Bug 135018 – Sometimes purgeable (or empty!) tiles are shown on screen when resuming the app

• Component: WebKit2
• Status: RESOLVED FIXED

[Tim Horton]

Empty tiles show up as black.

To combat this, we'll make sure we immediately dispatch view state changes *from inside the resume notification* so that the UI process is blocked *before* removing the snapshot.

We'll also temporarily detach the RemoteLayerTreeHost root layer (it'll get reattached on the next commit) so that even if our waitForDidUpdateViewState times out (500 ms), we'll show white instead of black.

We could also make said timeout longer in the resume case, but that will be a different patch.

<rdar://problem/17615038>

[Tim Horton]

Created attachment 235082 [details]
patch

[Tim Horton]

http://trac.webkit.org/changeset/171191

[Darin Adler]

Comment on attachment 235082 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=235082&action=review

> Source/WebKit2/UIProcess/DrawingAreaProxy.h:91
> +    virtual void hideContentUntilNextUpdate() { ASSERT_NOT_REACHED(); }

Doesn’t seem right.

If WKContentView knows that its drawing area is a RemoteLayerTreeDrawingAreaProxy, then it could be written to do a safe downcast and this function could be in that class instead of here in this base class.

If WKContentView doesn’t know that its drawing area is a RemoteLayerTreeDrawingAreaProxy, then we can’t ASSERT_NOT_REACHED.