From 486734a5d50ff9114b567b5e9eac6337248a80e6 Mon Sep 17 00:00:00 2001
From: Brian Paul <brian.paul@tungstengraphics.com>
Date: Thu, 4 Apr 2002 16:56:24 +0000
Subject: [PATCH] Texture combine alpha subtraction was wrong.  Fixed 16-bit
 channel glitches

---
 src/mesa/swrast/s_texture.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/mesa/swrast/s_texture.c b/src/mesa/swrast/s_texture.c
index e1ba9584177..617c04ca68a 100644
--- a/src/mesa/swrast/s_texture.c
+++ b/src/mesa/swrast/s_texture.c
@@ -1,4 +1,4 @@
-/* $Id: s_texture.c,v 1.57 2002/03/23 16:33:53 brianp Exp $ */
+/* $Id: s_texture.c,v 1.58 2002/04/04 16:56:24 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -2542,6 +2542,16 @@ texture_combine(const GLcontext *ctx,
    ASSERT(ctx->Extensions.EXT_texture_env_combine ||
           ctx->Extensions.ARB_texture_env_combine);
 
+   /*
+   printf("modeRGB 0x%x  modeA 0x%x  srcRGB1 0x%x  srcA1 0x%x  srcRGB2 0x%x  srcA2 0x%x\n",
+          textureUnit->CombineModeRGB,
+          textureUnit->CombineModeA,
+          textureUnit->CombineSourceRGB[0],
+          textureUnit->CombineSourceA[0],
+          textureUnit->CombineSourceRGB[1],
+          textureUnit->CombineSourceA[1]);
+   */
+
    /*
     * Do operand setup for up to 3 operands.  Loop over the terms.
     */
@@ -2689,7 +2699,7 @@ texture_combine(const GLcontext *ctx,
             const GLchan (*arg0)[4] = (const GLchan (*)[4]) argRGB[0];
             const GLchan (*arg1)[4] = (const GLchan (*)[4]) argRGB[1];
 #if CHAN_TYPE != GL_FLOAT
-            const GLint shift = 8 - RGBshift;
+            const GLint shift = CHAN_BITS - RGBshift;
 #endif
             for (i = 0; i < n; i++) {
 #if CHAN_TYPE == GL_FLOAT
@@ -2756,7 +2766,7 @@ texture_combine(const GLcontext *ctx,
             const GLchan (*arg1)[4] = (const GLchan (*)[4]) argRGB[1];
             const GLchan (*arg2)[4] = (const GLchan (*)[4]) argRGB[2];
 #if CHAN_TYPE != GL_FLOAT
-            const GLint shift = 8 - RGBshift;
+            const GLint shift = CHAN_BITS - RGBshift;
 #endif
             for (i = 0; i < n; i++) {
 #if CHAN_TYPE == GL_FLOAT
@@ -2861,7 +2871,7 @@ texture_combine(const GLcontext *ctx,
             const GLchan (*arg0)[4] = (const GLchan (*)[4]) argA[0];
             const GLchan (*arg1)[4] = (const GLchan (*)[4]) argA[1];
 #if CHAN_TYPE != GL_FLOAT
-            const GLint shift = 8 - Ashift;
+            const GLint shift = CHAN_BITS - Ashift;
 #endif
             for (i = 0; i < n; i++) {
 #if CHAN_TYPE == GL_FLOAT
@@ -2908,7 +2918,7 @@ texture_combine(const GLcontext *ctx,
             const GLchan (*arg1)[4] = (const GLchan (*)[4]) argA[1];
             const GLchan (*arg2)[4] = (const GLchan (*)[4]) argA[2];
 #if CHAN_TYPE != GL_FLOAT
-            const GLint shift = 8 - Ashift;
+            const GLint shift = CHAN_BITS - Ashift;
 #endif
             for (i=0; i<n; i++) {
 #if CHAN_TYPE == GL_FLOAT
@@ -2926,13 +2936,13 @@ texture_combine(const GLcontext *ctx,
          break;
       case GL_SUBTRACT_ARB:
          {
-            const GLchan (*arg0)[4] = (const GLchan (*)[4]) argRGB[0];
-            const GLchan (*arg1)[4] = (const GLchan (*)[4]) argRGB[1];
+            const GLchan (*arg0)[4] = (const GLchan (*)[4]) argA[0];
+            const GLchan (*arg1)[4] = (const GLchan (*)[4]) argA[1];
             for (i = 0; i < n; i++) {
 #if CHAN_TYPE == GL_FLOAT
                rgba[i][ACOMP] = (arg0[i][ACOMP] - arg1[i][ACOMP]) * Amult;
 #else
-               GLint a = ((GLint) arg0[i][ACOMP] - (GLint) arg1[i][ACOMP]) << RGBshift;
+               GLint a = ((GLint) arg0[i][ACOMP] - (GLint) arg1[i][ACOMP]) << Ashift;
                rgba[i][ACOMP] = (GLchan) CLAMP(a, 0, CHAN_MAX);
 #endif
             }
-- 
2.30.2