[Webkit-unassigned] [Bug 109560] Implement coordinated scrollbar for subframes and sublayers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=109560





--- Comment #4 from Tien-Ren Chen <trchen at chromium.org>  2013-02-12 12:48:57 PST ---
(In reply to comment #3)
> (From update of attachment 187822 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=187822&action=review
> 
> r- for abuse of setContentsToMedia.
> 
> > Source/WebCore/page/scrolling/chromium/ScrollingCoordinatorChromium.cpp:125
> > +    scrollbarGraphicsLayer->setContentsToMedia(scrollbarLayer->layer());
> 
> This seems like an abuse of setContentsToMedia.

I consider coordinated scrollbar to be a built-in plug-in provided by chromium compositor. Anyway we need to find some way to attach customized platform layer to a GraphicsLayer. What are the other choices that is less abusive?

> > Source/WebCore/rendering/RenderLayerBacking.cpp:1015
> >      if (needsHorizontalScrollbarLayer) {
> >          if (!m_layerForHorizontalScrollbar) {
> >              m_layerForHorizontalScrollbar = createGraphicsLayer("horizontal scrollbar");
> >              layersChanged = true;
> > +            if (scrollingCoordinator)
> > +                scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(m_owningLayer, HorizontalScrollbar);
> >          }
> >      } else if (m_layerForHorizontalScrollbar) {
> >          m_layerForHorizontalScrollbar.clear();
> >          layersChanged = true;
> > +        if (scrollingCoordinator)
> > +            scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(m_owningLayer, HorizontalScrollbar);
> 
> I'd prefer that you change the code so that you only need to call scrollableAreaScrollbarLayerDidChange in one or two places in this function, not 4 times.

Agree that looks ugly. I'll change that in next patch.

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