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cogl: Prefer swizzling to convert BGRA buffers

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If the GL implementation/hw supports the GL_*_texture_swizzle extension,
pretend that BGRA textures shall contain RGBA data, and let the flipping
happen when the texture will be used in the rendering pipeline.

This avoids rather expensive format conversions when forcing BGRA buffers
into RGBA textures, which happens rather often with WL_SHM_FORMAT_ARGB8888
buffers (like gtk+ uses) in little-endian machines.

In intel/mesa/wayland, the performance improvement is rather noticeable,
CPU% as seen by top decreases from 45-50% to 25-30% when running
gtk+/tests/scrolling-performance with a cairo renderer.

https://bugzilla.gnome.org/show_bug.cgi?id=779234
This commit is contained in:
Carlos Garnacho 2017-02-25 23:21:06 +01:00
parent 95c924460a
commit 1705a26fc7
2 changed files with 21 additions and 1 deletions
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10
cogl/cogl/driver/gl/gl/cogl-driver-gl.c
View File

@ -174,7 +174,15 @@ _cogl_driver_pixel_format_to_gl (CoglContext *context,
case COGL_PIXEL_FORMAT_BGRA_8888:
case COGL_PIXEL_FORMAT_BGRA_8888_PRE:
glintformat = GL_RGBA;
glformat = GL_BGRA;
/* If the driver has texture_swizzle, pretend internal
* and buffer format are the same here, the pixels
* will be flipped through this extension.
*/
if (_cogl_has_private_feature
(context, COGL_PRIVATE_FEATURE_TEXTURE_SWIZZLE))
glformat = GL_RGBA;
else
glformat = GL_BGRA;
gltype = GL_UNSIGNED_BYTE;
break;

12
cogl/cogl/driver/gl/gl/cogl-texture-driver-gl.c
View File

@ -114,6 +114,18 @@ _cogl_texture_driver_gen (CoglContext *ctx,
red_swizzle) );
}
/* If swizzle extension is available, prefer it to flip bgra buffers to rgba */
if ((internal_format == COGL_PIXEL_FORMAT_BGRA_8888 ||
internal_format == COGL_PIXEL_FORMAT_BGRA_8888_PRE) &&
_cogl_has_private_feature (ctx, COGL_PRIVATE_FEATURE_TEXTURE_SWIZZLE))
{
static const GLint bgra_swizzle[] = { GL_BLUE, GL_GREEN, GL_RED, GL_ALPHA };
GE( ctx, glTexParameteriv (gl_target,
GL_TEXTURE_SWIZZLE_RGBA,
bgra_swizzle) );
}
return tex;
}