Changeset 3598 for trunk/src/opengl/mesa/stencil.c

Timestamp:

May 23, 2000, 10:41:28 PM (25 years ago)

Author:

jeroen

Message:

* empty log message *

File:

• trunk/src/opengl/mesa/stencil.c (modified) (33 diffs)

trunk/src/opengl/mesa/stencil.c

@@ -1 @@
-/* $Id: stencil.c,v 1.2 2000-03-01 18:49:35 jeroen Exp $ */
+/* $Id: stencil.c,v 1.3 2000-05-23 20:40:54 jeroen Exp $ */
 
 /*
  * Mesa 3-D graphics library
- * Version:  3.1
+ * Version:  3.3
  *
  * Copyright (C) 1999  Brian Paul   All Rights Reserved.
@@ -31 +31 @@
 #include "all.h"
 #else
-#ifndef XFree86Server
-#include <stdlib.h>
-#include <string.h>
-#else
-#include "GL/xf86glx.h"
-#endif
+#include "glheader.h"
 #include "types.h"
 #include "context.h"
@@ -43 +38 @@
 #include "stencil.h"
 #include "enable.h"
+#include "mem.h"
+#include "depth.h"
 #endif
 
 
 
-/*
- * Return the address of a stencil buffer value given the window coords:
- */
-#define STENCIL_ADDRESS(X,Y)  (ctx->Buffer->Stencil + ctx->Buffer->Width * (Y) + (X))
-
-
-void gl_ClearStencil( GLcontext *ctx, GLint s )
-{
+void
+_mesa_ClearStencil( GLint s )
+{
+   GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glClearStencil");
    ctx->Stencil.Clear = (GLstencil) s;
@@ -65 +58 @@
 
 
-void gl_StencilFunc( GLcontext *ctx, GLenum func, GLint ref, GLuint mask )
-{
+void
+_mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
+{
+   GET_CURRENT_CONTEXT(ctx);
    GLint maxref;
 
@@ -98 +93 @@
 
 
-void gl_StencilMask( GLcontext *ctx, GLuint mask )
-{
+void
+_mesa_StencilMask( GLuint mask )
+{
+   GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glStencilMask");
    ctx->Stencil.WriteMask = (GLstencil) mask;
@@ -110 +107 @@
 
 
-void gl_StencilOp( GLcontext *ctx, GLenum fail, GLenum zfail, GLenum zpass )
-{
+void
+_mesa_StencilOp( GLenum fail, GLenum zfail, GLenum zpass )
+{
+   GET_CURRENT_CONTEXT(ctx);
    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glStencilOp");
    switch (fail) {
@@ -185 +184 @@
 
 /*
+ * Return the address of a stencil buffer value given the window coords:
+ */
+#define STENCIL_ADDRESS(X,Y)  \
+       (ctx->DrawBuffer->Stencil + ctx->DrawBuffer->Width * (Y) + (X))
+
+
+
+/*
  * Apply the given stencil operator to the array of stencil values.
  * Don't touch stencil[i] if mask[i] is zero.
- * Input:  n - number of pixels in the span
+ * Input:  n - size of stencil array
  *         oper - the stencil buffer operator
  *         stencil - array of stencil values
  *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
+ * Output:  stencil - modified values
  */
-static void apply_stencil_op( GLcontext *ctx, GLenum oper,
-                              GLuint n, GLstencil stencil[], GLubyte mask[] )
+static void apply_stencil_op( const GLcontext *ctx, GLenum oper,
+                              GLuint n, GLstencil stencil[],
+                              const GLubyte mask[] )
 {
    const GLstencil ref = ctx->Stencil.Ref;
@@ -205 +214 @@
          break;
       case GL_ZERO:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  stencil[i] = 0;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  stencil[i] = (GLstencil) (stencil[i] & invmask);
-               }
-            }
-         }
-         break;
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  stencil[i] = 0;
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  stencil[i] = (GLstencil) (stencil[i] & invmask);
+               }
+            }
+         }
+         break;
       case GL_REPLACE:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   stencil[i] = ref;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  GLstencil s = stencil[i];
-                  stencil[i] = (GLstencil) ((invmask & s ) | (wrtmask & ref));
-               }
-            }
-         }
-         break;
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  GLstencil s = stencil[i];
+                  stencil[i] = (GLstencil) ((invmask & s ) | (wrtmask & ref));
+               }
+            }
+         }
+         break;
       case GL_INCR:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  GLstencil s = stencil[i];
-                  if (s < STENCIL_MAX) {
-                     stencil[i] = (GLstencil) (s+1);
-                  }
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  /* VERIFY logic of adding 1 to a write-masked value */
-                  GLstencil s = stencil[i];
-                  if (s < STENCIL_MAX) {
-                     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s+1)));
-                  }
-               }
-            }
-         }
-         break;
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  GLstencil s = stencil[i];
+                  if (s < STENCIL_MAX) {
+                     stencil[i] = (GLstencil) (s+1);
+                  }
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  /* VERIFY logic of adding 1 to a write-masked value */
+                  GLstencil s = stencil[i];
+                  if (s < STENCIL_MAX) {
+                     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s+1)));
+                  }
+               }
+            }
+         }
+         break;
       case GL_DECR:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  GLstencil s = stencil[i];
-                  if (s>0) {
-                     stencil[i] = (GLstencil) (s-1);
-                  }
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  /* VERIFY logic of subtracting 1 to a write-masked value */
-                  GLstencil s = stencil[i];
-                  if (s>0) {
-                     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s-1)));
-                  }
-               }
-            }
-         }
-         break;
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  GLstencil s = stencil[i];
+                  if (s>0) {
+                     stencil[i] = (GLstencil) (s-1);
+                  }
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  /* VERIFY logic of subtracting 1 to a write-masked value */
+                  GLstencil s = stencil[i];
+                  if (s>0) {
+                     stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s-1)));
+                  }
+               }
+            }
+         }
+         break;
       case GL_INCR_WRAP_EXT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   stencil[i]++;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil s = stencil[i];
-                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (stencil[i]+1)));
-               }
-            }
-         }
-         break;
+                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s+1)));
+               }
+            }
+         }
+         break;
       case GL_DECR_WRAP_EXT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  stencil[i]--;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  stencil[i]--;
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil s = stencil[i];
-                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (stencil[i]-1)));
-               }
-            }
-         }
-         break;
+                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & (s-1)));
+               }
+            }
+         }
+         break;
       case GL_INVERT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  GLstencil s = stencil[i];
-                  stencil[i] = (GLstencil) ~s;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
-                  GLstencil s = stencil[i];
-                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & ~s));
-               }
-            }
-         }
-         break;
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  GLstencil s = stencil[i];
+                  stencil[i] = (GLstencil) ~s;
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
+                  GLstencil s = stencil[i];
+                  stencil[i] = (GLstencil) ((invmask & s) | (wrtmask & ~s));
+               }
+            }
+         }
+         break;
       default:
          gl_problem(ctx, "Bad stencil op in apply_stencil_op");
@@ -342 +351 @@
 
 
-
 /*
- * Apply stencil test to a span of pixels before depth buffering.
- * Input:  n - number of pixels in the span
- *         x, y - coordinate of left-most pixel in the span
+ * Apply stencil test to an array of stencil values (before depth buffering).
+ * Input:  n - number of pixels in the array
+ *         stencil - array of [n] stencil values
  *         mask - array [n] of flag:  0=skip the pixel, 1=stencil the pixel
  * Output:  mask - pixels which fail the stencil test will have their
  *                 mask flag set to 0.
- * Return:  0 = all pixels failed, 1 = zero or more pixels passed.
+ *          stencil - updated stencil values (where the test passed)
+ * Return:  GL_FALSE = all pixels failed, GL_TRUE = zero or more pixels passed.
  */
-GLint gl_stencil_span( GLcontext *ctx,
-                       GLuint n, GLint x, GLint y, GLubyte mask[] )
-{
-   GLubyte fail[MAX_WIDTH];
-   GLint allfail = 0;
+static GLboolean
+do_stencil_test( GLcontext *ctx, GLuint n, GLstencil stencil[],
+                 GLubyte mask[] )
+{
+   GLubyte fail[PB_SIZE];
+   GLboolean allfail = GL_FALSE;
    GLuint i;
    GLstencil r, s;
-   GLstencil *stencil;
-
-   stencil = STENCIL_ADDRESS( x, y );
+
+   ASSERT(n <= PB_SIZE);
 
    /*
@@ -376 +385 @@
          /* always fail */
          for (i=0;i<n;i++) {
-            if (mask[i]) {
-               mask[i] = 0;
-               fail[i] = 1;
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         allfail = 1;
-         break;
+            if (mask[i]) {
+               mask[i] = 0;
+               fail[i] = 1;
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         allfail = GL_TRUE;
+         break;
       case GL_LESS:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r < s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r < s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_LEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r <= s) {
-                  /* pass */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r <= s) {
+                  /* pass */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_GREATER:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r > s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r > s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_GEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r >= s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r >= s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_EQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r == s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r == s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_NOTEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
-               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
-               if (r != s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
+               s = (GLstencil) (stencil[i] & ctx->Stencil.ValueMask);
+               if (r != s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_ALWAYS:
-         /* always pass */
-         for (i=0;i<n;i++) {
-            fail[i] = 0;
-         }
-         break;
+         /* always pass */
+         for (i=0;i<n;i++) {
+            fail[i] = 0;
+         }
+         break;
       default:
          gl_problem(ctx, "Bad stencil func in gl_stencil_span");
@@ -515 +524 @@
    }
 
-   return (allfail) ? 0 : 1;
+   return !allfail;
 }
 
@@ -522 +531 @@
 
 /*
- * Apply the combination depth-buffer/stencil operator to a span of pixels.
+ * Apply stencil and depth testing to an array of pixels.
+ * Hardware or software stencil buffer acceptable.
  * Input:  n - number of pixels in the span
- *         x, y - location of leftmost pixel in span
  *         z - array [n] of z values
- * Input:  mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
- * Output:  mask - array [n] of flags (1=depth test passed, 0=failed)
+ *         stencil - array [n] of stencil values
+ *         mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
+ * Output:  stencil - modified stencil values
+ *          mask - array [n] of flags (1=stencil and depth test passed)
+ * Return: GL_TRUE - all fragments failed the testing
+ *         GL_FALSE - one or more fragments passed the testing
+ *
  */
-void gl_depth_stencil_span( GLcontext *ctx,
-                            GLuint n, GLint x, GLint y, const GLdepth z[],
-                            GLubyte mask[] )
-{
-   GLstencil *stencil = STENCIL_ADDRESS(x, y);
-
+static GLboolean
+stencil_and_depth_test_span( GLcontext *ctx, GLuint n, GLint x, GLint y,
+                             const GLdepth z[], GLstencil stencil[],
+                             GLubyte mask[] )
+{
+   ASSERT(ctx->Stencil.Enabled);
+   ASSERT(n <= PB_SIZE);
+
+   /*
+    * Apply the stencil test to the fragments.
+    * failMask[i] is 1 if the stencil test failed.
+    */
+   if (do_stencil_test( ctx, n, stencil, mask ) == GL_FALSE) {
+      /* all fragments failed the stencil test, we're done. */
+      return GL_FALSE;
+   }
+
+
+   /*
+    * Some fragments passed the stencil test, apply depth test to them
+    * and apply Zpass and Zfail stencil ops.
+    */
    if (ctx->Depth.Test==GL_FALSE) {
       /*
@@ -552 +582 @@
 
       /* apply the depth test */
-      if (ctx->Driver.DepthTestSpan)
-         (*ctx->Driver.DepthTestSpan)( ctx, n, x, y, z, mask );
+      _mesa_depth_test_span(ctx, n, x, y, z, mask);
 
       /* Set the stencil pass/fail flags according to result of depth testing.
@@ -561 +590 @@
        *    Depth test passed
        * else
-       *    assert(oldmask[i] && !newmask[i])
+       *    ASSERT(oldmask[i] && !newmask[i])
        *    Depth test failed
        * endif
@@ -579 +608 @@
       }
    }
+
+   return GL_TRUE;  /* one or more fragments passed both tests */
+}
+
+
+
+/*
+ * Apply stencil and depth testing to the span of pixels.
+ * Both software and hardware stencil buffers are acceptable.
+ * Input:  n - number of pixels in the span
+ *         x, y - location of leftmost pixel in span
+ *         z - array [n] of z values
+ *         mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
+ * Output:  mask - array [n] of flags (1=stencil and depth test passed)
+ * Return: GL_TRUE - all fragments failed the testing
+ *         GL_FALSE - one or more fragments passed the testing
+ *
+ */
+GLboolean
+gl_stencil_and_depth_test_span( GLcontext *ctx, GLuint n, GLint x, GLint y,
+                                const GLdepth z[], GLubyte mask[] )
+{
+   GLstencil stencilRow[MAX_WIDTH];
+   GLstencil *stencil;
+   GLboolean result;
+
+   ASSERT(ctx->Stencil.Enabled);
+   ASSERT(n <= MAX_WIDTH);
+
+   /* Get initial stencil values */
+   if (ctx->Driver.WriteStencilSpan) {
+      ASSERT(ctx->Driver.ReadStencilSpan);
+      /* Get stencil values from the hardware stencil buffer */
+      (*ctx->Driver.ReadStencilSpan)(ctx, n, x, y, stencilRow);
+      stencil = stencilRow;
+   }
+   else {
+      /* software stencil buffer */
+      stencil = STENCIL_ADDRESS(x, y);
+   }
+
+   /* do all the stencil/depth testing/updating */
+   result = stencil_and_depth_test_span( ctx, n, x, y, z, stencil, mask );
+
+   if (ctx->Driver.WriteStencilSpan) {
+      /* Write updated stencil values into hardware stencil buffer */
+      (ctx->Driver.WriteStencilSpan)(ctx, n, x, y, stencil, mask );
+   }
+
+   return result;
 }
 
@@ -586 +665 @@
 /*
  * Apply the given stencil operator for each pixel in the array whose
- * mask flag is set.
+ * mask flag is set.  This is for software stencil buffers only.
  * Input:  n - number of pixels in the span
  *         x, y - array of [n] pixels
@@ -592 +671 @@
  *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
  */
-static void apply_stencil_op_to_pixels( GLcontext *ctx,
-                                        GLuint n, const GLint x[],
-                                        const GLint y[],
-                                        GLenum oper, GLubyte mask[] )
-{
+static void
+apply_stencil_op_to_pixels( const GLcontext *ctx,
+                            GLuint n, const GLint x[], const GLint y[],
+                            GLenum oper, const GLubyte mask[] )
+{
+   const GLstencil ref = ctx->Stencil.Ref;
+   const GLstencil wrtmask = ctx->Stencil.WriteMask;
+   const GLstencil invmask = (GLstencil) (~ctx->Stencil.WriteMask);
    GLuint i;
-   GLstencil ref;
-   GLstencil wrtmask, invmask;
-
-   wrtmask = ctx->Stencil.WriteMask;
-   invmask = (GLstencil) (~ctx->Stencil.WriteMask);
-
-   ref = ctx->Stencil.Ref;
+
+   ASSERT(!ctx->Driver.WriteStencilSpan);  /* software stencil buffer only! */
 
    switch (oper) {
@@ -611 +688 @@
          break;
       case GL_ZERO:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = 0;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  *sptr = (GLstencil) (invmask & *sptr);
-               }
-            }
-         }
-         break;
+                  *sptr = (GLstencil) (invmask & *sptr);
+               }
+            }
+         }
+         break;
       case GL_REPLACE:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = ref;
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  *sptr = (GLstencil) ((invmask & *sptr ) | (wrtmask & ref));
-               }
-            }
-         }
-         break;
+                  *sptr = (GLstencil) ((invmask & *sptr ) | (wrtmask & ref));
+               }
+            }
+         }
+         break;
       case GL_INCR:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  if (*sptr < STENCIL_MAX) {
-                     *sptr = (GLstencil) (*sptr + 1);
-                  }
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+                  if (*sptr < STENCIL_MAX) {
+                     *sptr = (GLstencil) (*sptr + 1);
+                  }
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  if (*sptr < STENCIL_MAX) {
-                     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr+1)));
-                  }
-               }
-            }
-         }
-         break;
+                  if (*sptr < STENCIL_MAX) {
+                     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr+1)));
+                  }
+               }
+            }
+         }
+         break;
       case GL_DECR:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  if (*sptr>0) {
-                     *sptr = (GLstencil) (*sptr - 1);
-                  }
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+                  if (*sptr>0) {
+                     *sptr = (GLstencil) (*sptr - 1);
+                  }
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
-                  if (*sptr>0) {
-                     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
-                  }
-               }
-            }
-         }
-         break;
+                  if (*sptr>0) {
+                     *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
+                  }
+               }
+            }
+         }
+         break;
       case GL_INCR_WRAP_EXT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) (*sptr + 1);
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr+1)));
-               }
-            }
-         }
-         break;
+               }
+            }
+         }
+         break;
       case GL_DECR_WRAP_EXT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) (*sptr - 1);
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
-               }
-            }
-         }
-         break;
+               }
+            }
+         }
+         break;
       case GL_INVERT:
-         if (invmask==0) {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+         if (invmask==0) {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) (~*sptr);
-               }
-            }
-         }
-         else {
-            for (i=0;i<n;i++) {
-               if (mask[i]) {
+               }
+            }
+         }
+         else {
+            for (i=0;i<n;i++) {
+               if (mask[i]) {
                   GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
                   *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & ~*sptr));
-               }
-            }
-         }
-         break;
+               }
+            }
+         }
+         break;
       default:
          gl_problem(ctx, "Bad stencilop in apply_stencil_op_to_pixels");
@@ -753 +830 @@
 /*
  * Apply stencil test to an array of pixels before depth buffering.
+ * Used for software stencil buffer only.
  * Input:  n - number of pixels in the span
  *         x, y - array of [n] pixels to stencil
@@ -760 +838 @@
  * Return:  0 = all pixels failed, 1 = zero or more pixels passed.
  */
-GLint gl_stencil_pixels( GLcontext *ctx,
-                         GLuint n, const GLint x[], const GLint y[],
-                         GLubyte mask[] )
+static GLboolean
+stencil_test_pixels( GLcontext *ctx, GLuint n,
+                     const GLint x[], const GLint y[], GLubyte mask[] )
 {
    GLubyte fail[PB_SIZE];
    GLstencil r, s;
    GLuint i;
-   GLint allfail = 0;
+   GLboolean allfail = GL_FALSE;
+
+   ASSERT(!ctx->Driver.WriteStencilSpan);  /* software stencil buffer only! */
 
    /*
@@ -783 +863 @@
          /* always fail */
          for (i=0;i<n;i++) {
-            if (mask[i]) {
-               mask[i] = 0;
-               fail[i] = 1;
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         allfail = 1;
-         break;
+            if (mask[i]) {
+               mask[i] = 0;
+               fail[i] = 1;
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         allfail = GL_TRUE;
+         break;
       case GL_LESS:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r < s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r < s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_LEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r <= s) {
-                  /* pass */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r <= s) {
+                  /* pass */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_GREATER:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r > s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r > s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_GEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r >= s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r >= s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_EQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r == s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r == s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_NOTEQUAL:
-         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
-         for (i=0;i<n;i++) {
-            if (mask[i]) {
+         r = (GLstencil) (ctx->Stencil.Ref & ctx->Stencil.ValueMask);
+         for (i=0;i<n;i++) {
+            if (mask[i]) {
                GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
-               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
-               if (r != s) {
-                  /* passed */
-                  fail[i] = 0;
-               }
-               else {
-                  fail[i] = 1;
-                  mask[i] = 0;
-               }
-            }
-            else {
-               fail[i] = 0;
-            }
-         }
-         break;
+               s = (GLstencil) (*sptr & ctx->Stencil.ValueMask);
+               if (r != s) {
+                  /* passed */
+                  fail[i] = 0;
+               }
+               else {
+                  fail[i] = 1;
+                  mask[i] = 0;
+               }
+            }
+            else {
+               fail[i] = 0;
+            }
+         }
+         break;
       case GL_ALWAYS:
-         /* always pass */
-         for (i=0;i<n;i++) {
-            fail[i] = 0;
-         }
-         break;
+         /* always pass */
+         for (i=0;i<n;i++) {
+            fail[i] = 0;
+         }
+         break;
       default:
          gl_problem(ctx, "Bad stencil func in gl_stencil_pixels");
@@ -924 +1004 @@
    }
 
-   apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc, fail );
-
-   return (allfail) ? 0 : 1;
+   if (ctx->Stencil.FailFunc != GL_KEEP) {
+      apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc, fail );
+   }
+
+   return !allfail;
 }
 
@@ -933 +1015 @@
 
 /*
- * Apply the combination depth-buffer/stencil operator to a span of pixels.
- * Input:  n - number of pixels in the span
- *         x, y - array of [n] pixels to stencil
+ * Apply stencil and depth testing to an array of pixels.
+ * This is used both for software and hardware stencil buffers.
+ *
+ * The comments in this function are a bit sparse but the code is
+ * almost identical to stencil_and_depth_test_span(), which is well
+ * commented.
+ *
+ * Input:  n - number of pixels in the array
+ *         x, y - array of [n] pixel positions
  *         z - array [n] of z values
- * Input:  mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
- * Output:  mask - array [n] of flags (1=depth test passed, 0=failed)
+ *         mask - array [n] of flags  (1=test this pixel, 0=skip the pixel)
+ * Output: mask - array [n] of flags (1=stencil and depth test passed)
+ * Return: GL_TRUE - all fragments failed the testing
+ *         GL_FALSE - one or more fragments passed the testing
  */
-void gl_depth_stencil_pixels( GLcontext *ctx,
-                              GLuint n, const GLint x[], const GLint y[],
-                              const GLdepth z[], GLubyte mask[] )
-{
-   if (ctx->Depth.Test==GL_FALSE) {
-      /*
-       * No depth buffer, just apply zpass stencil function to active pixels.
-       */
-      apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.ZPassFunc, mask );
+GLboolean
+gl_stencil_and_depth_test_pixels( GLcontext *ctx,
+                                  GLuint n, const GLint x[], const GLint y[],
+                                  const GLdepth z[], GLubyte mask[] )
+{
+   ASSERT(ctx->Stencil.Enabled);
+   ASSERT(n <= PB_SIZE);
+
+   if (ctx->Driver.WriteStencilPixels) {
+      /*** Hardware stencil buffer ***/
+      GLstencil stencil[PB_SIZE];
+      GLubyte mask[PB_SIZE];
+
+      ASSERT(ctx->Driver.ReadStencilPixels);
+      (*ctx->Driver.ReadStencilPixels)(ctx, n, x, y, stencil);
+
+
+      if (do_stencil_test( ctx, n, stencil, mask ) == GL_FALSE) {
+         /* all fragments failed the stencil test, we're done. */
+         return GL_FALSE;
+      }
+
+      if (ctx->Depth.Test == GL_FALSE) {
+         apply_stencil_op( ctx, ctx->Stencil.ZPassFunc, n, stencil, mask );
+      }
+      else {
+         GLubyte passmask[PB_SIZE], failmask[PB_SIZE], oldmask[PB_SIZE];
+         GLuint i;
+
+         MEMCPY(oldmask, mask, n * sizeof(GLubyte));
+
+         _mesa_depth_test_pixels(ctx, n, x, y, z, mask);
+
+         for (i=0;i<n;i++) {
+            ASSERT(mask[i] == 0 || mask[i] == 1);
+            passmask[i] = oldmask[i] & mask[i];
+            failmask[i] = oldmask[i] & (mask[i] ^ 1);
+         }
+
+         if (ctx->Stencil.ZFailFunc != GL_KEEP) {
+            apply_stencil_op( ctx, ctx->Stencil.ZFailFunc, n, stencil, failmask );
+         }
+         if (ctx->Stencil.ZPassFunc != GL_KEEP) {
+            apply_stencil_op( ctx, ctx->Stencil.ZPassFunc, n, stencil, passmask );
+         }
+      }
+
+      /* Write updated stencil values into hardware stencil buffer */
+      (ctx->Driver.WriteStencilPixels)(ctx, n, x, y, stencil, mask );
+
+      return GL_TRUE;
+
    }
    else {
-      /*
-       * Perform depth buffering, then apply zpass or zfail stencil function.
-       */
-      GLubyte passmask[PB_SIZE], failmask[PB_SIZE], oldmask[PB_SIZE];
-      GLuint i;
-
-      /* save the current mask bits */
-      MEMCPY(oldmask, mask, n * sizeof(GLubyte));
-
-      /* apply the depth test */
-      if (ctx->Driver.DepthTestPixels)
-         (*ctx->Driver.DepthTestPixels)( ctx, n, x, y, z, mask );
-
-      /* Set the stencil pass/fail flags according to result of depth testing.
-       * if oldmask[i] == 0 then
-       *    Don't touch the stencil value
-       * else if oldmask[i] and newmask[i] then
-       *    Depth test passed
-       * else
-       *    assert(oldmask[i] && !newmask[i])
-       *    Depth test failed
-       * endif
-       */
-      for (i=0;i<n;i++) {
-         ASSERT(mask[i] == 0 || mask[i] == 1);
-         passmask[i] = oldmask[i] & mask[i];
-         failmask[i] = oldmask[i] & (mask[i] ^ 1);
-      }
-
-      /* apply the pass and fail operations */
-      apply_stencil_op_to_pixels( ctx, n, x, y,
-                                  ctx->Stencil.ZFailFunc, failmask );
-      apply_stencil_op_to_pixels( ctx, n, x, y,
-                                  ctx->Stencil.ZPassFunc, passmask );
-   }
-
+      /*** Software stencil buffer ***/
+
+      if (stencil_test_pixels(ctx, n, x, y, mask) == GL_FALSE) {
+         /* all fragments failed the stencil test, we're done. */
+         return GL_FALSE;
+      }
+
+
+      if (ctx->Depth.Test==GL_FALSE) {
+         apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.ZPassFunc, mask );
+      }
+      else {
+         GLubyte passmask[PB_SIZE], failmask[PB_SIZE], oldmask[PB_SIZE];
+         GLuint i;
+
+         MEMCPY(oldmask, mask, n * sizeof(GLubyte));
+
+         _mesa_depth_test_pixels(ctx, n, x, y, z, mask);
+
+         for (i=0;i<n;i++) {
+            ASSERT(mask[i] == 0 || mask[i] == 1);
+            passmask[i] = oldmask[i] & mask[i];
+            failmask[i] = oldmask[i] & (mask[i] ^ 1);
+         }
+
+         if (ctx->Stencil.ZFailFunc != GL_KEEP) {
+            apply_stencil_op_to_pixels( ctx, n, x, y,
+                                        ctx->Stencil.ZFailFunc, failmask );
+         }
+         if (ctx->Stencil.ZPassFunc != GL_KEEP) {
+            apply_stencil_op_to_pixels( ctx, n, x, y,
+                                        ctx->Stencil.ZPassFunc, passmask );
+         }
+      }
+
+      return GL_TRUE;  /* one or more fragments passed both tests */
+   }
 }
 
@@ -993 +1127 @@
 /*
  * Return a span of stencil values from the stencil buffer.
+ * Used for glRead/CopyPixels
  * Input:  n - how many pixels
  *         x,y - location of first pixel
@@ -998 +1133 @@
  */
 void gl_read_stencil_span( GLcontext *ctx,
-                           GLuint n, GLint x, GLint y, GLstencil stencil[] )
-{
-   if (ctx->Buffer->Stencil) {
-      const GLstencil *s = STENCIL_ADDRESS( x, y );
+                           GLint n, GLint x, GLint y, GLstencil stencil[] )
+{
+   ASSERT(n >= 0);
+   if (ctx->DrawBuffer->Stencil) {
+      if (ctx->Driver.ReadStencilSpan) {
+         (*ctx->Driver.ReadStencilSpan)( ctx, (GLuint) n, x, y, stencil );
+      }
+      else {
+         const GLstencil *s = STENCIL_ADDRESS( x, y );
 #if STENCIL_BITS == 8
-      MEMCPY( stencil, s, n * sizeof(GLstencil) );
+         MEMCPY( stencil, s, n * sizeof(GLstencil) );
 #else
-      GLuint i;
-      for (i=0;i<n;i++)
-         stencil[i] = s[i];
+         GLuint i;
+         for (i=0;i<n;i++)
+            stencil[i] = s[i];
 #endif
+      }
    }
 }
@@ -1016 +1157 @@
 /*
  * Write a span of stencil values to the stencil buffer.
+ * Used for glDraw/CopyPixels
  * Input:  n - how many pixels
- *         x,y - location of first pixel
+ *         x, y - location of first pixel
  *         stencil - the array of stencil values
  */
 void gl_write_stencil_span( GLcontext *ctx,
-                            GLuint n, GLint x, GLint y,
-                            const GLstencil stencil[] )
-{
-   if (ctx->Buffer->Stencil) {
-      GLstencil *s = STENCIL_ADDRESS( x, y );
+                            GLint n, GLint x, GLint y,
+                            const GLstencil stencil[] )
+{
+   ASSERT(n >= 0);
+   if (ctx->DrawBuffer->Stencil) {
+      /* do clipping */
+      if (y < ctx->DrawBuffer->Ymin || y > ctx->DrawBuffer->Ymax)
+         return;
+      if (x < ctx->DrawBuffer->Xmin) {
+         GLint diff = ctx->DrawBuffer->Xmin - x;
+         n -= diff;
+         stencil += diff;
+         x = ctx->DrawBuffer->Xmin;
+      }
+      if (x + n > ctx->DrawBuffer->Xmax) {
+         GLint diff = x + n - ctx->DrawBuffer->Xmax;
+         n -= diff;
+      }
+
+      ASSERT( n >= 0);
+
+      if (ctx->Driver.WriteStencilSpan) {
+         (*ctx->Driver.WriteStencilSpan)( ctx, n, x, y, stencil, NULL );
+      }
+      else {
+         GLstencil *s = STENCIL_ADDRESS( x, y );
 #if STENCIL_BITS == 8
-      MEMCPY( s, stencil, n * sizeof(GLstencil) );
+         MEMCPY( s, stencil, n * sizeof(GLstencil) );
 #else
-      GLuint i;
-      for (i=0;i<n;i++)
-         s[i] = stencil[i];
+         GLuint i;
+         for (i=0;i<n;i++)
+            s[i] = stencil[i];
 #endif
+      }
    }
 }
@@ -1044 +1208 @@
 void gl_alloc_stencil_buffer( GLcontext *ctx )
 {
-   GLuint buffersize = ctx->Buffer->Width * ctx->Buffer->Height;
+   GLuint buffersize = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
 
    /* deallocate current stencil buffer if present */
-   if (ctx->Buffer->Stencil) {
-      FREE(ctx->Buffer->Stencil);
-      ctx->Buffer->Stencil = NULL;
+   if (ctx->DrawBuffer->Stencil) {
+      FREE(ctx->DrawBuffer->Stencil);
+      ctx->DrawBuffer->Stencil = NULL;
    }
 
    /* allocate new stencil buffer */
-   ctx->Buffer->Stencil = (GLstencil *) MALLOC(buffersize * sizeof(GLstencil));
-   if (!ctx->Buffer->Stencil) {
+   ctx->DrawBuffer->Stencil = (GLstencil *) MALLOC(buffersize * sizeof(GLstencil));
+   if (!ctx->DrawBuffer->Stencil) {
       /* out of memory */
-      gl_set_enable( ctx, GL_STENCIL_TEST, GL_FALSE );
+      _mesa_set_enable( ctx, GL_STENCIL_TEST, GL_FALSE );
       gl_error( ctx, GL_OUT_OF_MEMORY, "gl_alloc_stencil_buffer" );
    }
@@ -1063 +1227 @@
 
 
-
 /*
- * Clear the stencil buffer.  If the stencil buffer doesn't exist yet we'll
- * allocate it now.
+ * Clear the software (malloc'd) stencil buffer.
  */
-void gl_clear_stencil_buffer( GLcontext *ctx )
-{
-   if (ctx->Visual->StencilBits==0 || !ctx->Buffer->Stencil) {
+static void
+clear_software_stencil_buffer( GLcontext *ctx )
+{
+   if (ctx->Visual->StencilBits==0 || !ctx->DrawBuffer->Stencil) {
       /* no stencil buffer */
       return;
@@ -1077 +1240 @@
    if (ctx->Scissor.Enabled) {
       /* clear scissor region only */
-      const GLint width = ctx->Buffer->Xmax - ctx->Buffer->Xmin + 1;
+      const GLint width = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin + 1;
       if (ctx->Stencil.WriteMask != STENCIL_MAX) {
          /* must apply mask to the clear */
          GLint y;
-         for (y=ctx->Buffer->Ymin; y<=ctx->Buffer->Ymax; y++) {
-            GLstencil *ptr = STENCIL_ADDRESS( ctx->Buffer->Xmin, y );
-            GLint x;
+         for (y = ctx->DrawBuffer->Ymin; y <= ctx->DrawBuffer->Ymax; y++) {
             const GLstencil mask = ctx->Stencil.WriteMask;
             const GLstencil invMask = ~mask;
             const GLstencil clearVal = (ctx->Stencil.Clear & mask);
-            for (x = 0; x < width; x++) {
-               ptr[x] = (ptr[x] & invMask) | clearVal;
+            GLstencil *stencil = STENCIL_ADDRESS( ctx->DrawBuffer->Xmin, y );
+            GLint i;
+            for (i = 0; i < width; i++) {
+               stencil[i] = (stencil[i] & invMask) | clearVal;
             }
          }
@@ -1095 +1258 @@
          /* no masking */
          GLint y;
-         for (y=ctx->Buffer->Ymin; y<=ctx->Buffer->Ymax; y++) {
-            GLstencil *ptr = STENCIL_ADDRESS( ctx->Buffer->Xmin, y );
+         for (y = ctx->DrawBuffer->Ymin; y <= ctx->DrawBuffer->Ymax; y++) {
+            GLstencil *stencil = STENCIL_ADDRESS( ctx->DrawBuffer->Xmin, y );
 #if STENCIL_BITS==8
-            MEMSET( ptr, ctx->Stencil.Clear, width * sizeof(GLstencil) );
+            MEMSET( stencil, ctx->Stencil.Clear, width * sizeof(GLstencil) );
 #else
-            GLint x;
-            for (x = 0; x < width; x++)
-               ptr[x] = ctx->Stencil.Clear;
+            GLint i;
+            for (i = 0; i < width; i++)
+               stencil[x] = ctx->Stencil.Clear;
 #endif
          }
@@ -1111 +1274 @@
       if (ctx->Stencil.WriteMask != STENCIL_MAX) {
          /* must apply mask to the clear */
-         const GLuint n = ctx->Buffer->Width * ctx->Buffer->Height;
-         GLstencil *buffer = ctx->Buffer->Stencil;
+         const GLuint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+         GLstencil *stencil = ctx->DrawBuffer->Stencil;
          const GLstencil mask = ctx->Stencil.WriteMask;
          const GLstencil invMask = ~mask;
@@ -1118 +1281 @@
          GLuint i;
          for (i = 0; i < n; i++) {
-            buffer[i] = (buffer[i] & invMask) | clearVal;
+            stencil[i] = (stencil[i] & invMask) | clearVal;
          }
       }
       else {
          /* clear whole buffer without masking */
-         const GLuint n = ctx->Buffer->Width * ctx->Buffer->Height;
-         GLstencil *buffer = ctx->Buffer->Stencil;
+         const GLuint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+         GLstencil *stencil = ctx->DrawBuffer->Stencil;
 
 #if STENCIL_BITS==8
-         MEMSET(buffer, ctx->Stencil.Clear, n * sizeof(GLstencil) );
+         MEMSET(stencil, ctx->Stencil.Clear, n * sizeof(GLstencil) );
 #else
          GLuint i;
          for (i = 0; i < n; i++) {
-            buffer[i] = ctx->Stencil.Clear;
+            stencil[i] = ctx->Stencil.Clear;
          }
 #endif
@@ -1137 +1300 @@
    }
 }
+
+
+
+/*
+ * Clear the hardware (in graphics card) stencil buffer.
+ * This is done with the Driver.WriteStencilSpan() and Driver.ReadStencilSpan()
+ * functions.
+ * Actually, if there is a hardware stencil buffer it really should have
+ * been cleared in Driver.Clear()!  However, if the hardware does not
+ * support scissored clears or masked clears (i.e. glStencilMask) then
+ * we have to use the span-based functions.
+ */
+static void
+clear_hardware_stencil_buffer( GLcontext *ctx )
+{
+   ASSERT(ctx->Driver.WriteStencilSpan);
+   ASSERT(ctx->Driver.ReadStencilSpan);
+
+   if (ctx->Scissor.Enabled) {
+      /* clear scissor region only */
+      const GLint x = ctx->DrawBuffer->Xmin;
+      const GLint width = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin + 1;
+      if (ctx->Stencil.WriteMask != STENCIL_MAX) {
+         /* must apply mask to the clear */
+         GLint y;
+         for (y = ctx->DrawBuffer->Ymin; y <= ctx->DrawBuffer->Ymax; y++) {
+            const GLstencil mask = ctx->Stencil.WriteMask;
+            const GLstencil invMask = ~mask;
+            const GLstencil clearVal = (ctx->Stencil.Clear & mask);
+            GLstencil stencil[MAX_WIDTH];
+            GLint i;
+            (*ctx->Driver.ReadStencilSpan)(ctx, x, y, width, stencil);
+            for (i = 0; i < width; i++) {
+               stencil[i] = (stencil[i] & invMask) | clearVal;
+            }
+            (*ctx->Driver.WriteStencilSpan)(ctx, x, y, width, stencil, NULL);
+         }
+      }
+      else {
+         /* no masking */
+         GLstencil stencil[MAX_WIDTH];
+         GLint y, i;
+         for (i = 0; i < width; i++) {
+            stencil[i] = ctx->Stencil.Clear;
+         }
+         for (y = ctx->DrawBuffer->Ymin; y <= ctx->DrawBuffer->Ymax; y++) {
+            (*ctx->Driver.WriteStencilSpan)(ctx, x, y, width, stencil, NULL);
+         }
+      }
+   }
+   else {
+      /* clear whole stencil buffer */
+      if (ctx->Stencil.WriteMask != STENCIL_MAX) {
+         /* must apply mask to the clear */
+         const GLstencil mask = ctx->Stencil.WriteMask;
+         const GLstencil invMask = ~mask;
+         const GLstencil clearVal = (ctx->Stencil.Clear & mask);
+         const GLint width = ctx->DrawBuffer->Width;
+         const GLint height = ctx->DrawBuffer->Height;
+         const GLint x = ctx->DrawBuffer->Xmin;
+         GLint y;
+         for (y = 0; y < height; y++) {
+            GLstencil stencil[MAX_WIDTH];
+            GLuint i;
+            (*ctx->Driver.ReadStencilSpan)(ctx, x, y, width, stencil);
+            for (i = 0; i < width; i++) {
+               stencil[i] = (stencil[i] & invMask) | clearVal;
+            }
+            (*ctx->Driver.WriteStencilSpan)(ctx, x, y, width, stencil, NULL);
+         }
+      }
+      else {
+         /* clear whole buffer without masking */
+         const GLint width = ctx->DrawBuffer->Width;
+         const GLint height = ctx->DrawBuffer->Width;
+         const GLint x = ctx->DrawBuffer->Xmin;
+         GLstencil stencil[MAX_WIDTH];
+         GLint y, i;
+         for (i = 0; i < width; i++) {
+            stencil[i] = ctx->Stencil.Clear;
+         }
+         for (y = 0; y < height; y++) {
+            (*ctx->Driver.WriteStencilSpan)(ctx, x, y, width, stencil, NULL);
+         }
+      }
+   }
+}
+
+
+
+/*
+ * Clear the stencil buffer.
+ */
+void gl_clear_stencil_buffer( GLcontext *ctx )
+{
+   if (ctx->Driver.WriteStencilSpan) {
+      ASSERT(ctx->Driver.ReadStencilSpan);
+      clear_hardware_stencil_buffer(ctx);
+   }
+   else {
+      clear_software_stencil_buffer(ctx);
+   }
+}
+