[PATCH 1/2] glamor: Fix bad rendering of glyphs after an a1 glyph upload.

[Keith Packard]

Eric Anholt <eric at anholt.net> writes:

> Fixes regressions since my "don't make an FBO for the glyph atlas"
> change.  The a1 upload was a fallback, as I expected.  However,
> fallback reads use glReadPixels() because there's no
> glGetTexSubImage2D() to match glTexSubImage2D().  We were just binding
> the 0 FBO value, so the glReadPixels() would throw a GL error instead
> of getting any data.  After the fallback was done we'd write back the
> undefined data to the atlas, blowing away the entire rest of the atlas
> because we didn't specify any bounds on our prepare.
>
> To fix the fallbacks to actually work, we'd need a prepare path that
> allocates some memory memory do a full glGetTexImage() into, then
> memcpy out of that.  Instead, just dodge the general fallback by
> implementing the specific upload we need to do here, which should also
> be *much* faster at uploading a1 glyphs since it's not
> readpixels/texsubimaging back and forth.
>
> Signed-off-by: Eric Anholt <eric at anholt.net>

Nice fix. However, it's doing a CopyPlane operation by hand, making it
LSB-specific. A shorter version just creates a temporary 8bpp CPU pixmap,
uses CopyPlane to get the glyph into that and uploads from there.

This works for me on ephyr

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-- 
-keith
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