Description: Clip area to stop refreshes outside the buffer
Author: dave@treblig.org
Bug: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-cirrus/+bug/1043513
Index: xserver-xorg-video-cirrus-1.5.1/src/cir_shadow.c
===================================================================
--- xserver-xorg-video-cirrus-1.5.1.orig/src/cir_shadow.c	2012-12-06 13:01:35.137930320 +0000
+++ xserver-xorg-video-cirrus-1.5.1/src/cir_shadow.c	2012-12-06 13:02:27.601929013 +0000
@@ -15,6 +15,25 @@
 #include "cir.h"
 #include "alp.h"
 
+static short
+shortClip(short i, short min, short max)
+{
+	if (i<min) return min;
+	if (i>max) return max;
+	return i;
+}
+
+static void
+boxClip(BoxPtr pbox, short minx, short maxx, short miny, short maxy)
+{
+	/* Hmm, I assume there is some builtin function somewhere to do this
+	I've had a quick look and it's not obvious - dag */
+	pbox->x1 = shortClip(pbox->x1, minx, maxx);
+	pbox->x2 = shortClip(pbox->x2, minx, maxx);
+	pbox->y1 = shortClip(pbox->y1, miny, maxy);
+	pbox->y2 = shortClip(pbox->y2, miny, maxy);
+}
+
 _X_EXPORT void
 cirRefreshArea(ScrnInfoPtr pScrn, int num, BoxPtr pbox)
 {
@@ -26,11 +45,14 @@
     FBPitch = BitmapBytePad(pScrn->displayWidth * pScrn->bitsPerPixel);
 
     while(num--) {
-	width = (pbox->x2 - pbox->x1) * Bpp;
-	height = pbox->y2 - pbox->y1;
-	src = pCir->ShadowPtr + (pbox->y1 * pCir->ShadowPitch) + 
-						(pbox->x1 * Bpp);
-	dst = pCir->FbBase + (pbox->y1 * FBPitch) + (pbox->x1 * Bpp);
+	BoxRec clipped = *pbox;
+	boxClip(&clipped, 0, pScrn->virtualX, 0, pScrn->virtualY);
+
+	width = (clipped.x2 - clipped.x1) * Bpp;
+	height = clipped.y2 - clipped.y1;
+	src = pCir->ShadowPtr + (clipped.y1 * pCir->ShadowPitch) + 
+						(clipped.x1 * Bpp);
+	dst = pCir->FbBase + (clipped.y1 * FBPitch) + (clipped.x1 * Bpp);
 
 	while(height--) {
 	    memcpy(dst, src, width);