Add new compositor message to get scroll_offset;
Add new layout query for computed value of overflow-x/y;
Implement layer_id method for ThreadSafeLayoutNode;
Add new layout query for layer_id;
Implement script interface for getting scrollTop and scrollLeft, as well as relavant helper functions.
This changes headless operation to strictly be a runtime option, rather
than a compile-time one. Note that the old headless version still relied
on a display server to support WebGL, while it now requires one all the
time.
Fixes#8573
has loaded.
This avoids a flash of unstyled content, which looks especially bad in
browser.html since unstyled content is white and browser.html has a
transparent background.
Closes#9996.
Instead, schedule a delayed composite after each frame of an animation.
The previous code would cause jank, because the following sequence
frequently occurred:
1. The page uses `requestAnimationFrame()` to request a frame.
2. The compositor receives the message, schedules a composite,
dispatches the rAF message to the script thread, composites, and goes to
sleep waiting for vblank (frame 1).
3. The script makes a change and sends it through the pipeline.
Eventually it gets painted and is sent to the compositor, but the
compositor is sleeping.
4. The compositor wakes up, sees the new painted content, page flips,
and goes to sleep (frame 2). Repeat from step 1.
The problem is that we have two composition frames, not just one. This
halves Web apps' framerate!
This commit fixes the problem by scheduling the composite in step 2 to
12 ms in the future. We already have this delayed-composition
functionality in the form of the scrolling timer, which I repurposed and
renamed to the "delayed composition timer" for this task. This change
gives the page 12 ms to prepare the frame, which seems to usually be
enough, especially with WebRender.
Note that simply removing the scheduled composite after rAF is not the
correct solution. If this is done, then pages that call rAF and don't
modify the page won't receive future rAFs, since the compositor will be
sleeping and won't be notified of vblank.
Fixes a bunch of jank in browser.html. The remaining jank seems to be a
problem with browser.html itself.
WebRender is an experimental GPU accelerated rendering backend for Servo.
The WebRender backend can be specified by running Servo with the -w option (otherwise the default rendering backend will be used).
WebRender has many bugs, and missing features - but it is usable to browse most websites - please report any WebRender specific rendering bugs you encounter!
