CHAPTER 6 Known Limitations

1. Webexplorer (at least webex103) is NOT palette aware. It never seems to remap its colors when OpenGL puts all its colors into the colormap. Hopefully some day Webexplorer will respond to changes in the colormap. If you are having trouble with Webex or have color corruption with other apps after exiting an OpenGL application, uncheck Workplace shell palette aware in the system object located in the System Setup folder, and click on the desktop. Please also read item 4 below before running with palette aware unchecked all the time. This only occurs in 256 color mode.
2. OpenGL application simultaneously, one of your apps might have the improper color in hardware color palette entry 0. This has only been observed in matrox millineum using 1.00 drivers. It is a display driver bug, and only occurs in 256 color mode.
3. OpenGL uses a lot of colors. If Workplace shell palette aware is not checked, images rendered using OpenGL might not appear cor- rectly. Workplace shell palette checkbox is located in the system object located in the System Setup folder. Even with WPS palette aware, there are 4 entries that we cannot change in the color palette on some adapters. This is an OS/2 problem, which should be fixed in the next release of OS/2. This only occurs when running in 256 color mode.
4. If you are running many OpenGL apps at once, you should have a statement in your config.sys set of PRIORITY=ABSOLUTE , this will mean that OS/2 will give equal priority to all threads.
5. OpenGL has problems with some display device drivers. If 24 bit mode, if your OpenGL rendering looks `quished' , try: set OGL_BIT_COUNT=32. If your rendering looks scattered or smeared across the screen, you can try playing with OGL_SCANLINE_SIZE. For example, if you are 1024x768x16bit per pixel, you can try: set OGL_SCANLINE_SIZE=2048. Since your screen width is 1024, and your depth is 16 bits (=2 bytes), 2048 would be a reasonable guess for the scanlinesize that your card is running at. Use these with care, especially if you plan to change res- olution and depth a lot. Only set them if you are having problems. If they are set we use them, otherwise we use what the display driver tells us to. You can learn more about what your device driver thinks by running &colon. dcr >foo 2>&.1, and then examining the output in foo.
6. OpenGL on Matrox Millenium in 24 bit mode. You must set OGL_BIT_COUNT=32, and also check the matrox docs for running DIVE demos in 24 bit.
7. There is a bug in glDrawPixels when using single buffered visuals. Symptom: drawing image outside window. Workaround: Use double buffered visuals. Will be fixed in the next release.
8. There is a problem using glAccum in single buffered visuals. Symp- tom: excetion when window is minimized, or contents of accumula- tion buffer include overlaying window bits. Workaround: Do not minimize a window that is using accumulation buffers and single buffered visuals. Do not occlude the window when rendering into accumulation buffers on single buffered visuals. Or you can use double buffered visuals. Will be fixed in the next release.
9. If you specify PGL_SINGLEBUFFER in your list of attribs passed into pglChooseConfig(), you will not find any visuals. Workaround: If you want a single buffered visual, you will get it if you do not request PGL_DOUBLEBUFFER. This will be fixed in the next release.