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[cogl_read_pixels] don't force a 4 byte pack alignment

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Technically this change shouldn't make a difference since we are
calling glReadPixels with GL_RGBA GL_UNSIGNED_BYTE which is a 4
byte format and it should always result in the same value according
to how OpenGL calculates the location of sequential rows.

i.e. k  = a/s * ceil(snl/a) where:
 a = alignment
 s = component size (1)
 n = number of components per pixel (4)
 l = number of pixels in a row
gives:
k = 4/1 * ceil(4l/4) and k = 1/1 * ceil(4l/1) which are equivalent

I'm changing it because I've seen i915 driver code that bails out of
hardware accelerated paths if the alignment isn't 1, and because
conceptually we have no alignment constraints here so even if the current
value has no effect, when we start reading back other formats it may upset
things.
This commit is contained in:
Robert Bragg 2009-11-03 12:54:45 +00:00
parent f59180d073
commit 1acf5cc36f
1 changed files with 5 additions and 5 deletions
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10
cogl/cogl.c
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@ -826,14 +826,14 @@ cogl_read_pixels (int x,
/* Setup the pixel store parameters that may have been changed by
Cogl */
glPixelStorei (GL_PACK_ALIGNMENT, 4);
GE (glPixelStorei (GL_PACK_ALIGNMENT, 1));
#ifdef HAVE_COGL_GL
glPixelStorei (GL_PACK_ROW_LENGTH, 0);
glPixelStorei (GL_PACK_SKIP_PIXELS, 0);
glPixelStorei (GL_PACK_SKIP_ROWS, 0);
GE (glPixelStorei (GL_PACK_ROW_LENGTH, 0));
GE (glPixelStorei (GL_PACK_SKIP_PIXELS, 0));
GE (glPixelStorei (GL_PACK_SKIP_ROWS, 0));
#endif /* HAVE_COGL_GL */
glReadPixels (x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
GE (glReadPixels (x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels));
/* NB: All offscreen rendering is done upside down so there is no need
* to flip in this case... */