Bug 76438

Summary:	Cairo does not expose all Pixman surface formats
Product:	cairo	Reporter:	Tal <tal.liron>
Component:	image backend	Assignee:	Chris Wilson <chris>
Status:	RESOLVED MOVED	QA Contact:	cairo-bugs mailing list <cairo-bugs>
Severity:	enhancement
Priority:	medium
Version:	1.12.16
Hardware:	All
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Tal 2014-03-21 10:25:18 UTC

For a reason unknown to me, cairo_format_t is much more limited than the many options Pixman supports.

The _cairo_image_surface_create_with_pixman_format function does let the user choose a format, but it is not normally exposed.

I can think of many use cases. In particular, my issue was interaction with OpenGL ES 2.0: I am using Cairo to write to byte arrays which I later turn into GL textures. However, OpenGL ES 2.0 only support GL_RGBA, whereas Cairo's CAIRO_FORMAT_ARGB32 is equivalent to PIXMAN_a8r8g8b8. What I really need is PIXMAN_a8b8g8r8.

Can this API be made public?

Comment 1 Tal 2014-03-21 10:50:45 UTC

My simple patch, for those needing this feature:

Edit cairo-image-surface.c, and add the following:

cairo_surface_t *cairo_image_surface_create_with_pixman_format(unsigned char *data, pixman_format_code_t pixman_format, int width, int height, int stride) {
	return _cairo_image_surface_create_with_pixman_format(data, pixman_format, width, height, stride);
}

An example of calling the newly-exposed API:

#include "cairo/cairo.h"
#include "pixman.h"

cairo_surface_t *cairo_image_surface_create_with_pixman_format(unsigned char *data, pixman_format_code_t pixman_format, int width, int height, int stride);

cairo_surface_t *surface = cairo_image_surface_create_with_pixman_format(NULL, PIXMAN_a8b8g8r8, width, height, -1);

Comment 2 Uli Schlachter 2014-03-21 11:04:53 UTC

Patch from 2012 available at (but also look at the following discussion!):

http://lists.cairographics.org/archives/cairo/2012-March/022852.html

Comment 3 Tal 2014-03-21 11:10:56 UTC

I'm confused as to why exposing the internal APIs is a problem. If it's a matter of hiding Pixman from Cairo users, then these "advanced" features could potentially be enabled by including an extra header file, "cairo/cairopixman.h" or something of the sort.

Is there any roadmap for solving this? In the meantime, I have to patch Cairo.

Comment 4 GitLab Migration User 2018-08-25 13:31:09 UTC

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