xorg 7.0 Screen corruption with mga module when composite is off
Submitted by Huw Blackwell
Assigned to Xorg Project Team
Bug passed upstream from Gentoo Bugzilla (https://bugs.gentoo.org Bug #140757).
Xorg 7.0 server causes screen corruption on a Matrox G200 8Mb card (HP Brio BA600, Pentium III 750, 512Mb) when Xserver is running. X server starts successfully from the command line, but wallpaper and text is so corrupted that it is unreadable (I hope to submit some photos of this). Shutting down the X server and returning to the command line (vesa fbuffer) results in continuing corruption of the text on screen and the command line. This occurs using xfce4 (latest stable version). This corruption can be rectified by starting X and using twm. This appears to resolve most of the corruption issues, though any programs run in it can suffer the same issue. Howevere, 9/10 times when the x server is shut down under twm the command line returns to it's previous uncorrupted state. When booted using recent kernels (2.6.16) the command line cursor does not appear at the command line, but further up the screen. When typing this corrupts the line it is on whilst the text appears at the command line. This can be resolved by using ctrl-alt to switch to a nother tyermianl causing the cursor to return to the command line. Switching back to the orignal terminal results in correct cursor position, and no further text corruption. This only effects the 2.6.16 series of kernels. Changing kernels (2.6.15-r1) resolves this but has no effect on the earlier problem.
This is always reproducible. It is solved by enabling the Xfce4 compositor, though this affects flash running in firefox, which requires a line of code to fix (see gentoo-wiki, article Xorg and Transparency).