xf86-video-intel: src/sna/sna_trapezoids.c

[Chris Wilson]

 src/sna/sna_trapezoids.c |   25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

New commits:
commit 3507437cdba62c28772822cce8c4b656448546db
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Aug 30 22:13:24 2011 +0100

    sna/trapezoids: Reject invalid traps after projecting onto the sample grid
    
    If either of the edges are degenerate on the sample grid, then the trap
    has zero height and must be skipped. (Otherwise if just one edge becomes
    degenerate than the polygon becomes unbalanced and the rasteriser will
    implode.)
    
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

diff --git a/src/sna/sna_trapezoids.c b/src/sna/sna_trapezoids.c
index 5571447..641378b 100644
--- a/src/sna/sna_trapezoids.c
+++ b/src/sna/sna_trapezoids.c
@@ -987,18 +987,15 @@ tor_add_edge(struct tor *converter,
 
 	y1 = dy + (edge->p1.y >> (16 - FAST_SAMPLES_Y_shift));
 	y2 = dy + (edge->p2.y >> (16 - FAST_SAMPLES_Y_shift));
-	assert (y1 < y2);
 
 	x1 = dx + (edge->p1.x >> (16 - FAST_SAMPLES_X_shift));
 	x2 = dx + (edge->p2.x >> (16 - FAST_SAMPLES_X_shift));
 
 	DBG(("%s: edge=(%d, %d), (%d, %d), top=%d, bottom=%d, dir=%d\n",
 	     __FUNCTION__, x1, y1, x2, y2, top, bottom, dir));
-	polygon_add_edge(converter->polygon,
-			 x1, x2,
-			 y1, y2,
-			 top, bottom,
-			 dir);
+	assert (y1 < y2);
+
+	polygon_add_edge(converter->polygon, x1, x2, y1, y2, top, bottom, dir);
 }
 
 static void
@@ -1954,6 +1951,14 @@ composite_unaligned_boxes(CARD8 op,
 	return true;
 }
 
+static inline bool
+fast_trapezoid_valid(xTrapezoid *t)
+{
+	return ((t->left.p1.y >> (16 - FAST_SAMPLES_Y_shift)) != (t->left.p2.y >> (16 - FAST_SAMPLES_Y_shift)) &&
+		(t->right.p1.y >> (16 - FAST_SAMPLES_Y_shift)) != (t->right.p2.y >> (16 - FAST_SAMPLES_Y_shift)) &&
+		(t->bottom >> (16 - FAST_SAMPLES_Y_shift)) > (t->top >> (16 - FAST_SAMPLES_Y_shift)));
+}
+
 static bool
 tor_span_converter(CARD8 op, PicturePtr src, PicturePtr dst,
 		   PictFormatPtr maskFormat, INT16 src_x, INT16 src_y,
@@ -2054,7 +2059,7 @@ tor_span_converter(CARD8 op, PicturePtr src, PicturePtr dst,
 	for (n = 0; n < ntrap; n++) {
 		int top, bottom;
 
-		if (!xTrapezoidValid(&traps[n]))
+		if (!fast_trapezoid_valid(&traps[n]))
 			continue;
 
 		if (pixman_fixed_to_int(traps[n].top) + dst->pDrawable->y >= extents.y2 ||
@@ -2063,8 +2068,6 @@ tor_span_converter(CARD8 op, PicturePtr src, PicturePtr dst,
 
 		top = dy + (traps[n].top >> (16 - FAST_SAMPLES_Y_shift));
 		bottom = dy + (traps[n].bottom >> (16 - FAST_SAMPLES_Y_shift));
-		if (top >= bottom)
-			continue;
 
 		tor_add_edge(&tor, dx, dy, top, bottom, &traps[n].left, 1);
 		tor_add_edge(&tor, dx, dy, top, bottom, &traps[n].right, -1);
@@ -2221,7 +2224,7 @@ tor_mask_converter(CARD8 op, PicturePtr src, PicturePtr dst,
 	for (n = 0; n < ntrap; n++) {
 		int top, bottom;
 
-		if (!xTrapezoidValid(&traps[n]))
+		if (!fast_trapezoid_valid(&traps[n]))
 			continue;
 
 		if (pixman_fixed_to_int(traps[n].top) - dst_y >= extents.y2 ||
@@ -2230,8 +2233,6 @@ tor_mask_converter(CARD8 op, PicturePtr src, PicturePtr dst,
 
 		top = dy + (traps[n].top >> (16 - FAST_SAMPLES_Y_shift));
 		bottom = dy + (traps[n].bottom >> (16 - FAST_SAMPLES_Y_shift));
-		if (top >= bottom)
-			continue;
 
 		tor_add_edge(&tor, dx, dy, top, bottom, &traps[n].left, 1);
 		tor_add_edge(&tor, dx, dy, top, bottom, &traps[n].right, -1);