[Webkit-unassigned] [Bug 100718] Invalidate non-composited content host when page scale factor changes

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=100718





--- Comment #10 from James Robinson <jamesr at chromium.org>  2012-11-18 20:47:55 PST ---
Patching this at the WebKit layer is wrong, we should fix this in WebCore.  It's not anything specific to chromium or any particular embedding of WebCore - when the page scale changes, all content on the page needs to be invalidated.  This isn't a theoretical concern - we expose a window.internals function to set the page scale from layout tests (implemented in WebCore/testing/InternalSettings.cpp) that hooks directly in to WebCore::Page.  This needs to have the same behavior as the actual product or layout tests intended to cover page scale will not actually cover all the logic we ship.

Invalidating from WebCore should be quite easy.  NCCH hosts the content that is not considered composited by WebCore (hence the name), so invalidations on the hostWindow are routed to NCCH.  Calling repaint() on root Document's RenderObject should result in a correctly-sized repaint coming out via WebCore::Chrome::invalidateContentsAndRootView().  That's how style changes (such as background color) are repainting, so if that path is not working then I would expect us to see significantly more breakage.

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