Implements https://github.com/whatwg/html/pull/10007 which basically
moves style, layout and painting from HTML processing task into HTML
task with "rendering" source.
The biggest difference is that now we no longer schedule HTML event loop
processing whenever we might need a repaint, but instead queue a global
rendering task 60 times per second that will check if any documents
need a style/layout/paint update.
That is a great simplification of our repaint scheduling model. Before
we had:
- Optional timer that schedules animation updates 60 hz
- Optional timer that schedules rAF updates
- PaintWhenReady state to schedule a paint if navigable doesn't have a
rendering opportunity on the last event loop iteration
Now all that is gone and replaced with a single timer that drives
repainting at 60 hz and we don't have to worry about excessive repaints.
In the future, hard-coded 60 hz refresh interval could be replaced with
CADisplayLink on macOS and similar API on linux to drive repainting in
synchronization with display's refresh rate.
This avoids an unecessary lossy conversion for the current time from
double to i32. And avoids an UBSAN failure on macOS that's dependent
on the current uptime.
From https://html.spec.whatwg.org/#list-of-animation-frame-callbacks:
Each target object has a map of animation frame callbacks, which is
an ordered map that must be initially empty, and an animation frame
callback identifier, which is a number that must initially be zero.
Previously, 'now' was set to the time `requestAnimationFrame()` was
called, and the EventLoop's 'now' was ignored. This was a little odd and
meant the time was always in the past.
Instead of using Core::EventLoop and Core::Timer directly, LibWeb now
goes through a Web::Platform abstraction layer instead.
This will allow us to plug in Qt's event loop (and QTimer) over in
Ladybird, to avoid having to deal with multiple event loops.
Previously requestAnimationFrame() callbacks were registered with a
static global RequestAnimationFrameDriver shared between all windows.
This led to callbacks still running after navigating away from a page
(This could be seen with the WASM GoL demo).
This commit moves the RequestAnimationFrameDriver (now
AnimationFrameCallbackDriver) to be a member of the HTML::Window
object, then uses the 'active document' parameter of
run_animation_frame_callbacks() to run only the active callbacks.
