[Webkit-unassigned] [Bug 66969] Chromium: Add a layer for rubber-band overhang painting to the hardware path.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=66969





--- Comment #47 from asvitkine at chromium.org  2011-09-13 09:16:59 PST ---
Created an attachment (id=107182)
 --> (https://bugs.webkit.org/attachment.cgi?id=107182&action=review)
Trace of rubber-banding with split horizontal / vertical overhang layers.

Here's a trace of rubber-banding on the same page in a Release build with a patch that has separate layers for the vertical and horizontal overhang layers.

James or Adrienne, could you take a glance at the trace and see what the performance of that is like?

I understand the desire to avoid any redrawing while scrolling, but I fear to do that for the overhang stuff would result in a lot of code that will be different between the compositor / non-compositor path that would be a maintenance burden if we ever decide to change how the overhang looks. (For instance, the fact that we currently draw a drop-shadow from the top of the window would affect the design of the layers used under the compositor if we wish to avoid re-drawing things.)

So I'm hoping just splitting horizontal / vertical overhang layers would provide good enough performance so that we wouldn't need to write/maintain a lot of compositor specific code to draw the overhang.

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