[Webkit-unassigned] [Bug 51262] WebPageProxy should delete its backing store after not painting for a while

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=51262





--- Comment #28 from Adam Roben (aroben) <aroben at apple.com>  2011-02-11 14:47:02 PST ---
(In reply to comment #26)
> > This could be problematic. If there's already an Update message in the queue from before the InvalidateEverything message reached DrawingAreaImpl, the Update won't contain an image of the entire view. Maybe we need to use a different message (i.e., DidDisplayNow). If we do that, we *will* need to generalize the m_lastDidSetSizeSequenceNumber logic.
> 
> Another option -- a little simpler but possibly less clear -- is for the message sender to keep an internal flag that says "I just sent an InvalidateEverything message, so from now on, ignore all update messages until I see an update message that covers the whole drawing region, at which point I will unset this flag."

That would work except when we're actually asked to paint by the native view. At that point we need to wait for an Update message and dispatch it immediately. But we don't currently have code that allows us to wait for a specific instance of a given message, only code that allows us to wait for the first instance of a given message.

We do however need logic like what you described, for the reasons stated in comments 22 and 23. But instead of a separate flag, I think we can just use "m_backingStore is null".

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