From ab44a97ef03edca719418e665bc3c2ff0990281a Mon Sep 17 00:00:00 2001
From: keithw <keithw>
Date: Mon, 21 Jan 2002 15:59:52 +0000
Subject: Fray Bentos' occlusion test patch

---
 xc/lib/GL/mesa/src/drv/tdfx/tdfx_dd.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/xc/lib/GL/mesa/src/drv/tdfx/tdfx_dd.c b/xc/lib/GL/mesa/src/drv/tdfx/tdfx_dd.c
index 132bea2ad..b783b1ea9 100644
--- a/xc/lib/GL/mesa/src/drv/tdfx/tdfx_dd.c
+++ b/xc/lib/GL/mesa/src/drv/tdfx/tdfx_dd.c
@@ -160,6 +160,7 @@ static GLboolean get_occlusion_result( GLcontext *ctx )
    GLboolean result;
 
    LOCK_HARDWARE( fxMesa );
+   fxMesa->Glide.grFinish(); /* required to flush the FIFO - FB 21-01-2002 */ 
 
    if (ctx->Depth.OcclusionTest) {
       if (ctx->OcclusionResult) {
@@ -168,13 +169,12 @@ static GLboolean get_occlusion_result( GLcontext *ctx )
       else {
 	 FxI32 zfail, in;
          fxMesa->Glide.grGet(GR_STATS_PIXELS_DEPTHFUNC_FAIL, 4, &zfail);
-	 /*zfail = FX_grGetInteger_NoLock(GR_STATS_PIXELS_DEPTHFUNC_FAIL);*/
          fxMesa->Glide.grGet(GR_STATS_PIXELS_IN, 4, &in);
-	 /*in = FX_grGetInteger_NoLock(GR_STATS_PIXELS_IN);*/
-	 if (in == zfail)
-	    result = GL_FALSE; /* geom was completely occluded */
-	 else
-	    result = GL_TRUE;  /* all or part of geom was visible */
+         /* Geometry is occluded if there is no input (in == 0) */
+         /* or if all pixels failed the depth test (zfail == in) */
+         /* The < 1 is there because I have empirically seen cases where */
+         /* zfail > in.... go figure.  FB - 21-01-2002. */
+         result = ((in - zfail) < 1 || in == 0) ? GL_FALSE : GL_TRUE;
       }
    }
    else {
-- 
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