rusty@BOSCO.BERKELEY.EDU (06/09/88)
How does one go about printing out the "default" color map? I'm on a
sun 3/60 (cgfour) running x11r2. My code looks something like
dpy = XOpenDisplay(NULL));
scr = DefaultScreen(dpy);
scrn = XScreenOfDisplay(dpy, scr);
nplanes = XDefaultDepth(dpy, scr);
ncells = XCellsOfScreen(scrn);
XAllocColorCells(dpy, XDefaultColormap(dpy, scr), 0, plane_masks,
nplanes, cmap_cells, ncells);
for (i = 0; i < nplanes; i++)
printf("plane_masks[%d] = 0x%x\n", i, plane_masks[i]);
for (i = 0; i < ncells; i++)
printf("cmap_cells[%d] = 0x%x\n", i, cmap_cells[i]);
If I run my program after starting up the server all I get is 0's.
The cgfour has a 256 cell color map and I just want to display a 16 by
16 grid with each color of the color map in a square.
Is there a good book that explains the concepts, principals, etc. of
color maps?jim@EXPO.LCS.MIT.EDU (Jim Fulton) (06/10/88)
There are a couple of problems with your example. One is relatively minor and the other is the reason why it failed. > nplanes = XDefaultDepth (dpy, scr); > ncells = XCellsOfScreen (scrn); > > XAllocColorCells(dpy, XDefaultColormap(dpy, scr), 0, plane_masks, > nplanes, cmap_cells, ncells); First off, the definitions of nplanes and ncells should probably be: nplanes = DisplayPlanes (dpy, scr); ncells = DisplayCells (dpy, scr); And, you'll have to make sure that plane_masks and cmap_cells are arrays containing nplanes and ncells entries each. But, in any case, it won't work. You are trying to allocate ncells*2^nplanes pixels (which on a display with 256 color cells and 8 planes will be 65536) out of a colormap that has at most 254 entries remaining (since BlackPixel and WhitePixel have been allocated by the server)! The reason why you are getting zeros is because the request is failing and you're not checking the return status. What you'll probably want to do is to try to allocate 256 pixels (through some combination of cells and planes), and, if that fails, create a new colormap using XCreateColormap with something along the lines of: visual = /* select the proper visual if DefaultVisual isn't right */ cmap = XCreateColormap (dpy, RootWindow (dpy, scr), visual, All); The visual determines what sort of colormap should be allocated. This is necessary for running on displays that provide more than one type of window (for example: 24 bit DirectColor and 16 bit PseudoColor, or 8 bit PseudoColor and 1 bit StaticGray). Once you have a colormap with all of the entries allocated, you can set them to be whatever you want. Then, whenever you are ready, you can install the colormap. Note that this will cause the rest of the screen to go "technicolor" if there is only one colormap. The Inter-Client Communications Conventions Manual describes installing colormaps in more detail (since it is something that affects the entire screen). Jim Fulton MIT X Consortium
august@ole.UUCP (Augustine Chan) (06/16/88)
In article <8806091630.AA02763@velveeta> rusty@cartan.berkeley.edu writes: >How does one go about printing out the "default" color map? I'm on a >sun 3/60 (cgfour) running x11r2. My code looks something like > > dpy = XOpenDisplay(NULL)); > scr = DefaultScreen(dpy); > scrn = XScreenOfDisplay(dpy, scr); > nplanes = XDefaultDepth(dpy, scr); > ncells = XCellsOfScreen(scrn); > > XAllocColorCells(dpy, XDefaultColormap(dpy, scr), 0, plane_masks, > nplanes, cmap_cells, ncells); > > for (i = 0; i < nplanes; i++) > printf("plane_masks[%d] = 0x%x\n", i, plane_masks[i]); > for (i = 0; i < ncells; i++) > printf("cmap_cells[%d] = 0x%x\n", i, cmap_cells[i]); > >If I run my program after starting up the server all I get is 0's. > >The cgfour has a 256 cell color map and I just want to display a 16 by >16 grid with each color of the color map in a square. > >Is there a good book that explains the concepts, principals, etc. of >color maps? There is a bit of misunderstanding here. Your XAllocColorCells() tries to allocate so-far unused slots in your Default Colormap. This routine will fail if all the slots in the default colormap is already in use. When the call fails, you'll get all 0's in the plane masks and the cells. Such is the case with, e.g., the Apollo DN3000 which has only 4 bit planes, and all 16 available slots are probably tied up the window manager. Your cgfour with 256 color cells should have room to spare unless your window manager + other X-things running have tied up all 256 slots. If successful the newly allocated cells are now at your disposal. You may use XStoreColor() or XStoreColors() to put your own rgb specifications into the slots. You have to keep track of which color goes into which slot (pixel value) for later use, e.g., in calls to XSetForeground. If the Default colormap is full and XAllocColorCells() fails, you can always Create your own color map, allocate cells in it and store your own colors in the cells. Once installed with XInstallColormap(), this new map will apply to the entire display and therefore will mess up the colors of everything except the window it is intended for. There is actually supposed to be another solution to your problem, without having to store your own colors, but the color you obtain will be only an approximation, the closest match in the standard map to your rgb specification. There is this function XGetStandardColormap() which supposedly fills a XStandardColormap structure, which has all the information needed for computing the pixel value of any rgb for the standard colormap. However I have not yet been able to get this function to return SUCCESS. The XGetStandardColormap() call in the program below returns a FAILURE status on an APollo DN3000 and a Sun/260. I would appreciate it if anyone out there could point out what we are doing wrong. /* ----------------------------- cut here -------------------------- */ #include <stdio.h> #include <X11/Xlib.h> #include <X11/Xutil.h> #include <X11/Xatom.h> int main() { Display *dpy; Window win; int scrn; int planes; XStandardColormap sc_map; if ((dpy = XOpenDisplay (NULL)) == NULL) { fprintf (stderr, "Could not connect to default X display.\n"); XCloseDisplay(dpy); exit (1); } scrn = XDefaultScreen(dpy); planes = XDisplayPlanes(dpy, scrn); printf("no of planes: %d\n", planes); win = XDefaultRootWindow(dpy); if (XGetStandardColormap(dpy, win, &sc_map, XA_RGB_COLOR_MAP) == 0) fprintf(stderr, "cannot obtain standard colormap\n"); else fprintf(stderr, "standard colormap obtained\n"); XCloseDisplay(dpy); } /* -------------------------- cut here ------------------------------- */ Augustine Chan Seattle Silicon Corp. Bellevue, Wash
jim@EXPO.LCS.MIT.EDU (Jim Fulton) (06/16/88)
>> [the allocating colors misexample] > > There is a bit of misunderstanding here. To say the least. For reference, the indicated code was attempting to allocate ncells*2^nplanes = 256*2^8 = 65536 color cells. Ugh. > [this was asking about why XGetStandardColormap wasn't working] > > I would appreciate it if anyone out there could point out what > we are doing wrong. Two things: 1. The publicly-available window managers don't create any standard colormaps, so there aren't any to fetch. Unless you have created a special program to load the colormaps, XGetStandardColormap won't work. See Section 9.2 of the Xlib manual and the ICCCM for more detailed information. 2. You were passing the colormap property type (XA_RGB_COLOR_MAP) instead of one of the standard colormap property names listed in Section 9.2.2 of the Xlib manual: XA_RGB_DEFAULT_MAP a "nice" collection of commonly-used colors XA_RGB_BEST_MAP the widest distribution of colors XA_RGB_RED_MAP XA_RGB_GREEN_MAP XA_RGB_BLUE_MAP ramps of the indicated colors XA_RGB_GRAY_MAP ramps of gray Jim Fulton MIT X Consortium
kochhar@endor.harvard.edu (Sandeep Kochhar) (03/12/90)
Config: X11R4, twm, Sparcstation I I have a program that creates a window and a colormap and associates the colormap with the window using XSetWindowColormap(). This works fine, in that when the cursor comes into the window, twm switches to my colormap, and when I move out of the window, it switches back, and so on. However, on random occasions (not always), I get the message twm: client illegally changed colormap (i = -1, j = -1 Also, sometimes on those occasions, twm doesn't install my colormap when I enter the program window. Anybody have any ideas? (Note: the only other colormap related calls I use are: XCreateColormap, XStoreColor, XLookupColor) Thanks. Sandeep Kochhar (617) 495-3988 mail: kochhar@harvard.harvard.edu Harvard University kochhar@harvard.csnet 33 Oxford st, kochhar@harvard.uucp Cambridge, MA 02138 kochhar@harvard.bitnet Fax: (617) 495-9837