Flash at end of opacity/transform transition sometimes

[Simon Fraser (smfr)]

Created attachment 41393 [details]
Testcase

In some content, there's a noticeable flash sometimes when a transform or opacity transition ends sometimes. I'm having a hard time making a reduced testcase, but the attached shows it sometimes.

[Simon Fraser (smfr)]

The flash happens because we remove the transition on the GraphicsLayer before we set the final opacity/transform style, so there's a window where it renders with the original opacity/transform.

[Simon Fraser (smfr)]

Created attachment 41394 [details]
Proto patch

[Chris Marrin]

Comment on attachment 41394 [details]
Proto patch

> diff --git a/WebCore/rendering/RenderLayerBacking.cpp b/WebCore/rendering/RenderLayerBacking.cpp
> index 4c82843..d7248d4 100644
> --- a/WebCore/rendering/RenderLayerBacking.cpp
> +++ b/WebCore/rendering/RenderLayerBacking.cpp
> @@ -89,8 +89,8 @@ void RenderLayerBacking::createGraphicsLayer()
>          m_graphicsLayer->setName("Anonymous Node");
>  #endif  // NDEBUG
>  
> -    updateLayerOpacity();
> -    updateLayerTransform();
> +    updateLayerOpacity(renderer()->style());
> +    updateLayerTransform(renderer()->style());
>  }
>  
>  void RenderLayerBacking::destroyGraphicsLayer()
> @@ -104,15 +104,13 @@ void RenderLayerBacking::destroyGraphicsLayer()
>      m_maskLayer = 0;
>  }
>  
> -void RenderLayerBacking::updateLayerOpacity()
> +void RenderLayerBacking::updateLayerOpacity(const RenderStyle* style)
>  {
> -    m_graphicsLayer->setOpacity(compositingOpacity(renderer()->opacity()));
> +    m_graphicsLayer->setOpacity(compositingOpacity(style->opacity()));
>  }

I don't see how these two are different? How is passing in renderer()->style() and setting the opacity to renderer()->style() is different?

What is the fix you're doing here?

[Simon Fraser (smfr)]

I just pass in style there so I can use toStyle lower down. Look at the rest of the patch.

[Simon Fraser (smfr)]

Created attachment 41462 [details]
Patch

[Simon Fraser (smfr)]

http://trac.webkit.org/changeset/49823