aob@beta.gov (Alexander O. Brown) (06/26/91)
How common are systems that only support TrueColor or StaticColor? Also, DirectColor is supposed to support PseudoColor. How would I change the visual from Direct to Pseudo? Or is there always a Pseudo visual avaiable if the default is Direct? Or do I simply just "simulate" Pseudo with code? Thanks, Alex Brown aob@lanl.gov
rthomson@mesa.dsd.es.com (Rich Thomson) (06/27/91)
In article <26521@beta.gov> aob@beta.gov (Alexander O. Brown) writes: >How common are systems that only support TrueColor or StaticColor? Our current server supports 8-bit PseudoColor, 24-bit TrueColor and 24-bit DirectColor. >Also, DirectColor is supposed to support PseudoColor. I'm not sure what you mean by this statement. DirectColor is more powerful than PseudoColor in that one can simulate PC with DC. >How would I change the visual from Direct to Pseudo? You can't change a visual. Visuals are static entities supported by the server. Although I am not 100% sure, I don't think you can change the visual class of a window. Visuals are used to specify attributes of a window when it is created. >Or is there always a Pseudo visual avaiable if the default is Direct? There is no guarantee of this. >Or do I simply just "simulate" Pseudo with code? This is what I would imagine. More and more high-performance workstations are supporting access to the hardware capabilities through X with a variety of visual types ("tools not rules"). It is best to make absolutely *NO* assumptions about visual classes. Use XMatchVisualInfo and its ilk to find out what list of visuals are supported on the server. Printing out a message like "This program requires a PseudoColor/DirectColor/StaticColor visual with a colormap of at least 8 entries." and then exiting is much more graceful than "Segmentation fault (core dumped)". I have seen much too much of the latter for programs that assume that the rest of the X world is just like their 8-bit pseudocolor workstation. The main reason we implemented a virtual screen with a 8-bit PC root window was to facilitate dumb applications that insist on using the same visual as the root window, or expect that everyone has 8-bit PC visuals. Although TrueColor and DirectColor visuals are inherintly more powerful than PC visuals (with the possible exception of some colormap cycling effects), almost nobody understands how to use them. There is a tutorial in the R4 source tree on how to use visuals, but it seems that most people are unaware of it. It seems like there is a need for a more widely distributed (and updated) tutorial on how to use visuals and how to select which visual you need. -- Rich -- ``Read my MIPS -- no new VAXes!!'' -- George Bush after sniffing freon Disclaimer: I speak for myself, except as noted. UUCP: ...!uunet!dsd.es.com!rthomson Rich Thomson Internet: rthomson@dsd.es.com PEXt Programmer
mouse@lightning.mcrcim.mcgill.EDU (der Mouse) (06/27/91)
> How common are systems that only support TrueColor or StaticColor? I don't know. Mouse-X on the color NeXTs will be a TrueColor-only server unless and until someone tells me where to find documentation on how to change the colormap, if this is in fact possible. But aside from that I've never seen one. (For that matter, I've never actually *seen* a color NeXT :-) > Also, DirectColor is supposed to support PseudoColor. It is? Where did you find that tidbit? > How would I change the visual from Direct to Pseudo? Or is there > always a Pseudo visual avaiable if the default is Direct? Or do I > simply just "simulate" Pseudo with code? It is certainly possible to simulate PseudoColor with DirectColor; look up what XAllocColorCells does for a DirectColor visual. (It amounts to taking one cell from each of the three colormaps and considering them as forming one cell in the pseudo-PseudoColor colormap.) der Mouse old: mcgill-vision!mouse new: mouse@larry.mcrcim.mcgill.edu
stripes@eng.umd.edu (Joshua Osborne) (06/29/91)
In article <26521@beta.gov> aob@beta.gov (Alexander O. Brown) writes: >How common are systems that only support TrueColor or StaticColor? I imagine DirectColor is going to be more common, we have gooten good at 8bit color, but "Visulation" (sorry 'bout the poor spelling) needs more colors to work well. I know you can have a >8bit PsudoColor, but deep displays are normally DirectColor (or TrueColor). TrueColor is only really going to be on 24bit deep displays (other displays offen emulate them); how common do you think they will be? I don't see any reason why StaticColor (only) systems would become more common. They are rare now. >Also, DirectColor is supposed to support PseudoColor. How >would I change the visual from Direct to Pseudo? You don't, and it can't allways "support" it. (i.e. if your DirectColor was 6bit/4bit/4bit (I think the RS/6000 has a display like this) then you only get 16 writable cells, you can't support a PsudoColor with more then 16 cells without a lot of tricks. > Or is there >always a Pseudo visual avaiable if the default is Direct? This is not true. And even if it was currently true, it doesn't mean it will stay that way. > Or >do I simply just "simulate" Pseudo with code? It isn't simple, but if you need writeable colorcells and you need to run on all color systems, you will need to "simulate" writeable cells. -- stripes@eng.umd.edu "Security for Unix is like Josh_Osborne@Real_World,The Multitasking for MS-DOS" "The dyslexic porgramer" - Kevin Lockwood "CNN is the only nuclear capable news network..." - lbruck@eng.umd.edu (Lewis Bruck)
andy@research.canon.oz.au (Andy Newman) (06/30/91)
In article <1991Jun28.202530.15560@eng.umd.edu> stripes@eng.umd.edu (Joshua Osborne) writes: >TrueColor is only really going to be on 24bit deep displays (other displays >offen emulate them); how common do you think they will be? And a 24 bit display with colour maps in its RAMDACs (like most displays that use Brooktree RAMDACS) can do DirectColor. -- Andy Newman (andy@research.canon.oz.au) " Well you can't have everything. Where would you put it? " - Steven Wright