Avoid VNC updates for offscreen windows

Windows aren't always directly shown, e.g. when the desktop is
composited. We should not be sending screen updates for these as the
framebuffer didn't actually change.

In the case of CopyWindow, we're even sending the wrong screen data,
which is how this bug was discovered.

diff --git a/unix/xserver/hw/vnc/vncHooks.c b/unix/xserver/hw/vnc/vncHooks.c
index 3838c10dab582fe47db411b3e477805c95acbbf2..7fe35ada3df67620ea2acca6c4d084b2f4017077 100644 (file)
--- a/unix/xserver/hw/vnc/vncHooks.c
+++ b/unix/xserver/hw/vnc/vncHooks.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
- * Copyright 2009-2017 Pierre Ossman for Cendio AB
+ * Copyright 2009-2024 Pierre Ossman for Cendio AB
  * 
  * This is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -469,39 +469,47 @@ static void vncHooksCopyWindow(WindowPtr pWin, DDXPointRec ptOldOrg,
                                RegionPtr pOldRegion)
 {
   int dx, dy;
-  BoxRec screen_box;
-  RegionRec copied, screen_rgn;
+  RegionRec copied;
 
   SCREEN_PROLOGUE(pWin->drawable.pScreen, CopyWindow);
 
-  RegionNull(&copied);
-  RegionCopy(&copied, pOldRegion);
+  if (is_visible(&pWin->drawable)) {
+    BoxRec screen_box;
+    RegionRec screen_rgn;
 
-  screen_box.x1 = 0;
-  screen_box.y1 = 0;
-  screen_box.x2 = pScreen->width;
-  screen_box.y2 = pScreen->height;
+    RegionNull(&copied);
+    RegionCopy(&copied, pOldRegion);
 
-  RegionInitBoxes(&screen_rgn, &screen_box, 1);
+    screen_box.x1 = 0;
+    screen_box.y1 = 0;
+    screen_box.x2 = pScreen->width;
+    screen_box.y2 = pScreen->height;
 
-  dx = pWin->drawable.x - ptOldOrg.x;
-  dy = pWin->drawable.y - ptOldOrg.y;
+    RegionInitBoxes(&screen_rgn, &screen_box, 1);
 
-  // RFB tracks copies in terms of destination rectangle, not source.
-  // We also need to copy with changes to the Window's clipping region.
-  // Finally, make sure we don't get copies to or from regions outside
-  // the framebuffer.
-  RegionIntersect(&copied, &copied, &screen_rgn);
-  RegionTranslate(&copied, dx, dy);
-  RegionIntersect(&copied, &copied, &screen_rgn);
-  RegionIntersect(&copied, &copied, &pWin->borderClip);
+    dx = pWin->drawable.x - ptOldOrg.x;
+    dy = pWin->drawable.y - ptOldOrg.y;
+
+    // RFB tracks copies in terms of destination rectangle, not source.
+    // We also need to copy with changes to the Window's clipping region.
+    // Finally, make sure we don't get copies to or from regions outside
+    // the framebuffer.
+    RegionIntersect(&copied, &copied, &screen_rgn);
+    RegionTranslate(&copied, dx, dy);
+    RegionIntersect(&copied, &copied, &screen_rgn);
+    RegionIntersect(&copied, &copied, &pWin->borderClip);
+
+    RegionUninit(&screen_rgn);
+  } else {
+    RegionNull(&copied);
+    dx = dy = 0;
+  }
 
   (*pScreen->CopyWindow) (pWin, ptOldOrg, pOldRegion);
 
   add_copied(pScreen, &copied, dx, dy);
 
   RegionUninit(&copied);
-  RegionUninit(&screen_rgn);
 
   SCREEN_EPILOGUE(CopyWindow);
 }
@@ -512,18 +520,23 @@ static void vncHooksCopyWindow(WindowPtr pWin, DDXPointRec ptOldOrg,
 static void vncHooksClearToBackground(WindowPtr pWin, int x, int y, int w,
                                       int h, Bool generateExposures)
 {
-  BoxRec box;
   RegionRec reg;
 
   SCREEN_PROLOGUE(pWin->drawable.pScreen, ClearToBackground);
 
-  box.x1 = x + pWin->drawable.x;
-  box.y1 = y + pWin->drawable.y;
-  box.x2 = w ? (box.x1 + w) : (pWin->drawable.x + pWin->drawable.width);
-  box.y2 = h ? (box.y1 + h) : (pWin->drawable.y + pWin->drawable.height);
+  if (is_visible(&pWin->drawable)) {
+    BoxRec box;
 
-  RegionInitBoxes(&reg, &box, 1);
-  RegionIntersect(&reg, &reg, &pWin->clipList);
+    box.x1 = x + pWin->drawable.x;
+    box.y1 = y + pWin->drawable.y;
+    box.x2 = w ? (box.x1 + w) : (pWin->drawable.x + pWin->drawable.width);
+    box.y2 = h ? (box.y1 + h) : (pWin->drawable.y + pWin->drawable.height);
+
+    RegionInitBoxes(&reg, &box, 1);
+    RegionIntersect(&reg, &reg, &pWin->clipList);
+  } else {
+    RegionNull(&reg);
+  }
 
   (*pScreen->ClearToBackground) (pWin, x, y, w, h, generateExposures);