Closed Bug 1505363 Opened 5 years ago Closed 5 years ago

Animated element sometimes flashes at the end of the animation


(Core :: Graphics: WebRender, defect, P4)




Tracking Status
firefox65 --- disabled
firefox66 --- fixed


(Reporter: nchevobbe, Assigned: sotaro)





(3 files)

Attached video end of animation glitch
**Steps to reproduce**
1. Go to `data:text/html,<meta charset=utf8><style>h1 {animation: 1.1s linear appears;}@keyframes appears {0% {opacity: 0;}100% {opacity: 1;}}</style><h1>Hello</h1>`

**Expected results**

The "Hello" text slowly appears. At the end of the animation, the text stays visible

**Actual results**

Sometimes, there's a flash at the end of the animation (see attached screencast, at 2-3s).
You can reload the tab a few times, I usually reproduce this in 3 tries.
This only seems to happen with webRender enabled

Priority: -- → P3
What platform do you see this on?
Flags: needinfo?(nchevobbe)
Flags: needinfo?(nchevobbe)
I tried the STR in comment 0 with latest nightly on osx, win10 and linux, but could not reproduce the problem.
It might be similar to Bug 1497852.
See Also: → 1497852
Getting a WR capture here would probably help. Might not be too hard to modify the code to just grab a capture for every frame in an OMTA and then just pick out the bad frame.
Nicolas, can you reproduce this problem on Windows?
Flags: needinfo?(nchevobbe)
Priority: P3 → P4
I could reproduce the problem by adding latency in LowPrioritySceneBuilder::process_transaction() from it. The problem seemed to be caused by async animation.
With attachment 9034650 [details] [diff] [review] , I reproduce  the parobem with STR in comment 0.

And when I disabled async animation by pref layers.offmainthreadcomposition.async-animations:false, I did not see the problem.
WebRenderBridgeParent::RemoveEpochDataPriorTo() seems to delete animation too early.

WebRenderLayerManager::DiscardCompositorAnimations() was called just before calling WrBridge()->EndTransaction() in WebRenderLayerManager::EndTransactionWithoutLayer(). Then WebRenderBridgeParent::RecvDeleteCompositorAnimations() was called just before WebRenderBridgeParent::RecvSetDisplayList() call. The RecvSetDisplayList() update WrEpoch. Then the RecvDeleteCompositorAnimations() stored old epoch in mCompositorAnimationsToDelete.
It seems better to call WebRenderLayerManager::DiscardCompositorAnimations() after calling WrBridge()->EndTransaction() in WebRenderLayerManager::EndTransactionWithoutLayer().
Blocks: 1458414
> Nicolas, can you reproduce this problem on Windows?

I tried with the STR, reloading the page ~50 times and couldn't reproduce it.
Flags: needinfo?(nchevobbe)
Blocks: 1497852
Pushed by
Call DiscardCompositorAnimations() after calling WrBridge()->EndTransaction() r=kats
OS: Mac OS X → All
Closed: 5 years ago
Resolution: --- → FIXED
Target Milestone: --- → mozilla66
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