s_depth.c

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/*
 * Mesa 3-D graphics library
 * Version:  7.2.1
 *
 * Copyright (C) 1999-2008  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/macros.h"
#include "main/imports.h"
#include "main/fbobject.h"

#include "s_depth.h"
#include "s_context.h"
#include "s_span.h"


static GLuint
depth_test_span16( GLcontext *ctx, GLuint n,
                   GLushort zbuffer[], const GLuint z[], GLubyte mask[] )
{
   GLuint passed = 0;

   /* switch cases ordered from most frequent to less frequent */
   switch (ctx->Depth.Func) {
      case GL_LESS:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          if (z[i] < zbuffer[i]) {
             /* pass */
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          if (z[i] < zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_LEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] <= zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] <= zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] >= zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] >= zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GREATER:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] > zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] > zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_NOTEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] != zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] != zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_EQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] == zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] == zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_ALWAYS:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          zbuffer[i] = z[i];
          passed++;
           }
        }
     }
     else {
        /* Don't update Z buffer or mask */
        passed = n;
     }
     break;
      case GL_NEVER:
         _mesa_bzero(mask, n * sizeof(GLubyte));
     break;
      default:
         _mesa_problem(ctx, "Bad depth func in depth_test_span16");
   }

   return passed;
}


static GLuint
depth_test_span32( GLcontext *ctx, GLuint n,
                   GLuint zbuffer[], const GLuint z[], GLubyte mask[] )
{
   GLuint passed = 0;

   /* switch cases ordered from most frequent to less frequent */
   switch (ctx->Depth.Func) {
      case GL_LESS:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          if (z[i] < zbuffer[i]) {
             /* pass */
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          if (z[i] < zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_LEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] <= zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] <= zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] >= zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] >= zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GREATER:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] > zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] > zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_NOTEQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] != zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] != zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_EQUAL:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] == zbuffer[i]) {
             zbuffer[i] = z[i];
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          if (z[i] == zbuffer[i]) {
             /* pass */
             passed++;
          }
          else {
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_ALWAYS:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0;i<n;i++) {
           if (mask[i]) {
          zbuffer[i] = z[i];
          passed++;
           }
        }
     }
     else {
        /* Don't update Z buffer or mask */
        passed = n;
     }
     break;
      case GL_NEVER:
         _mesa_bzero(mask, n * sizeof(GLubyte));
     break;
      default:
         _mesa_problem(ctx, "Bad depth func in depth_test_span32");
   }

   return passed;
}



/*
 * Apply depth test to span of fragments.
 */
static GLuint
depth_test_span( GLcontext *ctx, SWspan *span)
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_DepthBuffer;
   const GLint x = span->x;
   const GLint y = span->y;
   const GLuint count = span->end;
   const GLuint *zValues = span->array->z;
   GLubyte *mask = span->array->mask;
   GLuint passed;

   ASSERT((span->arrayMask & SPAN_XY) == 0);
   ASSERT(span->arrayMask & SPAN_Z);
   
   if (rb->GetPointer(ctx, rb, 0, 0)) {
      /* Directly access buffer */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         GLushort *zbuffer = (GLushort *) rb->GetPointer(ctx, rb, x, y);
         passed = depth_test_span16(ctx, count, zbuffer, zValues, mask);
      }
      else {
         GLuint *zbuffer = (GLuint *) rb->GetPointer(ctx, rb, x, y);
         ASSERT(rb->DataType == GL_UNSIGNED_INT);
         passed = depth_test_span32(ctx, count, zbuffer, zValues, mask);
      }
   }
   else {
      /* read depth values from buffer, test, write back */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         GLushort zbuffer[MAX_WIDTH];
         rb->GetRow(ctx, rb, count, x, y, zbuffer);
         passed = depth_test_span16(ctx, count, zbuffer, zValues, mask);
         rb->PutRow(ctx, rb, count, x, y, zbuffer, mask);
      }
      else {
         GLuint zbuffer[MAX_WIDTH];
         ASSERT(rb->DataType == GL_UNSIGNED_INT);
         rb->GetRow(ctx, rb, count, x, y, zbuffer);
         passed = depth_test_span32(ctx, count, zbuffer, zValues, mask);
         rb->PutRow(ctx, rb, count, x, y, zbuffer, mask);
      }
   }

   if (passed < count) {
      span->writeAll = GL_FALSE;
   }
   return passed;
}



#define Z_ADDRESS(X, Y)   (zStart + (Y) * stride + (X))


/*
 * Do depth testing for an array of fragments at assorted locations.
 */
static void
direct_depth_test_pixels16(GLcontext *ctx, GLushort *zStart, GLuint stride,
                           GLuint n, const GLint x[], const GLint y[],
                           const GLuint z[], GLubyte mask[] )
{
   /* switch cases ordered from most frequent to less frequent */
   switch (ctx->Depth.Func) {
      case GL_LESS:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] < *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] < *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_LEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] <= *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] <= *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] >= *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] >= *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GREATER:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] > *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] > *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_NOTEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] != *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] != *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_EQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] == *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] == *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_ALWAYS:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLushort *zptr = Z_ADDRESS(x[i], y[i]);
          *zptr = z[i];
           }
        }
     }
     else {
        /* Don't update Z buffer or mask */
     }
     break;
      case GL_NEVER:
     /* depth test never passes */
         _mesa_bzero(mask, n * sizeof(GLubyte));
     break;
      default:
         _mesa_problem(ctx, "Bad depth func in direct_depth_test_pixels");
   }
}



/*
 * Do depth testing for an array of fragments with direct access to zbuffer.
 */
static void
direct_depth_test_pixels32(GLcontext *ctx, GLuint *zStart, GLuint stride,
                           GLuint n, const GLint x[], const GLint y[],
                           const GLuint z[], GLubyte mask[] )
{
   /* switch cases ordered from most frequent to less frequent */
   switch (ctx->Depth.Func) {
      case GL_LESS:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] < *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] < *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_LEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] <= *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] <= *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] >= *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] >= *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_GREATER:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] > *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] > *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_NOTEQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] != *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] != *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_EQUAL:
         if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] == *zptr) {
             /* pass */
             *zptr = z[i];
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     else {
        /* Don't update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          if (z[i] == *zptr) {
             /* pass */
          }
          else {
             /* fail */
             mask[i] = 0;
          }
           }
        }
     }
     break;
      case GL_ALWAYS:
     if (ctx->Depth.Mask) {
        /* Update Z buffer */
            GLuint i;
        for (i=0; i<n; i++) {
           if (mask[i]) {
          GLuint *zptr = Z_ADDRESS(x[i], y[i]);
          *zptr = z[i];
           }
        }
     }
     else {
        /* Don't update Z buffer or mask */
     }
     break;
      case GL_NEVER:
     /* depth test never passes */
         _mesa_bzero(mask, n * sizeof(GLubyte));
     break;
      default:
         _mesa_problem(ctx, "Bad depth func in direct_depth_test_pixels");
   }
}




static GLuint
depth_test_pixels( GLcontext *ctx, SWspan *span )
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_DepthBuffer;
   const GLuint count = span->end;
   const GLint *x = span->array->x;
   const GLint *y = span->array->y;
   const GLuint *z = span->array->z;
   GLubyte *mask = span->array->mask;

   if (rb->GetPointer(ctx, rb, 0, 0)) {
      /* Directly access values */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         GLushort *zStart = (GLushort *) rb->Data;
         GLuint stride = rb->Width;
         direct_depth_test_pixels16(ctx, zStart, stride, count, x, y, z, mask);
      }
      else {
         GLuint *zStart = (GLuint *) rb->Data;
         GLuint stride = rb->Width;
         ASSERT(rb->DataType == GL_UNSIGNED_INT);
         direct_depth_test_pixels32(ctx, zStart, stride, count, x, y, z, mask);
      }
   }
   else {
      /* read depth values from buffer, test, write back */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         GLushort zbuffer[MAX_WIDTH];
         _swrast_get_values(ctx, rb, count, x, y, zbuffer, sizeof(GLushort));
         depth_test_span16(ctx, count, zbuffer, z, mask);
         rb->PutValues(ctx, rb, count, x, y, zbuffer, mask);
      }
      else {
         GLuint zbuffer[MAX_WIDTH];
         ASSERT(rb->DataType == GL_UNSIGNED_INT);
         _swrast_get_values(ctx, rb, count, x, y, zbuffer, sizeof(GLuint));
         depth_test_span32(ctx, count, zbuffer, z, mask);
         rb->PutValues(ctx, rb, count, x, y, zbuffer, mask);
      }
   }

   return count; /* not really correct, but OK */
}


GLuint
_swrast_depth_test_span( GLcontext *ctx, SWspan *span)
{
   if (span->arrayMask & SPAN_XY)
      return depth_test_pixels(ctx, span);
   else
      return depth_test_span(ctx, span);
}


GLboolean
_swrast_depth_bounds_test( GLcontext *ctx, SWspan *span )
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;
   struct gl_renderbuffer *rb = fb->_DepthBuffer;
   GLuint zMin = (GLuint) (ctx->Depth.BoundsMin * fb->_DepthMaxF + 0.5F);
   GLuint zMax = (GLuint) (ctx->Depth.BoundsMax * fb->_DepthMaxF + 0.5F);
   GLubyte *mask = span->array->mask;
   const GLuint count = span->end;
   GLuint i;
   GLboolean anyPass = GL_FALSE;

   if (rb->DataType == GL_UNSIGNED_SHORT) {
      /* get 16-bit values */
      GLushort zbuffer16[MAX_WIDTH], *zbuffer;
      if (span->arrayMask & SPAN_XY) {
         _swrast_get_values(ctx, rb, count, span->array->x, span->array->y,
                            zbuffer16, sizeof(GLushort));
         zbuffer = zbuffer16;
      }
      else {
         zbuffer = (GLushort*) rb->GetPointer(ctx, rb, span->x, span->y);
         if (!zbuffer) {
            rb->GetRow(ctx, rb, count, span->x, span->y, zbuffer16);
            zbuffer = zbuffer16;
         }
      }
      assert(zbuffer);

      /* Now do the tests */
      for (i = 0; i < count; i++) {
         if (mask[i]) {
            if (zbuffer[i] < zMin || zbuffer[i] > zMax)
               mask[i] = GL_FALSE;
            else
               anyPass = GL_TRUE;
         }
      }
   }
   else {
      /* get 32-bit values */
      GLuint zbuffer32[MAX_WIDTH], *zbuffer;
      ASSERT(rb->DataType == GL_UNSIGNED_INT);
      if (span->arrayMask & SPAN_XY) {
         _swrast_get_values(ctx, rb, count, span->array->x, span->array->y,
                            zbuffer32, sizeof(GLuint));
         zbuffer = zbuffer32;
      }
      else {
         zbuffer = (GLuint*) rb->GetPointer(ctx, rb, span->x, span->y);
         if (!zbuffer) {
            rb->GetRow(ctx, rb, count, span->x, span->y, zbuffer32);
            zbuffer = zbuffer32;
         }
      }
      assert(zbuffer);

      /* Now do the tests */
      for (i = 0; i < count; i++) {
         if (mask[i]) {
            if (zbuffer[i] < zMin || zbuffer[i] > zMax)
               mask[i] = GL_FALSE;
            else
               anyPass = GL_TRUE;
         }
      }
   }

   return anyPass;
}



/**********************************************************************/
/*****                      Read Depth Buffer                     *****/
/**********************************************************************/


void
_swrast_read_depth_span_float( GLcontext *ctx, struct gl_renderbuffer *rb,
                               GLint n, GLint x, GLint y, GLfloat depth[] )
{
   const GLfloat scale = 1.0F / ctx->DrawBuffer->_DepthMaxF;

   if (!rb) {
      /* really only doing this to prevent FP exceptions later */
      _mesa_bzero(depth, n * sizeof(GLfloat));
   }

   ASSERT(rb->_BaseFormat == GL_DEPTH_COMPONENT);

   if (y < 0 || y >= (GLint) rb->Height ||
       x + n <= 0 || x >= (GLint) rb->Width) {
      /* span is completely outside framebuffer */
      _mesa_bzero(depth, n * sizeof(GLfloat));
      return;
   }

   if (x < 0) {
      GLint dx = -x;
      GLint i;
      for (i = 0; i < dx; i++)
         depth[i] = 0.0;
      x = 0;
      n -= dx;
      depth += dx;
   }
   if (x + n > (GLint) rb->Width) {
      GLint dx = x + n - (GLint) rb->Width;
      GLint i;
      for (i = 0; i < dx; i++)
         depth[n - i - 1] = 0.0;
      n -= dx;
   }
   if (n <= 0) {
      return;
   }

   if (rb->DataType == GL_UNSIGNED_INT) {
      GLuint temp[MAX_WIDTH];
      GLint i;
      rb->GetRow(ctx, rb, n, x, y, temp);
      for (i = 0; i < n; i++) {
         depth[i] = temp[i] * scale;
      }
   }
   else if (rb->DataType == GL_UNSIGNED_SHORT) {
      GLushort temp[MAX_WIDTH];
      GLint i;
      rb->GetRow(ctx, rb, n, x, y, temp);
      for (i = 0; i < n; i++) {
         depth[i] = temp[i] * scale;
      }
   }
   else {
      _mesa_problem(ctx, "Invalid depth renderbuffer data type");
   }
}


void
_swrast_read_depth_span_uint( GLcontext *ctx, struct gl_renderbuffer *rb,
                              GLint n, GLint x, GLint y, GLuint depth[] )
{
   if (!rb) {
      /* really only doing this to prevent FP exceptions later */
      _mesa_bzero(depth, n * sizeof(GLfloat));
   }

   ASSERT(rb->_BaseFormat == GL_DEPTH_COMPONENT);

   if (y < 0 || y >= (GLint) rb->Height ||
       x + n <= 0 || x >= (GLint) rb->Width) {
      /* span is completely outside framebuffer */
      _mesa_bzero(depth, n * sizeof(GLfloat));
      return;
   }

   if (x < 0) {
      GLint dx = -x;
      GLint i;
      for (i = 0; i < dx; i++)
         depth[i] = 0;
      x = 0;
      n -= dx;
      depth += dx;
   }
   if (x + n > (GLint) rb->Width) {
      GLint dx = x + n - (GLint) rb->Width;
      GLint i;
      for (i = 0; i < dx; i++)
         depth[n - i - 1] = 0;
      n -= dx;
   }
   if (n <= 0) {
      return;
   }

   if (rb->DataType == GL_UNSIGNED_INT) {
      rb->GetRow(ctx, rb, n, x, y, depth);
      if (rb->DepthBits < 32) {
         GLuint shift = 32 - rb->DepthBits;
         GLint i;
         for (i = 0; i < n; i++) {
            GLuint z = depth[i];
            depth[i] = z << shift; /* XXX lsb bits? */
         }
      }
   }
   else if (rb->DataType == GL_UNSIGNED_SHORT) {
      GLushort temp[MAX_WIDTH];
      GLint i;
      rb->GetRow(ctx, rb, n, x, y, temp);
      if (rb->DepthBits == 16) {
         for (i = 0; i < n; i++) {
            GLuint z = temp[i];
            depth[i] = (z << 16) | z;
         }
      }
      else {
         GLuint shift = 16 - rb->DepthBits;
         for (i = 0; i < n; i++) {
            GLuint z = temp[i];
            depth[i] = (z << (shift + 16)) | (z << shift); /* XXX lsb bits? */
         }
      }
   }
   else {
      _mesa_problem(ctx, "Invalid depth renderbuffer data type");
   }
}



void
_swrast_clear_depth_buffer( GLcontext *ctx, struct gl_renderbuffer *rb )
{
   GLuint clearValue;
   GLint x, y, width, height;

   if (!rb || !ctx->Depth.Mask) {
      /* no depth buffer, or writing to it is disabled */
      return;
   }

   /* compute integer clearing value */
   if (ctx->Depth.Clear == 1.0) {
      clearValue = ctx->DrawBuffer->_DepthMax;
   }
   else {
      clearValue = (GLuint) (ctx->Depth.Clear * ctx->DrawBuffer->_DepthMaxF);
   }

   assert(rb->_BaseFormat == GL_DEPTH_COMPONENT);

   /* 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 is possible.  Either this is just malloc'd
       * memory, or perhaps the driver mmap'd the zbuffer memory.
       */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         if ((clearValue & 0xff) == ((clearValue >> 8) & 0xff) &&
             ((GLushort *) rb->GetPointer(ctx, rb, 0, 0) + width ==
              (GLushort *) rb->GetPointer(ctx, rb, 0, 1))) {
            /* optimized case */
            GLushort *dst = (GLushort *) rb->GetPointer(ctx, rb, x, y);
            GLuint len = width * height * sizeof(GLushort);
            _mesa_memset(dst, (clearValue & 0xff), len);
         }
         else {
            /* general case */
            GLint i, j;
            for (i = 0; i < height; i++) {
               GLushort *dst = (GLushort *) rb->GetPointer(ctx, rb, x, y + i);
               for (j = 0; j < width; j++) {
                  dst[j] = clearValue;
               }
            }
         }
      }
      else {
         GLint i, j;
         ASSERT(rb->DataType == GL_UNSIGNED_INT);
         for (i = 0; i < height; i++) {
            GLuint *dst = (GLuint *) rb->GetPointer(ctx, rb, x, y + i);
            for (j = 0; j < width; j++) {
               dst[j] = clearValue;
            }
         }
      }
   }
   else {
      /* Direct access not possible.  Use PutRow to write new values. */
      if (rb->DataType == GL_UNSIGNED_SHORT) {
         GLushort clearVal16 = (GLushort) (clearValue & 0xffff);
         GLint i;
         for (i = 0; i < height; i++) {
            rb->PutMonoRow(ctx, rb, width, x, y + i, &clearVal16, NULL);
         }
      }
      else if (rb->DataType == GL_UNSIGNED_INT) {
         GLint i;
         ASSERT(sizeof(clearValue) == sizeof(GLuint));
         for (i = 0; i < height; i++) {
            rb->PutMonoRow(ctx, rb, width, x, y + i, &clearValue, NULL);
         }
      }
      else {
         _mesa_problem(ctx, "bad depth renderbuffer DataType");
      }
   }
}