Added MesaLib-7.6

1 files changed, 1245 insertions, 0 deletions

diff --git a/mesalib/src/mesa/swrast/s_stencil.c b/mesalib/src/mesa/swrast/s_stencil.c
new file mode 100644
index 000000000..e9e9d3a4f
--- /dev/null
+++ b/mesalib/src/mesa/swrast/s_stencil.c
@@ -0,0 +1,1245 @@
+/*
+ * Mesa 3-D graphics library
+ * Version:  7.1
+ *
+ * Copyright (C) 1999-2007  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 "main/glheader.h"
+#include "main/context.h"
+#include "main/imports.h"
+
+#include "s_context.h"
+#include "s_depth.h"
+#include "s_stencil.h"
+#include "s_span.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
+
+*/
+
+
+/**
+ * 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
+ *         face - 0 or 1 for front or back face operation
+ *         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 face,
+                  GLuint n, GLstencil stencil[], const GLubyte mask[] )
+{
+   const GLstencil ref = ctx->Stencil.Ref[face];
+   const GLstencil wrtmask = ctx->Stencil.WriteMask[face];
+   const GLstencil invmask = (GLstencil) (~wrtmask);
+   const GLstencil stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
+   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 < stencilMax) {
+		     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 < stencilMax) {
+		     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:
+         _mesa_problem(ctx, "Bad stencil op in apply_stencil_op");
+   }
+}
+
+
+
+
+/**
+ * Apply stencil test to an array of stencil values (before depth buffering).
+ * Input:  face - 0 or 1 for front or back-face polygons
+ *         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 face, GLuint n, GLstencil stencil[],
+                 GLubyte mask[] )
+{
+   GLubyte fail[MAX_WIDTH];
+   GLboolean allfail = GL_FALSE;
+   GLuint i;
+   const GLuint valueMask = ctx->Stencil.ValueMask[face];
+   const GLstencil r = (GLstencil) (ctx->Stencil.Ref[face] & valueMask);
+   GLstencil s;
+
+   ASSERT(n <= MAX_WIDTH);
+
+   /*
+    * 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[face]) {
+      case GL_NEVER:
+         /* never pass; 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:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & valueMask);
+	       if (r < s) {
+		  /* passed */
+		  fail[i] = 0;
+	       }
+	       else {
+		  fail[i] = 1;
+		  mask[i] = 0;
+	       }
+	    }
+	    else {
+	       fail[i] = 0;
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & valueMask);
+	       if (r <= s) {
+		  /* pass */
+		  fail[i] = 0;
+	       }
+	       else {
+		  fail[i] = 1;
+		  mask[i] = 0;
+	       }
+	    }
+	    else {
+	       fail[i] = 0;
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & valueMask);
+	       if (r > s) {
+		  /* passed */
+		  fail[i] = 0;
+	       }
+	       else {
+		  fail[i] = 1;
+		  mask[i] = 0;
+	       }
+	    }
+	    else {
+	       fail[i] = 0;
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & valueMask);
+	       if (r >= s) {
+		  /* passed */
+		  fail[i] = 0;
+	       }
+	       else {
+		  fail[i] = 1;
+		  mask[i] = 0;
+	       }
+	    }
+	    else {
+	       fail[i] = 0;
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & valueMask);
+	       if (r == s) {
+		  /* passed */
+		  fail[i] = 0;
+	       }
+	       else {
+		  fail[i] = 1;
+		  mask[i] = 0;
+	       }
+	    }
+	    else {
+	       fail[i] = 0;
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = (GLstencil) (stencil[i] & 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:
+         _mesa_problem(ctx, "Bad stencil func in gl_stencil_span");
+         return 0;
+   }
+
+   if (ctx->Stencil.FailFunc[face] != GL_KEEP) {
+      apply_stencil_op( ctx, ctx->Stencil.FailFunc[face], face, n, stencil, fail );
+   }
+
+   return !allfail;
+}
+
+
+/**
+ * Compute the zpass/zfail masks by comparing the pre- and post-depth test
+ * masks.
+ */
+static INLINE void
+compute_pass_fail_masks(GLuint n, const GLubyte origMask[],
+                        const GLubyte newMask[],
+                        GLubyte passMask[], GLubyte failMask[])
+{
+   GLuint i;
+   for (i = 0; i < n; i++) {
+      ASSERT(newMask[i] == 0 || newMask[i] == 1);
+      passMask[i] = origMask[i] & newMask[i];
+      failMask[i] = origMask[i] & (newMask[i] ^ 1);
+   }
+}
+
+
+/**
+ * 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_FALSE - all fragments failed the testing
+ *         GL_TRUE - one or more fragments passed the testing
+ *
+ */
+static GLboolean
+stencil_and_ztest_span(GLcontext *ctx, SWspan *span, GLuint face)
+{
+   struct gl_framebuffer *fb = ctx->DrawBuffer;
+   struct gl_renderbuffer *rb = fb->_StencilBuffer;
+   GLstencil stencilRow[MAX_WIDTH];
+   GLstencil *stencil;
+   const GLuint n = span->end;
+   const GLint x = span->x;
+   const GLint y = span->y;
+   GLubyte *mask = span->array->mask;
+
+   ASSERT((span->arrayMask & SPAN_XY) == 0);
+   ASSERT(ctx->Stencil.Enabled);
+   ASSERT(n <= MAX_WIDTH);
+#ifdef DEBUG
+   if (ctx->Depth.Test) {
+      ASSERT(span->arrayMask & SPAN_Z);
+   }
+#endif
+
+   stencil = (GLstencil *) rb->GetPointer(ctx, rb, x, y);
+   if (!stencil) {
+      rb->GetRow(ctx, rb, n, x, y, stencilRow);
+      stencil = stencilRow;
+   }
+
+   /*
+    * Apply the stencil test to the fragments.
+    * failMask[i] is 1 if the stencil test failed.
+    */
+   if (do_stencil_test( ctx, face, n, stencil, mask ) == GL_FALSE) {
+      /* all fragments failed the stencil test, we're done. */
+      span->writeAll = GL_FALSE;
+      if (!rb->GetPointer(ctx, rb, 0, 0)) {
+         /* put updated stencil values into buffer */
+         rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
+      }
+      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[face], face, n, stencil, mask );
+   }
+   else {
+      /*
+       * Perform depth buffering, then apply zpass or zfail stencil function.
+       */
+      GLubyte passMask[MAX_WIDTH], failMask[MAX_WIDTH], origMask[MAX_WIDTH];
+
+      /* save the current mask bits */
+      _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));
+
+      /* apply the depth test */
+      _swrast_depth_test_span(ctx, span);
+
+      compute_pass_fail_masks(n, origMask, mask, passMask, failMask);
+
+      /* apply the pass and fail operations */
+      if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
+         apply_stencil_op( ctx, ctx->Stencil.ZFailFunc[face], face,
+                           n, stencil, failMask );
+      }
+      if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
+         apply_stencil_op( ctx, ctx->Stencil.ZPassFunc[face], face,
+                           n, stencil, passMask );
+      }
+   }
+
+   /*
+    * Write updated stencil values back into hardware stencil buffer.
+    */
+   if (!rb->GetPointer(ctx, rb, 0, 0)) {
+      rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
+   }
+   
+   span->writeAll = GL_FALSE;
+   
+   return GL_TRUE;  /* one or more fragments passed both tests */
+}
+
+
+
+/*
+ * Return the address of a stencil buffer value given the window coords:
+ */
+#define STENCIL_ADDRESS(X, Y)  (stencilStart + (Y) * stride + (X))
+
+
+
+/**
+ * Apply the given stencil operator for each pixel in the array whose
+ * mask flag is set.
+ * \note  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( GLcontext *ctx,
+                            GLuint n, const GLint x[], const GLint y[],
+                            GLenum oper, GLuint face, const GLubyte mask[] )
+{
+   struct gl_framebuffer *fb = ctx->DrawBuffer;
+   struct gl_renderbuffer *rb = fb->_StencilBuffer;
+   const GLstencil stencilMax = (1 << fb->Visual.stencilBits) - 1;
+   const GLstencil ref = ctx->Stencil.Ref[face];
+   const GLstencil wrtmask = ctx->Stencil.WriteMask[face];
+   const GLstencil invmask = (GLstencil) (~wrtmask);
+   GLuint i;
+   GLstencil *stencilStart = (GLubyte *) rb->Data;
+   const GLuint stride = rb->Width;
+
+   ASSERT(rb->GetPointer(ctx, rb, 0, 0));
+   ASSERT(sizeof(GLstencil) == 1);
+
+   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 < stencilMax) {
+		     *sptr = (GLstencil) (*sptr + 1);
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  if (*sptr < stencilMax) {
+		     *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:
+         _mesa_problem(ctx, "Bad stencilop in apply_stencil_op_to_pixels");
+   }
+}
+
+
+
+/**
+ * Apply stencil test to an array of pixels before depth buffering.
+ *
+ * \note 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  GL_FALSE = all pixels failed, GL_TRUE = zero or more pixels passed.
+ */
+static GLboolean
+stencil_test_pixels( GLcontext *ctx, GLuint face, GLuint n,
+                     const GLint x[], const GLint y[], GLubyte mask[] )
+{
+   const struct gl_framebuffer *fb = ctx->DrawBuffer;
+   struct gl_renderbuffer *rb = fb->_StencilBuffer;
+   GLubyte fail[MAX_WIDTH];
+   GLstencil r, s;
+   GLuint i;
+   GLboolean allfail = GL_FALSE;
+   const GLuint valueMask = ctx->Stencil.ValueMask[face];
+   const GLstencil *stencilStart = (GLstencil *) rb->Data;
+   const GLuint stride = rb->Width;
+
+   ASSERT(rb->GetPointer(ctx, rb, 0, 0));
+   ASSERT(sizeof(GLstencil) == 1);
+
+   /*
+    * 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[face]) {
+      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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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[face] & valueMask);
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               const GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = (GLstencil) (*sptr & 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:
+         _mesa_problem(ctx, "Bad stencil func in gl_stencil_pixels");
+         return 0;
+   }
+
+   if (ctx->Stencil.FailFunc[face] != GL_KEEP) {
+      apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc[face],
+                                  face, 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_FALSE - all fragments failed the testing
+ *         GL_TRUE - one or more fragments passed the testing
+ */
+static GLboolean
+stencil_and_ztest_pixels( GLcontext *ctx, SWspan *span, GLuint face )
+{
+   GLubyte passMask[MAX_WIDTH], failMask[MAX_WIDTH], origMask[MAX_WIDTH];
+   struct gl_framebuffer *fb = ctx->DrawBuffer;
+   struct gl_renderbuffer *rb = fb->_StencilBuffer;
+   const GLuint n = span->end;
+   const GLint *x = span->array->x;
+   const GLint *y = span->array->y;
+   GLubyte *mask = span->array->mask;
+
+   ASSERT(span->arrayMask & SPAN_XY);
+   ASSERT(ctx->Stencil.Enabled);
+   ASSERT(n <= MAX_WIDTH);
+
+   if (!rb->GetPointer(ctx, rb, 0, 0)) {
+      /* No direct access */
+      GLstencil stencil[MAX_WIDTH];
+
+      ASSERT(rb->DataType == GL_UNSIGNED_BYTE);
+      _swrast_get_values(ctx, rb, n, x, y, stencil, sizeof(GLubyte));
+
+      _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));          
+
+      (void) do_stencil_test(ctx, face, n, stencil, mask);
+
+      if (ctx->Depth.Test == GL_FALSE) {
+         apply_stencil_op(ctx, ctx->Stencil.ZPassFunc[face], face,
+                          n, stencil, mask);
+      }
+      else {
+         GLubyte tmpMask[MAX_WIDTH]; 
+         _mesa_memcpy(tmpMask, mask, n * sizeof(GLubyte));
+
+         _swrast_depth_test_span(ctx, span);
+
+         compute_pass_fail_masks(n, tmpMask, mask, passMask, failMask);
+
+         if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
+            apply_stencil_op(ctx, ctx->Stencil.ZFailFunc[face], face,
+                             n, stencil, failMask);
+         }
+         if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
+            apply_stencil_op(ctx, ctx->Stencil.ZPassFunc[face], face,
+                             n, stencil, passMask);
+         }
+      }
+
+      /* Write updated stencil values into hardware stencil buffer */
+      rb->PutValues(ctx, rb, n, x, y, stencil, origMask);
+
+      return GL_TRUE;
+   }
+   else {
+      /* Direct access to stencil buffer */
+
+      if (stencil_test_pixels(ctx, face, 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[face], face, mask);
+      }
+      else {
+         _mesa_memcpy(origMask, mask, n * sizeof(GLubyte));
+
+         _swrast_depth_test_span(ctx, span);
+
+         compute_pass_fail_masks(n, origMask, mask, passMask, failMask);
+
+         if (ctx->Stencil.ZFailFunc[face] != GL_KEEP) {
+            apply_stencil_op_to_pixels(ctx, n, x, y,
+                                       ctx->Stencil.ZFailFunc[face],
+                                       face, failMask);
+         }
+         if (ctx->Stencil.ZPassFunc[face] != GL_KEEP) {
+            apply_stencil_op_to_pixels(ctx, n, x, y,
+                                       ctx->Stencil.ZPassFunc[face],
+                                       face, passMask);
+         }
+      }
+
+      return GL_TRUE;  /* one or more fragments passed both tests */
+   }
+}
+
+
+/**
+ * /return GL_TRUE = one or more fragments passed,
+ * GL_FALSE = all fragments failed.
+ */
+GLboolean
+_swrast_stencil_and_ztest_span(GLcontext *ctx, SWspan *span)
+{
+   const GLuint face = (span->facing == 0) ? 0 : ctx->Stencil._BackFace;
+
+   if (span->arrayMask & SPAN_XY)
+      return stencil_and_ztest_pixels(ctx, span, face);
+   else
+      return stencil_and_ztest_span(ctx, span, face);
+}
+
+
+#if 0
+GLuint
+clip_span(GLuint bufferWidth, GLuint bufferHeight,
+          GLint x, GLint y, GLuint *count)
+{
+   GLuint n = *count;
+   GLuint skipPixels = 0;
+
+   if (y < 0 || y >= bufferHeight || x + n <= 0 || x >= bufferWidth) {
+      /* totally out of bounds */
+      n = 0;
+   }
+   else {
+      /* left clip */
+      if (x < 0) {
+         skipPixels = -x;
+         x = 0;
+         n -= skipPixels;
+      }
+      /* right clip */
+      if (x + n > bufferWidth) {
+         GLint dx = x + n - bufferWidth;
+         n -= dx;
+      }
+   }
+
+   *count = n;
+
+   return skipPixels;
+}
+#endif
+
+
+/**
+ * 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
+_swrast_read_stencil_span(GLcontext *ctx, struct gl_renderbuffer *rb,
+                          GLint n, GLint x, GLint y, GLstencil stencil[])
+{
+   if (y < 0 || y >= (GLint) rb->Height ||
+       x + n <= 0 || x >= (GLint) rb->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 > (GLint) rb->Width) {
+      GLint dx = x + n - rb->Width;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+   rb->GetRow(ctx, rb, n, x, y, stencil);
+}
+
+
+
+/**
+ * Write a span of stencil values to the stencil buffer.  This function
+ * applies the stencil write mask when needed.
+ * Used for glDraw/CopyPixels
+ * Input:  n - how many pixels
+ *         x, y - location of first pixel
+ *         stencil - the array of stencil values
+ */
+void
+_swrast_write_stencil_span(GLcontext *ctx, GLint n, GLint x, GLint y,
+                           const GLstencil stencil[] )
+{
+   struct gl_framebuffer *fb = ctx->DrawBuffer;
+   struct gl_renderbuffer *rb = fb->_StencilBuffer;
+   const GLuint stencilMax = (1 << fb->Visual.stencilBits) - 1;
+   const GLuint stencilMask = ctx->Stencil.WriteMask[0];
+
+   if (y < 0 || y >= (GLint) rb->Height ||
+       x + n <= 0 || x >= (GLint) rb->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 > (GLint) rb->Width) {
+      GLint dx = x + n - rb->Width;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+   if ((stencilMask & stencilMax) != stencilMax) {
+      /* need to apply writemask */
+      GLstencil destVals[MAX_WIDTH], newVals[MAX_WIDTH];
+      GLint i;
+      rb->GetRow(ctx, rb, n, x, y, destVals);
+      for (i = 0; i < n; i++) {
+         newVals[i]
+            = (stencil[i] & stencilMask) | (destVals[i] & ~stencilMask);
+      }
+      rb->PutRow(ctx, rb, n, x, y, newVals, NULL);
+   }
+   else {
+      rb->PutRow(ctx, rb, n, x, y, stencil, NULL);
+   }
+}
+
+
+
+/**
+ * Clear the stencil buffer.
+ */
+void
+_swrast_clear_stencil_buffer( GLcontext *ctx, struct gl_renderbuffer *rb )
+{
+   const GLubyte stencilBits = ctx->DrawBuffer->Visual.stencilBits;
+   const GLuint mask = ctx->Stencil.WriteMask[0];
+   const GLuint invMask = ~mask;
+   const GLuint clearVal = (ctx->Stencil.Clear & mask);
+   const GLuint stencilMax = (1 << stencilBits) - 1;
+   GLint x, y, width, height;
+
+   if (!rb || mask == 0)
+      return;
+
+   ASSERT(rb->DataType == GL_UNSIGNED_BYTE ||
+          rb->DataType == GL_UNSIGNED_SHORT);
+
+   ASSERT(rb->_BaseFormat == GL_STENCIL_INDEX);
+
+   /* compute region to clear */
+   x = ctx->DrawBuffer->_Xmin;
+   y = ctx->DrawBuffer->_Ymin;
+   width  = ctx->DrawBuffer->_Xmax - ctx->DrawBuffer->_Xmin;
+   height = ctx->DrawBuffer->_Ymax - ctx->DrawBuffer->_Ymin;
+
+   if (rb->GetPointer(ctx, rb, 0, 0)) {
+      /* Direct buffer access */
+      if ((mask & stencilMax) != stencilMax) {
+         /* need to mask the clear */
+         if (rb->DataType == GL_UNSIGNED_BYTE) {
+            GLint i, j;
+            for (i = 0; i < height; i++) {
+               GLubyte *stencil = (GLubyte*) rb->GetPointer(ctx, rb, x, y + i);
+               for (j = 0; j < width; j++) {
+                  stencil[j] = (stencil[j] & invMask) | clearVal;
+               }
+            }
+         }
+         else {
+            GLint i, j;
+            for (i = 0; i < height; i++) {
+               GLushort *stencil = (GLushort*) rb->GetPointer(ctx, rb, x, y + i);
+               for (j = 0; j < width; j++) {
+                  stencil[j] = (stencil[j] & invMask) | clearVal;
+               }
+            }
+         }
+      }
+      else {
+         /* no bit masking */
+         if (width == (GLint) rb->Width && rb->DataType == GL_UNSIGNED_BYTE) {
+            /* optimized case */
+            /* Note: bottom-to-top raster assumed! */
+            GLubyte *stencil = (GLubyte *) rb->GetPointer(ctx, rb, x, y);
+            GLuint len = width * height * sizeof(GLubyte);
+            _mesa_memset(stencil, clearVal, len);
+         }
+         else {
+            /* general case */
+            GLint i;
+            for (i = 0; i < height; i++) {
+               GLvoid *stencil = rb->GetPointer(ctx, rb, x, y + i);
+               if (rb->DataType == GL_UNSIGNED_BYTE) {
+                  _mesa_memset(stencil, clearVal, width);
+               }
+               else {
+                  _mesa_memset16((short unsigned int*) stencil, clearVal, width);
+               }
+            }
+         }
+      }
+   }
+   else {
+      /* no direct access */
+      if ((mask & stencilMax) != stencilMax) {
+         /* need to mask the clear */
+         if (rb->DataType == GL_UNSIGNED_BYTE) {
+            GLint i, j;
+            for (i = 0; i < height; i++) {
+               GLubyte stencil[MAX_WIDTH];
+               rb->GetRow(ctx, rb, width, x, y + i, stencil);
+               for (j = 0; j < width; j++) {
+                  stencil[j] = (stencil[j] & invMask) | clearVal;
+               }
+               rb->PutRow(ctx, rb, width, x, y + i, stencil, NULL);
+            }
+         }
+         else {
+            GLint i, j;
+            for (i = 0; i < height; i++) {
+               GLushort stencil[MAX_WIDTH];
+               rb->GetRow(ctx, rb, width, x, y + i, stencil);
+               for (j = 0; j < width; j++) {
+                  stencil[j] = (stencil[j] & invMask) | clearVal;
+               }
+               rb->PutRow(ctx, rb, width, x, y + i, stencil, NULL);
+            }
+         }
+      }
+      else {
+         /* no bit masking */
+         const GLubyte clear8 = (GLubyte) clearVal;
+         const GLushort clear16 = (GLushort) clearVal;
+         const void *clear;
+         GLint i;
+         if (rb->DataType == GL_UNSIGNED_BYTE) {
+            clear = &clear8;
+         }
+         else {
+            clear = &clear16;
+         }
+         for (i = 0; i < height; i++) {
+            rb->PutMonoRow(ctx, rb, width, x, y + i, clear, NULL);
+         }
+      }
+   }
+}