Fixed a number of minor GL_ARB_texture_env_combine/dot3 issues.

diff --git a/src/mesa/main/attrib.c b/src/mesa/main/attrib.c
index e856dc1f444ab09f18fc18a216e8590725fa2bc6..0acb2a95975d22393130a266f288443d55fedcfb 100644 (file)
--- a/src/mesa/main/attrib.c
+++ b/src/mesa/main/attrib.c
@@ -1,4 +1,4 @@
-/* $Id: attrib.c,v 1.48 2001/04/11 23:22:20 brianp Exp $ */
+/* $Id: attrib.c,v 1.49 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -602,7 +602,8 @@ pop_texture_group(GLcontext *ctx, const struct gl_texture_attrib *texAttrib)
          _mesa_TexEnvf(GL_TEXTURE_FILTER_CONTROL_EXT,
                        GL_TEXTURE_LOD_BIAS_EXT, unit->LodBias);
       }
-      if (ctx->Extensions.EXT_texture_env_combine) {
+      if (ctx->Extensions.EXT_texture_env_combine ||
+          ctx->Extensions.ARB_texture_env_combine) {
          _mesa_TexEnvi(GL_TEXTURE_ENV, GL_COMBINE_RGB_EXT,
                        unit->CombineModeRGB);
          _mesa_TexEnvi(GL_TEXTURE_ENV, GL_COMBINE_ALPHA_EXT,

diff --git a/src/mesa/main/enums.c b/src/mesa/main/enums.c
index 7b6dd53f02919eed630bfe7bb3f87122a5d4a50f..8510ce8105824e6a6adbb35f7b095c3144354f33 100644 (file)
--- a/src/mesa/main/enums.c
+++ b/src/mesa/main/enums.c
@@ -1,4 +1,4 @@
-/* $Id: enums.c,v 1.17 2001/04/16 21:07:33 brianp Exp $ */
+/* $Id: enums.c,v 1.18 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -833,6 +833,9 @@ enum_elt all_enums[] =
    { "GL_PRIMARY_COLOR_EXT", 0x8577 },
    { "GL_PREVIOUS_EXT", 0x8578 },
 
+   /* GL_ARB_texture_env_combine */
+   { "GL_SUBTRACT_ARB", 0x84E7 },
+
    /* GL_EXT_texture_env_dot3 */
    { "GL_DOT3_RGB_EXT", 0x8740 },
    { "GL_DOT3_RGBA_EXT", 0x8741 },

diff --git a/src/mesa/main/extensions.c b/src/mesa/main/extensions.c
index 372b2bb6879654e3a32201504c22044c1820de43..2c54d0edaf60564578b7f292f558fe317652668a 100644 (file)
--- a/src/mesa/main/extensions.c
+++ b/src/mesa/main/extensions.c
@@ -1,4 +1,4 @@
-/* $Id: extensions.c,v 1.56 2001/03/26 19:42:40 brianp Exp $ */
+/* $Id: extensions.c,v 1.57 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -62,8 +62,8 @@ static struct {
    { OFF, "GL_ARB_texture_compression",        F(ARB_texture_compression) },
    { OFF, "GL_ARB_texture_cube_map",           F(ARB_texture_cube_map) },
    { OFF, "GL_ARB_texture_env_add",            F(EXT_texture_env_add) },
-   { OFF, "GL_ARB_texture_env_combine",        F(EXT_texture_env_combine) },
-   { OFF, "GL_ARB_texture_env_dot3",           F(EXT_texture_env_dot3) },
+   { OFF, "GL_ARB_texture_env_combine",        F(ARB_texture_env_combine) },
+   { OFF, "GL_ARB_texture_env_dot3",           F(ARB_texture_env_dot3) },
    { ON,  "GL_ARB_tranpose_matrix",            0 },
    { ON,  "GL_EXT_abgr",                       0 },
    { ON,  "GL_EXT_bgra",                       0 },

diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 8113a243d4ed4852c3ee886caa39361287d08130..42a8b28c58aad07963e35f56763667decadf8b3c 100644 (file)
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1,4 +1,4 @@
-/* $Id: mtypes.h,v 1.38 2001/03/29 21:16:25 keithw Exp $ */
+/* $Id: mtypes.h,v 1.39 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -1173,6 +1173,8 @@ struct gl_extensions {
    GLboolean ARB_texture_border_clamp;
    GLboolean ARB_texture_compression;
    GLboolean ARB_texture_cube_map;
+   GLboolean ARB_texture_env_combine;
+   GLboolean ARB_texture_env_dot3;
    GLboolean EXT_blend_color;
    GLboolean EXT_blend_func_separate;
    GLboolean EXT_blend_logic_op;

diff --git a/src/mesa/main/texstate.c b/src/mesa/main/texstate.c
index a52d3ef862f72a8f9278fe1f50567e7638852d4d..3770df3898f3b129d1231e3b2c46d7536f94cd90 100644 (file)
--- a/src/mesa/main/texstate.c
+++ b/src/mesa/main/texstate.c
@@ -1,4 +1,4 @@
-/* $Id: texstate.c,v 1.43 2001/04/16 21:06:54 brianp Exp $ */
+/* $Id: texstate.c,v 1.44 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -68,6 +68,10 @@
 #define GL_CLAMP_TO_BORDER_ARB 0x812D
 #endif
 
+#ifndef GL_SUBTRACT_ARB
+#define GL_SUBTRACT_ARB 0x84E7
+#endif
+
 
 /**********************************************************************/
 /*                       Texture Environment                          */
@@ -101,7 +105,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
            }
            break;
         case GL_COMBINE_EXT:
-           if (!ctx->Extensions.EXT_texture_env_combine) {
+           if (!ctx->Extensions.EXT_texture_env_combine &&
+                !ctx->Extensions.ARB_texture_env_combine) {
               ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
               return;
            }
@@ -135,20 +140,33 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         break;
       }
       case GL_COMBINE_RGB_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
-           GLenum mode = (GLenum) (GLint) *param;
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
+           const GLenum mode = (GLenum) (GLint) *param;
            switch (mode) {
            case GL_REPLACE:
            case GL_MODULATE:
            case GL_ADD:
            case GL_ADD_SIGNED_EXT:
            case GL_INTERPOLATE_EXT:
+               /* OK */
               break;
+            case GL_SUBTRACT_ARB:
+               if (!ctx->Extensions.ARB_texture_env_combine) {
+                  ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
+                  return;
+               }
+               break;
            case GL_DOT3_RGB_EXT:
            case GL_DOT3_RGBA_EXT:
+              if (!ctx->Extensions.EXT_texture_env_dot3) {
+                  ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
+                 return;
+              }
+              break;
            case GL_DOT3_RGB_ARB:
            case GL_DOT3_RGBA_ARB:
-              if (!ctx->Extensions.EXT_texture_env_dot3) {
+              if (!ctx->Extensions.ARB_texture_env_dot3) {
                   ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
                  return;
               }
@@ -168,23 +186,31 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         }
          break;
       case GL_COMBINE_ALPHA_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
-           GLenum mode = (GLenum) (GLint) *param;
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
+           const GLenum mode = (GLenum) (GLint) *param;
            switch (mode) {
            case GL_REPLACE:
            case GL_MODULATE:
            case GL_ADD:
            case GL_ADD_SIGNED_EXT:
            case GL_INTERPOLATE_EXT:
-              if (texUnit->CombineModeA == mode)
-                 return;
-              FLUSH_VERTICES(ctx, _NEW_TEXTURE);
-              texUnit->CombineModeA = mode;
+               /* OK */
               break;
+            case GL_SUBTRACT_ARB:
+               if (!ctx->Extensions.ARB_texture_env_combine) {
+                  ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
+                  return;
+               }
+               break;
            default:
                ERROR(GL_INVALID_ENUM, "glTexEnv(param=%s)", mode);
               return;
            }
+            if (texUnit->CombineModeA == mode)
+               return;
+            FLUSH_VERTICES(ctx, _NEW_TEXTURE);
+            texUnit->CombineModeA = mode;
         }
         else {
             ERROR(GL_INVALID_ENUM, "glTexEnv(pname=%s)", pname);
@@ -194,7 +220,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
       case GL_SOURCE0_RGB_EXT:
       case GL_SOURCE1_RGB_EXT:
       case GL_SOURCE2_RGB_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+            ctx->Extensions.ARB_texture_env_combine) {
            GLenum source = (GLenum) (GLint) *param;
            GLuint s = pname - GL_SOURCE0_RGB_EXT;
            switch (source) {
@@ -220,7 +247,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
       case GL_SOURCE0_ALPHA_EXT:
       case GL_SOURCE1_ALPHA_EXT:
       case GL_SOURCE2_ALPHA_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLenum source = (GLenum) (GLint) *param;
            GLuint s = pname - GL_SOURCE0_ALPHA_EXT;
            switch (source) {
@@ -244,7 +272,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         break;
       case GL_OPERAND0_RGB_EXT:
       case GL_OPERAND1_RGB_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+            ctx->Extensions.ARB_texture_env_combine) {
            GLenum operand = (GLenum) (GLint) *param;
            GLuint s = pname - GL_OPERAND0_RGB_EXT;
            switch (operand) {
@@ -269,7 +298,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         break;
       case GL_OPERAND0_ALPHA_EXT:
       case GL_OPERAND1_ALPHA_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLenum operand = (GLenum) (GLint) *param;
            switch (operand) {
            case GL_SRC_ALPHA:
@@ -291,7 +321,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         }
         break;
       case GL_OPERAND2_RGB_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLenum operand = (GLenum) (GLint) *param;
            switch (operand) {
            case GL_SRC_COLOR:           /* ARB combine only */
@@ -313,7 +344,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         }
         break;
       case GL_OPERAND2_ALPHA_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLenum operand = (GLenum) (GLint) *param;
            switch (operand) {
            case GL_SRC_ALPHA:
@@ -334,7 +366,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         }
         break;
       case GL_RGB_SCALE_EXT:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLuint newshift;
            if (*param == 1.0) {
               newshift = 0;
@@ -361,7 +394,8 @@ _mesa_TexEnvfv( GLenum target, GLenum pname, const GLfloat *param )
         }
         break;
       case GL_ALPHA_SCALE:
-        if (ctx->Extensions.EXT_texture_env_combine) {
+        if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
            GLuint newshift;
            if (*param == 1.0) {
               newshift = 0;
@@ -478,7 +512,8 @@ _mesa_GetTexEnvfv( GLenum target, GLenum pname, GLfloat *params )
         COPY_4FV( params, texUnit->EnvColor );
         break;
       case GL_RGB_SCALE_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             if (texUnit->CombineScaleShiftRGB == 0)
                *params = 1.0;
             else if (texUnit->CombineScaleShiftRGB == 1)
@@ -492,7 +527,8 @@ _mesa_GetTexEnvfv( GLenum target, GLenum pname, GLfloat *params )
          }
          break;
       case GL_ALPHA_SCALE:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             if (texUnit->CombineScaleShiftA == 0)
                *params = 1.0;
             else if (texUnit->CombineScaleShiftA == 1)
@@ -534,7 +570,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
         params[3] = FLOAT_TO_INT( texUnit->EnvColor[3] );
          break;
       case GL_COMBINE_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineModeRGB;
          }
          else {
@@ -542,7 +579,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_COMBINE_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineModeA;
          }
          else {
@@ -550,7 +588,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE0_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceRGB[0];
          }
          else {
@@ -558,7 +597,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE1_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceRGB[1];
          }
          else {
@@ -566,7 +606,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE2_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceRGB[2];
          }
          else {
@@ -574,7 +615,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE0_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceA[0];
          }
          else {
@@ -582,7 +624,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE1_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceA[1];
          }
          else {
@@ -590,7 +633,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_SOURCE2_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineSourceA[2];
          }
          else {
@@ -598,7 +642,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND0_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandRGB[0];
          }
          else {
@@ -606,7 +651,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND1_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandRGB[1];
          }
          else {
@@ -614,7 +660,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND2_RGB_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandRGB[2];
          }
          else {
@@ -622,7 +669,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND0_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandA[0];
          }
          else {
@@ -630,7 +678,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND1_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandA[1];
          }
          else {
@@ -638,7 +687,8 @@ _mesa_GetTexEnviv( GLenum target, GLenum pname, GLint *params )
          }
          break;
       case GL_OPERAND2_ALPHA_EXT:
-         if (ctx->Extensions.EXT_texture_env_combine) {
+         if (ctx->Extensions.EXT_texture_env_combine ||
+             ctx->Extensions.ARB_texture_env_combine) {
             *params = (GLint) texUnit->CombineOperandA[2];
          }
          else {

diff --git a/src/mesa/swrast/s_texture.c b/src/mesa/swrast/s_texture.c
index 7f932f8b13ecab7ed5d2b10f8b29fce28bca2921..78c38c07fd97b5d429cddf370a66dbbda1f7c990 100644 (file)
--- a/src/mesa/swrast/s_texture.c
+++ b/src/mesa/swrast/s_texture.c
@@ -1,4 +1,4 @@
-/* $Id: s_texture.c,v 1.23 2001/04/12 15:18:07 brianp Exp $ */
+/* $Id: s_texture.c,v 1.24 2001/04/17 21:25:53 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -52,6 +52,10 @@
 #define GL_CLAMP_TO_BORDER_ARB 0x812D
 #endif
 
+#ifndef GL_SUBTRACT_ARB
+#define GL_SUBTRACT_ARB 0x84E7
+#endif
+
 
 /*
  * These values are used in the fixed-point arithmetic used
@@ -1763,7 +1767,8 @@ texture_combine(const GLcontext *ctx,
    const GLuint RGBshift = textureUnit->CombineScaleShiftRGB;
    const GLuint Ashift   = textureUnit->CombineScaleShiftA;
 
-   ASSERT(ctx->Extensions.EXT_texture_env_combine);
+   ASSERT(ctx->Extensions.EXT_texture_env_combine ||
+          ctx->Extensions.ARB_texture_env_combine);
 
    /*
     * Do operand setup for up to 3 operands.  Loop over the terms.
@@ -1968,6 +1973,20 @@ 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];
+            for (i = 0; i < n; i++) {
+               GLint r = ((GLint) arg0[i][RCOMP] - (GLint) arg1[i][RCOMP]) << RGBshift;
+               GLint g = ((GLint) arg0[i][GCOMP] - (GLint) arg1[i][GCOMP]) << RGBshift;
+               GLint b = ((GLint) arg0[i][BCOMP] - (GLint) arg1[i][BCOMP]) << RGBshift;
+               rgba[i][RCOMP] = (GLchan) CLAMP(r, 0, CHAN_MAX);
+               rgba[i][GCOMP] = (GLchan) CLAMP(g, 0, CHAN_MAX);
+               rgba[i][BCOMP] = (GLchan) CLAMP(b, 0, CHAN_MAX);
+            }
+         }
+         break;
       case GL_DOT3_RGB_EXT:
       case GL_DOT3_RGBA_EXT:
       case GL_DOT3_RGB_ARB:
@@ -2059,6 +2078,17 @@ 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];
+            for (i = 0; i < n; i++) {
+               GLint a = ((GLint) arg0[i][ACOMP] - (GLint) arg1[i][ACOMP]) << RGBshift;
+               rgba[i][ACOMP] = (GLchan) CLAMP(a, 0, CHAN_MAX);
+            }
+         }
+         break;
+
       default:
          _mesa_problem(NULL, "invalid combine mode");
    }