Mesa (master): i965: texture fixes: bordered textures, fallback rendering

[Robert Ellison]

Module: Mesa
Branch: master
Commit: 17c7852bf93c4d4edf0c2cf0bdc553d399e2f51a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=17c7852bf93c4d4edf0c2cf0bdc553d399e2f51a

Author: Robert Ellison <papillo at vmware.com>
Date:   Fri Feb 27 00:21:07 2009 -0700

i965: texture fixes: bordered textures, fallback rendering

i965 doesn't natively support GL_CLAMP; it treats it like
GL_CLAMP_TO_EDGE, which fails conformance tests.

This fix adds a clause to the check_fallbacks() test to check
whether GL_CLAMP is in use on any enabled 2D texture.  If so,
and if strict conformance is required (via INTEL_STRICT_CONFORMANCE),
a software fallback is mandated.

In addition, validate textures *before* checking for fallbacks,
rather than after; otherwise, the texture state is never validated
and can't be trusted.  (In particular, if texturing is enabled and
the sampler would access any level beyond level 0 of a texture, the
sampler will segfault, because texture validation sets the firstLevel
and lastLevel fields of a texture object so that the valid levels
will be mapped and accessed correctly.  If texture validation doesn't
occur, only level 0 is accessed correctly, and that only because
firstLevel and lastLevel happen to be set to 0.)

---

 src/mesa/drivers/dri/i965/brw_draw.c |   34 +++++++++++++++++++++++++++++++---
 1 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_draw.c b/src/mesa/drivers/dri/i965/brw_draw.c
index 3ca953d..7ab1ece 100644
--- a/src/mesa/drivers/dri/i965/brw_draw.c
+++ b/src/mesa/drivers/dri/i965/brw_draw.c
@@ -194,6 +194,9 @@ static GLboolean check_fallbacks( struct brw_context *brw,
    GLcontext *ctx = &brw->intel.ctx;
    GLuint i;
 
+   /* If we don't require strict OpenGL conformance, never 
+    * use fallbacks.
+    */
    if (!brw->intel.strict_conformance)
       return GL_FALSE;
 
@@ -230,13 +233,31 @@ static GLboolean check_fallbacks( struct brw_context *brw,
       }
    }
 
-
    if (ctx->Point.SmoothFlag) {
       for (i = 0; i < nr_prims; i++)
 	 if (prim[i].mode == GL_POINTS) 
 	    return GL_TRUE;
    }
+
+   /* BRW hardware doesn't handle GL_CLAMP texturing correctly;
+    * brw_wm_sampler_state:translate_wrap_mode() treats GL_CLAMP
+    * as GL_CLAMP_TO_EDGE instead.  If we're using GL_CLAMP, and
+    * we want strict conformance, force the fallback.
+    * Right now, we only do this for 2D textures.
+    */
+   {
+      int u;
+      for (u = 0; u < ctx->Const.MaxTextureCoordUnits; u++) {
+         if (ctx->Texture.Unit[u].Enabled) {
+            if (ctx->Texture.Unit[u].CurrentTex[TEXTURE_2D_INDEX]->WrapS == GL_CLAMP ||
+                ctx->Texture.Unit[u].CurrentTex[TEXTURE_2D_INDEX]->WrapT == GL_CLAMP) {
+                   return GL_TRUE;
+            }
+         }
+      }
+   }
       
+   /* Nothing stopping us from the fast path now */
    return GL_FALSE;
 }
 
@@ -261,11 +282,18 @@ static GLboolean brw_try_draw_prims( GLcontext *ctx,
    if (ctx->NewState)
       _mesa_update_state( ctx );
 
+   /* We have to validate the textures *before* checking for fallbacks;
+    * otherwise, the software fallback won't be able to rely on the
+    * texture state, the firstLevel and lastLevel fields won't be
+    * set in the intel texture object (they'll both be 0), and the 
+    * software fallback will segfault if it attempts to access any
+    * texture level other than level 0.
+    */
+   brw_validate_textures( brw );
+
    if (check_fallbacks(brw, prim, nr_prims))
       return GL_FALSE;
 
-   brw_validate_textures( brw );
-
    /* Bind all inputs, derive varying and size information:
     */
    brw_merge_inputs( brw, arrays );