Fun with buggy video card drivers

This is a potential PROBLEMS file entry, although we probably don't have to put it there unless a second person encounters the same problem. I have a colleague who was having some problems with cursor weirdnesses in XEmacs. As he moved the mouse across toolbar/menubar/scrollbar boundaries, it would turn into a red X for a few pixels. Usually it would change to something reasonable after moving across, but sometimes it would get stuck in red X mode, especially if he moved the mouse very quickly. Also, if he had the mouse over a buffer so that the pointer looked like this: \/ | | /\ (I'm sure that has a name, but I don't know what it is), it would stay that way if he rapidly moved the mouse horizontally off of the XEmacs frame. This was very annoying. My computer and his have almost identical hardware, and I wasn't having any such problem, so I agreed to help him figure it out. We didn't have any luck, although I verified with GDB that XEmacs itself was not responsible for the red X change. We both run RedHat 9, although I'm using vanilla RedHat and he has Ximian GNOME installed. I blamed Ximian and shrugged my shoulders in defeat. He tried snooping on X traffic when the problem occurred. In some mysterious way that he has not fully explained to me, this helped him track down the problem. Both of our computers have an nVidia GeForce MX 4 video card. When I first bought the computer, I had trouble with the XFree86 driver for that card (the X server would crash if I tried to change resolutions or color depths), so I switched to nVidia's own Linux driver. My colleague was still using the XFree86 driver. When he installed the nVidia driver, the problem vanished. The interesting part is that he didn't notice problems with any other application! We should give ourselves a collective pat on the back for so efficiently turning up video card driver problems. Suggested PROBLEMS file entry (under "Problems with running XEmacs", then "Linux": *** XEmacs fails to change the mouse cursor appropriately when the mouse is moved rapidly, turns it into a red "X", etc. Some users with nVidia GeForce 4 cards have reported this problem. It appears to be a bug in the XFree86 nv driver. Installing the driver available from www.nvidia.com reportedly fixes the problem. -- Jerry James http://www.ittc.ku.edu/~james/