[Glamor] [PATCH 1/2] Do not reduce a composite to a copy if we need to sample outside of the source

[Chris Wilson]

In order to maintain Render semantics, samples outside of the source
should return CLEAR. The copy routines instead are based on the core
protocol and expects the source rectangle to be wholly contained within
the drawable and so does no fixup.

Fixes the rendering of GTK icons.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 src/glamor_render.c |   31 ++++++++++++++++++++++---------
 1 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/src/glamor_render.c b/src/glamor_render.c
index b0630b1..b70ace2 100644
--- a/src/glamor_render.c
+++ b/src/glamor_render.c
@@ -602,7 +602,7 @@ glamor_composite_with_copy(CARD8 op,
 			   INT16 y_dest, CARD16 width, CARD16 height)
 {
 	RegionRec region;
-	int ret;
+	int ret = FALSE;
 
 	if (!source->pDrawable)
 		return FALSE;
@@ -622,14 +622,27 @@ glamor_composite_with_copy(CARD8 op,
 				      x_source, y_source,
 				      0, 0, x_dest, y_dest, width, height))
 		return TRUE;
-	ret = TRUE;
-	if (!glamor_copy_n_to_n_nf(source->pDrawable,
-			dest->pDrawable, NULL,
-	                REGION_RECTS(&region),
-		        REGION_NUM_RECTS(&region),
-			x_source - x_dest, y_source - y_dest,
-			FALSE, FALSE, 0, NULL))
-		ret = FALSE;
+	/* Fallback if we sample outside the source so that we swizzle the
+	 * clear color appropriately. If the source has an alpha channel,
+	 * we could rely on CLAMP_TO_BORDER working as required...
+	 */
+	if (region.extents.x1 + x_source - x_dest < 0)
+		goto cleanup_region;
+	if (region.extents.x2 + x_source - x_dest > source->pDrawable->width)
+		goto cleanup_region;
+
+	if (region.extents.y1 + y_source - y_dest < 0)
+		goto cleanup_region;
+	if (region.extents.y2 + y_source - y_dest > source->pDrawable->height)
+		goto cleanup_region;
+
+	ret = glamor_copy_n_to_n_nf(source->pDrawable,
+				    dest->pDrawable, NULL,
+				    REGION_RECTS(&region),
+				    REGION_NUM_RECTS(&region),
+				    x_source - x_dest, y_source - y_dest,
+				    FALSE, FALSE, 0, NULL);
+cleanup_region:
 	REGION_UNINIT(dest->pDrawable->pScreen, &region);
 	return ret;
 }
-- 
1.7.8.3