Offset rendering in pixman_composite_trapezoids() by (x_dst, y_dst)

Previously, this function would do coordinate calculations in such a
way that (x_dst, y_dst) would only affect the alignment of the source
image, but not of the traps, which would always be considered to be in
absolute destination coordinates. This is unlike the
pixman_image_composite() function which also registers the mask to the
destination.

This patch makes it so that traps are also offset by (x_dst, y_dst).

Also add a comment explaining how this function is supposed to
operate, and update tri-test.c and composite-trap-test.c to deal with
the new semantics.

1 files changed, 1 insertions, 1 deletions

diff --git a/demos/tri-test.c b/demos/tri-test.c
index ff4779e..a71869a 100644
--- a/demos/tri-test.c
+++ b/demos/tri-test.c
@@ -36,7 +36,7 @@ main (int argc, char **argv)
 				dest_img,
 				PIXMAN_a8,
 				200, 200,
-				35, 5,
+				-5, 5,
 				ARRAY_LENGTH (tris), tris);
     show_image (dest_img);