Conference bulova::decw_jan-89_to_nov-90

1030.0. "xsynchronize with event queue processing bug?" by CSC32::B_BRADACH () Wed Jun 28 1989 11:35

    I have a customer who is having a problem with xsynchronize().
    He is attempting to capture notify events, and examine the event queue
    to see how many entries are currently in the queue.
    
    The code example follows.  Any and all comments would be appreciated.
    
    thanks in advance
    
    bernie
    csc/cs
    
            CUT HERE
    =======================================================================
/*
 * Environment:
 *
 * VAXStation II/GPX running VMS 5.1-1 SDC version.  Program was compiled 
 * using VAX C version 2.4. The program must run on a color system.
 *
 * Problem: If XSynchronize is enabled, events get placed on the queue but
 *          XNextEvent fails to remove the entry from the queue.
 *
 *
 * Method to reproduce:
 *
 * Run the program.  Move the pointer into the window that this application
 * creates. You will get enter and exit notify events.  Once inside the window,
 * click MB1 (left mouse button).  This will issue a X call and show you the
 * number of entries on the queue 2 times per second.  Now, enter and leave the
 * window and XNextEvent will fail to remove the entries from the queue.  
 * XQlength reports the correct queue length.  If you comment out the call to
 * XSynchronize, the program will operate properly.
 *
 * This failure makes it difficult to debug the X.11 interface because we 
 * can not switch it into synchronous mode.
 *
 */

#include <stdio.h>
#include "decw$include:xlib.h"
#include "decw$include:xutil.h"

/*
 * Constant data
 */

#define SQUARE_HEIGHT	10
#define SQUARE_WIDTH	10
#define NUMBER_ROWS	10
#define NUMBER_COLUMNS	10
#define NUMBER_SQUARES	NUMBER_ROWS * NUMBER_COLUMNS

Display			*display;	/* connection to the X server */
Window			window;		/* application window */
GC			gc;		/* g context for drawing ops */
int			indexes[NUMBER_SQUARES + 1];
int			blink_interval[2] = {-5*1000*1000, -1};

cursor_blink()
{ int cnt;
                                                                 
  drawSquares(display, window, gc, indexes);
  cnt = XQLength(display);
  printf("Blink with QLength = %d\r\n", cnt);

  SYS$SETIMR(0, blink_interval, cursor_blink, 11, 0);
}

main()
{
  int			i;		/* index variable */
  Colormap		colormap;	/* application specific colormap */
  XEvent		event;		/* incoming events */
  XSetWindowAttributes	attr;		/* window attributes structure */
  int			numColors;	/* number of colors used */
  XColor		colorDefs[NUMBER_SQUARES];
  XColor		queryColor;

/*
 * Open the display
 */

  if ((display = XOpenDisplay("")) == NULL)
    fatalError("XOpenDisplay", "could not open display");

  XSynchronize(display, 1);

/*
 * Create a read/write colormap, with no entries allocated.
 */

  colormap = XCreateColormap(display, RootWindow(display, 0), 
			     DefaultVisual(display, 0), AllocNone);

/*
 * Create a window of the same visual type as our colormap
 */

  attr.event_mask = ExposureMask | ButtonPressMask |
		    EnterWindowMask | LeaveWindowMask;
  attr.colormap = colormap;

  window = XCreateWindow(display, RootWindow(display, 0), 0, 0,
			 NUMBER_COLUMNS * SQUARE_WIDTH,
			 NUMBER_ROWS * SQUARE_HEIGHT, 5, 
			 DefaultDepth(display, 0), InputOutput, 
			 DefaultVisual(display,0), 
			 CWColormap | CWEventMask, &attr);

/*
 * Map window
 */

  XMapWindow(display, window);
  XFlush(display);

/*
 * Allocate enties in out colormap
 */

  numColors = NUMBER_SQUARES;
  if (XAllocColorCells(display, colormap, False, NULL, 0, indexes, 
      		       numColors + 1) == 0)
    fatalError("XAllocColorCells", "Are we monochrome?");

/*
 * Define entries in out colormap
 */

  for (i = 0; i < numColors; i++) {
    colorDefs[i].pixel = indexes[i];
    colorDefs[i].flags = DoRed | DoGreen | DoBlue;
    colorDefs[i].red = i * 0xffff / numColors;
    colorDefs[i].green = i * 0xffff / numColors;
    colorDefs[i].blue = i * 0xffff / numColors;
  }
  
  XStoreColors(display, colormap, colorDefs, numColors);

/*
 * Create a GC for drawing operations
 */

gc = XCreateGC(display, window, 0, NULL);

/*
 * Process events until a button is pressed
 */

  while(1) {
    XNextEvent(display, &event);
    printf("Event to process\r\n");
    switch(event.type) {
    case Expose:
      drawSquares(display, window, gc, indexes);
      break;
    case ButtonPress:
      XInstallColormap(display, DefaultColormap(display, 0));
      SYS$SETIMR(0, blink_interval, cursor_blink, 11, 0);
      break;
    case EnterNotify:
      XInstallColormap(display, colormap);
      break;
    case LeaveNotify:
      XInstallColormap(display, DefaultColormap(display, 0));
      break;
    default:
      break;
    }
  }
}

/*
 * Draw a big square of smaller color squares
 */

drawSquares(display, window, gc, indexes)
Display	*display;
Window	window;
GC	gc;
int	*indexes;

{
  int	row, column, square;
  
  /*
   * Draw filled squares in different foreground colors
   */

  for (row = square = 0; row < NUMBER_ROWS; row++)
    for (column = 0; column < NUMBER_COLUMNS; column++, square++) {
      XSetForeground(display, gc, indexes[square]);
      XFillRectangle(display, window, gc, SQUARE_WIDTH * column,
		     SQUARE_HEIGHT * row,
		     SQUARE_WIDTH, SQUARE_HEIGHT);
    }
}

/*
 * Something bad happened
 */

fatalError(string1, string2)
char *string1;
char *string2;

{
  fprintf(stderr, "Fatal Error: %s in routine %s\n", string1, string2);
  exit();
}
    

    problem has been spr'd.
    
    bernie