Bug 29250

Summary:	use XCopyArea for operator SOURCE with compatible COLOR_ALPHA surfaces
Product:	cairo	Reporter:	Karl Tomlinson <bugs.freedesktop>
Component:	xlib backend	Assignee:	Karl Tomlinson <bugs.freedesktop>
Status:	RESOLVED FIXED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	normal
Priority:	medium
Version:	1.9.13
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	use XCopyArea for operator SOURCE with compatible COLOR_ALPHA surfaces

Description Karl Tomlinson 2010-07-25 14:50:46 UTC

My motivation here is that XCopyArea does what I want for simple self
copies, but XRenderComposite does not (at least not in all situations).

Also, even though I don't know why render should be slower than core, we
seem to get reports that it sometimes is, so there may be a performance
benefit on systems with some (buggy?) drivers.

XCopyArea is used for CONTENT_COLOR surfaces so it seems that it should also
be used for COLOR_ALPHA surfaces.

I'll attach a patch shortly.

Comment 1 Karl Tomlinson 2010-07-25 16:21:40 UTC

Created attachment 37387 [details] [review]
use XCopyArea for operator SOURCE with compatible COLOR_ALPHA surfaces

_operator_needs_alpha_composite was changed to take two _has_alpha arguments
instead of one (and started returning false for SOURCE) in
http://cgit.freedesktop.org/cairo/commit/?id=c25992479aca481d326f72665ebdcf0904273eac

The call added to _cairo_xlib_surface_composite in that changeset has since
been removed so _operator_needs_alpha_composite is now only used when the
source and destination have the same format.

I would have used a switch statement but -Wswitch-enum doesn't like
"default:".

I'm getting failures with svg12 outputting clear (blank) surfaces, but I
haven't marked them xfail because I'm getting a large number unexpected fails
for svg12 in other tests also.

I haven't run the test against win32 or quartz backends, but I expect it to
pass because, with Firefox, we only got reports of self-copy bugs on X11.

Comment 2 Chris Wilson 2010-07-26 05:47:56 UTC

With my driver author's hat on, this patch should not be necessary. Humph.

Comment 3 Chris Wilson 2012-04-10 16:00:33 UTC

Ok, cairo-1.12 should use the simpler XCopyArea for compatible surfaces and SOURCE (or reduced OVER) operators.


However, I see you have a test case as well, so I may as well add that to the repository.

Comment 4 Chris Wilson 2012-05-01 10:52:09 UTC

Principal bug should be fixed, excluding !owns_pixmap. :(

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