font: port over radial gradient fills

color-types/src/lib.rs

@@ -221,6 +221,38 @@ impl SrgbaPixel {
 #[cfg_attr(feature = "use_serde", derive(Serialize, Deserialize))]
 pub struct SrgbaTuple(pub f32, pub f32, pub f32, pub f32);
 
+impl SrgbaTuple {
+    pub fn premultiply(self) -> Self {
+        let SrgbaTuple(r, g, b, a) = self;
+        Self(r * a, g * a, b * a, a)
+    }
+
+    pub fn demultiply(self) -> Self {
+        let SrgbaTuple(r, g, b, a) = self;
+        if a != 0. {
+            Self(r / a, g / a, b / a, a)
+        } else {
+            self
+        }
+    }
+
+    pub fn interpolate(self, other: Self, k: f64) -> Self {
+        let k = k as f32;
+
+        let SrgbaTuple(r0, g0, b0, a0) = self.premultiply();
+        let SrgbaTuple(r1, g1, b1, a1) = other.premultiply();
+
+        let r = SrgbaTuple(
+            r0 + k * (r1 - r0),
+            g0 + k * (g1 - g0),
+            b0 + k * (b1 - b0),
+            a0 + k * (a1 - a0),
+        );
+
+        r.demultiply()
+    }
+}
+
 impl ToDynamic for SrgbaTuple {
     fn to_dynamic(&self) -> Value {
         self.to_string().to_dynamic()
@@ -237,6 +269,13 @@ impl FromDynamic for SrgbaTuple {
     }
 }
 
+impl From<SrgbaPixel> for SrgbaTuple {
+    fn from(pixel: SrgbaPixel) -> SrgbaTuple {
+        let (r, g, b, a) = pixel.as_srgba_tuple();
+        SrgbaTuple(r, g, b, a)
+    }
+}
+
 impl From<(f32, f32, f32, f32)> for SrgbaTuple {
     fn from((r, g, b, a): (f32, f32, f32, f32)) -> SrgbaTuple {
         SrgbaTuple(r, g, b, a)

wezterm-font/src/hbwrap.rs

@@ -864,8 +864,12 @@ impl ColorLine {
             color_stops: color_stops
                 .into_iter()
                 .map(|stop| ColorStop {
-                    offset: stop.offset,
-                    color: hb_color_to_srgba_pixel(stop.color),
+                    offset: stop.offset.into(),
+                    color: if stop.is_foreground != 0 {
+                        SrgbaPixel::rgba(0xff, 0xff, 0xff, 0xff)
+                    } else {
+                        hb_color_to_srgba_pixel(stop.color)
+                    },
                 })
                 .collect(),
             extend: hb_extend_to_cairo(extend),

wezterm-font/src/rasterizer/colr.rs

@@ -1,9 +1,17 @@
-use cairo::{Context, Extend, LinearGradient, Matrix, Operator, RadialGradient};
-use wezterm_color_types::SrgbaPixel;
+use cairo::{Context, Extend, LinearGradient, Matrix, Mesh, MeshCorner, Operator, RadialGradient};
+use wezterm_color_types::{SrgbaPixel, SrgbaTuple};
+
+/* The gradient related routines in this file were ported from HarfBuzz, which
+ * were in turn ported from BlackRenderer by Black Foundry.
+ * Used by permission to relicense to HarfBuzz license,
+ * which is in turn compatible with wezterm's license.
+ *
+ * https://github.com/BlackFoundryCom/black-renderer
+ */
 
 #[derive(Clone, Debug)]
 pub struct ColorStop {
-    pub offset: f32,
+    pub offset: f64,
     pub color: SrgbaPixel,
 }
 
@@ -148,16 +156,346 @@ pub fn paint_radial_gradient(
     Ok(())
 }
 
+#[derive(Copy, Clone, Debug)]
+struct Point {
+    x: f64,
+    y: f64,
+}
+
+impl Point {
+    fn dot(&self, other: Self) -> f64 {
+        (self.x * other.x) + (self.y * other.y)
+    }
+
+    fn normalize(self) -> Self {
+        let len = self.dot(self).sqrt();
+        Self {
+            x: self.x / len,
+            y: self.y / len,
+        }
+    }
+
+    pub fn sum(self, other: Self) -> Self {
+        Self {
+            x: self.x + other.x,
+            y: self.y + other.y,
+        }
+    }
+
+    pub fn difference(self, other: Self) -> Self {
+        Self {
+            x: self.x - other.x,
+            y: self.y - other.y,
+        }
+    }
+
+    pub fn scale(self, factor: f64) -> Self {
+        Self {
+            x: self.x * factor,
+            y: self.y * factor,
+        }
+    }
+
+    /// Compute a vector from the supplied angle
+    pub fn from_angle(angle: f64) -> Self {
+        let (y, x) = angle.sin_cos();
+        Self { x, y }
+    }
+}
+
+fn interpolate(f0: f64, f1: f64, f: f64) -> f64 {
+    f0 + f * (f1 - f0)
+}
+
+#[derive(Debug)]
+struct Patch {
+    p0: Point,
+    c0: Point,
+    c1: Point,
+    p1: Point,
+    color0: SrgbaTuple,
+    color1: SrgbaTuple,
+}
+
+impl Patch {
+    fn add_to_mesh(&self, center: Point, mesh: &Mesh) {
+        mesh.begin_patch();
+        mesh.move_to(center.x, center.y);
+        mesh.line_to(self.p0.x, self.p0.y);
+        mesh.curve_to(
+            self.c0.x, self.c0.y, self.c1.x, self.c1.y, self.p1.x, self.p1.y,
+        );
+        mesh.line_to(center.x, center.y);
+
+        fn set_corner_color(mesh: &Mesh, corner: MeshCorner, color: SrgbaTuple) {
+            let SrgbaTuple(r, g, b, a) = color;
+
+            mesh.set_corner_color_rgba(corner, r.into(), g.into(), b.into(), a.into());
+        }
+
+        set_corner_color(mesh, MeshCorner::MeshCorner0, self.color0);
+        set_corner_color(mesh, MeshCorner::MeshCorner1, self.color0);
+        set_corner_color(mesh, MeshCorner::MeshCorner2, self.color1);
+        set_corner_color(mesh, MeshCorner::MeshCorner3, self.color1);
+
+        mesh.end_patch();
+    }
+}
+
+fn add_sweep_gradient_patches(
+    mesh: &Mesh,
+    center: Point,
+    radius: f64,
+    a0: f64,
+    c0: SrgbaTuple,
+    a1: f64,
+    c1: SrgbaTuple,
+) {
+    const MAX_ANGLE: f64 = std::f64::consts::PI / 8.;
+    let num_splits = ((a1 - a0).abs() / MAX_ANGLE).ceil() as usize;
+
+    let mut p0 = Point::from_angle(a0);
+    let mut color0 = c0;
+
+    for idx in 0..num_splits {
+        let k = (idx as f64 + 1.) / num_splits as f64;
+
+        let angle1 = interpolate(a0, a1, k);
+        let color1 = c0.interpolate(c1, k);
+
+        let p1 = Point::from_angle(angle1);
+
+        let a = p0.sum(p1).normalize();
+        let u = Point { x: -a.y, y: a.x };
+
+        fn compute_control(a: Point, u: Point, p: Point, center: Point, radius: f64) -> Point {
+            let c = a.sum(u.scale(p.difference(a).dot(p) / u.dot(p)));
+            c.difference(p)
+                .scale(0.33333)
+                .sum(c)
+                .scale(radius)
+                .sum(center)
+        }
+
+        let patch = Patch {
+            color0,
+            color1,
+            p0: center.sum(p0.scale(radius)),
+            p1: center.sum(p1.scale(radius)),
+            c0: compute_control(a, u, p0, center, radius),
+            c1: compute_control(a, u, p1, center, radius),
+        };
+
+        patch.add_to_mesh(center, mesh);
+
+        p0 = p1;
+        color0 = color1;
+    }
+}
+
+const PI_TIMES_2: f64 = std::f64::consts::PI * 2.;
+
+fn apply_sweep_gradient_patches(
+    mesh: &Mesh,
+    mut color_line: ColorLine,
+    center: Point,
+    radius: f64,
+    mut start_angle: f64,
+    mut end_angle: f64,
+) {
+    if start_angle == end_angle {
+        if color_line.extend == Extend::Pad {
+            if start_angle > 0. {
+                let c = color_line.color_stops[0].color.into();
+                add_sweep_gradient_patches(mesh, center, radius, 0., c, start_angle, c);
+            }
+            if end_angle < PI_TIMES_2 {
+                let c = color_line.color_stops.last().unwrap().color.into();
+                add_sweep_gradient_patches(mesh, center, radius, end_angle, c, PI_TIMES_2, c);
+            }
+        }
+        return;
+    }
+
+    if end_angle < start_angle {
+        std::mem::swap(&mut start_angle, &mut end_angle);
+        color_line.color_stops.reverse();
+        for stop in &mut color_line.color_stops {
+            stop.offset = 1.0 - stop.offset;
+        }
+    }
+
+    let angles: Vec<f64> = color_line
+        .color_stops
+        .iter()
+        .map(|stop| start_angle + stop.offset * (end_angle - start_angle))
+        .collect();
+    let colors: Vec<SrgbaTuple> = color_line
+        .color_stops
+        .iter()
+        .map(|stop| stop.color.into())
+        .collect();
+
+    let n_stops = angles.len();
+
+    if color_line.extend == Extend::Pad {
+        let mut color0 = colors[0];
+        let mut pos = 0;
+        while pos < n_stops {
+            if angles[pos] >= 0. {
+                if pos > 0 {
+                    let k = (0. - angles[pos - 1]) / (angles[pos] - angles[pos - 1]);
+
+                    color0 = colors[pos - 1].interpolate(colors[pos], k);
+                }
+                break;
+            }
+            pos += 1;
+        }
+        if pos == n_stops {
+            /* everything is below 0 */
+            color0 = colors[n_stops - 1];
+            add_sweep_gradient_patches(mesh, center, radius, 0., color0, PI_TIMES_2, color0);
+            return;
+        }
+
+        add_sweep_gradient_patches(mesh, center, radius, 0., color0, angles[pos], colors[pos]);
+
+        pos += 1;
+        while pos < n_stops {
+            if angles[pos] <= PI_TIMES_2 {
+                add_sweep_gradient_patches(
+                    mesh,
+                    center,
+                    radius,
+                    angles[pos - 1],
+                    colors[pos - 1],
+                    angles[pos],
+                    colors[pos],
+                );
+            } else {
+                let k = (PI_TIMES_2 - angles[pos - 1]) / (angles[pos] - angles[pos - 1]);
+                let color1 = colors[pos - 1].interpolate(colors[pos], k);
+                add_sweep_gradient_patches(
+                    mesh,
+                    center,
+                    radius,
+                    angles[pos - 1],
+                    colors[pos - 1],
+                    PI_TIMES_2,
+                    color1,
+                );
+                break;
+            }
+            pos += 1;
+        }
+
+        if pos == n_stops {
+            /* everything is below 2*M_PI */
+            color0 = colors[n_stops - 1];
+            add_sweep_gradient_patches(
+                mesh,
+                center,
+                radius,
+                angles[n_stops - 1],
+                color0,
+                PI_TIMES_2,
+                color0,
+            );
+            return;
+        }
+    } else {
+        let span = angles[n_stops - 1] - angles[0];
+        let mut k = 0isize;
+        if angles[0] >= 0. {
+            let mut ss = angles[0];
+            while ss > 0. {
+                if span > 0. {
+                    ss -= span;
+                    k -= 1;
+                } else {
+                    ss += span;
+                    k += 1;
+                }
+            }
+        } else if angles[0] < 0. {
+            let mut ee = angles[n_stops - 1];
+            while ee < 0. {
+                if span > 0. {
+                    ee += span;
+                    k += 1;
+                } else {
+                    ee -= span;
+                    k -= 1;
+                }
+            }
+        }
+
+        debug_assert!(
+            angles[0] + (k as f64) * span <= 0. && 0. < angles[n_stops - 1] + (k as f64) * span
+        );
+        let span = span.abs();
+
+        for l in k..k.min(1000) {
+            for i in 1..n_stops {
+                let (a0, a1, c0, c1);
+
+                if l % 2 != 0 && color_line.extend == Extend::Reflect {
+                    a0 = angles[0] + angles[n_stops - 1] - angles[n_stops - 1 - (i - 1)]
+                        + (l as f64) * span;
+                    a1 = angles[0] + angles[n_stops - 1] - angles[n_stops - 1 - i]
+                        + (l as f64) * span;
+                    c0 = colors[n_stops - 1 - (i - 1)];
+                    c1 = colors[n_stops - 1 - i];
+                } else {
+                    a0 = angles[i - 1] + (l as f64) * span;
+                    a1 = angles[i] + (l as f64) * span;
+                    c0 = colors[i - 1];
+                    c1 = colors[i];
+                }
+
+                if a1 < 0. {
+                    continue;
+                }
+
+                if a0 < 0. {
+                    let f = (0. - a0) / (a1 - a0);
+                    let color = c0.interpolate(c1, f);
+                    add_sweep_gradient_patches(mesh, center, radius, 0., color, a1, c1);
+                } else if a1 >= PI_TIMES_2 {
+                    let f = (PI_TIMES_2 - a0) / (a1 - a0);
+                    let color = c0.interpolate(c1, f);
+                    add_sweep_gradient_patches(mesh, center, radius, a0, c0, PI_TIMES_2, color);
+                    return;
+                } else {
+                    add_sweep_gradient_patches(mesh, center, radius, a0, c0, a1, c1);
+                }
+            }
+        }
+    }
+}
+
 pub fn paint_sweep_gradient(
     context: &Context,
     x0: f64,
     y0: f64,
     start_angle: f64,
     end_angle: f64,
-    mut color_line: ColorLine,
+    color_line: ColorLine,
 ) -> anyhow::Result<()> {
-    let (min_stop, max_stop) = normalize_color_line(&mut color_line);
-    anyhow::bail!("NOT IMPL: SweepGradient");
+    let (x1, y1, x2, y2) = context.clip_extents()?;
+
+    let max_x = ((x1 - x0) * (x1 - x0)).max((x2 - x0) * (x2 - x0));
+    let max_y = ((y1 - y0) * (y1 - y0)).max((y2 - y0) * (y2 - y0));
+    let radius = (max_x + max_y).sqrt();
+
+    let mesh = Mesh::new();
+    let center = Point { x: x0, y: y0 };
+    apply_sweep_gradient_patches(&mesh, color_line, center, radius, start_angle, end_angle);
+    context.set_source(mesh)?;
+    context.paint()?;
+
+    Ok(())
 }
 
 fn normalize_color_line(color_line: &mut ColorLine) -> (f64, f64) {
@@ -179,12 +517,6 @@ fn normalize_color_line(color_line: &mut ColorLine) -> (f64, f64) {
         }
     }
 
-    // NOTE: hb-cairo-utils will call back out to some other state
-    // to fill in the color when is_foreground is true, defaulting
-    // to black with alpha varying by the alpha channel of the
-    // color value in the stop. Do we need to do something like
-    // that here?
-
     (smallest as f64, largest as f64)
 }