http://ftp.aanet.ru/pub/Linux/X11/apps/xscreensaver-2.31.tar.gz

[xscreensaver] / hacks / kumppa.c

diff --git a/hacks/kumppa.c b/hacks/kumppa.c
index 953f3c30e1920df7c315f505a6881bc7f9fc0a68..96db47c361d285d4c4d0d6f91374cb62c0dea217 100644 (file)
--- a/hacks/kumppa.c
+++ b/hacks/kumppa.c
@@ -145,7 +145,7 @@ int x,y;
 int dx,dy;
 
 rx=Xrottable[stateX+1]-Xrottable[stateX];
-ry=Yrottable[stateX+1]-Yrottable[stateY];
+ry=Yrottable[stateY+1]-Yrottable[stateY];
 
 
 for (x=0;x<=rx;x++)
@@ -334,6 +334,23 @@ return (True);
 }
 
 
+#ifdef HAVE_XDBE_EXTENSION
+static XErrorHandler old_handler = 0;
+static Bool got_BadMatch = False;
+static int
+BadMatch_ehandler (Display *dpy, XErrorEvent *error)
+{
+  if (error->error_code == BadMatch) {
+    got_BadMatch = True;
+    return 0;
+  } else if (old_handler)
+    return old_handler(dpy, error);
+  else
+    exit(1);
+}
+#endif /* HAVE_XDBE_EXTENSION */
+
+
 Bool InitializeAll(void)
 {
 XGCValues xgcv;
@@ -388,7 +405,44 @@ if (usedouble)
                usedouble=False;
                }
        }
-if (usedouble) win[1]=XdbeAllocateBackBufferName(dpy,win[0],XdbeUndefined);
+if (usedouble)
+  {
+    /* We need to trap an X error when calling XdbeAllocateBackBufferName,
+       because there is no way to know beforehand whether the call will
+       succeed!  This is a totally fucked design, but the man page says:
+
+       ERRORS
+         BadMatch
+              The specified window is not an InputOutput window or
+              its visual does not support DBE.
+
+       With SGI's O2 X server, some visuals support double-buffering (the
+       12-bit pseudocolor visuals) and others yield a BadMatch error, as
+       documented.
+
+       However, it doesn't matter, because using the DBUF extension seems
+       to make it run *slower* instead of faster anyway.
+
+                                                        -- jwz, 1-Jul-98
+     */
+    XSync(dpy, False);
+    old_handler = XSetErrorHandler (BadMatch_ehandler);
+    got_BadMatch = False;
+    win[1] = 0;
+    win[1] = XdbeAllocateBackBufferName(dpy,win[0],XdbeUndefined);
+    XSync(dpy, False);
+    XSetErrorHandler (old_handler);
+    old_handler = 0;
+    XSync(dpy, False);
+    if (got_BadMatch || !win[1])
+      {
+       fprintf(stderr, "%s: visual 0x%x does not support double-buffering.\n",
+               progname, XVisualIDFromVisual(xgwa.visual));
+       usedouble = False;
+       win[1] = win[0];
+       got_BadMatch = False;
+      }
+  }
 #endif /* HAVE_XDBE_EXTENSION */
 
 delay=get_integer_resource("delay","Integer");