Moved software rasterizer functionality to new directory.

1 files changed, 1303 insertions, 0 deletions

diff --git a/src/mesa/swrast/s_stencil.c b/src/mesa/swrast/s_stencil.c
new file mode 100644
index 0000000000..c957a683a1
--- /dev/null
+++ b/src/mesa/swrast/s_stencil.c
@@ -0,0 +1,1303 @@
+/* $Id: s_stencil.c,v 1.1 2000/10/31 18:00:04 keithw Exp $ */
+
+/*
+ * Mesa 3-D graphics library
+ * Version:  3.5
+ * 
+ * Copyright (C) 1999-2000  Brian Paul   All Rights Reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+
+#include "glheader.h"
+#include "context.h"
+#include "macros.h"
+#include "mem.h"
+
+#include "s_depth.h"
+#include "s_pb.h"
+#include "s_stencil.h"
+
+
+
+
+
+/* Stencil Logic:
+
+IF stencil test fails THEN
+   Apply fail-op to stencil value   
+   Don't write the pixel (RGBA,Z)
+ELSE
+   IF doing depth test && depth test fails THEN
+      Apply zfail-op to stencil value   
+      Write RGBA and Z to appropriate buffers
+   ELSE
+      Apply zpass-op to stencil value
+ENDIF
+
+*/
+
+
+
+
+/*
+ * 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 - 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( const GLcontext *ctx, GLenum oper,
+                              GLuint n, GLstencil stencil[],
+                              const GLubyte mask[] )
+{
+   const GLstencil ref = ctx->Stencil.Ref;
+   const GLstencil wrtmask = ctx->Stencil.WriteMask;
+   const GLstencil invmask = (GLstencil) (~ctx->Stencil.WriteMask);
+   GLuint i;
+
+   switch (oper) {
+      case GL_KEEP:
+         /* do nothing */
+         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;
+      case GL_REPLACE:
+	 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;
+      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;
+      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;
+      case GL_INCR_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]) {
+                  GLstencil s = stencil[i];
+                  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]) {
+                  GLstencil s = stencil[i];
+                  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;
+      default:
+         gl_problem(ctx, "Bad stencil op in apply_stencil_op");
+   }
+}
+
+
+
+
+/*
+ * 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.
+ *          stencil - updated stencil values (where the test passed)
+ * Return:  GL_FALSE = all pixels failed, GL_TRUE = zero or more pixels passed.
+ */
+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;
+
+   ASSERT(n <= PB_SIZE);
+
+   /*
+    * Perform stencil test.  The results of this operation are stored
+    * in the fail[] array:
+    *   IF fail[i] is non-zero THEN
+    *       the stencil fail operator is to be applied
+    *   ELSE
+    *       the stencil fail operator is not to be applied
+    *   ENDIF
+    */
+   switch (ctx->Stencil.Function) {
+      case GL_NEVER:
+         /* always fail */
+         for (i=0;i<n;i++) {
+	    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;
+      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;
+      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;
+      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;
+      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;
+      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;
+      case GL_ALWAYS:
+	 /* always pass */
+	 for (i=0;i<n;i++) {
+	    fail[i] = 0;
+	 }
+	 break;
+      default:
+         gl_problem(ctx, "Bad stencil func in gl_stencil_span");
+         return 0;
+   }
+
+   if (ctx->Stencil.FailFunc != GL_KEEP) {
+      apply_stencil_op( ctx, ctx->Stencil.FailFunc, n, stencil, fail );
+   }
+
+   return !allfail;
+}
+
+
+
+
+/*
+ * Apply stencil and depth testing to an array of pixels.
+ * Hardware or software stencil buffer acceptable.
+ * Input:  n - number of pixels in the span
+ *         z - array [n] of z values
+ *         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
+ * 
+ */
+static GLboolean
+stencil_and_ztest_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) {
+      /*
+       * No depth buffer, just apply zpass stencil function to active pixels.
+       */
+      apply_stencil_op( ctx, ctx->Stencil.ZPassFunc, n, stencil, mask );
+   }
+   else {
+      /*
+       * Perform depth buffering, then apply zpass or zfail stencil function.
+       */
+      GLubyte passmask[MAX_WIDTH], failmask[MAX_WIDTH], oldmask[MAX_WIDTH];
+      GLuint i;
+
+      /* save the current mask bits */
+      MEMCPY(oldmask, mask, n * sizeof(GLubyte));
+
+      /* apply the depth test */
+      _mesa_depth_test_span(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 */
+      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 );
+      }
+   }
+
+   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
+_mesa_stencil_and_ztest_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_ztest_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;
+}
+
+
+
+
+/*
+ * Apply the given stencil operator for each pixel in the array whose
+ * 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
+ *         operator - the stencil buffer operator
+ *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
+ */
+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;
+
+   ASSERT(!ctx->Driver.WriteStencilSpan);  /* software stencil buffer only! */
+
+   switch (oper) {
+      case GL_KEEP:
+         /* do nothing */
+         break;
+      case GL_ZERO:
+	 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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  *sptr = (GLstencil) (invmask & *sptr);
+	       }
+	    }
+	 }
+	 break;
+      case GL_REPLACE:
+	 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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  *sptr = (GLstencil) ((invmask & *sptr ) | (wrtmask & ref));
+	       }
+	    }
+	 }
+	 break;
+      case GL_INCR:
+	 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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  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]) {
+                  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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (GLstencil) (*sptr + 1);
+	       }
+	    }
+	 }
+	 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;
+      case GL_DECR_WRAP_EXT:
+	 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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & (*sptr-1)));
+	       }
+	    }
+	 }
+	 break;
+      case GL_INVERT:
+	 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]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (GLstencil) ((invmask & *sptr) | (wrtmask & ~*sptr));
+	       }
+	    }
+	 }
+	 break;
+      default:
+         gl_problem(ctx, "Bad stencilop in apply_stencil_op_to_pixels");
+   }
+}
+
+
+
+/*
+ * 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
+ *         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.
+ */
+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;
+   GLboolean allfail = GL_FALSE;
+
+   ASSERT(!ctx->Driver.WriteStencilSpan);  /* software stencil buffer only! */
+
+   /*
+    * Perform stencil test.  The results of this operation are stored
+    * in the fail[] array:
+    *   IF fail[i] is non-zero THEN
+    *       the stencil fail operator is to be applied
+    *   ELSE
+    *       the stencil fail operator is not to be applied
+    *   ENDIF
+    */
+
+   switch (ctx->Stencil.Function) {
+      case GL_NEVER:
+         /* always fail */
+         for (i=0;i<n;i++) {
+	    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]) {
+               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;
+      case GL_LEQUAL:
+	 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;
+      case GL_GREATER:
+	 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;
+      case GL_GEQUAL:
+	 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;
+      case GL_EQUAL:
+	 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;
+      case GL_NOTEQUAL:
+	 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;
+      case GL_ALWAYS:
+	 /* always pass */
+	 for (i=0;i<n;i++) {
+	    fail[i] = 0;
+	 }
+	 break;
+      default:
+         gl_problem(ctx, "Bad stencil func in gl_stencil_pixels");
+         return 0;
+   }
+
+   if (ctx->Stencil.FailFunc != GL_KEEP) {
+      apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc, fail );
+   }
+
+   return !allfail;
+}
+
+
+
+
+/*
+ * 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_ztest_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
+ *         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
+_mesa_stencil_and_ztest_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 {
+      /*** 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 */
+   }
+}
+
+
+
+/*
+ * 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
+ * Output:  stencil - the array of stencil values
+ */
+void
+_mesa_read_stencil_span( GLcontext *ctx,
+                         GLint n, GLint x, GLint y, GLstencil stencil[] )
+{
+   if (y < 0 || y >= ctx->DrawBuffer->Height ||
+       x + n <= 0 || x >= ctx->DrawBuffer->Width) {
+      /* span is completely outside framebuffer */
+      return; /* undefined values OK */
+   }
+
+   if (x < 0) {
+      GLint dx = -x;
+      x = 0;
+      n -= dx;
+      stencil += dx;
+   }
+   if (x + n > ctx->DrawBuffer->Width) {
+      GLint dx = x + n - ctx->DrawBuffer->Width;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+
+   ASSERT(n >= 0);
+   if (ctx->Driver.ReadStencilSpan) {
+      (*ctx->Driver.ReadStencilSpan)( ctx, (GLuint) n, x, y, stencil );
+   }
+   else if (ctx->DrawBuffer->Stencil) {
+      const GLstencil *s = STENCIL_ADDRESS( x, y );
+#if STENCIL_BITS == 8
+      MEMCPY( stencil, s, n * sizeof(GLstencil) );
+#else
+      GLuint i;
+      for (i=0;i<n;i++)
+         stencil[i] = s[i];
+#endif
+   }
+}
+
+
+
+/*
+ * 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
+ *         stencil - the array of stencil values
+ */
+void
+_mesa_write_stencil_span( GLcontext *ctx, GLint n, GLint x, GLint y,
+                          const GLstencil stencil[] )
+{
+   if (y < 0 || y >= ctx->DrawBuffer->Height ||
+       x + n <= 0 || x >= ctx->DrawBuffer->Width) {
+      /* span is completely outside framebuffer */
+      return; /* undefined values OK */
+   }
+
+   if (x < 0) {
+      GLint dx = -x;
+      x = 0;
+      n -= dx;
+      stencil += dx;
+   }
+   if (x + n > ctx->DrawBuffer->Width) {
+      GLint dx = x + n - ctx->DrawBuffer->Width;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+   if (ctx->Driver.WriteStencilSpan) {
+      (*ctx->Driver.WriteStencilSpan)( ctx, n, x, y, stencil, NULL );
+   }
+   else if (ctx->DrawBuffer->Stencil) {
+      GLstencil *s = STENCIL_ADDRESS( x, y );
+#if STENCIL_BITS == 8
+      MEMCPY( s, stencil, n * sizeof(GLstencil) );
+#else
+      GLuint i;
+      for (i=0;i<n;i++)
+         s[i] = stencil[i];
+#endif
+   }
+}
+
+
+
+/*
+ * Allocate a new stencil buffer.  If there's an old one it will be
+ * deallocated first.  The new stencil buffer will be uninitialized.
+ */
+void
+_mesa_alloc_stencil_buffer( GLcontext *ctx )
+{
+   GLuint buffersize = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+
+   /* deallocate current stencil buffer if present */
+   if (ctx->DrawBuffer->Stencil) {
+      FREE(ctx->DrawBuffer->Stencil);
+      ctx->DrawBuffer->Stencil = NULL;
+   }
+
+   /* allocate new stencil buffer */
+   ctx->DrawBuffer->Stencil = (GLstencil *) MALLOC(buffersize * sizeof(GLstencil));
+   if (!ctx->DrawBuffer->Stencil) {
+      /* out of memory */
+/*        _mesa_set_enable( ctx, GL_STENCIL_TEST, GL_FALSE ); */
+      gl_error( ctx, GL_OUT_OF_MEMORY, "_mesa_alloc_stencil_buffer" );
+   }
+}
+
+
+
+/*
+ * Clear the software (malloc'd) stencil buffer.
+ */
+static void
+clear_software_stencil_buffer( GLcontext *ctx )
+{
+   if (ctx->Visual.StencilBits==0 || !ctx->DrawBuffer->Stencil) {
+      /* no stencil buffer */
+      return;
+   }
+
+   if (ctx->Scissor.Enabled) {
+      /* clear scissor region only */
+      const GLint width = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin;
+      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 = STENCIL_ADDRESS( ctx->DrawBuffer->Xmin, y );
+            GLint i;
+            for (i = 0; i < width; i++) {
+               stencil[i] = (stencil[i] & invMask) | clearVal;
+            }
+         }
+      }
+      else {
+         /* no masking */
+         GLint y;
+         for (y = ctx->DrawBuffer->Ymin; y < ctx->DrawBuffer->Ymax; y++) {
+            GLstencil *stencil = STENCIL_ADDRESS( ctx->DrawBuffer->Xmin, y );
+#if STENCIL_BITS==8
+            MEMSET( stencil, ctx->Stencil.Clear, width * sizeof(GLstencil) );
+#else
+            GLint i;
+            for (i = 0; i < width; i++)
+               stencil[x] = ctx->Stencil.Clear;
+#endif
+         }
+      }
+   }
+   else {
+      /* clear whole stencil buffer */
+      if (ctx->Stencil.WriteMask != STENCIL_MAX) {
+         /* must apply mask to the clear */
+         const GLuint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+         GLstencil *stencil = ctx->DrawBuffer->Stencil;
+         const GLstencil mask = ctx->Stencil.WriteMask;
+         const GLstencil invMask = ~mask;
+         const GLstencil clearVal = (ctx->Stencil.Clear & mask);
+         GLuint i;
+         for (i = 0; i < n; i++) {
+            stencil[i] = (stencil[i] & invMask) | clearVal;
+         }
+      }
+      else {
+         /* clear whole buffer without masking */
+         const GLuint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+         GLstencil *stencil = ctx->DrawBuffer->Stencil;
+
+#if STENCIL_BITS==8
+         MEMSET(stencil, ctx->Stencil.Clear, n * sizeof(GLstencil) );
+#else
+         GLuint i;
+         for (i = 0; i < n; i++) {
+            stencil[i] = ctx->Stencil.Clear;
+         }
+#endif
+      }
+   }
+}
+
+
+
+/*
+ * 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;
+      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
+_mesa_clear_stencil_buffer( GLcontext *ctx )
+{
+   if (ctx->Driver.WriteStencilSpan) {
+      ASSERT(ctx->Driver.ReadStencilSpan);
+      clear_hardware_stencil_buffer(ctx);
+   }
+   else {
+      clear_software_stencil_buffer(ctx);
+   }
+}
+