+
+
+/* It's possible that a race condition could have led to the saver
+ window being unexpectedly still mapped. This can happen like so:
+
+ - screen is blanked
+ - hack is launched
+ - that hack tries to grab a screen image (it does this by
+ first unmapping the saver window, then remapping it.)
+ - hack unmaps window
+ - hack waits
+ - user becomes active
+ - hack re-maps window (*)
+ - driver kills subprocess
+ - driver unmaps window (**)
+
+ The race is that (*) might have been sent to the server before
+ the client process was killed, but, due to scheduling randomness,
+ might not have been received by the server until after (**).
+ In other words, (*) and (**) might happen out of order, meaning
+ the driver will unmap the window, and then after that, the
+ recently-dead client will re-map it. This leaves the user
+ locked out (it looks like a desktop, but it's not!)
+
+ To avoid this: after un-blanking the screen, we launch a timer
+ that wakes up once a second for ten seconds, and makes damned
+ sure that the window is still unmapped.
+ */
+
+void
+de_race_timer (XtPointer closure, XtIntervalId *id)
+{
+ saver_info *si = (saver_info *) closure;
+ saver_preferences *p = &si->prefs;
+ int secs = 1;
+
+ if (id == 0) /* if id is 0, this is the initialization call. */
+ {
+ si->de_race_ticks = 10;
+ if (p->verbose_p)
+ fprintf (stderr, "%s: starting de-race timer (%d seconds.)\n",
+ blurb(), si->de_race_ticks);
+ }
+ else
+ {
+ int i;
+ XSync (si->dpy, False);
+ for (i = 0; i < si->nscreens; i++)
+ {
+ saver_screen_info *ssi = &si->screens[i];
+ Window w = ssi->screensaver_window;
+ XWindowAttributes xgwa;
+ XGetWindowAttributes (si->dpy, w, &xgwa);
+ if (xgwa.map_state != IsUnmapped)
+ {
+ if (p->verbose_p)
+ fprintf (stderr,
+ "%s: %d: client race! emergency unmap 0x%lx.\n",
+ blurb(), i, (unsigned long) w);
+ XUnmapWindow (si->dpy, w);
+ }
+ else if (p->debug_p)
+ fprintf (stderr, "%s: %d: (de-race of 0x%lx is cool.)\n",
+ blurb(), i, (unsigned long) w);
+ }
+ XSync (si->dpy, False);
+
+ si->de_race_ticks--;
+ }
+
+ if (id && *id == si->de_race_id)
+ si->de_race_id = 0;
+
+ if (si->de_race_id) abort();
+
+ if (si->de_race_ticks <= 0)
+ {
+ si->de_race_id = 0;
+ if (p->verbose_p)
+ fprintf (stderr, "%s: de-race completed.\n", blurb());
+ }
+ else
+ {
+ si->de_race_id = XtAppAddTimeOut (si->app, secs * 1000,
+ de_race_timer, closure);
+ }
+}