DGA Problems (segfault when exiting)

DGA Problems (segfault when exiting)

Post by Jeff Week » Wed, 29 Oct 1997 04:00:00

I've written a little DGA driver for my portable graphics library and it
seems to work fine, except that every time I exit a program that uses
it, I get a segfault:

Using DGA version 1.0
video memory unprotecting
MemBase = 0x401a9000, Width = 1024, BankSize = 2097152
Running at 1024x768x16
video memory protecting
Segmentation fault

If anybody can tell me how I can get rid of this, I'd be very grateful.
For completeness I will include a few relavent functions.  You'll notice
I don't support banking yet... that's simply because I haven't gotten to
that stage.  My card doesn't require banking, so it's currently not a

int detect(void) {
  int major, minor, event_base, error_base;

  // Try to connect to the X Server
  display = XOpenDisplay(NULL);
  if( display == NULL ) return 1;

  if(!XF86DGAQueryVersion(display,&major,&minor)) {
    printf("DGA version query failed\n");
    return 1;

  if(!XF86DGAQueryExtension(display,&event_base,&error_base)) {
    printf("DGA extension query failed\n");
    return 1;

  // Fail if the extension version in the server is too old
  if(major < 1 || (major == 1 && minor < 0)) {
    printf("DGA extension is too old, get version 1.0 or higher\n");
    return 1;
  else printf("Using DGA version %d.%d", major, minor);

  // Flag that we're using the MIT-SHM driver
  petal.magic = DGA;
  return 0;


int set_mode(char *window_name, int x, int y, int bpp) {
  XSetWindowAttributes xswa;
  int ram, mem_size;
  unsigned long mask;
  int width, height;

  XF86DGAGetViewPortSize(display, DefaultScreen(display), &width,
  screen = DefaultScreenOfDisplay(display);
  gc = XDefaultGC(display,DefaultScreen(display));

  // override redirect tells the window manger to just ignore us
  xswa.override_redirect = True;
  xswa.event_mask = ButtonPressMask | ButtonReleaseMask |
ButtonMotionMask |
                    StructureNotifyMask | KeyPressMask | KeyReleaseMask;
  xswa.background_pixel = BlackPixelOfScreen(screen);
  mask = CWEventMask | CWOverrideRedirect | CWBackPixel;

  // Create the window
  printf("Creating window\n");
  window = XCreateWindow(display, DefaultRootWindow(display), 0, 0,
                         width, height, 0, CopyFromParent, InputOutput,
                         CopyFromParent, mask, &xswa);

  // Setup some properties
  // XSetStandardProperties(display, window, window_name, window_name,
None, NULL, 0, NULL);

  if(!window) {
    printf("Unable to open window.\n");
    return 1;


  XF86DGAGetVideo(display, DefaultScreen(display), &address,
&bytes_per_line, &bank_size, &ram);
  XF86DGADirectVideo(display, DefaultScreen(display),
                     XF86DGADirectGraphics /*| XF86DGADirectMouse |

  printf("MemBase = 0x%x, Width = %i, BankSize = %i\n", address,
bytes_per_line, bank_size);

  if(bank_size < (ram * 1024)) {
    printf("Banked memory... ");

  printf("Setting viewport\n");

  // Setup some info about the mode we're in
  petal.max_x = width;
  petal.max_y = height;
  petal.bpp = DefaultDepthOfScreen(screen);
  if(petal.bpp == 15) petal.size = (width * height) << 1;
  else petal.size = width * height * (petal.bpp >> 3);

  return 0;


void deinit(void) {
  // give control back to the X server
  // and delete our window, etc.
  XFreeGC(display, gc);
  XDestroyWindow(display, window);


Thanks again,

PS: Please reply via email where possible.

            - Code X Software -
       Programming to a Higher Power

  web:   http://www.execulink.com/~pweeks/


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Hi All,

I was wondering if anyone else has experienced this problem. Basically,
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I have an ASUS GeForce2 GTS card (nvidia chipset), but at the moment I do
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I can reproduce the crash at will, if anyone wants to see the logs.

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