Subject:   -60- What's wrong with blink() in IRIX 4.0.x?
Date: 10 Jun 1993 00:00:01 EST

  - blink() is broken all the way up through 4.0.5F, where blink() only
    blinks to black.

  - you can work-around this blink() problem by doing the following:

      blink(rate, index, red<<8, green<<8, blue<<8)

  - ~4Dgifts/examples/glpg/ch04/blinker.c has three main problems:

      - it doesn't do the above work-around.
      - it doesn't do a gflush after mapping colors.
      - it doesn't turn blinking off initially.

  - what happens is that if a program starts anything blinking and
    exits without ever turning blinking off with blink(-1, 0, 0, 0, 0)
    then the next program to attempt blinking will not be able to
    blink.  this happens if for instance you close the blinker window
    before its 10 second sleep() has completed.

  - a simple idea for a work-around for this problem: programs which do
    blinking should turn their blinking on when they have focus; they
    should turn all blinking off when they lose focus.  This is not
    perfect but is a plausible attempt at sharing the 20 blinking
    system-wide colormap entries.

  Here is a copy of ~4Dgifts/examples/glpg/ch04/blinker.c that contains
  the above workarounds, except for input-focus:

  #include <gl/gl.h>

  #define MAXBLINKS       20    /* maximum number of blinking entries */
  #define FIRSTBLINKCI    64    /* avoid the first 64 colors */

  main()
  {
      int i;

      prefsize(400, 400);
      winopen("blinker");
      ortho2(-0.5, 20.0*MAXBLINKS + 9.5, -0.5, 500.5);
      color(BLACK);
      clear();

      /* always turn blinking off before calling 'blink' */
      blink (-1, 0, 0, 0, 0);

      for (i = MAXBLINKS - 1; i >= 0 ; i--) {
  	mapcolor(i + FIRSTBLINKCI, 255, 255, 255);
  	/* always call gflush() after mapcolors() */
  	gflush();
  	color(i + FIRSTBLINKCI);
  	sboxfi(i*20 + 10, 10, i*20 + 20, 490);
  	/* GL bug in blink -- must left-shift r,g,b values */
  	blink(i + 1, i + FIRSTBLINKCI, 255 << 8, 0 << 8, 0 << 8);
      }
      sleep(10);
      blink(-1, 0, 0, 0, 0);      /* stop all blinking */
      gexit();
      return 0;
  }