LibWeb: Add <canvas> element and start fleshing out CRC2D

This patch adds HTMLCanvasElement along with a LayoutCanvas object.
The DOM and layout parts are very similar to <img> elements.

The <canvas> element holds a Gfx::Bitmap which is sized according to
the "width" and "height" attributes on the element.

Calling .getContext("2d") on a <canvas> element gives you a context
object that draws into the underlying Gfx::Bitmap of the <canvas>.
The context weakly points to the <canvas> which allows it to outlive
the canvas element if needed.

This is really quite cool. :^)

3 files changed, 122 insertions, 0 deletions

diff --git a/Libraries/LibWeb/Layout/LayoutCanvas.cpp b/Libraries/LibWeb/Layout/LayoutCanvas.cpp
new file mode 100644
index 0000000000..39b81f8454
--- /dev/null
+++ b/Libraries/LibWeb/Layout/LayoutCanvas.cpp
@@ -0,0 +1,64 @@
+/*
+ * 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.
+ */
+
+#include <LibGUI/Painter.h>
+#include <LibGfx/Font.h>
+#include <LibGfx/StylePainter.h>
+#include <LibWeb/Layout/LayoutCanvas.h>
+
+namespace Web {
+
+LayoutCanvas::LayoutCanvas(const HTMLCanvasElement& element, NonnullRefPtr<StyleProperties> style)
+    : LayoutReplaced(element, move(style))
+{
+}
+
+LayoutCanvas::~LayoutCanvas()
+{
+}
+
+void LayoutCanvas::layout()
+{
+    rect().set_width(node().preferred_width());
+    rect().set_height(node().preferred_height());
+    LayoutReplaced::layout();
+}
+
+void LayoutCanvas::render(RenderingContext& context)
+{
+    if (!is_visible())
+        return;
+
+    // FIXME: This should be done at a different level. Also rect() does not include padding etc!
+    if (!context.viewport_rect().intersects(enclosing_int_rect(rect())))
+        return;
+
+    if (node().bitmap())
+        context.painter().draw_scaled_bitmap(enclosing_int_rect(rect()), *node().bitmap(), node().bitmap()->rect());
+    LayoutReplaced::render(context);
+}
+
+}
diff --git a/Libraries/LibWeb/Layout/LayoutCanvas.h b/Libraries/LibWeb/Layout/LayoutCanvas.h
new file mode 100644
index 0000000000..e2613fc780
--- /dev/null
+++ b/Libraries/LibWeb/Layout/LayoutCanvas.h
@@ -0,0 +1,57 @@
+/*
+ * 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 <LibWeb/DOM/HTMLCanvasElement.h>
+#include <LibWeb/Layout/LayoutReplaced.h>
+
+namespace Web {
+
+class HTMLCanvasElement;
+
+class LayoutCanvas : public LayoutReplaced {
+public:
+    LayoutCanvas(const HTMLCanvasElement&, NonnullRefPtr<StyleProperties>);
+    virtual ~LayoutCanvas() override;
+
+    virtual void layout() override;
+    virtual void render(RenderingContext&) override;
+
+    const HTMLCanvasElement& node() const { return static_cast<const HTMLCanvasElement&>(LayoutReplaced::node()); }
+
+private:
+    virtual const char* class_name() const override { return "LayoutCanvas"; }
+    virtual bool is_canvas() const override { return true; }
+};
+
+template<>
+inline bool is<LayoutCanvas>(const LayoutNode& node)
+{
+    return node.is_canvas();
+}
+
+}
diff --git a/Libraries/LibWeb/Layout/LayoutNode.h b/Libraries/LibWeb/Layout/LayoutNode.h
index 9d4f0a05c7..22557a9fce 100644
--- a/Libraries/LibWeb/Layout/LayoutNode.h
+++ b/Libraries/LibWeb/Layout/LayoutNode.h
@@ -87,6 +87,7 @@ public:
     virtual bool is_replaced() const { return false; }
     virtual bool is_widget() const { return false; }
     virtual bool is_image() const { return false; }
+    virtual bool is_canvas() const { return false; }
     virtual bool is_box() const { return false; }
     virtual bool is_table() const { return false; }
     virtual bool is_table_row() const { return false; }