Avoid intersecting screen with empty clipList in vncHooksCopyArea. The

result would be empty, which means that we are not sending CopyRect
updates even though we can. Improves vertical scrolling with Firefox
and Adobe reader.



git-svn-id: svn://svn.code.sf.net/p/tigervnc/code/trunk@4324 3789f03b-4d11-0410-bbf8-ca57d06f2519

unix/xserver/hw/vnc/vncHooks.cc

@@ -816,7 +816,9 @@ static RegionPtr vncHooksCopyArea(DrawablePtr pSrc, DrawablePtr pDst,
     box.y2 = box.y1 + h;
 
     src.init(&box, 0);
-    REGION_INTERSECT(pScreen, src.reg, src.reg, &((WindowPtr)pSrc)->clipList);
+    if (REGION_NOTEMPTY(pScreen, &((WindowPtr)pSrc)->clipList)) {
+	REGION_INTERSECT(pScreen, src.reg, src.reg, &((WindowPtr)pSrc)->clipList);
+    }
     REGION_TRANSLATE(pScreen, src.reg,
                      dstx + pDst->x - srcx - pSrc->x,
                      dsty + pDst->y - srcy - pSrc->y);