Add a big nasty fallback for AlphaTest -- seems to always be wrong

on CLE266 because Z values are written even for fragments which
fail the test.

src/mesa/drivers/dri/unichrome/via_context.c

@@ -504,7 +504,8 @@ viaCreateContext(const __GLcontextModes *mesaVis,
     if (getenv("VIA_NO_RAST"))
        FALLBACK(vmesa, VIA_FALLBACK_USER_DISABLE, 1);
 
-	
+    if (getenv("VIA_CONFORM"))
+       vmesa->strictConformance = 1;
 
     /* I don't understand why this isn't working:
      */

src/mesa/drivers/dri/unichrome/via_context.h

@@ -66,6 +66,7 @@ enum VIACHIPTAGS {
 #define VIA_FALLBACK_USER_DISABLE      	0x800
 #define VIA_FALLBACK_PROJ_TEXTURE      	0x1000
 #define VIA_FALLBACK_STIPPLE		0x2000
+#define VIA_FALLBACK_ALPHATEST		0x4000
 
 #define VIA_DMA_BUFSIZ                  4096
 #define VIA_DMA_HIGHWATER               (VIA_DMA_BUFSIZ - 128)
@@ -284,6 +285,8 @@ struct via_context_t {
    GLuint nDoneFirstFlip;
    GLuint agpFullCount;
 
+   GLboolean strictConformance;
+
    /* Configuration cache
     */
    driOptionCache optionCache;

src/mesa/drivers/dri/unichrome/via_ioctl.c

@@ -531,8 +531,11 @@ static void via_emit_cliprect(viaContextPtr vmesa,
 	    
    vb[4] = ((HC_SubA_HDBBasL << 24) | (offset & 0xFFFFFF));
    vb[5] = ((HC_SubA_HDBBasH << 24) | ((offset & 0xFF000000)) >> 24); 
-   vb[6] = ((HC_SubA_HDBFM << 24) | HC_HDBLoc_Local | format | pitch);            
-   vb[7] = 0xcccccccc;
+   vb[6] = ((HC_SubA_HDBFM << 24) | HC_HDBLoc_Local | format | pitch);     
+
+   /* Seems to be ignored on CLE266:
+    */
+   vb[7] = ((HC_SubA_HSPXYOS << 24) | ((32 - vmesa->drawXoff) << HC_HSPXOS_SHIFT));
 }
 
 

src/mesa/drivers/dri/unichrome/via_state.c

@@ -784,7 +784,11 @@ static void viaPolygonStipple( GLcontext *ctx, const GLubyte *mask )
     GLubyte *s = (GLubyte *)vmesa->stipple;
     int i;
 
-    /* Fallback for the CLE266 case as it doesn't seem to work */
+    /* Fallback for the CLE266 case.  Stipple works on the CLE266, but
+     * the stipple x/y offset registers don't seem to be respected,
+     * meaning that when drawXoff != 0, the stipple is rotated left or
+     * right by a few pixels, giving incorrect results.
+     */
     if (vmesa->viaScreen->deviceID == VIA_CLE266) {
    	FALLBACK( vmesa, VIA_FALLBACK_STIPPLE, ctx->Polygon.StippleFlag);
     } else {
@@ -1599,6 +1603,17 @@ void viaValidateState( GLcontext *ctx )
     else
         vmesa->regEnable &= ~HC_HenCS_MASK;
 
+    /* CLE266 gets this wrong at least: Pixels which fail alpha test
+     * are incorrectly writen to the z buffer.  This is a pretty big
+     * slowdown, it would be good to find out this wasn't necessary:
+     */
+    if (vmesa->viaScreen->deviceID == VIA_CLE266) {
+       GLboolean fallback = (ctx->Color.AlphaEnabled && 
+			     ctx->Color.AlphaFunc != GL_ALWAYS &&
+			     ctx->Depth.Mask);
+       FALLBACK( vmesa, VIA_FALLBACK_ALPHATEST, fallback );
+    }
+
     vmesa->newEmitState |= vmesa->newState;
     vmesa->newState = 0;
 }