LibWeb: Add barebones CanvasGradient object

Also add the CanvasRenderingContext2D APIs to go along with it.
Note that it can't be used for anything yet.

Userland/Libraries/LibWeb/HTML/CanvasGradient.cpp

@@ -0,0 +1,53 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/HTML/CanvasGradient.h>
+
+namespace Web::HTML {
+
+NonnullRefPtr<CanvasGradient> CanvasGradient::create_radial(double x0, double y0, double r0, double x1, double y1, double r1)
+{
+    (void)x0;
+    (void)y0;
+    (void)r0;
+    (void)x1;
+    (void)y1;
+    (void)r1;
+    return adopt_ref(*new CanvasGradient(Type::Radial));
+}
+
+NonnullRefPtr<CanvasGradient> CanvasGradient::create_linear(double x0, double y0, double x1, double y1)
+{
+    (void)x0;
+    (void)y0;
+    (void)x1;
+    (void)y1;
+    return adopt_ref(*new CanvasGradient(Type::Linear));
+}
+
+NonnullRefPtr<CanvasGradient> CanvasGradient::create_conic(double start_angle, double x, double y)
+{
+    (void)start_angle;
+    (void)x;
+    (void)y;
+    return adopt_ref(*new CanvasGradient(Type::Conic));
+}
+
+CanvasGradient::CanvasGradient(Type type)
+    : m_type(type)
+{
+}
+
+CanvasGradient::~CanvasGradient()
+{
+}
+
+void CanvasGradient::add_color_stop(double offset, String const& color)
+{
+    dbgln("CanvasGradient#addColorStop({}, '{}')", offset, color);
+}
+
+}

Userland/Libraries/LibWeb/HTML/CanvasGradient.h

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <LibWeb/Bindings/Wrappable.h>
+
+namespace Web::HTML {
+
+class CanvasGradient final
+    : public RefCounted<CanvasGradient>
+    , public Bindings::Wrappable {
+public:
+    using WrapperType = Bindings::CanvasGradientWrapper;
+
+    enum class Type {
+        Linear,
+        Radial,
+        Conic,
+    };
+
+    static NonnullRefPtr<CanvasGradient> create_radial(double x0, double y0, double r0, double x1, double y1, double r1);
+    static NonnullRefPtr<CanvasGradient> create_linear(double x0, double y0, double x1, double y1);
+    static NonnullRefPtr<CanvasGradient> create_conic(double start_angle, double x, double y);
+
+    void add_color_stop(double offset, String const& color);
+
+    ~CanvasGradient();
+
+private:
+    explicit CanvasGradient(Type);
+
+    Type m_type {};
+};
+
+}

Userland/Libraries/LibWeb/HTML/CanvasGradient.idl

@@ -0,0 +1,5 @@
+[Exposed=(Window,Worker)]
+interface CanvasGradient {
+    // opaque object
+    undefined addColorStop(double offset, DOMString color);
+};

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.cpp

@@ -496,4 +496,19 @@ CanvasRenderingContext2D::PreparedText CanvasRenderingContext2D::prepare_text(St
     return prepared_text;
 }
 
+NonnullRefPtr<CanvasGradient> CanvasRenderingContext2D::create_radial_gradient(double x0, double y0, double r0, double x1, double y1, double r1)
+{
+    return CanvasGradient::create_radial(x0, y0, r0, x1, y1, r1);
+}
+
+NonnullRefPtr<CanvasGradient> CanvasRenderingContext2D::create_linear_gradient(double x0, double y0, double x1, double y1)
+{
+    return CanvasGradient::create_linear(x0, y0, x1, y1);
+}
+
+NonnullRefPtr<CanvasGradient> CanvasRenderingContext2D::create_conic_gradient(double start_angle, double x, double y)
+{
+    return CanvasGradient::create_conic(start_angle, x, y);
+}
+
 }

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.h

@@ -14,6 +14,7 @@
 #include <LibGfx/Path.h>
 #include <LibWeb/Bindings/Wrappable.h>
 #include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/HTML/CanvasGradient.h>
 #include <LibWeb/Layout/InlineNode.h>
 #include <LibWeb/Layout/LineBox.h>
 
@@ -83,6 +84,10 @@ public:
 
     RefPtr<TextMetrics> measure_text(String const& text);
 
+    NonnullRefPtr<CanvasGradient> create_radial_gradient(double x0, double y0, double r0, double x1, double y1, double r1);
+    NonnullRefPtr<CanvasGradient> create_linear_gradient(double x0, double y0, double x1, double y1);
+    NonnullRefPtr<CanvasGradient> create_conic_gradient(double start_angle, double x, double y);
+
 private:
     explicit CanvasRenderingContext2D(HTMLCanvasElement&);
 

Userland/Libraries/LibWeb/HTML/CanvasRenderingContext2D.idl

@@ -40,4 +40,9 @@ interface CanvasRenderingContext2D {
     readonly attribute HTMLCanvasElement canvas;
 
     TextMetrics measureText(DOMString text);
+
+    CanvasGradient createRadialGradient(double x0, double y0, double r0, double x1, double y1, double r1);
+    CanvasGradient createLinearGradient(double x0, double y0, double x1, double y1);
+    CanvasGradient createConicGradient(double startAngle, double x, double y);
+
 };