Subject: Re: bug#8426: Glyph and cursor problem with emacs

From: David De La Harpe Golden <[email-masked]>
Date: Tue, 05 Apr 2011 20:41:28 +0100

On 05/04/11 11:06, Matthew Carey wrote:

> My other box with the same OS and architecture does not exhibit the problem.

The exact same architecture?  Particularly, same gfx card and same 
version of said driver for said card, with same xorg.conf config 
options?  It's just the perennially annoying closed x11 drivers for 
ati/amd and nvidia hardware often have bizarre 2D drawing glitches, and 
they can be dependent on the precise version, configuration options 
(like which AccelMethod is in use) and whether compositing is enabled 
[1][2] (in contrast, the open drivers are typically slow for 3D but 
really good for 2D)

> 2 No other applications seem to be affected this way on the box.

That _could_ be just luck / the subset of apps used by the driver 
authors for testing coinciding with yours.  Emacs handles its own 
drawing to the main window with direct xlib calls, and may do things 
legally but still differently to some other apps.

> If I use the same emacs installation forwarding X output to another machine it
> works fine.

Well, as Eli points out, that does strongly suggest it's an X server 
level problem, not an emacs problem.  If it were, say, some call to 
XFillRectangle being misplaced in the emacs binary you'd expect it to 
occur on all X servers you tried.

The chances of DejaVu Sans Mono metrics being messed up seem slim, and 
also xft/xrender based font rendering, unlike the old core x11 
server-side font rendering, uses client-side tesselation to trapezoids 
and you say the same emacs works on another x11 server, so that's not 
the problem. While it's been actively developed (descended from 
Bitstream Vera) and therefore there are different versions of it 
floating about, it's an extremely widely used font, and the one I use 
with emacs with no such problems.

[1] http://ati.cchtml.com/
[2] 
https://wiki.archlinux.org/index.php/ATI_Catalyst#Catalyst_10.6.2F10.7.2F10.8.2F10.9_:_black.2Fgrey.2Fwhite_boxes.2Fartifacts_in_firefox.2Fthunderbird