From 06542019a86d4b9e4f4dfb7a73aa131910465230 Mon Sep 17 00:00:00 2001
From: Brian <brian.paul@tungstengraphics.com>
Date: Mon, 2 Jul 2007 08:46:57 -0600
Subject: [PATCH] avoid unnecessary clamping of depth values (bug 11448)

---
 src/mesa/main/image.c | 79 ++++++++++++++++++++++++++++---------------
 1 file changed, 51 insertions(+), 28 deletions(-)

diff --git a/src/mesa/main/image.c b/src/mesa/main/image.c
index caaf2816571..e2e7f806ab1 100644
--- a/src/mesa/main/image.c
+++ b/src/mesa/main/image.c
@@ -1,6 +1,6 @@
 /*
  * Mesa 3-D graphics library
- * Version:  7.0
+ * Version:  7.1
  *
  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
  *
@@ -3878,7 +3878,7 @@ _mesa_pack_stencil_span( const GLcontext *ctx, GLuint n,
                     SWAP4BYTE(value);                                   \
                 }                                                       \
             }                                                           \
-            depthValues[i] = CLAMP(GLTYPE2FLOAT(value), 0.0F, 1.0F);    \
+            depthValues[i] = GLTYPE2FLOAT(value);                       \
         }                                                               \
     } while (0)
 
@@ -3889,6 +3889,7 @@ _mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
                          const struct gl_pixelstore_attrib *srcPacking )
 {
    GLfloat depthTemp[MAX_WIDTH], *depthValues;
+   GLboolean needClamp = GL_FALSE;
 
    /* Look for special cases first.
     * Not only are these faster, they're less prone to numeric conversion
@@ -3918,7 +3919,7 @@ _mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
       /* XXX may want to add additional cases here someday */
    }
 
-   /* general case path */
+   /* general case path follows */
 
    if (dstType == GL_FLOAT) {
       depthValues = (GLfloat *) dest;
@@ -3927,29 +3928,31 @@ _mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
       depthValues = depthTemp;
    }
 
-   /* XXX we need to obey srcPacking->SwapBytes here!!! */
-   (void) srcPacking;
-
-   /* convert incoming values to GLfloat */
+   /* Convert incoming values to GLfloat.  Some conversions will require
+    * clamping, below.
+    */
    switch (srcType) {
       case GL_BYTE:
-          DEPTH_VALUES(GLbyte, BYTE_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLbyte, BYTE_TO_FLOAT);
+         needClamp = GL_TRUE;
+         break;
       case GL_UNSIGNED_BYTE:
-          DEPTH_VALUES(GLubyte, UBYTE_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLubyte, UBYTE_TO_FLOAT);
+         break;
       case GL_SHORT:
-          DEPTH_VALUES(GLshort, SHORT_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLshort, SHORT_TO_FLOAT);
+         needClamp = GL_TRUE;
+         break;
       case GL_UNSIGNED_SHORT:
-          DEPTH_VALUES(GLushort, USHORT_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLushort, USHORT_TO_FLOAT);
+         break;
       case GL_INT:
-          DEPTH_VALUES(GLint, INT_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLint, INT_TO_FLOAT);
+         needClamp = GL_TRUE;
+         break;
       case GL_UNSIGNED_INT:
-          DEPTH_VALUES(GLuint, UINT_TO_FLOAT);
-          break;
+         DEPTH_VALUES(GLuint, UINT_TO_FLOAT);
+         break;
       case GL_UNSIGNED_INT_24_8_EXT: /* GL_EXT_packed_depth_stencil */
          if (dstType == GL_UNSIGNED_INT &&
              depthScale == (GLfloat) 0xffffff &&
@@ -3981,19 +3984,21 @@ _mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
          }
          break;
       case GL_FLOAT:
-          DEPTH_VALUES(GLfloat, 1*);
-          break;
+         DEPTH_VALUES(GLfloat, 1*);
+         needClamp = GL_TRUE;
+         break;
       case GL_HALF_FLOAT_ARB:
          {
             GLuint i;
             const GLhalfARB *src = (const GLhalfARB *) source;
             for (i = 0; i < n; i++) {
-                GLhalfARB value = src[i];
-                if (srcPacking->SwapBytes) {
-                    SWAP2BYTE(value);
-                }
+               GLhalfARB value = src[i];
+               if (srcPacking->SwapBytes) {
+                  SWAP2BYTE(value);
+               }
                depthValues[i] = _mesa_half_to_float(value);
             }
+            needClamp = GL_TRUE;
          }
          break;
       default:
@@ -4001,12 +4006,30 @@ _mesa_unpack_depth_span( const GLcontext *ctx, GLuint n,
          return;
    }
 
+   /* apply depth scale and bias */
+   {
+      const GLfloat scale = ctx->Pixel.DepthScale;
+      const GLfloat bias = ctx->Pixel.DepthBias;
+      if (scale != 1.0 || bias != 0.0) {
+         GLuint i;
+         for (i = 0; i < n; i++) {
+            depthValues[i] = depthValues[i] * scale + bias;
+         }
+         needClamp = GL_TRUE;
+      }
+   }
 
-   /* apply depth scale and bias and clamp to [0,1] */
-   if (ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0) {
-      _mesa_scale_and_bias_depth(ctx, n, depthValues);
+   /* clamp to [0, 1] */
+   if (needClamp) {
+      GLuint i;
+      for (i = 0; i < n; i++) {
+         depthValues[i] = CLAMP(depthValues[i], 0.0, 1.0);
+      }
    }
 
+   /*
+    * Convert values to dstType
+    */
    if (dstType == GL_UNSIGNED_INT) {
       GLuint *zValues = (GLuint *) dest;
       GLuint i;
-- 
2.30.2