[Webkit-unassigned] [Bug 92368] [META][GTK][WK2] Enable UI_SIDE_COMPOSITING for WebKit2 GTK

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=92368





--- Comment #7 from Huang Dongsung <luxtella at company100.net>  2012-07-27 03:18:32 PST ---
(In reply to comment #6)
> (In reply to comment #4)
> > The thing that's missing from this bug is the answer to the question "Why?" From my discussions with the Qt folks, I concluded that UI-side compositing was the solution to actual problems that they were facing. What is the goal for implementing this for GTK+ especially since we do not yet have full support for touch events? Wouldn't it be better to wait until we know this will solve actual problems? I think it's important to consider these questions, since UI-side compositing *greatly* increases the complexity of the code. Thus in my opinion, it's not appropriate to implement it for the sake of an educational exercise or simply because other ports do.
> 
> There are two reasons why we should implement UI_SIDE_COMPOSITING.
> 1. We are facing on the problem "Xlib: unexpected async reply" on specific embedded system. Because WebProcess and UIProcess have "thread unsafe Xlib connection" at the same time, we need to maintain single Xlib connection.
> 
> 2. In the embedded system, it is important to reduce workload of the main thread/process.
> 
> 
> Anyway, I will send an email to start discussion on webkit-gtk mailing list.

I agree on Gwang Yoon's reasons, especially #2.

Only AC from GTK WebKit2 runs on the main thread.
Mac uses CA that has its own thread.
Chrome guys implemented Chrome Compositor that runs on the impl thread.
Qt and EFL uses UI_SIDE_COMPOSITING.

I think there is an agreement on running AC off the main thread, in order to increase scrolling performance.
So, GTK should also implement AC off of the main thread, UI_SIDE_COMPOSITING already exists which can be reused.
IMHO, this change does not increase the complexity because it will just reuse the existing implementation.

GTK, Qt and EFL guys can focus on improving UI_SIDE_COMPOSITING.

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