Another optimization

common/rfb/Watermark.cxx

@@ -216,6 +216,17 @@ void packWatermark(const Region &changed) {
         const Rect &bounding = changed.get_bounding_rect();
 
 	for (y = 0; y < rh; y++) {
+		// Is the entire line outside the changed area?
+		if (bounding.tl.y > y || bounding.br.y < y) {
+			for (x = 0; x < rw; x++) {
+				pix[cur] = 0;
+
+				if (cur || (y == rh - 1 && x == rw - 1))
+					*dst++ = pix[0] | (pix[1] << 4);
+
+				cur ^= 1;
+			}
+		} else {
 			for (x = 0; x < rw; x++) {
 				pix[cur] = 0;
 				if (bounding.contains(Point(x, y)) && changed.contains(x, y))
@@ -227,6 +238,7 @@ void packWatermark(const Region &changed) {
 				cur ^= 1;
 			}
 		}
+	}
 
 	uLong destLen = MAXW * MAXH / 2;
 	if (compress2(watermarkData, &destLen, watermarkTmp, rw * rh / 2 + 1, 1) != Z_OK)