LibWeb: Add basic support for requestAnimationFrame()

We now support rAF, driven by GUI::DisplayLink callbacks. It's a bit
strange how we keep registering new callbacks over and over.
That's something we can definitely optimize.

This allows you to update animations/whatever without doing it more
often than the browser can display.

3 files changed, 31 insertions, 2 deletions

diff --git a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
index 4e2bc49d7b..393e26d2d3 100644
--- a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
+++ b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.cpp
@@ -30,7 +30,19 @@ void CanvasRenderingContext2D::fill_rect(int x, int y, int width, int height)
     if (!painter)
         return;
 
-    painter->fill_rect({ x, y, width, height }, m_fill_style);
+    Gfx::Rect rect(x, y, width, height);
+    painter->fill_rect(rect, m_fill_style);
+    did_draw(rect);
+}
+
+void CanvasRenderingContext2D::did_draw(const Gfx::Rect&)
+{
+    // FIXME: Make use of the rect to reduce the invalidated area when possible.
+    if (!m_element)
+        return;
+    if (!m_element->layout_node())
+        return;
+    m_element->layout_node()->set_needs_display();
 }
 
 OwnPtr<Gfx::Painter> CanvasRenderingContext2D::painter()
diff --git a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
index 8a36742015..ec84dfe815 100644
--- a/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
+++ b/Libraries/LibWeb/DOM/CanvasRenderingContext2D.h
@@ -28,6 +28,8 @@ public:
 private:
     explicit CanvasRenderingContext2D(HTMLCanvasElement&);
 
+    void did_draw(const Gfx::Rect&);
+
     OwnPtr<Gfx::Painter> painter();
 
     WeakPtr<HTMLCanvasElement> m_element;
diff --git a/Libraries/LibWeb/DOM/Document.cpp b/Libraries/LibWeb/DOM/Document.cpp
index f4a120bc6e..4f7498c2ec 100644
--- a/Libraries/LibWeb/DOM/Document.cpp
+++ b/Libraries/LibWeb/DOM/Document.cpp
@@ -28,6 +28,7 @@
 #include <AK/StringBuilder.h>
 #include <LibCore/Timer.h>
 #include <LibGUI/Application.h>
+#include <LibGUI/DisplayLink.h>
 #include <LibGUI/MessageBox.h>
 #include <LibJS/Interpreter.h>
 #include <LibJS/Runtime/Function.h>
@@ -360,11 +361,25 @@ JS::Interpreter& Document::interpreter()
             (void)Core::Timer::construct(
                 arguments[1].to_i32(), [this, callback] {
                     const_cast<JS::Function*>(static_cast<const JS::Function*>(callback.cell()))->call(*m_interpreter, {});
-                }).leak_ref();
+                })
+                .leak_ref();
 
             return JS::js_undefined();
         });
 
+        m_interpreter->global_object().put_native_function("requestAnimationFrame", [this](JS::Object*, const Vector<JS::Value>& arguments) -> JS::Value {
+            if (arguments.size() < 1)
+                return JS::js_undefined();
+            ASSERT(arguments[0].is_object());
+            ASSERT(arguments[0].as_object()->is_function());
+            auto callback = make_handle(const_cast<JS::Object*>(arguments[0].as_object()));
+            i32 link_id = GUI::DisplayLink::register_callback([this, callback](i32 link_id) {
+                const_cast<JS::Function*>(static_cast<const JS::Function*>(callback.cell()))->call(*m_interpreter, {});
+                GUI::DisplayLink::unregister_callback(link_id);
+            });
+            return JS::Value(link_id);
+        });
+
         m_interpreter->global_object().put_native_property(
             "document",
             [this](JS::Object*) {