[cairo] [PATCH] fix _cairo_rectangle_intersect

[Jeff Muizelaar]

_cairo_rectangle_intersect gives bad results whenever
MIN (dest->x + dest->width, src->x + src->width) - out.x
is negative because of assignment to an unsigned short.

The appended patch fixes the problem by using variables of type int for
the computation results.

There are still problems when x + width is > 655536, but at
least that is a lot more rare. Are there any reasons width and height
are unsigned to begin with?


2005-02-23  Jeff Muizelaar <jrmuizel at nit.ca>

	* src/cairo_gstate.c (_cairo_rectangle_intersect)
	make the computation correct when the intersection
	negative width

Index: src/cairo_gstate.c
===================================================================
RCS file: /cvs/cairo/cairo/src/cairo_gstate.c,v
retrieving revision 1.84
diff -u -r1.84 cairo_gstate.c
--- src/cairo_gstate.c	22 Feb 2005 19:35:03 -0000	1.84
+++ src/cairo_gstate.c	23 Feb 2005 19:13:02 -0000
@@ -1414,18 +1414,21 @@
 _cairo_rectangle_intersect (cairo_rectangle_t *dest, cairo_rectangle_t *src)
 {
     cairo_rectangle_t out;
+    int width, height;
 
     out.x = MAX (dest->x, src->x);
     out.y = MAX (dest->y, src->y);
-    out.width = MIN (dest->x + dest->width, src->x + src->width) - out.x;
-    out.height = MIN (dest->y + dest->height, src->y + src->height) - out.y;
+    width = MIN (dest->x + dest->width, src->x + src->width) - out.x;
+    height = MIN (dest->y + dest->height, src->y + src->height) - out.y;
 
-    if (out.width <= 0 || out.height <= 0) {
+    if (width <= 0 || height <= 0) {
 	dest->x = 0;
 	dest->y = 0;
 	dest->width = 0;
 	dest->height = 0;
     } else {
+	dest->width = width;
+	dest->height = height;
 	*dest = out;
     }	
 }