Re: [patch] ConfigureNotify events

[Alexander Malmberg]

My nice plan to clean up the backend interface semantics and
back/Source/x11/ internals has been thwarted by X's inability (enhanced
by window managers) to place windows accurately. The good news is that
this makes the patch for this (and window decorations) nice and small
since almost nothing changes. The bad news is that things are as bad as
before since almost nothing changes. :)

With this patch, I don't get any window drifting (other than the
occasional pixel, but I get that in non-GNUstep apps as well). For those
interested, an explanation of what was going in is in the source.
Testing is appreciated. If this version works ok, I'll commit it and the
window decoration changes.

- Alexander Malmberg

Index: Source/x11/XGServerEvent.m
===================================================================
RCS file: /cvsroot/gnustep/gnustep/core/back/Source/x11/XGServerEvent.m,v
retrieving revision 1.21
diff -u -r1.21 XGServerEvent.m
--- Source/x11/XGServerEvent.m  4 Feb 2004 00:59:59 -0000       1.21
+++ Source/x11/XGServerEvent.m  27 Mar 2004 17:39:18 -0000
@@ -685,34 +685,45 @@
                      xEvent.xconfigure.send_event ? 'T' : 'F');
          if (cWin == 0 || xEvent.xconfigure.window != cWin->ident)
            generic.cachedWindow = [XGServer 
_windowForXWindow:xEvent.xconfigure.window];
-         /*
-          * Ignore events for unmapped windows.
-                */
-         if (cWin != 0 && cWin->map_state == IsViewable)
+
+         if (cWin != 0)
            {
              NSRect       r, x, n, h;
              NSTimeInterval ts = (NSTimeInterval)generic.lastMotion;
 
-             /*
-              * Get OpenStep frame coordinates from X frame.
-              * If it's not from the window mmanager, ignore x and y.
-              */
              r = cWin->xframe;
+
+             x = NSMakeRect(xEvent.xconfigure.x,
+                            xEvent.xconfigure.y,
+                            xEvent.xconfigure.width,
+                            xEvent.xconfigure.height);
+
+             /*
+             According to the ICCCM, coordinates in synthetic events
+             (ie. non-zero send_event) are in root space, while coordinates
+             in real events are in the parent window's space. The parent
+             window might be some window manager window, so we can't
+             directly use those coordinates.
+
+             Thus, if the event is real, we use XTranslateCoordinates to
+             get the root space coordinates.
+             */
              if (xEvent.xconfigure.send_event == 0)
                {
-                 x = NSMakeRect(r.origin.x, r.origin.y,
-                                xEvent.xconfigure.width, 
xEvent.xconfigure.height);
-               }
-             else
-               {
-                 x = NSMakeRect(xEvent.xconfigure.x, 
-                                xEvent.xconfigure.y,
-                                xEvent.xconfigure.width, 
-                                xEvent.xconfigure.height);
-                 cWin->xframe.origin = x.origin;
+                 int root_x, root_y;
+                 Window root_child;
+                 XTranslateCoordinates(dpy, xEvent.xconfigure.window,
+                                       RootWindow(dpy, cWin->screen),
+                                       0, 0,
+                                       &root_x, &root_y,
+                                       &root_child);
+                 x.origin.x = root_x;
+                 x.origin.y = root_y;
                }
+
+             cWin->xframe = x;
              n = [self _XFrameToOSFrame: x for: cWin];
-             NSDebugLLog(@"Moving", 
+             NSDebugLLog(@"Moving",
                          @"Update win %d:\n   original:%@\n   new:%@",
                          cWin->number, NSStringFromRect(r), 
                          NSStringFromRect(x));
@@ -722,18 +733,26 @@
              h = [self _OSFrameToXHints: n for: cWin];
              cWin->siz_hints.width = h.size.width;
              cWin->siz_hints.height = h.size.height;
-             //if (xEvent.xconfigure.send_event != 0)
-             {
-               cWin->siz_hints.x = h.origin.x;
-               cWin->siz_hints.y = h.origin.y;
-             }
+
+             /*
+             We only update the position hints if we're on the screen.
+             Otherwise, the window manager might not have added decorations
+             (if any) to the window yet. Since we compensate for decorations
+             when we set the position, this will confuse us and we'll end
+             up compensating twice, which makes windows drift.
+             */
+             if (cWin->map_state == IsViewable)
+               {
+                 cWin->siz_hints.x = h.origin.x;
+                 cWin->siz_hints.y = h.origin.y;
+               }
 
              /*
               * create GNUstep event(s)
               */
              if (!NSEqualSizes(r.size, x.size))
                {
-                 /* Resize events move the origin. There's no goo
+                 /* Resize events move the origin. There's no good
                     place to pass this info back, so we put it in
                     the event location field */
                  e = [NSEvent otherEventWithType: NSAppKitDefined