">project_pt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">query</span>: <span class="ident">Pt2D</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Pt2D</span> {
        <span class="kw">match</span> <span class="self">self</span>
            .<span class="ident">to_geo</span>()
            .<span class="ident">closest_point</span>(<span class="kw-2">&amp;</span><span class="ident">geo::Point::new</span>(<span class="ident">query</span>.<span class="ident">x</span>(), <span class="ident">query</span>.<span class="ident">y</span>()))
        {
            <span class="ident">geo::Closest::Intersection</span>(<span class="ident">hit</span>) <span class="op">|</span> <span class="ident">geo::Closest::SinglePoint</span>(<span class="ident">hit</span>) <span class="op">=</span><span class="op">&gt;</span> {
                <span class="ident">Pt2D::new</span>(<span class="ident">hit</span>.<span class="ident">x</span>(), <span class="ident">hit</span>.<span class="ident">y</span>())
            }
            <span class="ident">geo::Closest::Indeterminate</span> <span class="op">=</span><span class="op">&gt;</span> <span class="macro">unreachable!</span>(),
        }
    }

    <span class="doccomment">/// Returns the angle from the start to end of this polyline.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">overall_angle</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Angle</span> {
        <span class="self">self</span>.<span class="ident">first_pt</span>().<span class="ident">angle_to</span>(<span class="self">self</span>.<span class="ident">last_pt</span>())
    }

    <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn</span> <span class="ident">to_geo</span>(<span class="kw-2">&amp;</span><span class="self">self</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">geo::LineString</span><span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="ident">pts</span>: <span class="ident">Vec</span><span class="op">&lt;</span><span class="ident">geo::Point</span><span class="op">&lt;</span><span class="ident">f64</span><span class="op">&gt;</span><span class="op">&gt;</span> <span class="op">=</span> <span class="self">self</span>
            .<span class="ident">pts</span>
            .<span class="ident">iter</span>()
            .<span class="ident">map</span>(<span class="op">|</span><span class="ident">pt</span><span class="op">|</span> <span class="ident">geo::Point::new</span>(<span class="ident">pt</span>.<span class="ident">x</span>(), <span class="ident">pt</span>.<span class="ident">y</span>()))
            .<span class="ident">collect</span>();
        <span class="ident">pts</span>.<span class="ident">into</span>()
    }

    <span class="doccomment">/// Walk along the PolyLine, starting `buffer_ends` from the start and ending `buffer_ends`</span>
    <span class="doccomment">/// before the end. Advance in increments of `step_size`. Returns the point and angle at each</span>
    <span class="doccomment">/// step.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">step_along</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">step_size</span>: <span class="ident">Distance</span>, <span class="ident">buffer_ends</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> {
        <span class="self">self</span>.<span class="ident">step_along_start_end</span>(<span class="ident">step_size</span>, <span class="ident">buffer_ends</span>, <span class="ident">buffer_ends</span>)
    }

    <span class="doccomment">/// Walk along the PolyLine, from `start_buffer` to `length - end_buffer`. Advance in</span>
    <span class="doccomment">/// increments of `step_size`. Returns the point and angle at each step.</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">step_along_start_end</span>(
        <span class="kw-2">&amp;</span><span class="self">self</span>,
        <span class="ident">step_size</span>: <span class="ident">Distance</span>,
        <span class="ident">start_buffer</span>: <span class="ident">Distance</span>,
        <span class="ident">end_buffer</span>: <span class="ident">Distance</span>,
    ) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">Vec</span><span class="op">&lt;</span>(<span class="ident">Pt2D</span>, <span class="ident">Angle</span>)<span class="op">&gt;</span> {
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">Vec::new</span>();
        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dist_along</span> <span class="op">=</span> <span class="ident">start_buffer</span>;
        <span class="kw">let</span> <span class="ident">length</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">length</span>();
        <span class="kw">while</span> <span class="ident">dist_along</span> <span class="op">&lt;</span> <span class="ident">length</span> <span class="op">-</span> <span class="ident">end_buffer</span> {
            <span class="ident">result</span>.<span class="ident">push</span>(<span class="self">self</span>.<span class="ident">must_dist_along</span>(<span class="ident">dist_along</span>));
            <span class="ident">dist_along</span> <span class="op">+</span><span class="op">=</span> <span class="ident">step_size</span>;
        }
        <span class="ident">result</span>
    }

    <span class="doccomment">///</span>
    <span class="doccomment">/// ```</span>
    <span class="doccomment">/// use geom::{PolyLine, Pt2D, Distance};</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// let polyline = PolyLine::must_new(vec![</span>
    <span class="doccomment">///     Pt2D::new(0.0, 0.0),</span>
    <span class="doccomment">///     Pt2D::new(0.0, 10.0),</span>
    <span class="doccomment">///     Pt2D::new(10.0, 20.0),</span>
    <span class="doccomment">/// ]);</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// assert_eq!(</span>
    <span class="doccomment">///     polyline.interpolate_points(Distance::meters(20.0)).points(),</span>
    <span class="doccomment">///     &amp;vec![</span>
    <span class="doccomment">///         Pt2D::new(0.0, 0.0),</span>
    <span class="doccomment">///         Pt2D::new(0.0, 10.0),</span>
    <span class="doccomment">///         Pt2D::new(10.0, 20.0),</span>
    <span class="doccomment">///     ]</span>
    <span class="doccomment">/// );</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// assert_eq!(</span>
    <span class="doccomment">///     polyline.interpolate_points(Distance::meters(10.0)).points(),</span>
    <span class="doccomment">///     &amp;vec![</span>
    <span class="doccomment">///         Pt2D::new(0.0, 0.0),</span>
    <span class="doccomment">///         Pt2D::new(0.0, 10.0),</span>
    <span class="doccomment">///         Pt2D::new(5.0, 15.0),</span>
    <span class="doccomment">///         Pt2D::new(10.0, 20.0),</span>
    <span class="doccomment">///     ]</span>
    <span class="doccomment">/// );</span>
    <span class="doccomment">///</span>
    <span class="doccomment">/// ```</span>
    <span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">interpolate_points</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">max_step</span>: <span class="ident">Distance</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">PolyLine</span> {
        <span class="kw">if</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">len</span>() <span class="op">&lt;</span> <span class="number">2</span> {
            <span class="kw">return</span> <span class="self">self</span>.<span class="ident">clone</span>();
        }

        <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">output</span> <span class="op">=</span> <span class="macro">vec!</span>[];
        <span class="kw">for</span> <span class="ident">line</span> <span class="kw">in</span> <span class="self">self</span>.<span class="ident">lines</span>() {
            <span class="kw">let</span> <span class="ident">points</span> <span class="op">=</span> (<span class="ident">line</span>.<span class="ident">length</span>() <span class="op">/</span> <span class="ident">max_step</span>).<span class="ident">ceil</span>();
            <span class="kw">let</span> <span class="ident">step_size</span> <span class="op">=</span> <span class="ident">line</span>.<span class="ident">length</span>() <span class="op">/</span> <span class="ident">points</span>;
            <span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..(<span class="ident">points</span> <span class="kw">as</span> <span class="ident">usize</span>) {
                <span class="ident">output</span>.<span class="ident">push</span>(<span class="ident">line</span>.<span class="ident">must_dist_along</span>(<span class="ident">step_size</span> <span class="op">*</span> <span class="ident">i</span> <span class="kw">as</span> <span class="ident">f64</span>));
            }
        }

        <span class="ident">output</span>.<span class="ident">push</span>(<span class="kw-2">*</span><span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">last</span>().<span class="ident">unwrap</span>());

        <span class="ident">PolyLine::new</span>(<span class="ident">output</span>).<span class="ident">unwrap</span>()
    }
}

<span class="kw">impl</span> <span class="ident">fmt::Display</span> <span class="kw">for</span> <span class="ident">PolyLine</span> {
    <span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&amp;</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&amp;</span><span class="kw-2">mut</span> <span class="ident">fmt::Formatter</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="ident">fmt::Result</span> {
        <span class="macro">writeln!</span>(<span class="ident">f</span>, <span class="string">&quot;PolyLine::new(vec![     // length {}&quot;</span>, <span class="self">self</span>.<span class="ident">length</span>)<span class="question-mark">?</span>;
        <span class="kw">for</span> (<span class="ident">idx</span>, <span class="ident">pt</span>) <span class="kw">in</span> <span class="self">self</span>.<span class="ident">pts</span>.<span class="ident">iter</span>().<span class="ident">enumerate</span>() {
            <span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">&quot;  Pt2D::new({}, {}),&quot;</span>, <span class="ident">pt</span>.<span class="ident">x</span>(), <span class="ident">pt</span>.<span class="ident">y</span>())<span class="question-mark">?</span>;
            <span class="kw">if</span> <span class="ident">idx</span> <span class="op">&gt;</span> <span class="number">0</span> {
                <span class="kw">let</span> <span class="ident">line</span> <span class="op">=</span> <span class="ident">Line::must_new</span>(<span class="self">self</span>.<span class="ident">pts</span>[<span class="ident">idx</span> <span class="op">-</span> <span class="number">1</span>], <span class="kw-2">*</span><span class="ident">pt</span>);
                <span class="macro">write!</span>(
                    <span class="ident">f</span>,
                    <span class="string">&quot;    // {}, {} (+ {} @ {})&quot;</span>,
                    <span class="ident">pt</span>.<span class="ident">x</span>() <span class="op">-</span> <span class="self">self</span>.<span class="ident">pts</span>[<span class="ident">idx</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">x</span>(),
                    <span class="ident">pt</span>.<span class="ident">y</span>() <span class="op">-</span> <span class="self">self</span>.<span class="ident">pts</span>[<span class="ident">idx</span> <span class="op">-</span> <span class="number">1</span>].<span class="ident">y</span>(),
                    <span class="ident">line</span>.<span class="ident">length</span>(),
                    <span class="ident">line</span>.<span class="ident">angle</span>(),
                )<span class="question-mark">?</span>;
            }
            <span class="macro">writeln!</span>(<span class="ident">f</span>)<span class="question-mark">?</span>;
        }
        <span class="macro">write!</span>(<span class="ident">f</span>, <span class="string">&quot;])&quot;</span>)
    }
}

<span class="kw">fn</span> <span class="ident">fix_angles</span>(<span class="ident">orig</span>: <span class="kw-2">&amp;</span><span class="ident">PolyLine</span>, <span class="ident">result</span>: <span class="ident">PolyLine</span>) <span class="op">-</span><span class="op">&gt;</span> <span class="prelude-ty">Result</span><span class="op">&lt;</span><span class="ident">PolyLine</span><span class="op">&gt;</span> {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pts</span> <span class="op">=</span> <span class="ident">result</span>.<span class="ident">pts</span>.<span class="ident">clone</span>();

    <span class="comment">// Check that the angles roughly match up between the original and shifted line</span>
    <span class="kw">for</span> (<span class="ident">idx</span>, (<span class="ident">orig_l</span>, <span class="ident">shifted_l</span>)) <span class="kw">in</span> <span class="ident">orig</span>.<span class="ident">lines</span>().<span class="ident">zip</span>(<span class="ident">result</span>.<span class="ident">lines</span>()).<span class="ident">enumerate</span>() {
        <span class="kw">let</span> <span class="ident">orig_angle</span> <span class="op">=</span> <span class="ident">orig_l</span>.<span class="ident">angle</span>();
        <span class="kw">let</span> <span class="ident">shifted_angle</span> <span class="op">=</span> <span class="ident">shifted_l</span>.<span class="ident">angle</span>();

        <span class="kw">if</span> <span class="op">!</span><span class="ident">orig_angle</span>.<span class="ident">approx_eq</span>(<span class="ident">shifted_angle</span>, <span class="number">1.0</span>) {
            <span class="comment">// When this happens, the rotation is usually right around 180 -- so try swapping</span>
            <span class="comment">// the points!</span>
            <span class="comment">/*println!(
                &quot;Points changed angles from {} to {} (rot {})&quot;,
                orig_angle, shifted_angle, rot
            );*/</span>
            <span class="ident">pts</span>.<span class="ident">swap</span>(<span class="ident">idx</span>, <span class="ident">idx</span> <span class="op">+</span> <span class="number">1</span>);
            <span class="comment">// TODO Start the fixing over. but make sure we won&#39;t infinite loop...</span>
            <span class="comment">//return fix_angles(orig, result);</span>
        }
    }

    <span class="comment">// When we swap points, length of the entire PolyLine may change! Recalculating is vital.</span>
    <span class="ident">PolyLine::new</span>(<span class="ident">pts</span>)
}

<span class="comment">// Also returns the duplicates.</span>
<span class="kw">fn</span> <span class="ident">to_set</span>(<span class="ident">pts</span>: <span class="kw-2">&amp;</span>[<span class="ident">Pt2D</span>]) <span class="op">-</span><span class="op">&gt;</span> (<span class="ident">HashSet</span><span class="op">&lt;</span><span class="ident">HashablePt2D</span><span class="op">&gt;</span>, <span class="ident">HashSet</span><span class="op">&lt;</span><span class="ident">HashablePt2D</span><span class="op">&gt;</span>) {
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">deduped</span> <span class="op">=</span> <span class="ident">HashSet::new</span>();
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">dupes</span> <span class="op">=</span> <span class="ident">HashSet::new</span>();
    <span class="kw">for</span> <span class="ident">pt</span> <span class="kw">in</span> <span class="ident">pts</span> {
        <span class="kw">let</span> <span class="ident">pt</span> <span class="op">=</span> <span class="ident">pt</span>.<span class="ident">to_hashable</span>();
        <span class="kw">if</span> <span class="ident">deduped</span>.<span class="ident">contains</span>(<span class="kw-2">&amp;</span><span class="ident">pt</span>) {
            <span class="ident">dupes</span>.<span class="ident">insert</span>(<span class="ident">pt</span>);
        } <span class="kw">else</span> {
            <span class="ident">deduped</span>.<span class="ident">insert</span>(<span class="ident">pt</span>);
        }
    }
    (<span class="ident">deduped</span>, <span class="ident">dupes</span>)
}
</pre></div>
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