[cairo-bugs] [Bug 88203] Replaying recording surfaces with OVER has far worse performance than when using the SOURCE operator

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88203

--- Comment #1 from Emanuele Aina <emanuele.aina at collabora.com> ---
Note that I'm really not knowledgeable enough to understand how the different
compositing operators should work with recording surfaces, but I was surprised
that replaying a recording surface is actually replaying it on a clear surface
and then compositing it, rather than replaying it directly.

Citing the documentation:
> If you want to replay a surface so that the results in target will be 
> identical to the results that would have been obtained if the original 
> operations applied to the recording surface had instead been applied to the 
> target surface, you can use code like this: [snip]

With the extra copy this does not seem the case: if rendering directly would
give different results then the documentation is misleading, but if rendering
directly would give the same result then the intermediate surface would not be
needed.

To be honest I'm not sure what should be the meaning of using operators other
than SOURCE and OVER to replay a recording surface. If the user actually meant
to use an intermediate surface, why bother using a recording surface then?

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