regular CEF requires the user to either run the cef main loop or
poll on a function to drain events. now the engine will trigger a callback
in some application thread which will notify it that there is work
to be done by the browser
this changes the way that applications will use servo. whereas previously
it was only necessary to call initialize() -> makecurrent, it's now necessary
to explicitly call the composite() method in order to trigger the gl rendering.
any other composite attempts (by servo) will trigger the on_paint() method,
informing the app that a frame is ready. it's then up to the app to schedule
the composite() such that the frame is rendered in a timely manner
platforms other than macos will not need/use a get_backing_rect() method since
there is no virtual pixel scaling, and this method will need to be usable
even before browsers are finished setting up, so ensure we can at least pass
initial window size back
also check method pointer availability before calling into a null function
I've done a bit of job to get this done. Right now readback is still used, but we have a `LayerId` -> `CanvasRenderer` map on the paint task, that we can use to get rid of that.
I'd want review, to see if this is a good approach (I know it's not the initial `CanvasId` -> renderer approach, but it's pretty similar, since a canvas involves a `PaintLayer`).
I had to do a bit of refactoring to avoid cyclic dependencies between canvas and gfx. I'd want you to review them too.
It's mergeable and doesn't break any tests :P
Some of my main concerns:
* Does the canvas render really need to be behind an `Arc<Mutex<T>>`?
* I can't clone a `NativeSurface` right now (that's why the `SendNativeSurface()` msg is unimplemented in the WebGL task). It should be easy to add that to rust-layers, supposing the caller is responsible to mark it as non-leaking, any reason to not do it?
cc @jdm @pcwalton
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The basic idea is it's safe to output an image for reftest by testing:
- That the compositor doesn't have any animations active.
- That the compositor is not waiting on any outstanding paint messages to arrive.
- That the script tasks are "idle" and therefore won't cause reflow.
- This currently means page loaded, onload fired, reftest-wait not active, first reflow triggered.
- It could easily be expanded to handle pending timers etc.
- That the "epoch" that the layout tasks have last laid out after script went idle, is reflected by the compositor in all visible layers for that pipeline.
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<!-- Reviewable:end -->
The basic idea is it's safe to output an image for reftest by testing:
- That the compositor doesn't have any animations active.
- That the compositor is not waiting on any outstanding paint messages to arrive.
- That the script tasks are "idle" and therefore won't cause reflow.
- This currently means page loaded, onload fired, reftest-wait not active, first reflow triggered.
- It could easily be expanded to handle pending timers etc.
- That the "epoch" that the layout tasks have last laid out after script went idle, is reflected by the compositor in all visible layers for that pipeline.
