EXA glyph corruption

[Daniel Drake]

On Thu, 2008-08-28 at 21:15 +0200, Maarten Maathuis wrote:
> On Thu, Aug 28, 2008 at 9:01 PM, Daniel Drake <dsd at laptop.org> wrote:
> > Hi,
> >
> > I'm working on OLPC's upcoming software release, including an update
> > from Fedora 7 to Fedora 9. Fedora 9 ships xserver 1.4.99.906.
> >
> > Unfortunately, we encounter a rendering bug with one of our applications
> > (etoys). Certain components that move around the screen render badly
> > (leave trails, etc) when interacting with the mouse cursor.
> > http://dev.laptop.org/ticket/7612
> >
> > An etoys developer narrowed this down to a small program to reproduce
> > the issue:
> > http://dev.laptop.org/attachment/ticket/7612/sqcursortest.c
> >
> > It moves a green square around the screen. If you let the green square
> > move onto the mouse cursor, you get graphical corruption. See
> > http://dev.laptop.org/~dsd/20080822/xshm-bug.png for a screenshot - the
> > mouse cursor didn't get included in the screenshot, but it is in the
> > white area inside the green square. The square should be solid green
> > even with the mouse cursor on top.
> >
> > I noticed that Fedora recently added an "exa master upgrade" patch to
> > their xserver test builds - backporting the most recent EXA code from
> > master. Decided to give this a try in hope that it solves the bug.
> > Here is the patch:
> > http://dev.laptop.org/~dsd/20080822/xserver-1.4.99-exa-master-upgrade.patch
> >
> > The good news is that it solves the bug, here is a new screenshot:
> > http://dev.laptop.org/~dsd/20080822/xshm-bug-fixed.png
> > The mouse cursor is on top of the green square in that screenshot with
> > no rendering glitches.
> >
> > The bad news is that text rendering is now quite badly broken:
> > http://dev.laptop.org/~dsd/20080822/text-not-ok.png
> > with the older X server build, that same screen looks like:
> > http://dev.laptop.org/~dsd/20080822/text-ok.png
> >
> 
> Getting your glyphs cut off is a "known" bug, on CURRENT master it
> appears when you provide a composite implementation (then it enables
> the glyph cache, previously it enabled it unconditionally), but
> fallback at some stage during font rendering.

OK, glad to hear it's not just us then. So I guess my next question is,
what inside of
http://dev.laptop.org/~dsd/20080822/xserver-1.4.99-exa-master-upgrade.patch would have solved our etoys/sqcursortest rendering bug, and can I separate it from the glyph bug?

> If provide a composite implementation, then i guess you don't support
> rendering onto PICT_a8 surfaces (or PICT_A8 pixmaps at all)?

We provide a composite implementation but we don't do A8 (although we
can do A8 masks).

Thanks,
Daniel