[Mesa-dev] [PATCH] i965: fix inverted point sprite origin when rendering to FBO

[Yuanhan Liu]

When rendering to FBO, rendering is inverted. At the same time, we would
also make sure the point sprite origin is inverted. Or, we will get an
inverted result correspoinding to rendering to the default winsys FBO.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44613

NOTE: This is a candidate for stable release branches.

v2: add the simliar logic to ivb, too (comments from Ian)
    simplify the logic operation (comments from Brian)

v3: pick a better comment from Eric
    use != for the logic instead of ^ (comments from Ian)

Signed-off-by: Yuanhan Liu <yuanhan.liu at linux.intel.com>
---
 src/mesa/drivers/dri/i965/brw_defines.h   |    1 +
 src/mesa/drivers/dri/i965/gen6_sf_state.c |   13 +++++++++++--
 src/mesa/drivers/dri/i965/gen7_sf_state.c |   18 +++++++++++++++---
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
index 4d90a99..029be87 100644
--- a/src/mesa/drivers/dri/i965/brw_defines.h
+++ b/src/mesa/drivers/dri/i965/brw_defines.h
@@ -1128,6 +1128,7 @@ enum brw_message_target {
 /* DW1 (for gen6) */
 # define GEN6_SF_NUM_OUTPUTS_SHIFT			22
 # define GEN6_SF_SWIZZLE_ENABLE				(1 << 21)
+# define GEN6_SF_POINT_SPRITE_UPPERLEFT			(0 << 20)
 # define GEN6_SF_POINT_SPRITE_LOWERLEFT			(1 << 20)
 # define GEN6_SF_URB_ENTRY_READ_LENGTH_SHIFT		11
 # define GEN6_SF_URB_ENTRY_READ_OFFSET_SHIFT		4
diff --git a/src/mesa/drivers/dri/i965/gen6_sf_state.c b/src/mesa/drivers/dri/i965/gen6_sf_state.c
index 548c5a3..163b54c 100644
--- a/src/mesa/drivers/dri/i965/gen6_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen6_sf_state.c
@@ -129,6 +129,7 @@ upload_sf_state(struct brw_context *brw)
    float point_size;
    uint16_t attr_overrides[FRAG_ATTRIB_MAX];
    bool userclip_active;
+   uint32_t point_sprite_origin;
 
    /* _NEW_TRANSFORM */
    userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
@@ -258,8 +259,16 @@ upload_sf_state(struct brw_context *brw)
    /* Clamp to the hardware limits and convert to fixed point */
    dw4 |= U_FIXED(CLAMP(point_size, 0.125, 255.875), 3);
 
-   if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT)
-      dw1 |= GEN6_SF_POINT_SPRITE_LOWERLEFT;
+   /*
+    * Window coordinates in an FBO are inverted, which means point
+    * sprite origin must be inverted, too.
+    */
+   if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo) {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_LOWERLEFT;
+   } else {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_UPPERLEFT;
+   }
+   dw1 |= point_sprite_origin;
 
    /* _NEW_LIGHT */
    if (ctx->Light.ProvokingVertex != GL_FIRST_VERTEX_CONVENTION) {
diff --git a/src/mesa/drivers/dri/i965/gen7_sf_state.c b/src/mesa/drivers/dri/i965/gen7_sf_state.c
index 7691cb2..da7ef81 100644
--- a/src/mesa/drivers/dri/i965/gen7_sf_state.c
+++ b/src/mesa/drivers/dri/i965/gen7_sf_state.c
@@ -48,6 +48,9 @@ upload_sbe_state(struct brw_context *brw)
    int urb_entry_read_offset = 1;
    bool userclip_active = (ctx->Transform.ClipPlanesEnabled != 0);
    uint16_t attr_overrides[FRAG_ATTRIB_MAX];
+   /* _NEW_BUFFERS */
+   bool render_to_fbo = ctx->DrawBuffer->Name != 0;
+   uint32_t point_sprite_origin;
 
    brw_compute_vue_map(&vue_map, intel, userclip_active, vs_outputs_written);
    urb_entry_read_length = (vue_map.num_slots + 1)/2 - urb_entry_read_offset;
@@ -65,9 +68,18 @@ upload_sbe_state(struct brw_context *brw)
       urb_entry_read_length << GEN7_SBE_URB_ENTRY_READ_LENGTH_SHIFT |
       urb_entry_read_offset << GEN7_SBE_URB_ENTRY_READ_OFFSET_SHIFT;
 
-   /* _NEW_POINT */
-   if (ctx->Point.SpriteOrigin == GL_LOWER_LEFT)
-      dw1 |= GEN6_SF_POINT_SPRITE_LOWERLEFT;
+   /* _NEW_POINT
+    *
+    * Window coordinates in an FBO are inverted, which means point
+    * sprite origin must be inverted.
+    */
+   if ((ctx->Point.SpriteOrigin == GL_LOWER_LEFT) != render_to_fbo) {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_LOWERLEFT;
+   } else {
+      point_sprite_origin = GEN6_SF_POINT_SPRITE_UPPERLEFT;
+   }
+   dw1 |= point_sprite_origin;
+
 
    dw10 = 0;
    dw11 = 0;
-- 
1.7.4.4