media-libs/arc-mesa-img/files/10.3-drivers-dri-i965-gen6-Clamp-scissor-state-instead-of.patch

From f390b920db89fd332f6c1398c886de43cdc4e868 Mon Sep 17 00:00:00 2001
From: Corbin Simpson <simpsoco@chromium.org>
Date: Thu, 28 Aug 2014 14:48:31 -0700
Subject: [PATCH 11/39] CHROMIUM: i965: Clamp scissor state instead of
 truncating on gen6.

Replaces one undefined behavior with another, slightly more friendly,
undefined behavior.

This changes glScissor() behavior on i965 to clamp instead of truncate
out-of-range scissors. Technically either behavior is acceptable, but
clamping has more predictable results on out-of-range scissors.

BUG=chromium:360217
TEST=Watched some Youtube on Link; can't reproduce original bug as reported.

Signed-off-by: Corbin Simpson <simpsoco@chromium.org>
Signed-off-by: Prince Agyeman <prince.agyeman@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Signed-off-by: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Gurchetan Singh <gurchetansingh@chromium.org>
---
 src/mesa/drivers/dri/i965/genX_state_upload.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/genX_state_upload.c b/src/mesa/drivers/dri/i965/genX_state_upload.c
index ef04603..092cef1 100644
--- a/src/mesa/drivers/dri/i965/genX_state_upload.c
+++ b/src/mesa/drivers/dri/i965/genX_state_upload.c
@@ -2243,6 +2243,13 @@ const struct brw_tracked_state genX(cc_vp) = {
 
 /* ---------------------------------------------------------------------- */
 
+/* Clamp scissors to 16-bit unsigned values; otherwise, the compiler truncates
+ * them to fit inside the bitfields, which is often not what is desired.
+ * My reading of GL and GLES specs suggests that overly-large scissor values are
+ * not an erroring condition and that the actual behavior is undefined, so
+ * switching from truncation to clamping is probably not a problem. ~ C. */
+#define CLAMP_SCISSOR(X) CLAMP(X, 0x0000, 0xffff)
+
 static inline void
 set_scissor_bits(const struct gl_context *ctx, int i,
                  bool render_to_fbo, unsigned fb_width, unsigned fb_height,
@@ -2269,16 +2276,16 @@ set_scissor_bits(const struct gl_context *ctx, int i,
       sc->ScissorRectangleYMax = 0;
    } else if (render_to_fbo) {
       /* texmemory: Y=0=bottom */
-      sc->ScissorRectangleXMin = bbox[0];
-      sc->ScissorRectangleXMax = bbox[1] - 1;
-      sc->ScissorRectangleYMin = bbox[2];
-      sc->ScissorRectangleYMax = bbox[3] - 1;
+      sc->ScissorRectangleXMin = CLAMP_SCISSOR(bbox[0]);
+      sc->ScissorRectangleXMax = CLAMP_SCISSOR(bbox[1] - 1);
+      sc->ScissorRectangleYMin = CLAMP_SCISSOR(bbox[2]);
+      sc->ScissorRectangleYMax = CLAMP_SCISSOR(bbox[3] - 1);
    } else {
       /* memory: Y=0=top */
-      sc->ScissorRectangleXMin = bbox[0];
-      sc->ScissorRectangleXMax = bbox[1] - 1;
-      sc->ScissorRectangleYMin = fb_height - bbox[3];
-      sc->ScissorRectangleYMax = fb_height - bbox[2] - 1;
+      sc->ScissorRectangleXMin = CLAMP_SCISSOR(bbox[0]);
+      sc->ScissorRectangleXMax = CLAMP_SCISSOR(bbox[1] - 1);
+      sc->ScissorRectangleYMin = CLAMP_SCISSOR(fb_height - bbox[3]);
+      sc->ScissorRectangleYMax = CLAMP_SCISSOR(fb_height - bbox[2] - 1);
    }
 }
 
-- 
2.7.4