From 0d93e249c3b9a0cdfc8d182e94b40fb8b8015f9f Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 16 Apr 2020 21:06:03 +0200
Subject: [PATCH] LibWeb: Add some basic path drawing functionality to the
 canvas element

This patch adds the following methods to CanvasRenderingContext2D:

- beginPath()
- moveTo(x, y)
- lineTo(x, y)
- closePath()
- stroke()

We also add the lineWidth property. :^)
---
 Base/home/anon/www/canvas-path.html           | 40 +++++++++++
 Base/home/anon/www/welcome.html               |  1 +
 .../CanvasRenderingContext2DWrapper.cpp       | 71 +++++++++++++++++++
 .../CanvasRenderingContext2DWrapper.h         |  7 ++
 .../LibWeb/DOM/CanvasRenderingContext2D.cpp   | 31 ++++++++
 .../LibWeb/DOM/CanvasRenderingContext2D.h     | 13 ++++
 6 files changed, 163 insertions(+)
 create mode 100644 Base/home/anon/www/canvas-path.html
diff --git a/Base/home/anon/www/canvas-path.html b/Base/home/anon/www/canvas-path.html
new file mode 100644
index 0000000000..76d4edc44e
--- /dev/null
+++ b/Base/home/anon/www/canvas-path.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<html>
+<head></title>
+<body>
+<canvas width=300 height=300></canvas>
+<script>
+
+function drawHouse() {
+
+var ctx = document.querySelectorAll("canvas")[0].getContext("2d");
+ctx.fillStyle = 'black';
+ctx.fillRect(0, 0, 300, 300);
+
+ctx.fillStyle = 'white';
+ctx.strokeStyle = 'red';
+
+// Set line width
+ctx.lineWidth = 10;
+
+// Wall
+ctx.strokeRect(75, 140, 150, 110);
+
+// Door
+ctx.fillRect(130, 190, 40, 60);
+
+// Roof
+ctx.beginPath();
+ctx.moveTo(50, 140);
+ctx.lineTo(150, 60);
+ctx.lineTo(250, 140);
+ctx.closePath();
+ctx.stroke();
+
+}
+
+drawHouse();
+
+</script>
+</body>
+</html>
diff --git a/Base/home/anon/www/welcome.html b/Base/home/anon/www/welcome.html
index 880fb86146..db445643f2 100644
--- a/Base/home/anon/www/welcome.html
+++ b/Base/home/anon/www/welcome.html
@@ -28,6 +28,7 @@ span#ua {
     <p>Your user agent is: <b><span id="ua"></span></b></p>
     <p>Some small test pages:</p>
     <ul>
+        <li><a href="canvas-path.html">canvas path house!</a></li>
         <li><a href="img-canvas.html">canvas drawImage() test</a></li>
         <li><a href="trigonometry.html">canvas + trigonometry functions</a></li>
         <li><a href="qsa.html">querySelectorAll test</a></li>
diff --git a/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.cpp b/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.cpp
index 27e6fef139..255d266204 100644
--- a/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.cpp
+++ b/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.cpp
@@ -53,6 +53,14 @@ CanvasRenderingContext2DWrapper::CanvasRenderingContext2DWrapper(CanvasRendering
     put_native_property("strokeStyle", stroke_style_getter, stroke_style_setter);
     put_native_function("strokeRect", stroke_rect, 4);
     put_native_function("drawImage", draw_image, 3);
+
+    put_native_function("beginPath", begin_path, 0);
+    put_native_function("closePath", close_path, 0);
+    put_native_function("stroke", stroke, 0);
+    put_native_function("moveTo", move_to, 0);
+    put_native_function("lineTo", line_to, 0);
+
+    put_native_property("lineWidth", line_width_getter, line_width_setter);
 }
 
 CanvasRenderingContext2DWrapper::~CanvasRenderingContext2DWrapper()
@@ -162,5 +170,68 @@ void CanvasRenderingContext2DWrapper::stroke_style_setter(JS::Interpreter& inter
         impl->set_stroke_style(value.to_string());
 }
 
+JS::Value CanvasRenderingContext2DWrapper::line_width_getter(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    return JS::Value(impl->line_width());
+}
+
+void CanvasRenderingContext2DWrapper::line_width_setter(JS::Interpreter& interpreter, JS::Value value)
+{
+    if (auto* impl = impl_from(interpreter))
+        impl->set_line_width(value.to_double());
+}
+
+JS::Value CanvasRenderingContext2DWrapper::begin_path(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    impl->begin_path();
+    return JS::js_undefined();
+}
+
+JS::Value CanvasRenderingContext2DWrapper::close_path(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    impl->close_path();
+    return JS::js_undefined();
+}
+
+JS::Value CanvasRenderingContext2DWrapper::stroke(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    impl->stroke();
+    return JS::js_undefined();
+}
+
+JS::Value CanvasRenderingContext2DWrapper::move_to(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    double x = interpreter.argument(0).to_double();
+    double y = interpreter.argument(1).to_double();
+    impl->move_to(x, y);
+    return JS::js_undefined();
+}
+
+JS::Value CanvasRenderingContext2DWrapper::line_to(JS::Interpreter& interpreter)
+{
+    auto* impl = impl_from(interpreter);
+    if (!impl)
+        return {};
+    double x = interpreter.argument(0).to_double();
+    double y = interpreter.argument(1).to_double();
+    impl->line_to(x, y);
+    return JS::js_undefined();
+}
+
 }
 }
diff --git a/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.h b/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.h
index 55b494a6eb..5822dc77fb 100644
--- a/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.h
+++ b/Libraries/LibWeb/Bindings/CanvasRenderingContext2DWrapper.h
@@ -51,6 +51,13 @@ private:
     static void fill_style_setter(JS::Interpreter&, JS::Value);
     static JS::Value stroke_style_getter(JS::Interpreter&);
     static void stroke_style_setter(JS::Interpreter&, JS::Value);
+    static JS::Value line_width_getter(JS::Interpreter&);
+    static void line_width_setter(JS::Interpreter&, JS::Value);
+    static JS::Value begin_path(JS::Interpreter&);
+    static JS::Value close_path(JS::Interpreter&);
+    static JS::Value stroke(JS::Interpreter&);
+    static JS::Value move_to(JS::Interpreter&);
+    static JS::Value line_to(JS::Interpreter&);
 
     NonnullRefPtr<CanvasRenderingContext2D> m_impl;
 };
diff --git a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
index 92c8b3d68c..e0a9320780 100644
--- a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
+++ b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
@@ -134,4 +134,35 @@ OwnPtr<Gfx::Painter> CanvasRenderingContext2D::painter()
     return make<Gfx::Painter>(*m_element->bitmap());
 }
 
+void CanvasRenderingContext2D::begin_path()
+{
+    m_path = Gfx::Path();
+}
+
+void CanvasRenderingContext2D::close_path()
+{
+    m_path.close();
+}
+
+void CanvasRenderingContext2D::move_to(float x, float y)
+{
+    m_path.move_to({ x, y });
+}
+
+void CanvasRenderingContext2D::line_to(float x, float y)
+{
+    m_path.line_to({ x, y });
+}
+
+void CanvasRenderingContext2D::stroke()
+{
+    dbg() << "stroke path " << m_path;
+
+    auto painter = this->painter();
+    if (!painter)
+        return;
+
+    painter->stroke_path(m_path, m_stroke_style, m_line_width);
+}
+
 }
diff --git a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
index c92446f9d0..dce9683d88 100644
--- a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
+++ b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
@@ -30,6 +30,7 @@
 #include <LibGfx/AffineTransform.h>
 #include <LibGfx/Color.h>
 #include <LibGfx/Forward.h>
+#include <LibGfx/Path.h>
 #include <LibWeb/Bindings/Wrappable.h>
 
 namespace Web {
@@ -61,6 +62,15 @@ public:
     void scale(float sx, float sy);
     void translate(float x, float y);
 
+    void set_line_width(float line_width) { m_line_width = line_width; }
+    float line_width() const { return m_line_width; }
+
+    void begin_path();
+    void close_path();
+    void move_to(float x, float y);
+    void line_to(float x, float y);
+    void stroke();
+
 private:
     explicit CanvasRenderingContext2D(HTMLCanvasElement&);
 
@@ -73,6 +83,9 @@ private:
     Gfx::AffineTransform m_transform;
     Gfx::Color m_fill_style;
     Gfx::Color m_stroke_style;
+    float m_line_width { 1 };
+
+    Gfx::Path m_path;
 };
 
 }
