[cairo-bugs] [Bug 15479] Unpredictable performance of cairo-xlib with non-integer translations of a source surface pattern

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=15479


Carl Worth <cworth at cworth.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Cairo performance issues    |Unpredictable performance of
                   |when compositing surfaces   |cairo-xlib with non-integer
                   |together on various graphics|translations of a source
                   |cards                       |surface pattern




--- Comment #1 from Carl Worth <cworth at cworth.org>  2008-04-14 10:52:31 PST ---
Hi Karl,

I don't see what you're hoping to get out of the cairo bug report here.

I looked through the (long) GNOME bugzilla thread on this issue before
I could get any sense of what the issue is at all.

And what I *finally* got was:

    cairo_set_set_source_surface (cr, non_integer_X, non_integer_Y);
    cairo_paint (cr);

Is slow for some particular combinations of X servers/drivers.

I don't doubt that for a second, but I don't see what change could
happen in cairo to fix the issue.

Obviously, the ideal thing long-term is to fix the X drivers in all
cases so that compositing a surface with a transformation more
sophisticated than integer-translation-only is fast.

In the meantime, you have various workarounds possible in your
application, all of which were mentioned in the bugzilla entry:

   * Use integer translations

   * Force software-rendering by using cairo_image_surface and then
     copying only the final result.

Is there anything that you can see that we could change in cairo to
help here? I'm not seeing anything obvious.

Thanks,

-Carl


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