LibGfx: Add Gfx::Path, a basic 2D path with <canvas> semantics

This will be used to implement painting of 2D paths. This first patch
adds support for line_to(), move_to() and close().

It will try to have the same semantics as the HTML <canvas> element.

To stroke a Path, simply pass it to Painter::stroke_path().

Libraries/LibGfx/Forward.h

@@ -42,6 +42,7 @@ class ImageDecoder;
 class Painter;
 class Palette;
 class PaletteImpl;
+class Path;
 class Point;
 class Rect;
 class ShareableBitmap;

Libraries/LibGfx/Makefile

@@ -11,6 +11,7 @@ OBJS = \
     PNGLoader.o \
     Painter.o \
     Palette.o \
+    Path.o \
     Point.o \
     Rect.o \
     ShareableBitmap.o \

Libraries/LibGfx/Painter.cpp

@@ -35,6 +35,7 @@
 #include <AK/StringBuilder.h>
 #include <AK/Utf8View.h>
 #include <LibGfx/CharacterBitmap.h>
+#include <LibGfx/Path.h>
 #include <math.h>
 #include <stdio.h>
 #include <unistd.h>
@@ -1010,4 +1011,24 @@ PainterStateSaver::~PainterStateSaver()
     m_painter.restore();
 }
 
+void Painter::stroke_path(const Path& path, Color color, int thickness)
+{
+    FloatPoint cursor;
+
+    for (auto& segment : path.segments()) {
+        switch (segment.type) {
+        case Path::Segment::Type::Invalid:
+            ASSERT_NOT_REACHED();
+            break;
+        case Path::Segment::Type::MoveTo:
+            cursor = segment.point;
+            break;
+        case Path::Segment::Type::LineTo:
+            draw_line(Point(cursor.x(), cursor.y()), Point(segment.point.x(), segment.point.y()), color, thickness);
+            cursor = segment.point;
+            break;
+        }
+    }
+}
+
 }

Libraries/LibGfx/Painter.h

@@ -69,6 +69,8 @@ public:
     void draw_emoji(const Point&, const Gfx::Bitmap&, const Font&);
     void draw_glyph_or_emoji(const Point&, u32 codepoint, const Font&, Color);
 
+    void stroke_path(const Path&, Color, int thickness);
+
     const Font& font() const { return *state().font; }
     void set_font(const Font& font) { state().font = &font; }
 

Libraries/LibGfx/Path.cpp

@@ -0,0 +1,76 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StringBuilder.h>
+#include <LibGfx/Path.h>
+
+namespace Gfx {
+
+void Path::close()
+{
+    if (m_segments.size() <= 1)
+        return;
+
+    auto& last_point = m_segments.last().point;
+
+    for (ssize_t i = m_segments.size() - 1; i >= 0; --i) {
+        auto& segment = m_segments[i];
+        if (segment.type == Segment::Type::MoveTo) {
+            if (last_point == segment.point)
+                return;
+            m_segments.append({ Segment::Type::LineTo, segment.point });
+            return;
+        }
+    }
+}
+
+String Path::to_string() const
+{
+    StringBuilder builder;
+    builder.append("Path { ");
+    for (auto& segment : m_segments) {
+        switch (segment.type) {
+        case Segment::Type::MoveTo:
+            builder.append("MoveTo");
+            break;
+        case Segment::Type::LineTo:
+            builder.append("LineTo");
+            break;
+        case Segment::Type::Invalid:
+            builder.append("Invalid");
+            break;
+        }
+        builder.append('(');
+        builder.append(segment.point.to_string());
+        builder.append(')');
+
+        builder.append(' ');
+    }
+    builder.append("}");
+    return builder.to_string();
+}
+
+}

Libraries/LibGfx/Path.h

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Vector.h>
+#include <LibGfx/FloatPoint.h>
+#include <LibGfx/Forward.h>
+
+namespace Gfx {
+
+class Path {
+public:
+    struct Segment {
+        enum class Type {
+            Invalid,
+            MoveTo,
+            LineTo,
+        };
+
+        Type type { Type::Invalid };
+        FloatPoint point;
+    };
+
+    Path() {}
+
+    void move_to(const FloatPoint& point)
+    {
+        m_segments.append({ Segment::Type::MoveTo, point });
+    }
+
+    void line_to(const FloatPoint& point)
+    {
+        m_segments.append({ Segment::Type::LineTo, point });
+    }
+
+    void close();
+
+    const Vector<Segment>& segments() const { return m_segments; }
+
+    String to_string() const;
+
+private:
+    Vector<Segment> m_segments;
+};
+
+inline const LogStream& operator<<(const LogStream& stream, const Path& path)
+{
+    return stream << path.to_string();
+}
+
+}