Initial import.

1 files changed, 1677 insertions, 0 deletions

diff --git a/src/mesa/swrast/s_span.c b/src/mesa/swrast/s_span.c
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+++ b/src/mesa/swrast/s_span.c
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+/*
+ * Mesa 3-D graphics library
+ * Version:  6.3
+ *
+ * Copyright (C) 1999-2004  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.
+ */
+
+
+/**
+ * \file swrast/s_span.c
+ * \brief Span processing functions used by all rasterization functions.
+ * This is where all the per-fragment tests are performed
+ * \author Brian Paul
+ */
+
+#include "glheader.h"
+#include "colormac.h"
+#include "context.h"
+#include "macros.h"
+#include "imports.h"
+
+#include "s_alpha.h"
+#include "s_alphabuf.h"
+#include "s_blend.h"
+#include "s_context.h"
+#include "s_depth.h"
+#include "s_fog.h"
+#include "s_logic.h"
+#include "s_masking.h"
+#include "s_nvfragprog.h"
+#include "s_span.h"
+#include "s_stencil.h"
+#include "s_texture.h"
+
+
+/**
+ * Init span's Z interpolation values to the RasterPos Z.
+ * Used during setup for glDraw/CopyPixels.
+ */
+void
+_swrast_span_default_z( GLcontext *ctx, struct sw_span *span )
+{
+   if (ctx->Visual.depthBits <= 16)
+      span->z = FloatToFixed(ctx->Current.RasterPos[2] * ctx->DepthMax + 0.5F);
+   else
+      span->z = (GLint) (ctx->Current.RasterPos[2] * ctx->DepthMax + 0.5F);
+   span->zStep = 0;
+   span->interpMask |= SPAN_Z;
+}
+
+
+/**
+ * Init span's fog interpolation values to the RasterPos fog.
+ * Used during setup for glDraw/CopyPixels.
+ */
+void
+_swrast_span_default_fog( GLcontext *ctx, struct sw_span *span )
+{
+   span->fog = _swrast_z_to_fogfactor(ctx, ctx->Current.RasterDistance);
+   span->fogStep = span->dfogdx = span->dfogdy = 0.0F;
+   span->interpMask |= SPAN_FOG;
+}
+
+
+/**
+ * Init span's color or index interpolation values to the RasterPos color.
+ * Used during setup for glDraw/CopyPixels.
+ */
+void
+_swrast_span_default_color( GLcontext *ctx, struct sw_span *span )
+{
+   if (ctx->Visual.rgbMode) {
+      GLchan r, g, b, a;
+      UNCLAMPED_FLOAT_TO_CHAN(r, ctx->Current.RasterColor[0]);
+      UNCLAMPED_FLOAT_TO_CHAN(g, ctx->Current.RasterColor[1]);
+      UNCLAMPED_FLOAT_TO_CHAN(b, ctx->Current.RasterColor[2]);
+      UNCLAMPED_FLOAT_TO_CHAN(a, ctx->Current.RasterColor[3]);
+#if CHAN_TYPE == GL_FLOAT
+      span->red = r;
+      span->green = g;
+      span->blue = b;
+      span->alpha = a;
+#else
+      span->red   = IntToFixed(r);
+      span->green = IntToFixed(g);
+      span->blue  = IntToFixed(b);
+      span->alpha = IntToFixed(a);
+#endif
+      span->redStep = 0;
+      span->greenStep = 0;
+      span->blueStep = 0;
+      span->alphaStep = 0;
+      span->interpMask |= SPAN_RGBA;
+   }
+   else {
+      span->index = FloatToFixed(ctx->Current.RasterIndex);
+      span->indexStep = 0;
+      span->interpMask |= SPAN_INDEX;
+   }
+}
+
+
+/**
+ * Init span's texcoord interpolation values to the RasterPos texcoords.
+ * Used during setup for glDraw/CopyPixels.
+ */
+void
+_swrast_span_default_texcoords( GLcontext *ctx, struct sw_span *span )
+{
+   GLuint i;
+   for (i = 0; i < ctx->Const.MaxTextureUnits; i++) {
+      const GLfloat *tc = ctx->Current.RasterTexCoords[i];
+      if (tc[3] > 0.0F) {
+         /* use (s/q, t/q, r/q, 1) */
+         span->tex[i][0] = tc[0] / tc[3];
+         span->tex[i][1] = tc[1] / tc[3];
+         span->tex[i][2] = tc[2] / tc[3];
+         span->tex[i][3] = 1.0;
+      }
+      else {
+         ASSIGN_4V(span->tex[i], 0.0F, 0.0F, 0.0F, 1.0F);
+      }
+      ASSIGN_4V(span->texStepX[i], 0.0F, 0.0F, 0.0F, 0.0F);
+      ASSIGN_4V(span->texStepY[i], 0.0F, 0.0F, 0.0F, 0.0F);
+   }
+   span->interpMask |= SPAN_TEXTURE;
+}
+
+
+/* Fill in the span.color.rgba array from the interpolation values */
+static void
+interpolate_colors(GLcontext *ctx, struct sw_span *span)
+{
+   const GLuint n = span->end;
+   GLchan (*rgba)[4] = span->array->rgba;
+   GLuint i;
+   (void) ctx;
+
+   ASSERT((span->interpMask & SPAN_RGBA)  &&
+	  !(span->arrayMask & SPAN_RGBA));
+
+   if (span->interpMask & SPAN_FLAT) {
+      /* constant color */
+      GLchan color[4];
+      color[RCOMP] = FixedToChan(span->red);
+      color[GCOMP] = FixedToChan(span->green);
+      color[BCOMP] = FixedToChan(span->blue);
+      color[ACOMP] = FixedToChan(span->alpha);
+      for (i = 0; i < n; i++) {
+         COPY_CHAN4(span->array->rgba[i], color);
+      }
+   }
+   else {
+      /* interpolate */
+#if CHAN_TYPE == GL_FLOAT
+      GLfloat r = span->red;
+      GLfloat g = span->green;
+      GLfloat b = span->blue;
+      GLfloat a = span->alpha;
+      const GLfloat dr = span->redStep;
+      const GLfloat dg = span->greenStep;
+      const GLfloat db = span->blueStep;
+      const GLfloat da = span->alphaStep;
+#else
+      GLfixed r = span->red;
+      GLfixed g = span->green;
+      GLfixed b = span->blue;
+      GLfixed a = span->alpha;
+      const GLint dr = span->redStep;
+      const GLint dg = span->greenStep;
+      const GLint db = span->blueStep;
+      const GLint da = span->alphaStep;
+#endif
+      for (i = 0; i < n; i++) {
+         rgba[i][RCOMP] = FixedToChan(r);
+         rgba[i][GCOMP] = FixedToChan(g);
+         rgba[i][BCOMP] = FixedToChan(b);
+         rgba[i][ACOMP] = FixedToChan(a);
+         r += dr;
+         g += dg;
+         b += db;
+         a += da;
+      }
+   }
+   span->arrayMask |= SPAN_RGBA;
+}
+
+
+/* Fill in the span.color.index array from the interpolation values */
+static void
+interpolate_indexes(GLcontext *ctx, struct sw_span *span)
+{
+   GLfixed index = span->index;
+   const GLint indexStep = span->indexStep;
+   const GLuint n = span->end;
+   GLuint *indexes = span->array->index;
+   GLuint i;
+   (void) ctx;
+   ASSERT((span->interpMask & SPAN_INDEX)  &&
+	  !(span->arrayMask & SPAN_INDEX));
+
+   if ((span->interpMask & SPAN_FLAT) || (indexStep == 0)) {
+      /* constant color */
+      index = FixedToInt(index);
+      for (i = 0; i < n; i++) {
+         indexes[i] = index;
+      }
+   }
+   else {
+      /* interpolate */
+      for (i = 0; i < n; i++) {
+         indexes[i] = FixedToInt(index);
+         index += indexStep;
+      }
+   }
+   span->arrayMask |= SPAN_INDEX;
+}
+
+
+/* Fill in the span.->array->spec array from the interpolation values */
+static void
+interpolate_specular(GLcontext *ctx, struct sw_span *span)
+{
+   (void) ctx;
+   if (span->interpMask & SPAN_FLAT) {
+      /* constant color */
+      const GLchan r = FixedToChan(span->specRed);
+      const GLchan g = FixedToChan(span->specGreen);
+      const GLchan b = FixedToChan(span->specBlue);
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         span->array->spec[i][RCOMP] = r;
+         span->array->spec[i][GCOMP] = g;
+         span->array->spec[i][BCOMP] = b;
+      }
+   }
+   else {
+      /* interpolate */
+#if CHAN_TYPE == GL_FLOAT
+      GLfloat r = span->specRed;
+      GLfloat g = span->specGreen;
+      GLfloat b = span->specBlue;
+#else
+      GLfixed r = span->specRed;
+      GLfixed g = span->specGreen;
+      GLfixed b = span->specBlue;
+#endif
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         span->array->spec[i][RCOMP] = FixedToChan(r);
+         span->array->spec[i][GCOMP] = FixedToChan(g);
+         span->array->spec[i][BCOMP] = FixedToChan(b);
+         r += span->specRedStep;
+         g += span->specGreenStep;
+         b += span->specBlueStep;
+      }
+   }
+   span->arrayMask |= SPAN_SPEC;
+}
+
+
+/* Fill in the span.array.fog values from the interpolation values */
+static void
+interpolate_fog(const GLcontext *ctx, struct sw_span *span)
+{
+   GLfloat *fog = span->array->fog;
+   const GLfloat fogStep = span->fogStep;
+   GLfloat fogCoord = span->fog;
+   const GLuint haveW = (span->interpMask & SPAN_W);
+   const GLfloat wStep = haveW ? span->dwdx : 0.0F;
+   GLfloat w = haveW ? span->w : 1.0F;
+   GLuint i;
+   for (i = 0; i < span->end; i++) {
+      fog[i] = fogCoord / w;
+      fogCoord += fogStep;
+      w += wStep;
+   }
+   span->arrayMask |= SPAN_FOG;
+}
+
+
+/* Fill in the span.zArray array from the interpolation values */
+void
+_swrast_span_interpolate_z( const GLcontext *ctx, struct sw_span *span )
+{
+   const GLuint n = span->end;
+   GLuint i;
+
+   ASSERT((span->interpMask & SPAN_Z)  &&
+	  !(span->arrayMask & SPAN_Z));
+
+   if (ctx->Visual.depthBits <= 16) {
+      GLfixed zval = span->z;
+      GLdepth *z = span->array->z; 
+      for (i = 0; i < n; i++) {
+         z[i] = FixedToInt(zval);
+         zval += span->zStep;
+      }
+   }
+   else {
+      /* Deep Z buffer, no fixed->int shift */
+      GLfixed zval = span->z;
+      GLdepth *z = span->array->z;
+      for (i = 0; i < n; i++) {
+         z[i] = zval;
+         zval += span->zStep;
+      }
+   }
+   span->arrayMask |= SPAN_Z;
+}
+
+
+/*
+ * This the ideal solution, as given in the OpenGL spec.
+ */
+#if 0
+static GLfloat
+compute_lambda(GLfloat dsdx, GLfloat dsdy, GLfloat dtdx, GLfloat dtdy,
+               GLfloat dqdx, GLfloat dqdy, GLfloat texW, GLfloat texH,
+               GLfloat s, GLfloat t, GLfloat q, GLfloat invQ)
+{
+   GLfloat dudx = texW * ((s + dsdx) / (q + dqdx) - s * invQ);
+   GLfloat dvdx = texH * ((t + dtdx) / (q + dqdx) - t * invQ);
+   GLfloat dudy = texW * ((s + dsdy) / (q + dqdy) - s * invQ);
+   GLfloat dvdy = texH * ((t + dtdy) / (q + dqdy) - t * invQ);
+   GLfloat x = SQRTF(dudx * dudx + dvdx * dvdx);
+   GLfloat y = SQRTF(dudy * dudy + dvdy * dvdy);
+   GLfloat rho = MAX2(x, y);
+   GLfloat lambda = LOG2(rho);
+   return lambda;
+}
+#endif
+
+
+/*
+ * This is a faster approximation
+ */
+GLfloat
+_swrast_compute_lambda(GLfloat dsdx, GLfloat dsdy, GLfloat dtdx, GLfloat dtdy,
+                     GLfloat dqdx, GLfloat dqdy, GLfloat texW, GLfloat texH,
+                     GLfloat s, GLfloat t, GLfloat q, GLfloat invQ)
+{
+   GLfloat dsdx2 = (s + dsdx) / (q + dqdx) - s * invQ;
+   GLfloat dtdx2 = (t + dtdx) / (q + dqdx) - t * invQ;
+   GLfloat dsdy2 = (s + dsdy) / (q + dqdy) - s * invQ;
+   GLfloat dtdy2 = (t + dtdy) / (q + dqdy) - t * invQ;
+   GLfloat maxU, maxV, rho, lambda;
+   dsdx2 = FABSF(dsdx2);
+   dsdy2 = FABSF(dsdy2);
+   dtdx2 = FABSF(dtdx2);
+   dtdy2 = FABSF(dtdy2);
+   maxU = MAX2(dsdx2, dsdy2) * texW;
+   maxV = MAX2(dtdx2, dtdy2) * texH;
+   rho = MAX2(maxU, maxV);
+   lambda = LOG2(rho);
+   return lambda;
+}
+
+
+/**
+ * Fill in the span.texcoords array from the interpolation values.
+ * Note: in the places where we divide by Q (or mult by invQ) we're
+ * really doing two things: perspective correction and texcoord
+ * projection.  Remember, for texcoord (s,t,r,q) we need to index
+ * texels with (s/q, t/q, r/q).
+ * If we're using a fragment program, we never do the division
+ * for texcoord projection.  That's done by the TXP instruction
+ * or user-written code.
+ */
+static void
+interpolate_texcoords(GLcontext *ctx, struct sw_span *span)
+{
+   ASSERT(span->interpMask & SPAN_TEXTURE);
+   ASSERT(!(span->arrayMask & SPAN_TEXTURE));
+
+   if (ctx->Texture._EnabledCoordUnits > 1) {
+      /* multitexture */
+      GLuint u;
+      span->arrayMask |= SPAN_TEXTURE;
+      for (u = 0; u < ctx->Const.MaxTextureUnits; u++) {
+         if (ctx->Texture._EnabledCoordUnits & (1 << u)) {
+            const struct gl_texture_object *obj =ctx->Texture.Unit[u]._Current;
+            GLfloat texW, texH;
+            GLboolean needLambda;
+            if (obj) {
+               const struct gl_texture_image *img = obj->Image[0][obj->BaseLevel];
+               needLambda = (obj->MinFilter != obj->MagFilter)
+                  || ctx->FragmentProgram._Enabled;
+               texW = img->WidthScale;
+               texH = img->HeightScale;
+            }
+            else {
+               /* using a fragment program */
+               texW = 1.0;
+               texH = 1.0;
+               needLambda = GL_FALSE;
+            }
+            if (needLambda) {
+               GLfloat (*texcoord)[4] = span->array->texcoords[u];
+               GLfloat *lambda = span->array->lambda[u];
+               const GLfloat dsdx = span->texStepX[u][0];
+               const GLfloat dsdy = span->texStepY[u][0];
+               const GLfloat dtdx = span->texStepX[u][1];
+               const GLfloat dtdy = span->texStepY[u][1];
+               const GLfloat drdx = span->texStepX[u][2];
+               const GLfloat dqdx = span->texStepX[u][3];
+               const GLfloat dqdy = span->texStepY[u][3];
+               GLfloat s = span->tex[u][0];
+               GLfloat t = span->tex[u][1];
+               GLfloat r = span->tex[u][2];
+               GLfloat q = span->tex[u][3];
+               GLuint i;
+               if (ctx->FragmentProgram._Enabled) {
+                  /* do perspective correction but don't divide s, t, r by q */
+                  const GLfloat dwdx = span->dwdx;
+                  GLfloat w = span->w;
+                  for (i = 0; i < span->end; i++) {
+                     const GLfloat invW = 1.0F / w;
+                     texcoord[i][0] = s * invW;
+                     texcoord[i][1] = t * invW;
+                     texcoord[i][2] = r * invW;
+                     texcoord[i][3] = q * invW;
+                     lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+                                                        dqdx, dqdy, texW, texH,
+                                                        s, t, q, invW);
+                     s += dsdx;
+                     t += dtdx;
+                     r += drdx;
+                     q += dqdx;
+                     w += dwdx;
+                  }
+
+               }
+               else {
+                  for (i = 0; i < span->end; i++) {
+                     const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+                     texcoord[i][0] = s * invQ;
+                     texcoord[i][1] = t * invQ;
+                     texcoord[i][2] = r * invQ;
+                     texcoord[i][3] = q;
+                     lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+                                                        dqdx, dqdy, texW, texH,
+                                                        s, t, q, invQ);
+                     s += dsdx;
+                     t += dtdx;
+                     r += drdx;
+                     q += dqdx;
+                  }
+               }
+               span->arrayMask |= SPAN_LAMBDA;
+            }
+            else {
+               GLfloat (*texcoord)[4] = span->array->texcoords[u];
+               GLfloat *lambda = span->array->lambda[u];
+               const GLfloat dsdx = span->texStepX[u][0];
+               const GLfloat dtdx = span->texStepX[u][1];
+               const GLfloat drdx = span->texStepX[u][2];
+               const GLfloat dqdx = span->texStepX[u][3];
+               GLfloat s = span->tex[u][0];
+               GLfloat t = span->tex[u][1];
+               GLfloat r = span->tex[u][2];
+               GLfloat q = span->tex[u][3];
+               GLuint i;
+               if (ctx->FragmentProgram._Enabled) {
+                  /* do perspective correction but don't divide s, t, r by q */
+                  const GLfloat dwdx = span->dwdx;
+                  GLfloat w = span->w;
+                  for (i = 0; i < span->end; i++) {
+                     const GLfloat invW = 1.0F / w;
+                     texcoord[i][0] = s * invW;
+                     texcoord[i][1] = t * invW;
+                     texcoord[i][2] = r * invW;
+                     texcoord[i][3] = q * invW;
+                     lambda[i] = 0.0;
+                     s += dsdx;
+                     t += dtdx;
+                     r += drdx;
+                     q += dqdx;
+                     w += dwdx;
+                  }
+               }
+               else if (dqdx == 0.0F) {
+                  /* Ortho projection or polygon's parallel to window X axis */
+                  const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+                  for (i = 0; i < span->end; i++) {
+                     texcoord[i][0] = s * invQ;
+                     texcoord[i][1] = t * invQ;
+                     texcoord[i][2] = r * invQ;
+                     texcoord[i][3] = q;
+                     lambda[i] = 0.0;
+                     s += dsdx;
+                     t += dtdx;
+                     r += drdx;
+                  }
+               }
+               else {
+                  for (i = 0; i < span->end; i++) {
+                     const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+                     texcoord[i][0] = s * invQ;
+                     texcoord[i][1] = t * invQ;
+                     texcoord[i][2] = r * invQ;
+                     texcoord[i][3] = q;
+                     lambda[i] = 0.0;
+                     s += dsdx;
+                     t += dtdx;
+                     r += drdx;
+                     q += dqdx;
+                  }
+               }
+            } /* lambda */
+         } /* if */
+      } /* for */
+   }
+   else {
+      /* single texture */
+      const struct gl_texture_object *obj = ctx->Texture.Unit[0]._Current;
+      GLfloat texW, texH;
+      GLboolean needLambda;
+      if (obj) {
+         const struct gl_texture_image *img = obj->Image[0][obj->BaseLevel];
+         needLambda = (obj->MinFilter != obj->MagFilter)
+            || ctx->FragmentProgram._Enabled;
+         texW = (GLfloat) img->WidthScale;
+         texH = (GLfloat) img->HeightScale;
+      }
+      else {
+         needLambda = GL_FALSE;
+         texW = texH = 1.0;
+      }
+      span->arrayMask |= SPAN_TEXTURE;
+      if (needLambda) {
+         /* just texture unit 0, with lambda */
+         GLfloat (*texcoord)[4] = span->array->texcoords[0];
+         GLfloat *lambda = span->array->lambda[0];
+         const GLfloat dsdx = span->texStepX[0][0];
+         const GLfloat dsdy = span->texStepY[0][0];
+         const GLfloat dtdx = span->texStepX[0][1];
+         const GLfloat dtdy = span->texStepY[0][1];
+         const GLfloat drdx = span->texStepX[0][2];
+         const GLfloat dqdx = span->texStepX[0][3];
+         const GLfloat dqdy = span->texStepY[0][3];
+         GLfloat s = span->tex[0][0];
+         GLfloat t = span->tex[0][1];
+         GLfloat r = span->tex[0][2];
+         GLfloat q = span->tex[0][3];
+         GLuint i;
+         if (ctx->FragmentProgram._Enabled) {
+            /* do perspective correction but don't divide s, t, r by q */
+            const GLfloat dwdx = span->dwdx;
+            GLfloat w = span->w;
+            for (i = 0; i < span->end; i++) {
+               const GLfloat invW = 1.0F / w;
+               texcoord[i][0] = s * invW;
+               texcoord[i][1] = t * invW;
+               texcoord[i][2] = r * invW;
+               texcoord[i][3] = q * invW;
+               lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+                                                  dqdx, dqdy, texW, texH,
+                                                  s, t, q, invW);
+               s += dsdx;
+               t += dtdx;
+               r += drdx;
+               q += dqdx;
+               w += dwdx;
+            }
+         }
+         else {
+            /* tex.c */
+            for (i = 0; i < span->end; i++) {
+               const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+               lambda[i] = _swrast_compute_lambda(dsdx, dsdy, dtdx, dtdy,
+                                                dqdx, dqdy, texW, texH,
+                                                s, t, q, invQ);
+               texcoord[i][0] = s * invQ;
+               texcoord[i][1] = t * invQ;
+               texcoord[i][2] = r * invQ;
+               texcoord[i][3] = q;
+               s += dsdx;
+               t += dtdx;
+               r += drdx;
+               q += dqdx;
+            }
+         }
+         span->arrayMask |= SPAN_LAMBDA;
+      }
+      else {
+         /* just texture 0, without lambda */
+         GLfloat (*texcoord)[4] = span->array->texcoords[0];
+         const GLfloat dsdx = span->texStepX[0][0];
+         const GLfloat dtdx = span->texStepX[0][1];
+         const GLfloat drdx = span->texStepX[0][2];
+         const GLfloat dqdx = span->texStepX[0][3];
+         GLfloat s = span->tex[0][0];
+         GLfloat t = span->tex[0][1];
+         GLfloat r = span->tex[0][2];
+         GLfloat q = span->tex[0][3];
+         GLuint i;
+         if (ctx->FragmentProgram._Enabled) {
+            /* do perspective correction but don't divide s, t, r by q */
+            const GLfloat dwdx = span->dwdx;
+            GLfloat w = span->w;
+            for (i = 0; i < span->end; i++) {
+               const GLfloat invW = 1.0F / w;
+               texcoord[i][0] = s * invW;
+               texcoord[i][1] = t * invW;
+               texcoord[i][2] = r * invW;
+               texcoord[i][3] = q * invW;
+               s += dsdx;
+               t += dtdx;
+               r += drdx;
+               q += dqdx;
+               w += dwdx;
+            }
+         }
+         else if (dqdx == 0.0F) {
+            /* Ortho projection or polygon's parallel to window X axis */
+            const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+            for (i = 0; i < span->end; i++) {
+               texcoord[i][0] = s * invQ;
+               texcoord[i][1] = t * invQ;
+               texcoord[i][2] = r * invQ;
+               texcoord[i][3] = q;
+               s += dsdx;
+               t += dtdx;
+               r += drdx;
+            }
+         }
+         else {
+            for (i = 0; i < span->end; i++) {
+               const GLfloat invQ = (q == 0.0F) ? 1.0F : (1.0F / q);
+               texcoord[i][0] = s * invQ;
+               texcoord[i][1] = t * invQ;
+               texcoord[i][2] = r * invQ;
+               texcoord[i][3] = q;
+               s += dsdx;
+               t += dtdx;
+               r += drdx;
+               q += dqdx;
+            }
+         }
+      }
+   }
+}
+
+
+/**
+ * Apply the current polygon stipple pattern to a span of pixels.
+ */
+static void
+stipple_polygon_span( GLcontext *ctx, struct sw_span *span )
+{
+   const GLuint highbit = 0x80000000;
+   const GLuint stipple = ctx->PolygonStipple[span->y % 32];
+   GLubyte *mask = span->array->mask;
+   GLuint i, m;
+
+   ASSERT(ctx->Polygon.StippleFlag);
+   ASSERT((span->arrayMask & SPAN_XY) == 0);
+
+   m = highbit >> (GLuint) (span->x % 32);
+
+   for (i = 0; i < span->end; i++) {
+      if ((m & stipple) == 0) {
+	 mask[i] = 0;
+      }
+      m = m >> 1;
+      if (m == 0) {
+         m = highbit;
+      }
+   }
+   span->writeAll = GL_FALSE;
+}
+
+
+/**
+ * Clip a pixel span to the current buffer/window boundaries:
+ * DrawBuffer->_Xmin, _Xmax, _Ymin, _Ymax.  This will accomplish
+ * window clipping and scissoring.
+ * Return:   GL_TRUE   some pixels still visible
+ *           GL_FALSE  nothing visible
+ */
+static GLuint
+clip_span( GLcontext *ctx, struct sw_span *span )
+{
+   const GLint xmin = ctx->DrawBuffer->_Xmin;
+   const GLint xmax = ctx->DrawBuffer->_Xmax;
+   const GLint ymin = ctx->DrawBuffer->_Ymin;
+   const GLint ymax = ctx->DrawBuffer->_Ymax;
+
+   if (span->arrayMask & SPAN_XY) {
+      /* arrays of x/y pixel coords */
+      const GLint *x = span->array->x;
+      const GLint *y = span->array->y;
+      const GLint n = span->end;
+      GLubyte *mask = span->array->mask;
+      GLint i;
+      if (span->arrayMask & SPAN_MASK) {
+         /* note: using & intead of && to reduce branches */
+         for (i = 0; i < n; i++) {
+            mask[i] &= (x[i] >= xmin) & (x[i] < xmax)
+                     & (y[i] >= ymin) & (y[i] < ymax);
+         }
+      }
+      else {
+         /* note: using & intead of && to reduce branches */
+         for (i = 0; i < n; i++) {
+            mask[i] = (x[i] >= xmin) & (x[i] < xmax)
+                    & (y[i] >= ymin) & (y[i] < ymax);
+         }
+      }
+      return GL_TRUE;  /* some pixels visible */
+   }
+   else {
+      /* horizontal span of pixels */
+      const GLint x = span->x;
+      const GLint y = span->y;
+      const GLint n = span->end;
+
+      /* Trivial rejection tests */
+      if (y < ymin || y >= ymax || x + n <= xmin || x >= xmax) {
+         span->end = 0;
+         return GL_FALSE;  /* all pixels clipped */
+      }
+
+      /* Clip to the left */
+      if (x < xmin) {
+         ASSERT(x + n > xmin);
+         span->writeAll = GL_FALSE;
+         _mesa_bzero(span->array->mask, (xmin - x) * sizeof(GLubyte));
+      }
+
+      /* Clip to right */
+      if (x + n > xmax) {
+         ASSERT(x < xmax);
+         span->end = xmax - x;
+      }
+
+      return GL_TRUE;  /* some pixels visible */
+   }
+}
+
+
+
+/**
+ * Draw to more than one color buffer (or none).
+ */
+static void
+multi_write_index_span( GLcontext *ctx, struct sw_span *span )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   GLuint bufferBit;
+
+   /* loop over four possible dest color buffers */
+   for (bufferBit = 1; bufferBit <= 8; bufferBit <<= 1) {
+      if (bufferBit & ctx->Color._DrawDestMask) {
+         GLuint indexTmp[MAX_WIDTH];
+         ASSERT(span->end < MAX_WIDTH);
+
+         /* Set the current read/draw buffer */
+         swrast->CurrentBufferBit = bufferBit;
+         (*swrast->Driver.SetBuffer)(ctx, ctx->DrawBuffer, bufferBit);
+
+         /* make copy of incoming indexes */
+         MEMCPY( indexTmp, span->array->index, span->end * sizeof(GLuint) );
+
+         if (ctx->Color.IndexLogicOpEnabled) {
+            _swrast_logicop_ci_span(ctx, span, indexTmp);
+         }
+
+         if (ctx->Color.IndexMask != 0xffffffff) {
+            _swrast_mask_index_span(ctx, span, indexTmp);
+         }
+
+         if (span->arrayMask & SPAN_XY) {
+            /* array of pixel coords */
+            (*swrast->Driver.WriteCI32Pixels)(ctx, span->end,
+                                              span->array->x, span->array->y,
+                                              indexTmp, span->array->mask);
+         }
+         else {
+            /* horizontal run of pixels */
+            (*swrast->Driver.WriteCI32Span)(ctx, span->end, span->x, span->y,
+                                            indexTmp, span->array->mask);
+         }
+      }
+   }
+
+   /* restore default dest buffer */
+   _swrast_use_draw_buffer(ctx);
+}
+
+
+/**
+ * Draw to more than one RGBA color buffer (or none).
+ * All fragment operations, up to (but not) blending/logicop should
+ * have been done first.
+ */
+static void
+multi_write_rgba_span( GLcontext *ctx, struct sw_span *span )
+{
+   const GLuint colorMask = *((GLuint *) ctx->Color.ColorMask);
+   GLuint bufferBit;
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+
+   ASSERT(colorMask != 0x0);
+
+   if (ctx->Color.DrawBuffer == GL_NONE)
+      return;
+
+   /* loop over four possible dest color buffers */
+   for (bufferBit = 1; bufferBit <= 8; bufferBit <<= 1) {
+      if (bufferBit & ctx->Color._DrawDestMask) {
+         GLchan rgbaTmp[MAX_WIDTH][4];
+         ASSERT(span->end < MAX_WIDTH);
+
+         /* Set the current read/draw buffer */
+         swrast->CurrentBufferBit = bufferBit;
+         (*swrast->Driver.SetBuffer)(ctx, ctx->DrawBuffer, bufferBit);
+
+         /* make copy of incoming colors */
+         MEMCPY( rgbaTmp, span->array->rgba, 4 * span->end * sizeof(GLchan) );
+
+         if (ctx->Color._LogicOpEnabled) {
+            _swrast_logicop_rgba_span(ctx, span, rgbaTmp);
+         }
+         else if (ctx->Color.BlendEnabled) {
+            _swrast_blend_span(ctx, span, rgbaTmp);
+         }
+
+         if (colorMask != 0xffffffff) {
+            _swrast_mask_rgba_span(ctx, span, rgbaTmp);
+         }
+
+         if (span->arrayMask & SPAN_XY) {
+            /* array of pixel coords */
+            (*swrast->Driver.WriteRGBAPixels)(ctx, span->end,
+                                              span->array->x, span->array->y,
+                                              (const GLchan (*)[4]) rgbaTmp,
+                                              span->array->mask);
+            if (SWRAST_CONTEXT(ctx)->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_alpha_pixels(ctx, span->end,
+                                        span->array->x, span->array->y,
+                                        (const GLchan (*)[4]) rgbaTmp,
+                                        span->array->mask);
+            }
+         }
+         else {
+            /* horizontal run of pixels */
+            (*swrast->Driver.WriteRGBASpan)(ctx, span->end, span->x, span->y,
+                                            (const GLchan (*)[4]) rgbaTmp,
+                                            span->array->mask);
+            if (swrast->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_alpha_span(ctx, span->end, span->x, span->y,
+                                      (const GLchan (*)[4]) rgbaTmp,
+                                      span->array->mask);
+            }
+         }
+      }
+   }
+
+   /* restore default dest buffer */
+   _swrast_use_draw_buffer(ctx);
+}
+
+
+
+/**
+ * This function may modify any of the array values in the span.
+ * span->interpMask and span->arrayMask may be changed but will be restored
+ * to their original values before returning.
+ */
+void
+_swrast_write_index_span( GLcontext *ctx, struct sw_span *span)
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLuint origInterpMask = span->interpMask;
+   const GLuint origArrayMask = span->arrayMask;
+
+   ASSERT(span->end <= MAX_WIDTH);
+   ASSERT(span->primitive == GL_POINT  ||  span->primitive == GL_LINE ||
+	  span->primitive == GL_POLYGON  ||  span->primitive == GL_BITMAP);
+   ASSERT((span->interpMask | span->arrayMask) & SPAN_INDEX);
+   ASSERT((span->interpMask & span->arrayMask) == 0);
+
+   if (span->arrayMask & SPAN_MASK) {
+      /* mask was initialized by caller, probably glBitmap */
+      span->writeAll = GL_FALSE;
+   }
+   else {
+      MEMSET(span->array->mask, 1, span->end);
+      span->writeAll = GL_TRUE;
+   }
+
+   /* Clipping */
+   if ((swrast->_RasterMask & CLIP_BIT) || (span->primitive != GL_POLYGON)) {
+      if (!clip_span(ctx, span)) {
+         return;
+      }
+   }
+
+   /* Depth bounds test */
+   if (ctx->Depth.BoundsTest && ctx->Visual.depthBits > 0) {
+      if (!_swrast_depth_bounds_test(ctx, span)) {
+         return;
+      }
+   }
+
+#ifdef DEBUG
+   if (span->arrayMask & SPAN_XY) {
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         if (span->array->mask[i]) {
+            assert(span->array->x[i] >= ctx->DrawBuffer->_Xmin);
+            assert(span->array->x[i] < ctx->DrawBuffer->_Xmax);
+            assert(span->array->y[i] >= ctx->DrawBuffer->_Ymin);
+            assert(span->array->y[i] < ctx->DrawBuffer->_Ymax);
+         }
+      }
+   }
+#endif
+
+   /* Polygon Stippling */
+   if (ctx->Polygon.StippleFlag && span->primitive == GL_POLYGON) {
+      stipple_polygon_span(ctx, span);
+   }
+
+   /* Depth test and stencil */
+   if (ctx->Depth.Test || ctx->Stencil.Enabled) {
+      if (span->interpMask & SPAN_Z)
+         _swrast_span_interpolate_z(ctx, span);
+
+      if (ctx->Stencil.Enabled) {
+         if (!_swrast_stencil_and_ztest_span(ctx, span)) {
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+      else {
+         ASSERT(ctx->Depth.Test);
+         if (!_swrast_depth_test_span(ctx, span)) {
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+   }
+
+   /* if we get here, something passed the depth test */
+   if (ctx->Depth.OcclusionTest) {
+      ctx->OcclusionResult = GL_TRUE;
+   }
+
+#if FEATURE_ARB_occlusion_query
+   if (ctx->Occlusion.Active) {
+      /* update count of 'passed' fragments */
+      GLuint i;
+      for (i = 0; i < span->end; i++)
+         ctx->Occlusion.PassedCounter += span->array->mask[i];
+   }
+#endif
+
+   /* we have to wait until after occlusion to do this test */
+   if (ctx->Color.DrawBuffer == GL_NONE || ctx->Color.IndexMask == 0) {
+      /* write no pixels */
+      span->arrayMask = origArrayMask;
+      return;
+   }
+
+   /* Interpolate the color indexes if needed */
+   if (span->interpMask & SPAN_INDEX) {
+      interpolate_indexes(ctx, span);
+      /* clear the bit - this allows the WriteMonoCISpan optimization below */
+      span->interpMask &= ~SPAN_INDEX;
+   }
+
+   /* Fog */
+   if (ctx->Fog.Enabled) {
+      _swrast_fog_ci_span(ctx, span);
+   }
+
+   /* Antialias coverage application */
+   if (span->arrayMask & SPAN_COVERAGE) {
+      GLuint i;
+      GLuint *index = span->array->index;
+      GLfloat *coverage = span->array->coverage;
+      for (i = 0; i < span->end; i++) {
+         ASSERT(coverage[i] < 16);
+         index[i] = (index[i] & ~0xf) | ((GLuint) coverage[i]);
+      }
+   }
+
+   if (swrast->_RasterMask & MULTI_DRAW_BIT) {
+      /* draw to zero or two or more buffers */
+      multi_write_index_span(ctx, span);
+   }
+   else {
+      /* normal situation: draw to exactly one buffer */
+      if (ctx->Color.IndexLogicOpEnabled) {
+         _swrast_logicop_ci_span(ctx, span, span->array->index);
+      }
+
+      if (ctx->Color.IndexMask != 0xffffffff) {
+         _swrast_mask_index_span(ctx, span, span->array->index);
+      }
+
+      /* write pixels */
+      if (span->arrayMask & SPAN_XY) {
+         /* array of pixel coords */
+         if ((span->interpMask & SPAN_INDEX) && span->indexStep == 0) {
+            /* all pixels have same color index */
+            (*swrast->Driver.WriteMonoCIPixels)(ctx, span->end,
+                                                span->array->x, span->array->y,
+                                                FixedToInt(span->index),
+                                                span->array->mask);
+         }
+         else {
+            (*swrast->Driver.WriteCI32Pixels)(ctx, span->end, span->array->x,
+                                              span->array->y, span->array->index,
+                                              span->array->mask );
+         }
+      }
+      else {
+         /* horizontal run of pixels */
+         if ((span->interpMask & SPAN_INDEX) && span->indexStep == 0) {
+            /* all pixels have same color index */
+            (*swrast->Driver.WriteMonoCISpan)(ctx, span->end, span->x, span->y,
+                                              FixedToInt(span->index),
+                                              span->array->mask);
+         }
+         else {
+            (*swrast->Driver.WriteCI32Span)(ctx, span->end, span->x, span->y,
+                                            span->array->index,
+                                            span->array->mask);
+         }
+      }
+   }
+
+   span->interpMask = origInterpMask;
+   span->arrayMask = origArrayMask;
+}
+
+
+/**
+ * This function may modify any of the array values in the span.
+ * span->interpMask and span->arrayMask may be changed but will be restored
+ * to their original values before returning.
+ */
+void
+_swrast_write_rgba_span( GLcontext *ctx, struct sw_span *span)
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLuint colorMask = *((GLuint *) ctx->Color.ColorMask);
+   const GLuint origInterpMask = span->interpMask;
+   const GLuint origArrayMask = span->arrayMask;
+   GLboolean monoColor;
+
+   ASSERT(span->end <= MAX_WIDTH);
+   ASSERT(span->primitive == GL_POINT  ||  span->primitive == GL_LINE ||
+	  span->primitive == GL_POLYGON  ||  span->primitive == GL_BITMAP);
+   ASSERT((span->interpMask & span->arrayMask) == 0);
+   ASSERT((span->interpMask | span->arrayMask) & SPAN_RGBA);
+#ifdef DEBUG
+   if (ctx->Fog.Enabled)
+      ASSERT((span->interpMask | span->arrayMask) & SPAN_FOG);
+   if (ctx->Depth.Test)
+      ASSERT((span->interpMask | span->arrayMask) & SPAN_Z);
+#endif
+
+   if (span->arrayMask & SPAN_MASK) {
+      /* mask was initialized by caller, probably glBitmap */
+      span->writeAll = GL_FALSE;
+   }
+   else {
+      MEMSET(span->array->mask, 1, span->end);
+      span->writeAll = GL_TRUE;
+   }
+
+   /* Determine if we have mono-chromatic colors */
+   monoColor = (span->interpMask & SPAN_RGBA) &&
+      span->redStep == 0 && span->greenStep == 0 &&
+      span->blueStep == 0 && span->alphaStep == 0;
+
+   /* Clipping */
+   if ((swrast->_RasterMask & CLIP_BIT) || (span->primitive != GL_POLYGON)) {
+      if (!clip_span(ctx, span)) {
+         return;
+      }
+   }
+
+   /* Depth bounds test */
+   if (ctx->Depth.BoundsTest && ctx->Visual.depthBits > 0) {
+      if (!_swrast_depth_bounds_test(ctx, span)) {
+         return;
+      }
+   }
+
+#ifdef DEBUG
+   if (span->arrayMask & SPAN_XY) {
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         if (span->array->mask[i]) {
+            assert(span->array->x[i] >= ctx->DrawBuffer->_Xmin);
+            assert(span->array->x[i] < ctx->DrawBuffer->_Xmax);
+            assert(span->array->y[i] >= ctx->DrawBuffer->_Ymin);
+            assert(span->array->y[i] < ctx->DrawBuffer->_Ymax);
+         }
+      }
+   }
+#endif
+
+   /* Polygon Stippling */
+   if (ctx->Polygon.StippleFlag && span->primitive == GL_POLYGON) {
+      stipple_polygon_span(ctx, span);
+   }
+
+   /* Fragment program */
+   if (ctx->FragmentProgram._Enabled) {
+      /* Now we may need to interpolate the colors and texcoords */
+      if ((span->interpMask & SPAN_RGBA) &&
+          (span->arrayMask & SPAN_RGBA) == 0) {
+         interpolate_colors(ctx, span);
+         span->interpMask &= ~SPAN_RGBA;
+      }
+      if (span->interpMask & SPAN_SPEC) {
+         interpolate_specular(ctx, span);
+      }
+      if ((span->interpMask & SPAN_TEXTURE)
+          && (span->arrayMask & SPAN_TEXTURE) == 0)
+         interpolate_texcoords(ctx, span);
+      _swrast_exec_fragment_program(ctx, span);
+      monoColor = GL_FALSE;
+   }
+
+   /* Do the alpha test */
+   if (ctx->Color.AlphaEnabled) {
+      if (!_swrast_alpha_test(ctx, span)) {
+         span->interpMask = origInterpMask;
+         span->arrayMask = origArrayMask;
+	 return;
+      }
+   }
+
+   /* Stencil and Z testing */
+   if (ctx->Stencil.Enabled || ctx->Depth.Test) {
+      if (span->interpMask & SPAN_Z)
+         _swrast_span_interpolate_z(ctx, span);
+
+      if (ctx->Stencil.Enabled) {
+         if (!_swrast_stencil_and_ztest_span(ctx, span)) {
+            span->interpMask = origInterpMask;
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+      else {
+         ASSERT(ctx->Depth.Test);
+         ASSERT(span->arrayMask & SPAN_Z);
+         /* regular depth testing */
+         if (!_swrast_depth_test_span(ctx, span)) {
+            span->interpMask = origInterpMask;
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+   }
+
+   /* if we get here, something passed the depth test */
+   if (ctx->Depth.OcclusionTest) {
+      ctx->OcclusionResult = GL_TRUE;
+   }
+
+#if FEATURE_ARB_occlusion_query
+   if (ctx->Occlusion.Active) {
+      /* update count of 'passed' fragments */
+      GLuint i;
+      for (i = 0; i < span->end; i++)
+         ctx->Occlusion.PassedCounter += span->array->mask[i];
+   }
+#endif
+
+   /* can't abort span-writing until after occlusion testing */
+   if (colorMask == 0x0) {
+      span->interpMask = origInterpMask;
+      span->arrayMask = origArrayMask;
+      return;
+   }
+
+   /* Now we may need to interpolate the colors */
+   if ((span->interpMask & SPAN_RGBA) && (span->arrayMask & SPAN_RGBA) == 0) {
+      interpolate_colors(ctx, span);
+      /* clear the bit - this allows the WriteMonoCISpan optimization below */
+      span->interpMask &= ~SPAN_RGBA;
+   }
+
+   /* Fog */
+   if (swrast->_FogEnabled) {
+      _swrast_fog_rgba_span(ctx, span);
+      monoColor = GL_FALSE;
+   }
+
+   /* Antialias coverage application */
+   if (span->arrayMask & SPAN_COVERAGE) {
+      GLchan (*rgba)[4] = span->array->rgba;
+      GLfloat *coverage = span->array->coverage;
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         rgba[i][ACOMP] = (GLchan) (rgba[i][ACOMP] * coverage[i]);
+      }
+      monoColor = GL_FALSE;
+   }
+
+   if (swrast->_RasterMask & MULTI_DRAW_BIT) {
+      multi_write_rgba_span(ctx, span);
+   }
+   else {
+      /* normal: write to exactly one buffer */
+      if (ctx->Color._LogicOpEnabled) {
+         _swrast_logicop_rgba_span(ctx, span, span->array->rgba);
+         monoColor = GL_FALSE;
+      }
+      else if (ctx->Color.BlendEnabled) {
+         _swrast_blend_span(ctx, span, span->array->rgba);
+         monoColor = GL_FALSE;
+      }
+
+      /* Color component masking */
+      if (colorMask != 0xffffffff) {
+         _swrast_mask_rgba_span(ctx, span, span->array->rgba);
+         monoColor = GL_FALSE;
+      }
+
+      /* write pixels */
+      if (span->arrayMask & SPAN_XY) {
+         /* array of pixel coords */
+         if (monoColor) {
+            /* all pixels have same color */
+            GLchan color[4];
+            color[RCOMP] = FixedToChan(span->red);
+            color[GCOMP] = FixedToChan(span->green);
+            color[BCOMP] = FixedToChan(span->blue);
+            color[ACOMP] = FixedToChan(span->alpha);
+            (*swrast->Driver.WriteMonoRGBAPixels)(ctx, span->end,
+                     span->array->x, span->array->y, color, span->array->mask);
+            if (SWRAST_CONTEXT(ctx)->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_mono_alpha_pixels(ctx, span->end,
+                                              span->array->x, span->array->y,
+                                              color[ACOMP], span->array->mask);
+            }
+         }
+         else {
+            (*swrast->Driver.WriteRGBAPixels)(ctx, span->end,
+                                       span->array->x, span->array->y,
+                                       (const GLchan (*)[4]) span->array->rgba,
+                                       span->array->mask);
+            if (SWRAST_CONTEXT(ctx)->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_alpha_pixels(ctx, span->end,
+                                       span->array->x, span->array->y,
+                                       (const GLchan (*)[4]) span->array->rgba,
+                                       span->array->mask);
+            }
+         }
+      }
+      else {
+         /* horizontal run of pixels */
+         if (monoColor) {
+            /* all pixels have same color */
+            GLchan color[4];
+            color[RCOMP] = FixedToChan(span->red);
+            color[GCOMP] = FixedToChan(span->green);
+            color[BCOMP] = FixedToChan(span->blue);
+            color[ACOMP] = FixedToChan(span->alpha);
+            (*swrast->Driver.WriteMonoRGBASpan)(ctx, span->end, span->x,
+                                           span->y, color, span->array->mask);
+            if (swrast->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_mono_alpha_span(ctx, span->end, span->x, span->y,
+                      color[ACOMP],
+                      span->writeAll ? ((const GLubyte *) NULL) : span->array->mask);
+            }
+         }
+         else {
+            /* each pixel is a different color */
+            (*swrast->Driver.WriteRGBASpan)(ctx, span->end, span->x, span->y,
+                      (const GLchan (*)[4]) span->array->rgba,
+                      span->writeAll ? ((const GLubyte *) NULL) : span->array->mask);
+            if (swrast->_RasterMask & ALPHABUF_BIT) {
+               _swrast_write_alpha_span(ctx, span->end, span->x, span->y,
+                      (const GLchan (*)[4]) span->array->rgba,
+                      span->writeAll ? ((const GLubyte *) NULL) : span->array->mask);
+            }
+         }
+      }
+   }
+
+   span->interpMask = origInterpMask;
+   span->arrayMask = origArrayMask;
+}
+
+
+/**
+ * Add specular color to base color.  This is used only when
+ * GL_LIGHT_MODEL_COLOR_CONTROL = GL_SEPARATE_SPECULAR_COLOR.
+ */
+static void
+add_colors(GLuint n, GLchan rgba[][4], GLchan specular[][4] )
+{
+   GLuint i;
+   for (i = 0; i < n; i++) {
+#if CHAN_TYPE == GL_FLOAT
+      /* no clamping */
+      rgba[i][RCOMP] += specular[i][RCOMP];
+      rgba[i][GCOMP] += specular[i][GCOMP];
+      rgba[i][BCOMP] += specular[i][BCOMP];
+#else
+      GLint r = rgba[i][RCOMP] + specular[i][RCOMP];
+      GLint g = rgba[i][GCOMP] + specular[i][GCOMP];
+      GLint b = rgba[i][BCOMP] + specular[i][BCOMP];
+      rgba[i][RCOMP] = (GLchan) MIN2(r, CHAN_MAX);
+      rgba[i][GCOMP] = (GLchan) MIN2(g, CHAN_MAX);
+      rgba[i][BCOMP] = (GLchan) MIN2(b, CHAN_MAX);
+#endif
+   }
+}
+
+
+/**
+ * This function may modify any of the array values in the span.
+ * span->interpMask and span->arrayMask may be changed but will be restored
+ * to their original values before returning.
+ */
+void
+_swrast_write_texture_span( GLcontext *ctx, struct sw_span *span)
+{
+   const GLuint colorMask = *((GLuint *) ctx->Color.ColorMask);
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLuint origInterpMask = span->interpMask;
+   const GLuint origArrayMask = span->arrayMask;
+
+   ASSERT(span->primitive == GL_POINT  ||  span->primitive == GL_LINE ||
+	  span->primitive == GL_POLYGON  ||  span->primitive == GL_BITMAP);
+   ASSERT(span->end <= MAX_WIDTH);
+   ASSERT((span->interpMask & span->arrayMask) == 0);
+   ASSERT(ctx->Texture._EnabledCoordUnits || ctx->FragmentProgram._Enabled);
+
+   /*
+   printf("%s()  interp 0x%x  array 0x%x\n", __FUNCTION__, span->interpMask, span->arrayMask);
+   */
+
+   if (span->arrayMask & SPAN_MASK) {
+      /* mask was initialized by caller, probably glBitmap */
+      span->writeAll = GL_FALSE;
+   }
+   else {
+      MEMSET(span->array->mask, 1, span->end);
+      span->writeAll = GL_TRUE;
+   }
+
+   /* Clipping */
+   if ((swrast->_RasterMask & CLIP_BIT) || (span->primitive != GL_POLYGON)) {
+      if (!clip_span(ctx, span)) {
+	 return;
+      }
+   }
+
+#ifdef DEBUG
+   if (span->arrayMask & SPAN_XY) {
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         if (span->array->mask[i]) {
+            assert(span->array->x[i] >= ctx->DrawBuffer->_Xmin);
+            assert(span->array->x[i] < ctx->DrawBuffer->_Xmax);
+            assert(span->array->y[i] >= ctx->DrawBuffer->_Ymin);
+            assert(span->array->y[i] < ctx->DrawBuffer->_Ymax);
+         }
+      }
+   }
+#endif
+
+   /* Polygon Stippling */
+   if (ctx->Polygon.StippleFlag && span->primitive == GL_POLYGON) {
+      stipple_polygon_span(ctx, span);
+   }
+
+   /* Need texture coordinates now */
+   if ((span->interpMask & SPAN_TEXTURE)
+       && (span->arrayMask & SPAN_TEXTURE) == 0)
+      interpolate_texcoords(ctx, span);
+
+   /* Texture with alpha test */
+   if (ctx->Color.AlphaEnabled) {
+
+      /* Now we need the rgba array, fill it in if needed */
+      if ((span->interpMask & SPAN_RGBA) && (span->arrayMask & SPAN_RGBA) == 0)
+         interpolate_colors(ctx, span);
+
+      if (span->interpMask & SPAN_SPEC)
+         interpolate_specular(ctx, span);
+
+      if (span->interpMask & SPAN_FOG)
+         interpolate_fog(ctx, span);
+
+      /* Texturing without alpha is done after depth-testing which
+       * gives a potential speed-up.
+       */
+      if (ctx->FragmentProgram._Enabled)
+         _swrast_exec_fragment_program( ctx, span );
+      else
+         _swrast_texture_span( ctx, span );
+
+      /* Do the alpha test */
+      if (!_swrast_alpha_test(ctx, span)) {
+         span->arrayMask = origArrayMask;
+	 return;
+      }
+   }
+
+   /* Stencil and Z testing */
+   if (ctx->Stencil.Enabled || ctx->Depth.Test) {
+      if (span->interpMask & SPAN_Z)
+         _swrast_span_interpolate_z(ctx, span);
+
+      if (ctx->Stencil.Enabled) {
+         if (!_swrast_stencil_and_ztest_span(ctx, span)) {
+            span->interpMask = origInterpMask;
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+      else {
+         ASSERT(ctx->Depth.Test);
+         ASSERT(span->arrayMask & SPAN_Z);
+         /* regular depth testing */
+         if (!_swrast_depth_test_span(ctx, span)) {
+            span->interpMask = origInterpMask;
+            span->arrayMask = origArrayMask;
+            return;
+         }
+      }
+   }
+
+   /* if we get here, some fragments passed the depth test */
+   if (ctx->Depth.OcclusionTest) {
+      ctx->OcclusionResult = GL_TRUE;
+   }
+
+#if FEATURE_ARB_occlusion_query
+   if (ctx->Occlusion.Active) {
+      /* update count of 'passed' fragments */
+      GLuint i;
+      for (i = 0; i < span->end; i++)
+         ctx->Occlusion.PassedCounter += span->array->mask[i];
+   }
+#endif
+
+   /* We had to wait until now to check for glColorMask(F,F,F,F) because of
+    * the occlusion test.
+    */
+   if (colorMask == 0x0) {
+      span->interpMask = origInterpMask;
+      span->arrayMask = origArrayMask;
+      return;
+   }
+
+   /* Texture without alpha test */
+   if (!ctx->Color.AlphaEnabled) {
+
+      /* Now we need the rgba array, fill it in if needed */
+      if ((span->interpMask & SPAN_RGBA) && (span->arrayMask & SPAN_RGBA) == 0)
+         interpolate_colors(ctx, span);
+
+      if (span->interpMask & SPAN_SPEC)
+         interpolate_specular(ctx, span);
+
+      if (span->interpMask & SPAN_FOG)
+         interpolate_fog(ctx, span);
+
+      if (ctx->FragmentProgram._Enabled)
+         _swrast_exec_fragment_program( ctx, span );
+      else
+         _swrast_texture_span( ctx, span );
+   }
+
+   ASSERT(span->arrayMask & SPAN_RGBA);
+
+   if (!ctx->FragmentProgram._Enabled) {
+      /* Add base and specular colors */
+      if (ctx->Fog.ColorSumEnabled ||
+          (ctx->Light.Enabled &&
+           ctx->Light.Model.ColorControl == GL_SEPARATE_SPECULAR_COLOR)) {
+         if (span->interpMask & SPAN_SPEC) {
+            interpolate_specular(ctx, span);
+         }
+         ASSERT(span->arrayMask & SPAN_SPEC);
+         add_colors( span->end, span->array->rgba, span->array->spec );
+      }
+   }
+
+   /* Fog */
+   if (swrast->_FogEnabled) {
+      _swrast_fog_rgba_span(ctx, span);
+   }
+
+   /* Antialias coverage application */
+   if (span->arrayMask & SPAN_COVERAGE) {
+      GLchan (*rgba)[4] = span->array->rgba;
+      GLfloat *coverage = span->array->coverage;
+      GLuint i;
+      for (i = 0; i < span->end; i++) {
+         rgba[i][ACOMP] = (GLchan) (rgba[i][ACOMP] * coverage[i]);
+      }
+   }
+
+   if (swrast->_RasterMask & MULTI_DRAW_BIT) {
+      multi_write_rgba_span(ctx, span);
+   }
+   else {
+      /* normal: write to exactly one buffer */
+      if (ctx->Color._LogicOpEnabled) {
+         _swrast_logicop_rgba_span(ctx, span, span->array->rgba);
+      }
+      else if (ctx->Color.BlendEnabled) {
+         _swrast_blend_span(ctx, span, span->array->rgba);
+      }
+
+      /* Color component masking */
+      if (colorMask != 0xffffffff) {
+         _swrast_mask_rgba_span(ctx, span, span->array->rgba);
+      }
+
+      /* write pixels */
+      if (span->arrayMask & SPAN_XY) {
+         /* array of pixel coords */
+         (*swrast->Driver.WriteRGBAPixels)(ctx, span->end, span->array->x,
+             span->array->y, (const GLchan (*)[4]) span->array->rgba, span->array->mask);
+         if (SWRAST_CONTEXT(ctx)->_RasterMask & ALPHABUF_BIT) {
+            _swrast_write_alpha_pixels(ctx, span->end,
+                                     span->array->x, span->array->y,
+                                     (const GLchan (*)[4]) span->array->rgba,
+                                     span->array->mask);
+         }
+      }
+      else {
+         /* horizontal run of pixels */
+         (*swrast->Driver.WriteRGBASpan)(ctx, span->end, span->x, span->y,
+                                       (const GLchan (*)[4]) span->array->rgba,
+                                       span->writeAll ? NULL : span->array->mask);
+         if (swrast->_RasterMask & ALPHABUF_BIT) {
+            _swrast_write_alpha_span(ctx, span->end, span->x, span->y,
+                                   (const GLchan (*)[4]) span->array->rgba,
+                                   span->writeAll ? NULL : span->array->mask);
+         }
+      }
+   }
+
+   span->interpMask = origInterpMask;
+   span->arrayMask = origArrayMask;
+}
+
+
+
+/**
+ * Read RGBA pixels from frame buffer.  Clipping will be done to prevent
+ * reading ouside the buffer's boundaries.
+ */
+void
+_swrast_read_rgba_span( GLcontext *ctx, GLframebuffer *buffer,
+                      GLuint n, GLint x, GLint y, GLchan rgba[][4] )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLint bufWidth = (GLint) buffer->Width;
+   const GLint bufHeight = (GLint) buffer->Height;
+
+   if (y < 0 || y >= bufHeight || x + (GLint) n < 0 || x >= bufWidth) {
+      /* completely above, below, or right */
+      /* XXX maybe leave undefined? */
+      _mesa_bzero(rgba, 4 * n * sizeof(GLchan));
+   }
+   else {
+      GLint skip, length;
+      if (x < 0) {
+         /* left edge clippping */
+         skip = -x;
+         length = (GLint) n - skip;
+         if (length < 0) {
+            /* completely left of window */
+            return;
+         }
+         if (length > bufWidth) {
+            length = bufWidth;
+         }
+      }
+      else if ((GLint) (x + n) > bufWidth) {
+         /* right edge clipping */
+         skip = 0;
+         length = bufWidth - x;
+         if (length < 0) {
+            /* completely to right of window */
+            return;
+         }
+      }
+      else {
+         /* no clipping */
+         skip = 0;
+         length = (GLint) n;
+      }
+
+      (*swrast->Driver.ReadRGBASpan)( ctx, length, x + skip, y, rgba + skip );
+      if (buffer->UseSoftwareAlphaBuffers) {
+         _swrast_read_alpha_span(ctx, length, x + skip, y, rgba + skip);
+      }
+   }
+}
+
+
+/**
+ * Read CI pixels from frame buffer.  Clipping will be done to prevent
+ * reading ouside the buffer's boundaries.
+ */
+void
+_swrast_read_index_span( GLcontext *ctx, GLframebuffer *buffer,
+                       GLuint n, GLint x, GLint y, GLuint indx[] )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLint bufWidth = (GLint) buffer->Width;
+   const GLint bufHeight = (GLint) buffer->Height;
+
+   if (y < 0 || y >= bufHeight || x + (GLint) n < 0 || x >= bufWidth) {
+      /* completely above, below, or right */
+      _mesa_bzero(indx, n * sizeof(GLuint));
+   }
+   else {
+      GLint skip, length;
+      if (x < 0) {
+         /* left edge clippping */
+         skip = -x;
+         length = (GLint) n - skip;
+         if (length < 0) {
+            /* completely left of window */
+            return;
+         }
+         if (length > bufWidth) {
+            length = bufWidth;
+         }
+      }
+      else if ((GLint) (x + n) > bufWidth) {
+         /* right edge clipping */
+         skip = 0;
+         length = bufWidth - x;
+         if (length < 0) {
+            /* completely to right of window */
+            return;
+         }
+      }
+      else {
+         /* no clipping */
+         skip = 0;
+         length = (GLint) n;
+      }
+
+      (*swrast->Driver.ReadCI32Span)( ctx, length, skip + x, y, indx + skip );
+   }
+}