[Webkit-unassigned] [Bug 41682] Certain page elements cause XGetImage and software fallback rendering

Mon Jul 19 06:08:26 PDT 2010

https://bugs.webkit.org/show_bug.cgi?id=41682

--- Comment #9 from Jonathan Morton <jonathan.morton at movial.com>  2010-07-19 06:08:26 PST ---
> Have a look at the patch and see if this works for you. If performance is still problem due to the use clipping, I can unroll the clipping and set up the source and target bounding boxes ourselves (but I'd save that part until it's absolutely necessary, readability issue).

I think we managed to eliminate the XGetImage calls with some tweaks to the Qt X11 backend.  However, we are still seeing (and this is clearer now) multiple XPutImage calls for the entire atlas map.

We think this probably does have something to do with the source-clipping.  If an image containing only the clipped area was uploaded, this would already be a big win on our hardware, avoiding a lot of work in QX11Pixmap::fromImage() and traffic on the slow GPU bus, and VRAM pollution as well.

We've looked into the possibility of recognising the clipped area at the driver level, but this is proving difficult to do reliably due to EXA's design.

Do you think that such a thing would be easy to implement in Qt or Webkit?

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