LibWeb: Implement CanvasRenderingContext2D.createPattern()

This is a first pass at implementing CRC2D.createPattern() and the
associated CanvasPattern object. This implementation only works for a
few of the required image sources [like CRC2D.drawImage()], and does
not yet support transforms. Other than that it supports everything
else (which is mainly the various repeat modes).

Userland/Libraries/LibWeb/HTML/CanvasPattern.h

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2023, MacDue <macdue@dueutil.tech>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibGfx/PaintStyle.h>
+#include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/HTML/Canvas/CanvasDrawImage.h>
+
+namespace Web::HTML {
+
+class CanvasPatternPaintStyle final : public Gfx::PaintStyle {
+public:
+    enum class Repetition {
+        Repeat,
+        RepeatX,
+        RepeatY,
+        NoRepeat
+    };
+
+    static NonnullRefPtr<CanvasPatternPaintStyle> create(Gfx::Bitmap const& bitmap, Repetition repetition)
+    {
+        return adopt_ref(*new CanvasPatternPaintStyle(bitmap, repetition));
+    }
+
+    virtual void paint(Gfx::IntRect physical_bounding_box, PaintFunction paint) const override;
+
+private:
+    CanvasPatternPaintStyle(Gfx::Bitmap const& bitmap, Repetition repetition)
+        : m_bitmap(bitmap)
+        , m_repetition(repetition)
+    {
+    }
+
+    NonnullRefPtr<Gfx::Bitmap const> m_bitmap;
+    Repetition m_repetition { Repetition::Repeat };
+};
+
+class CanvasPattern final : public Bindings::PlatformObject {
+    WEB_PLATFORM_OBJECT(CanvasPattern, Bindings::PlatformObject);
+
+public:
+    static WebIDL::ExceptionOr<JS::GCPtr<CanvasPattern>> create(JS::Realm&, CanvasImageSource const& image, StringView repetition);
+
+    ~CanvasPattern();
+
+    NonnullRefPtr<Gfx::PaintStyle> to_gfx_paint_style() { return m_pattern; }
+
+private:
+    CanvasPattern(JS::Realm&, CanvasPatternPaintStyle&);
+
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
+
+    NonnullRefPtr<CanvasPatternPaintStyle> m_pattern;
+};
+
+}