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From: Jim Blandy <jimb@mozilla.com>
Subject: Saturate when rounding up trapezoid edges
diff --git a/pixman/pixman-edge-imp.h b/pixman/pixman-edge-imp.h
index a4698eddb281..39e8d71d2568 100644
--- a/pixman/pixman-edge-imp.h
+++ b/pixman/pixman-edge-imp.h
@@ -53,10 +53,13 @@ RASTERIZE_EDGES (pixman_image_t *image,
* when the sample point lies exactly on the line, we round towards
* north-west.
*
+ * Use 64 bits to get a saturating add, in case lx or rx are near
+ * the limits of pixman_fixed_t.
+ *
* (The AA case does a similar adjustment in RENDER_SAMPLES_X)
*/
- lx += X_FRAC_FIRST(1) - pixman_fixed_e;
- rx += X_FRAC_FIRST(1) - pixman_fixed_e;
+ lx = (pixman_fixed_t) MIN ((int64_t) lx + (X_FRAC_FIRST(1) - pixman_fixed_e), INT32_MAX);
+ rx = (pixman_fixed_t) MIN ((int64_t) rx + (X_FRAC_FIRST(1) - pixman_fixed_e), INT32_MAX);
#endif
/* clip X */
if (lx < 0)