Bug 201487 – Generate event region for both the main graphics layer and the scrolled contents layer

• Component: Scrolling
• Status: RESOLVED FIXED

[Antti Koivisto]

We currently generate region for one of them only. With borders both need it.

[Antti Koivisto]

Created attachment 378041 [details]
patch

[Simon Fraser (smfr)]

Comment on attachment 378041 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=378041&action=review

Are there behavioral changes from using RenderLayerBacking::paintIntoLayer() now that can be tested?

> Source/WebCore/rendering/RenderLayerBacking.cpp:1601
> +        auto clipRect = enclosingIntRect(compositedBounds());

Isn't this wrong for the scrolled contents? You need to expand the clip there.

An issue with generating the event region for the entire scrolled contents is that you're potentially traversing a massive render tree, most of which is not visible. Ideally we'd generate event regions for areas with live tiles only.

> Source/WebCore/rendering/RenderLayerBacking.cpp:1604
> +        auto layerOffset = toIntSize(graphicsLayer.scrollOffset()) - roundedIntSize(graphicsLayer.offsetFromRenderer());

I think it would be a bit nicer to pass in the data to apply the scrolling offset. I don't really like GraphicsLayers knowing about scrolling.

[Antti Koivisto]

(In reply to Simon Fraser (smfr) from comment #2)
> Comment on attachment 378041 [details]
> patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=378041&action=review
> 
> Are there behavioral changes from using RenderLayerBacking::paintIntoLayer()
> now that can be tested?
> 
> > Source/WebCore/rendering/RenderLayerBacking.cpp:1601
> > +        auto clipRect = enclosingIntRect(compositedBounds());
> 
> Isn't this wrong for the scrolled contents? You need to expand the clip
> there.

Fixed this to provide the layer size as the dirty rect (it worked before in common cases because the dirty rect is mostly ignored). 

> An issue with generating the event region for the entire scrolled contents
> is that you're potentially traversing a massive render tree, most of which
> is not visible. Ideally we'd generate event regions for areas with live
> tiles only.

On the other hand we won't need to update the event region during scrolling if we generate it all at once (separate invalidation bit will enable that).

[Antti Koivisto]

Created attachment 378091 [details]
patch

[Antti Koivisto]

Created attachment 378093 [details]
patch

[Antti Koivisto]

Created attachment 378094 [details]
patch

[WebKit Commit Bot]

Comment on attachment 378094 [details]
patch

Clearing flags on attachment: 378094

Committed r249536: <https://trac.webkit.org/changeset/249536>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/55074928>