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From: Jim Blandy <jimb@mozilla.com>
Subject: Round translation distances in 48/16 fixpoint.
diff --git a/pixman/pixman-fast-path.c b/pixman/pixman-fast-path.c
index d510cacbf803..41f9dca1cbca 100644
--- a/pixman/pixman-fast-path.c
+++ b/pixman/pixman-fast-path.c
@@ -1772,10 +1772,15 @@ fast_composite_rotate_90_##suffix (pixman_implementation_t *imp, \
\
PIXMAN_IMAGE_GET_LINE (dest_image, dest_x, dest_y, pix_type, \
dst_stride, dst_line, 1); \
+ /* Round in pixman_fixed_48_16_t, to avoid overflows. Since \
+ * matrix values are pixman_fixed_16_16_t, even if the value rounds \
+ * up, it will still represent a value < 65537, and fit in an int. */ \
src_x_t = -src_y + pixman_fixed_to_int ( \
+ (pixman_fixed_48_16_t) \
src_image->common.transform->matrix[0][2] + \
pixman_fixed_1 / 2 - pixman_fixed_e) - height;\
src_y_t = src_x + pixman_fixed_to_int ( \
+ (pixman_fixed_48_16_t) \
src_image->common.transform->matrix[1][2] + \
pixman_fixed_1 / 2 - pixman_fixed_e); \
PIXMAN_IMAGE_GET_LINE (src_image, src_x_t, src_y_t, pix_type, \
@@ -1796,10 +1801,15 @@ fast_composite_rotate_270_##suffix (pixman_implementation_t *imp, \
\
PIXMAN_IMAGE_GET_LINE (dest_image, dest_x, dest_y, pix_type, \
dst_stride, dst_line, 1); \
+ /* Round in pixman_fixed_48_16_t, to avoid overflows. Since \
+ * matrix values are pixman_fixed_16_16_t, even if the value rounds \
+ * up, it will still represent a value < 65537, and fit in an int. */ \
src_x_t = src_y + pixman_fixed_to_int ( \
+ (pixman_fixed_48_16_t) \
src_image->common.transform->matrix[0][2] + \
pixman_fixed_1 / 2 - pixman_fixed_e); \
src_y_t = -src_x + pixman_fixed_to_int ( \
+ (pixman_fixed_48_16_t) \
src_image->common.transform->matrix[1][2] + \
pixman_fixed_1 / 2 - pixman_fixed_e) - width; \
PIXMAN_IMAGE_GET_LINE (src_image, src_x_t, src_y_t, pix_type, \