From afb833d4e89c312460a4ab9ed6a7a8ca4ebbfe1c Mon Sep 17 00:00:00 2001
From: jtg <jtg>
Date: Thu, 19 Aug 1999 00:55:39 +0000
Subject: Initial revision

---
 src/mesa/main/stencil.c | 1107 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 1107 insertions(+)
 create mode 100644 src/mesa/main/stencil.c

(limited to 'src/mesa/main/stencil.c')

diff --git a/src/mesa/main/stencil.c b/src/mesa/main/stencil.c
new file mode 100644
index 0000000000..69bd70188b
--- /dev/null
+++ b/src/mesa/main/stencil.c
@@ -0,0 +1,1107 @@
+/* $Id: stencil.c,v 1.1 1999/08/19 00:55:41 jtg Exp $ */
+
+/*
+ * Mesa 3-D graphics library
+ * Version:  3.1
+ * 
+ * Copyright (C) 1999  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.
+ */
+
+
+#ifdef PC_HEADER
+#include "all.h"
+#else
+#include <stdlib.h>
+#include <string.h>
+#include "context.h"
+#include "macros.h"
+#include "pb.h"
+#include "stencil.h"
+#include "types.h"
+#ifdef XFree86Server
+#include "GL/xf86glx.h"
+#endif
+#endif
+
+
+#if STENCIL_BITS==8
+#  define STENCIL_MAX 0xff
+#elif STENCIL_BITS==16
+#  define STENCIL_MAX 0xffff
+#else
+   illegal number of stencil bits
+#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 )
+{
+   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glClearStencil");
+   ctx->Stencil.Clear = (GLstencil) s;
+
+   if (ctx->Driver.ClearStencil) {
+      (*ctx->Driver.ClearStencil)( ctx, s );
+   }
+}
+
+
+
+void gl_StencilFunc( GLcontext *ctx, GLenum func, GLint ref, GLuint mask )
+{
+   GLint maxref;
+
+   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glStencilFunc");
+
+   switch (func) {
+      case GL_NEVER:
+      case GL_LESS:
+      case GL_LEQUAL:
+      case GL_GREATER:
+      case GL_GEQUAL:
+      case GL_EQUAL:
+      case GL_NOTEQUAL:
+      case GL_ALWAYS:
+         ctx->Stencil.Function = func;
+         break;
+      default:
+         gl_error( ctx, GL_INVALID_ENUM, "glStencilFunc" );
+         return;
+   }
+
+   maxref = (1 << STENCIL_BITS) - 1;
+   ctx->Stencil.Ref = CLAMP( ref, 0, maxref );
+   ctx->Stencil.ValueMask = mask;
+
+   if (ctx->Driver.StencilFunc) {
+      (*ctx->Driver.StencilFunc)( ctx, func, ctx->Stencil.Ref, mask );
+   }
+}
+
+
+
+void gl_StencilMask( GLcontext *ctx, GLuint mask )
+{
+   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glStencilMask");
+   ctx->Stencil.WriteMask = (GLstencil) mask;
+
+   if (ctx->Driver.StencilMask) {
+      (*ctx->Driver.StencilMask)( ctx, mask );
+   }
+}
+
+
+
+void gl_StencilOp( GLcontext *ctx, GLenum fail, GLenum zfail, GLenum zpass )
+{
+   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glStencilOp");
+   switch (fail) {
+      case GL_KEEP:
+      case GL_ZERO:
+      case GL_REPLACE:
+      case GL_INCR:
+      case GL_DECR:
+      case GL_INVERT:
+      case GL_INCR_WRAP_EXT:
+      case GL_DECR_WRAP_EXT:
+         ctx->Stencil.FailFunc = fail;
+         break;
+      default:
+         gl_error( ctx, GL_INVALID_ENUM, "glStencilOp" );
+         return;
+   }
+   switch (zfail) {
+      case GL_KEEP:
+      case GL_ZERO:
+      case GL_REPLACE:
+      case GL_INCR:
+      case GL_DECR:
+      case GL_INVERT:
+      case GL_INCR_WRAP_EXT:
+      case GL_DECR_WRAP_EXT:
+         ctx->Stencil.ZFailFunc = zfail;
+         break;
+      default:
+         gl_error( ctx, GL_INVALID_ENUM, "glStencilOp" );
+         return;
+   }
+   switch (zpass) {
+      case GL_KEEP:
+      case GL_ZERO:
+      case GL_REPLACE:
+      case GL_INCR:
+      case GL_DECR:
+      case GL_INVERT:
+      case GL_INCR_WRAP_EXT:
+      case GL_DECR_WRAP_EXT:
+         ctx->Stencil.ZPassFunc = zpass;
+         break;
+      default:
+         gl_error( ctx, GL_INVALID_ENUM, "glStencilOp" );
+         return;
+   }
+
+   if (ctx->Driver.StencilOp) {
+      (*ctx->Driver.StencilOp)( ctx, fail, zfail, zpass );
+   }
+}
+
+
+
+/* Stencil Logic:
+
+IF stencil test fails THEN
+   Don't write the pixel (RGBA,Z)
+   Execute FailOp
+ELSE
+   Write the pixel
+ENDIF
+
+Perform Depth Test
+
+IF depth test passes OR no depth buffer THEN
+   Execute ZPass
+   Write the pixel
+ELSE
+   Execute ZFail
+ENDIF
+
+*/
+
+
+
+
+/*
+ * Apply the given stencil operator for each pixel in the span whose
+ * mask flag is set.
+ * Input:  n - number of pixels in the span
+ *         x, y - location of leftmost pixel in the span
+ *         oper - the stencil buffer operator
+ *         mask - array [n] of flag:  1=apply operator, 0=don't apply operator
+ */
+static void apply_stencil_op_to_span( GLcontext *ctx,
+                                      GLuint n, GLint x, GLint y,
+				      GLenum oper, GLubyte mask[] )
+{
+   const GLstencil ref = ctx->Stencil.Ref;
+   const GLstencil wrtmask = ctx->Stencil.WriteMask;
+   const GLstencil invmask = ~ctx->Stencil.WriteMask;
+   GLstencil *stencil = STENCIL_ADDRESS( x, y );
+   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] = 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] = (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] = 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] = (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] = 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] = (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] = (invmask & s) | (wrtmask & (stencil[i]+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] = (invmask & s) | (wrtmask & (stencil[i]-1));
+	       }
+	    }
+	 }
+	 break;
+      case GL_INVERT:
+	 if (invmask==0) {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  GLstencil s = stencil[i];
+		  stencil[i] = ~s;
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  GLstencil s = stencil[i];
+		  stencil[i] = (invmask & s) | (wrtmask & ~s);
+	       }
+	    }
+	 }
+	 break;
+      default:
+         gl_problem(ctx, "Bad stencilop in apply_stencil_op_to_span");
+   }
+}
+
+
+
+
+/*
+ * 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
+ *         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.
+ */
+GLint gl_stencil_span( GLcontext *ctx,
+                       GLuint n, GLint x, GLint y, GLubyte mask[] )
+{
+   GLubyte fail[MAX_WIDTH];
+   GLint allfail = 0;
+   GLuint i;
+   GLstencil r, s;
+   GLstencil *stencil;
+
+   stencil = STENCIL_ADDRESS( x, y );
+
+   /*
+    * 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 = 1;
+	 break;
+      case GL_LESS:
+	 r = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+	       s = 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;
+   }
+
+   apply_stencil_op_to_span( ctx, n, x, y, ctx->Stencil.FailFunc, fail );
+
+   return (allfail) ? 0 : 1;
+}
+
+
+
+
+/*
+ * Apply the combination depth-buffer/stencil operator to a span of pixels.
+ * 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) 
+ */
+void gl_depth_stencil_span( GLcontext *ctx,
+                            GLuint n, GLint x, 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_span( ctx, n, x, y, ctx->Stencil.ZPassFunc, mask );
+   }
+   else {
+      /*
+       * Perform depth buffering, then apply zpass or zfail stencil function.
+       */
+      GLubyte passmask[MAX_WIDTH], failmask[MAX_WIDTH], oldmask[MAX_WIDTH];
+      GLuint i;
+
+      /* init pass and fail masks to zero, copy mask[] to oldmask[] */
+      for (i=0;i<n;i++) {
+	 passmask[i] = failmask[i] = 0;
+         oldmask[i] = mask[i];
+      }
+
+      /* apply the depth test */
+      if (ctx->Driver.DepthTestSpan)
+         (*ctx->Driver.DepthTestSpan)( ctx, n, x, y, z, mask );
+
+      /* set the stencil pass/fail flags according to result of depth test */
+      for (i=0;i<n;i++) {
+         if (oldmask[i]) {
+            if (mask[i]) {
+               passmask[i] = 1;
+            }
+            else {
+               failmask[i] = 1;
+            }
+         }
+      }
+
+      /* apply the pass and fail operations */
+      apply_stencil_op_to_span( ctx, n, x, y, ctx->Stencil.ZFailFunc, failmask );
+      apply_stencil_op_to_span( ctx, n, x, y, ctx->Stencil.ZPassFunc, passmask );
+   }
+}
+
+
+
+
+/*
+ * Apply the given stencil operator for each pixel in the array whose
+ * mask flag is set.
+ * 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, GLubyte mask[] )
+{
+   GLuint i;
+   GLstencil ref;
+   GLstencil wrtmask, invmask;
+
+   wrtmask = ctx->Stencil.WriteMask;
+   invmask = ~ctx->Stencil.WriteMask;
+
+   ref = ctx->Stencil.Ref;
+
+   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 = 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 = (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 = *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 = (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 = *sptr - 1;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+		  if (*sptr>0) {
+		     *sptr = (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 = *sptr + 1;
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (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 = *sptr - 1;
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (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 = ~*sptr;
+	       }
+	    }
+	 }
+	 else {
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+                  GLstencil *sptr = STENCIL_ADDRESS( x[i], y[i] );
+                  *sptr = (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.
+ * 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.
+ */
+GLint gl_stencil_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;
+
+   /*
+    * 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 = 1;
+	 break;
+      case GL_LESS:
+	 r = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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 = ctx->Stencil.Ref & ctx->Stencil.ValueMask;
+	 for (i=0;i<n;i++) {
+	    if (mask[i]) {
+               GLstencil *sptr = STENCIL_ADDRESS(x[i],y[i]);
+	       s = *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;
+   }
+
+   apply_stencil_op_to_pixels( ctx, n, x, y, ctx->Stencil.FailFunc, fail );
+
+   return (allfail) ? 0 : 1;
+}
+
+
+
+
+/*
+ * 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
+ *         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) 
+ */
+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 );
+   }
+   else {
+      /*
+       * Perform depth buffering, then apply zpass or zfail stencil function.
+       */
+      GLubyte passmask[PB_SIZE], failmask[PB_SIZE], oldmask[PB_SIZE];
+      GLuint i;
+
+      /* init pass and fail masks to zero */
+      for (i=0;i<n;i++) {
+	 passmask[i] = failmask[i] = 0;
+         oldmask[i] = mask[i];
+      }
+
+      /* 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 test */
+      for (i=0;i<n;i++) {
+         if (oldmask[i]) {
+            if (mask[i]) {
+               passmask[i] = 1;
+            }
+            else {
+               failmask[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 );
+   }
+
+}
+
+
+
+/*
+ * Return a span of stencil values from the stencil buffer.
+ * Input:  n - how many pixels
+ *         x,y - location of first pixel
+ * Output:  stencil - the array of stencil values
+ */
+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 );
+#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.
+ * Input:  n - how many pixels
+ *         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 );
+#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 gl_alloc_stencil_buffer( GLcontext *ctx )
+{
+   GLuint buffersize = ctx->Buffer->Width * ctx->Buffer->Height;
+
+   /* deallocate current stencil buffer if present */
+   if (ctx->Buffer->Stencil) {
+      free(ctx->Buffer->Stencil);
+      ctx->Buffer->Stencil = NULL;
+   }
+
+   /* allocate new stencil buffer */
+   ctx->Buffer->Stencil = (GLstencil *) malloc(buffersize * sizeof(GLstencil));
+   if (!ctx->Buffer->Stencil) {
+      /* out of memory */
+      ctx->Stencil.Enabled = GL_FALSE;
+      gl_error( ctx, GL_OUT_OF_MEMORY, "gl_alloc_stencil_buffer" );
+   }
+}
+
+
+
+
+/*
+ * Clear the stencil buffer.  If the stencil buffer doesn't exist yet we'll
+ * allocate it now.
+ */
+void gl_clear_stencil_buffer( GLcontext *ctx )
+{
+   if (ctx->Visual->StencilBits==0 || !ctx->Buffer->Stencil) {
+      /* no stencil buffer */
+      return;
+   }
+
+   if (ctx->Scissor.Enabled) {
+      /* clear scissor region only */
+      GLint y;
+      GLint width = ctx->Buffer->Xmax - ctx->Buffer->Xmin + 1;
+      for (y=ctx->Buffer->Ymin; y<=ctx->Buffer->Ymax; y++) {
+         GLstencil *ptr = STENCIL_ADDRESS( ctx->Buffer->Xmin, y );
+#if STENCIL_BITS==8
+         MEMSET( ptr, ctx->Stencil.Clear, width * sizeof(GLstencil) );
+#else
+         GLint x;
+         for (x = 0; x < width; x++)
+            ptr[x] = ctx->Stencil.Clear;
+#endif
+      }
+   }
+   else {
+      /* clear whole stencil buffer */
+#if STENCIL_BITS==8
+      MEMSET( ctx->Buffer->Stencil, ctx->Stencil.Clear,
+              ctx->Buffer->Width * ctx->Buffer->Height * sizeof(GLstencil) );
+#else
+      GLuint i;
+      GLuint pixels = ctx->Buffer->Width * ctx->Buffer->Height;
+      GLstencil *buffer = ctx->Buffer->Stencil;
+      for (i = 0; i < pixels; i++)
+         ptr[i] = ctx->Stencil.Clear;
+#endif
+   }
+}
-- 
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