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From: rshankar@top.cis.syr.edu (Ravi V. Shankar)
Newsgroups: comp.windows.x
Subject: XDrawLine doesn't draw lines! Looking for help.
Message-ID: <1991Jan23.235111.23319@rodan.acs.syr.edu>
Date: 24 Jan 91 06:12:57 GMT
Reply-To: rshankar@top.cis.syr.edu (Ravi V. Shankar)
Organization: CIS Dept., Syracuse University
Lines: 70


  I seem to be running into a problem when I use XDrawLine to draw a set
  of lines. My program is pretty basic. It reads from a text file
  4 values at a time and draws a line using the read values as coordinates
  for the two endpoints.

  The program does not give any errors during compilation. But I seem to
  get different results each time I execute the compiled code. Sometimes
  I get all lines drawn properly, sometimes none, sometimes a few.

  I've given a portion of the code below for anyone who has patience to
  read it. I would appreciate any comments/suggestions. Please reply
  directly to me through email.


  Thanks,
  Ravi

  P.S. I use a color monitor on a Sun/4 (just in case you need this info)

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  .....

  theWindowAttributes.border_pixel = BlackPixel(theDisplay, theScreen);
  theWindowAttributes.background_pixel = WhitePixel(theDisplay, theScreen);
  theWindowAttributes.override_redirect = False;

  theWindowMask = (CWBackPixel | CWBorderPixel | CWOverrideRedirect );

  theNewWindow = XCreateWindow( theDisplay,
				    RootWindow( theDisplay, theScreen ),
					0, 0,
					512, 512,
					border_width,
					theDepth,
					InputOutput,
					theVisual,
					theWindowMask,
					&theWindowAttributes );

  theGC = XCreateGC (theDisplay, theNewWindow,(unsigned long)0, &theGCValues);

  theColormap = DefaultColormap(theDisplay, theScreen);

  XSetFunction(theDisplay, theGC, GXset);
  XSetForeground(theDisplay, theGC, BlackPixel(theDisplay, theScreen));
  XMapWindow(theDisplay, theNewWindow);
  XFlush(theDisplay);

  line_fin = fopen("data/lines.dat","r");

  for (i=0; i<44; i++) {

    fscanf(line_fin,"%d %d %d %d\n", &x1, &y1, &x2, &y2);
    XDrawLine(theDisplay, theNewWindow, theGC, x1, y1, x2, y2);


    }

  XFlush(theDisplay);
  fclose(line_fin);
  sleep(2);

  XDestroyWindow( theDisplay, theNewWindow);
  XFlush(theDisplay);

  .......

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