LibHTML: Implement the <blink> element

Just in time for Serenity's 1st birthday, here is the <blink> element!

This patch adds a bunch of different mechanisms to enable partial
repaints of the layout tree (LayoutNode::set_needs_display()))
It also adds LayoutNode::is_visible(), which can be toggled to prevent
a LayoutNode from rendering anything (it still takes up space though.)

1 files changed, 6 insertions, 0 deletions

diff --git a/Libraries/LibHTML/HtmlView.cpp b/Libraries/LibHTML/HtmlView.cpp
index b909fbb2bd..a1c0c8162c 100644
--- a/Libraries/LibHTML/HtmlView.cpp
+++ b/Libraries/LibHTML/HtmlView.cpp
@@ -17,6 +17,12 @@ HtmlView::HtmlView(GWidget* parent)
     : GScrollableWidget(parent)
     , m_main_frame(Frame::create())
 {
+    main_frame().on_set_needs_display = [this](auto& content_rect) {
+        Rect adjusted_rect = content_rect;
+        adjusted_rect.set_location(to_widget_position(content_rect.location()));
+        update(adjusted_rect);
+    };
+
     set_frame_shape(FrameShape::Container);
     set_frame_shadow(FrameShadow::Sunken);
     set_frame_thickness(2);