svn merge ^/branches/released .

1 files changed, 929 insertions, 929 deletions

diff --git a/mesalib/src/mesa/swrast/s_tritemp.h b/mesalib/src/mesa/swrast/s_tritemp.h
index 0aa8739f4..340c410ca 100644
--- a/mesalib/src/mesa/swrast/s_tritemp.h
+++ b/mesalib/src/mesa/swrast/s_tritemp.h
@@ -1,929 +1,929 @@
-/*
- * Mesa 3-D graphics library
- * Version:  7.0
- *
- * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
- *
- * Permission is hereby granted, free of charge, to any person obtaining a
- * copy of this software and associated documentation files (the "Software"),
- * to deal in the Software without restriction, including without limitation
- * the rights to use, copy, modify, merge, publish, distribute, sublicense,
- * and/or sell copies of the Software, and to permit persons to whom the
- * Software is furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included
- * in all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
- * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
- * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
- * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
- * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
- */
-
-/*
- * Triangle Rasterizer Template
- *
- * This file is #include'd to generate custom triangle rasterizers.
- *
- * The following macros may be defined to indicate what auxillary information
- * must be interpolated across the triangle:
- *    INTERP_Z        - if defined, interpolate integer Z values
- *    INTERP_RGB      - if defined, interpolate integer RGB values
- *    INTERP_ALPHA    - if defined, interpolate integer Alpha values
- *    INTERP_INT_TEX  - if defined, interpolate integer ST texcoords
- *                         (fast, simple 2-D texture mapping, without
- *                         perspective correction)
- *    INTERP_ATTRIBS  - if defined, interpolate arbitrary attribs (texcoords,
- *                         varying vars, etc)  This also causes W to be
- *                         computed for perspective correction).
- *
- * When one can directly address pixels in the color buffer the following
- * macros can be defined and used to compute pixel addresses during
- * rasterization (see pRow):
- *    PIXEL_TYPE          - the datatype of a pixel (GLubyte, GLushort, GLuint)
- *    BYTES_PER_ROW       - number of bytes per row in the color buffer
- *    PIXEL_ADDRESS(X,Y)  - returns the address of pixel at (X,Y) where
- *                          Y==0 at bottom of screen and increases upward.
- *
- * Similarly, for direct depth buffer access, this type is used for depth
- * buffer addressing (see zRow):
- *    DEPTH_TYPE          - either GLushort or GLuint
- *
- * Optionally, one may provide one-time setup code per triangle:
- *    SETUP_CODE    - code which is to be executed once per triangle
- *
- * The following macro MUST be defined:
- *    RENDER_SPAN(span) - code to write a span of pixels.
- *
- * This code was designed for the origin to be in the lower-left corner.
- *
- * Inspired by triangle rasterizer code written by Allen Akin.  Thanks Allen!
- *
- *
- * Some notes on rasterization accuracy:
- *
- * This code uses fixed point arithmetic (the GLfixed type) to iterate
- * over the triangle edges and interpolate ancillary data (such as Z,
- * color, secondary color, etc).  The number of fractional bits in
- * GLfixed and the value of SUB_PIXEL_BITS has a direct bearing on the
- * accuracy of rasterization.
- *
- * If SUB_PIXEL_BITS=4 then we'll snap the vertices to the nearest
- * 1/16 of a pixel.  If we're walking up a long, nearly vertical edge
- * (dx=1/16, dy=1024) we'll need 4 + 10 = 14 fractional bits in
- * GLfixed to walk the edge without error.  If the maximum viewport
- * height is 4K pixels, then we'll need 4 + 12 = 16 fractional bits.
- *
- * Historically, Mesa has used 11 fractional bits in GLfixed, snaps
- * vertices to 1/16 pixel and allowed a maximum viewport height of 2K
- * pixels.  11 fractional bits is actually insufficient for accurately
- * rasterizing some triangles.  More recently, the maximum viewport
- * height was increased to 4K pixels.  Thus, Mesa should be using 16
- * fractional bits in GLfixed.  Unfortunately, there may be some issues
- * with setting FIXED_FRAC_BITS=16, such as multiplication overflow.
- * This will have to be examined in some detail...
- *
- * For now, if you find rasterization errors, particularly with tall,
- * sliver triangles, try increasing FIXED_FRAC_BITS and/or decreasing
- * SUB_PIXEL_BITS.
- */
-
-
-/*
- * Some code we unfortunately need to prevent negative interpolated colors.
- */
-#ifndef CLAMP_INTERPOLANT
-#define CLAMP_INTERPOLANT(CHANNEL, CHANNELSTEP, LEN)		\
-do {								\
-   GLfixed endVal = span.CHANNEL + (LEN) * span.CHANNELSTEP;	\
-   if (endVal < 0) {						\
-      span.CHANNEL -= endVal;					\
-   }								\
-   if (span.CHANNEL < 0) {					\
-      span.CHANNEL = 0;						\
-   }								\
-} while (0)
-#endif
-
-
-static void NAME(GLcontext *ctx, const SWvertex *v0,
-                                 const SWvertex *v1,
-                                 const SWvertex *v2 )
-{
-   typedef struct {
-      const SWvertex *v0, *v1;   /* Y(v0) < Y(v1) */
-      GLfloat dx;	/* X(v1) - X(v0) */
-      GLfloat dy;	/* Y(v1) - Y(v0) */
-      GLfloat dxdy;	/* dx/dy */
-      GLfixed fdxdy;	/* dx/dy in fixed-point */
-      GLfloat adjy;	/* adjust from v[0]->fy to fsy, scaled */
-      GLfixed fsx;	/* first sample point x coord */
-      GLfixed fsy;
-      GLfixed fx0;	/* fixed pt X of lower endpoint */
-      GLint lines;	/* number of lines to be sampled on this edge */
-   } EdgeT;
-
-   const SWcontext *swrast = SWRAST_CONTEXT(ctx);
-#ifdef INTERP_Z
-   const GLint depthBits = ctx->DrawBuffer->Visual.depthBits;
-   const GLint fixedToDepthShift = depthBits <= 16 ? FIXED_SHIFT : 0;
-   const GLfloat maxDepth = ctx->DrawBuffer->_DepthMaxF;
-#define FixedToDepth(F)  ((F) >> fixedToDepthShift)
-#endif
-   EdgeT eMaj, eTop, eBot;
-   GLfloat oneOverArea;
-   const SWvertex *vMin, *vMid, *vMax;  /* Y(vMin)<=Y(vMid)<=Y(vMax) */
-   GLfloat bf = SWRAST_CONTEXT(ctx)->_BackfaceSign;
-   const GLint snapMask = ~((FIXED_ONE / (1 << SUB_PIXEL_BITS)) - 1); /* for x/y coord snapping */
-   GLfixed vMin_fx, vMin_fy, vMid_fx, vMid_fy, vMax_fx, vMax_fy;
-
-   SWspan span;
-
-   (void) swrast;
-
-   INIT_SPAN(span, GL_POLYGON);
-   span.y = 0; /* silence warnings */
-
-#ifdef INTERP_Z
-   (void) fixedToDepthShift;
-#endif
-
-   /*
-   printf("%s()\n", __FUNCTION__);
-   printf("  %g, %g, %g\n",
-          v0->attrib[FRAG_ATTRIB_WPOS][0],
-          v0->attrib[FRAG_ATTRIB_WPOS][1],
-          v0->attrib[FRAG_ATTRIB_WPOS][2]);
-   printf("  %g, %g, %g\n",
-          v1->attrib[FRAG_ATTRIB_WPOS][0],
-          v1->attrib[FRAG_ATTRIB_WPOS][1],
-          v1->attrib[FRAG_ATTRIB_WPOS][2]);
-   printf("  %g, %g, %g\n",
-          v2->attrib[FRAG_ATTRIB_WPOS][0],
-          v2->attrib[FRAG_ATTRIB_WPOS][1],
-          v2->attrib[FRAG_ATTRIB_WPOS][2]);
-   */
-
-   /* Compute fixed point x,y coords w/ half-pixel offsets and snapping.
-    * And find the order of the 3 vertices along the Y axis.
-    */
-   {
-      const GLfixed fy0 = FloatToFixed(v0->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;
-      const GLfixed fy1 = FloatToFixed(v1->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;
-      const GLfixed fy2 = FloatToFixed(v2->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;
-      if (fy0 <= fy1) {
-         if (fy1 <= fy2) {
-            /* y0 <= y1 <= y2 */
-            vMin = v0;   vMid = v1;   vMax = v2;
-            vMin_fy = fy0;  vMid_fy = fy1;  vMax_fy = fy2;
-         }
-         else if (fy2 <= fy0) {
-            /* y2 <= y0 <= y1 */
-            vMin = v2;   vMid = v0;   vMax = v1;
-            vMin_fy = fy2;  vMid_fy = fy0;  vMax_fy = fy1;
-         }
-         else {
-            /* y0 <= y2 <= y1 */
-            vMin = v0;   vMid = v2;   vMax = v1;
-            vMin_fy = fy0;  vMid_fy = fy2;  vMax_fy = fy1;
-            bf = -bf;
-         }
-      }
-      else {
-         if (fy0 <= fy2) {
-            /* y1 <= y0 <= y2 */
-            vMin = v1;   vMid = v0;   vMax = v2;
-            vMin_fy = fy1;  vMid_fy = fy0;  vMax_fy = fy2;
-            bf = -bf;
-         }
-         else if (fy2 <= fy1) {
-            /* y2 <= y1 <= y0 */
-            vMin = v2;   vMid = v1;   vMax = v0;
-            vMin_fy = fy2;  vMid_fy = fy1;  vMax_fy = fy0;
-            bf = -bf;
-         }
-         else {
-            /* y1 <= y2 <= y0 */
-            vMin = v1;   vMid = v2;   vMax = v0;
-            vMin_fy = fy1;  vMid_fy = fy2;  vMax_fy = fy0;
-         }
-      }
-
-      /* fixed point X coords */
-      vMin_fx = FloatToFixed(vMin->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;
-      vMid_fx = FloatToFixed(vMid->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;
-      vMax_fx = FloatToFixed(vMax->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;
-   }
-
-   /* vertex/edge relationship */
-   eMaj.v0 = vMin;   eMaj.v1 = vMax;   /*TODO: .v1's not needed */
-   eTop.v0 = vMid;   eTop.v1 = vMax;
-   eBot.v0 = vMin;   eBot.v1 = vMid;
-
-   /* compute deltas for each edge:  vertex[upper] - vertex[lower] */
-   eMaj.dx = FixedToFloat(vMax_fx - vMin_fx);
-   eMaj.dy = FixedToFloat(vMax_fy - vMin_fy);
-   eTop.dx = FixedToFloat(vMax_fx - vMid_fx);
-   eTop.dy = FixedToFloat(vMax_fy - vMid_fy);
-   eBot.dx = FixedToFloat(vMid_fx - vMin_fx);
-   eBot.dy = FixedToFloat(vMid_fy - vMin_fy);
-
-   /* compute area, oneOverArea and perform backface culling */
-   {
-      const GLfloat area = eMaj.dx * eBot.dy - eBot.dx * eMaj.dy;
-
-      if (IS_INF_OR_NAN(area) || area == 0.0F)
-         return;
-
-      if (area * bf * swrast->_BackfaceCullSign < 0.0)
-         return;
-
-      oneOverArea = 1.0F / area;
-
-      /* 0 = front, 1 = back */
-      span.facing = oneOverArea * bf > 0.0F;
-   }
-
-   /* Edge setup.  For a triangle strip these could be reused... */
-   {
-      eMaj.fsy = FixedCeil(vMin_fy);
-      eMaj.lines = FixedToInt(FixedCeil(vMax_fy - eMaj.fsy));
-      if (eMaj.lines > 0) {
-         eMaj.dxdy = eMaj.dx / eMaj.dy;
-         eMaj.fdxdy = SignedFloatToFixed(eMaj.dxdy);
-         eMaj.adjy = (GLfloat) (eMaj.fsy - vMin_fy);  /* SCALED! */
-         eMaj.fx0 = vMin_fx;
-         eMaj.fsx = eMaj.fx0 + (GLfixed) (eMaj.adjy * eMaj.dxdy);
-      }
-      else {
-         return;  /*CULLED*/
-      }
-
-      eTop.fsy = FixedCeil(vMid_fy);
-      eTop.lines = FixedToInt(FixedCeil(vMax_fy - eTop.fsy));
-      if (eTop.lines > 0) {
-         eTop.dxdy = eTop.dx / eTop.dy;
-         eTop.fdxdy = SignedFloatToFixed(eTop.dxdy);
-         eTop.adjy = (GLfloat) (eTop.fsy - vMid_fy); /* SCALED! */
-         eTop.fx0 = vMid_fx;
-         eTop.fsx = eTop.fx0 + (GLfixed) (eTop.adjy * eTop.dxdy);
-      }
-
-      eBot.fsy = FixedCeil(vMin_fy);
-      eBot.lines = FixedToInt(FixedCeil(vMid_fy - eBot.fsy));
-      if (eBot.lines > 0) {
-         eBot.dxdy = eBot.dx / eBot.dy;
-         eBot.fdxdy = SignedFloatToFixed(eBot.dxdy);
-         eBot.adjy = (GLfloat) (eBot.fsy - vMin_fy);  /* SCALED! */
-         eBot.fx0 = vMin_fx;
-         eBot.fsx = eBot.fx0 + (GLfixed) (eBot.adjy * eBot.dxdy);
-      }
-   }
-
-   /*
-    * Conceptually, we view a triangle as two subtriangles
-    * separated by a perfectly horizontal line.  The edge that is
-    * intersected by this line is one with maximal absolute dy; we
-    * call it a ``major'' edge.  The other two edges are the
-    * ``top'' edge (for the upper subtriangle) and the ``bottom''
-    * edge (for the lower subtriangle).  If either of these two
-    * edges is horizontal or very close to horizontal, the
-    * corresponding subtriangle might cover zero sample points;
-    * we take care to handle such cases, for performance as well
-    * as correctness.
-    *
-    * By stepping rasterization parameters along the major edge,
-    * we can avoid recomputing them at the discontinuity where
-    * the top and bottom edges meet.  However, this forces us to
-    * be able to scan both left-to-right and right-to-left.
-    * Also, we must determine whether the major edge is at the
-    * left or right side of the triangle.  We do this by
-    * computing the magnitude of the cross-product of the major
-    * and top edges.  Since this magnitude depends on the sine of
-    * the angle between the two edges, its sign tells us whether
-    * we turn to the left or to the right when travelling along
-    * the major edge to the top edge, and from this we infer
-    * whether the major edge is on the left or the right.
-    *
-    * Serendipitously, this cross-product magnitude is also a
-    * value we need to compute the iteration parameter
-    * derivatives for the triangle, and it can be used to perform
-    * backface culling because its sign tells us whether the
-    * triangle is clockwise or counterclockwise.  In this code we
-    * refer to it as ``area'' because it's also proportional to
-    * the pixel area of the triangle.
-    */
-
-   {
-      GLint scan_from_left_to_right;  /* true if scanning left-to-right */
-
-      /*
-       * Execute user-supplied setup code
-       */
-#ifdef SETUP_CODE
-      SETUP_CODE
-#endif
-
-      scan_from_left_to_right = (oneOverArea < 0.0F);
-
-
-      /* compute d?/dx and d?/dy derivatives */
-#ifdef INTERP_Z
-      span.interpMask |= SPAN_Z;
-      {
-         GLfloat eMaj_dz = vMax->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];
-         GLfloat eBot_dz = vMid->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];
-         span.attrStepX[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj_dz * eBot.dy - eMaj.dy * eBot_dz);
-         if (span.attrStepX[FRAG_ATTRIB_WPOS][2] > maxDepth ||
-             span.attrStepX[FRAG_ATTRIB_WPOS][2] < -maxDepth) {
-            /* probably a sliver triangle */
-            span.attrStepX[FRAG_ATTRIB_WPOS][2] = 0.0;
-            span.attrStepY[FRAG_ATTRIB_WPOS][2] = 0.0;
-         }
-         else {
-            span.attrStepY[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj.dx * eBot_dz - eMaj_dz * eBot.dx);
-         }
-         if (depthBits <= 16)
-            span.zStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_WPOS][2]);
-         else
-            span.zStep = (GLint) span.attrStepX[FRAG_ATTRIB_WPOS][2];
-      }
-#endif
-#ifdef INTERP_RGB
-      span.interpMask |= SPAN_RGBA;
-      if (ctx->Light.ShadeModel == GL_SMOOTH) {
-         GLfloat eMaj_dr = (GLfloat) (vMax->color[RCOMP] - vMin->color[RCOMP]);
-         GLfloat eBot_dr = (GLfloat) (vMid->color[RCOMP] - vMin->color[RCOMP]);
-         GLfloat eMaj_dg = (GLfloat) (vMax->color[GCOMP] - vMin->color[GCOMP]);
-         GLfloat eBot_dg = (GLfloat) (vMid->color[GCOMP] - vMin->color[GCOMP]);
-         GLfloat eMaj_db = (GLfloat) (vMax->color[BCOMP] - vMin->color[BCOMP]);
-         GLfloat eBot_db = (GLfloat) (vMid->color[BCOMP] - vMin->color[BCOMP]);
-#  ifdef INTERP_ALPHA
-         GLfloat eMaj_da = (GLfloat) (vMax->color[ACOMP] - vMin->color[ACOMP]);
-         GLfloat eBot_da = (GLfloat) (vMid->color[ACOMP] - vMin->color[ACOMP]);
-#  endif
-         span.attrStepX[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj_dr * eBot.dy - eMaj.dy * eBot_dr);
-         span.attrStepY[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj.dx * eBot_dr - eMaj_dr * eBot.dx);
-         span.attrStepX[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj_dg * eBot.dy - eMaj.dy * eBot_dg);
-         span.attrStepY[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj.dx * eBot_dg - eMaj_dg * eBot.dx);
-         span.attrStepX[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj_db * eBot.dy - eMaj.dy * eBot_db);
-         span.attrStepY[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj.dx * eBot_db - eMaj_db * eBot.dx);
-         span.redStep   = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][0]);
-         span.greenStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][1]);
-         span.blueStep  = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][2]);
-#  ifdef INTERP_ALPHA
-         span.attrStepX[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);
-         span.attrStepY[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);
-         span.alphaStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][3]);
-#  endif /* INTERP_ALPHA */
-      }
-      else {
-         ASSERT(ctx->Light.ShadeModel == GL_FLAT);
-         span.interpMask |= SPAN_FLAT;
-         span.attrStepX[FRAG_ATTRIB_COL0][0] = span.attrStepY[FRAG_ATTRIB_COL0][0] = 0.0F;
-         span.attrStepX[FRAG_ATTRIB_COL0][1] = span.attrStepY[FRAG_ATTRIB_COL0][1] = 0.0F;
-         span.attrStepX[FRAG_ATTRIB_COL0][2] = span.attrStepY[FRAG_ATTRIB_COL0][2] = 0.0F;
-	 span.redStep   = 0;
-	 span.greenStep = 0;
-	 span.blueStep  = 0;
-#  ifdef INTERP_ALPHA
-         span.attrStepX[FRAG_ATTRIB_COL0][3] = span.attrStepY[FRAG_ATTRIB_COL0][3] = 0.0F;
-	 span.alphaStep = 0;
-#  endif
-      }
-#endif /* INTERP_RGB */
-#ifdef INTERP_INT_TEX
-      {
-         GLfloat eMaj_ds = (vMax->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;
-         GLfloat eBot_ds = (vMid->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;
-         GLfloat eMaj_dt = (vMax->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;
-         GLfloat eBot_dt = (vMid->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;
-         span.attrStepX[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj_ds * eBot.dy - eMaj.dy * eBot_ds);
-         span.attrStepY[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj.dx * eBot_ds - eMaj_ds * eBot.dx);
-         span.attrStepX[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj_dt * eBot.dy - eMaj.dy * eBot_dt);
-         span.attrStepY[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj.dx * eBot_dt - eMaj_dt * eBot.dx);
-         span.intTexStep[0] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][0]);
-         span.intTexStep[1] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][1]);
-      }
-#endif
-#ifdef INTERP_ATTRIBS
-      {
-         /* attrib[FRAG_ATTRIB_WPOS][3] is 1/W */
-         const GLfloat wMax = vMax->attrib[FRAG_ATTRIB_WPOS][3];
-         const GLfloat wMin = vMin->attrib[FRAG_ATTRIB_WPOS][3];
-         const GLfloat wMid = vMid->attrib[FRAG_ATTRIB_WPOS][3];
-         {
-            const GLfloat eMaj_dw = wMax - wMin;
-            const GLfloat eBot_dw = wMid - wMin;
-            span.attrStepX[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj_dw * eBot.dy - eMaj.dy * eBot_dw);
-            span.attrStepY[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj.dx * eBot_dw - eMaj_dw * eBot.dx);
-         }
-         ATTRIB_LOOP_BEGIN
-            if (swrast->_InterpMode[attr] == GL_FLAT) {
-               ASSIGN_4V(span.attrStepX[attr], 0.0, 0.0, 0.0, 0.0);
-               ASSIGN_4V(span.attrStepY[attr], 0.0, 0.0, 0.0, 0.0);
-            }
-            else {
-               GLuint c;
-               for (c = 0; c < 4; c++) {
-                  GLfloat eMaj_da = vMax->attrib[attr][c] * wMax - vMin->attrib[attr][c] * wMin;
-                  GLfloat eBot_da = vMid->attrib[attr][c] * wMid - vMin->attrib[attr][c] * wMin;
-                  span.attrStepX[attr][c] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);
-                  span.attrStepY[attr][c] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);
-               }
-            }
-         ATTRIB_LOOP_END
-      }
-#endif
-
-      /*
-       * We always sample at pixel centers.  However, we avoid
-       * explicit half-pixel offsets in this code by incorporating
-       * the proper offset in each of x and y during the
-       * transformation to window coordinates.
-       *
-       * We also apply the usual rasterization rules to prevent
-       * cracks and overlaps.  A pixel is considered inside a
-       * subtriangle if it meets all of four conditions: it is on or
-       * to the right of the left edge, strictly to the left of the
-       * right edge, on or below the top edge, and strictly above
-       * the bottom edge.  (Some edges may be degenerate.)
-       *
-       * The following discussion assumes left-to-right scanning
-       * (that is, the major edge is on the left); the right-to-left
-       * case is a straightforward variation.
-       *
-       * We start by finding the half-integral y coordinate that is
-       * at or below the top of the triangle.  This gives us the
-       * first scan line that could possibly contain pixels that are
-       * inside the triangle.
-       *
-       * Next we creep down the major edge until we reach that y,
-       * and compute the corresponding x coordinate on the edge.
-       * Then we find the half-integral x that lies on or just
-       * inside the edge.  This is the first pixel that might lie in
-       * the interior of the triangle.  (We won't know for sure
-       * until we check the other edges.)
-       *
-       * As we rasterize the triangle, we'll step down the major
-       * edge.  For each step in y, we'll move an integer number
-       * of steps in x.  There are two possible x step sizes, which
-       * we'll call the ``inner'' step (guaranteed to land on the
-       * edge or inside it) and the ``outer'' step (guaranteed to
-       * land on the edge or outside it).  The inner and outer steps
-       * differ by one.  During rasterization we maintain an error
-       * term that indicates our distance from the true edge, and
-       * select either the inner step or the outer step, whichever
-       * gets us to the first pixel that falls inside the triangle.
-       *
-       * All parameters (z, red, etc.) as well as the buffer
-       * addresses for color and z have inner and outer step values,
-       * so that we can increment them appropriately.  This method
-       * eliminates the need to adjust parameters by creeping a
-       * sub-pixel amount into the triangle at each scanline.
-       */
-
-      {
-         GLint subTriangle;
-         GLfixed fxLeftEdge = 0, fxRightEdge = 0;
-         GLfixed fdxLeftEdge = 0, fdxRightEdge = 0;
-         GLfixed fError = 0, fdError = 0;
-#ifdef PIXEL_ADDRESS
-         PIXEL_TYPE *pRow = NULL;
-         GLint dPRowOuter = 0, dPRowInner;  /* offset in bytes */
-#endif
-#ifdef INTERP_Z
-#  ifdef DEPTH_TYPE
-         struct gl_renderbuffer *zrb
-            = ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
-         DEPTH_TYPE *zRow = NULL;
-         GLint dZRowOuter = 0, dZRowInner;  /* offset in bytes */
-#  endif
-         GLuint zLeft = 0;
-         GLfixed fdzOuter = 0, fdzInner;
-#endif
-#ifdef INTERP_RGB
-         GLint rLeft = 0, fdrOuter = 0, fdrInner;
-         GLint gLeft = 0, fdgOuter = 0, fdgInner;
-         GLint bLeft = 0, fdbOuter = 0, fdbInner;
-#endif
-#ifdef INTERP_ALPHA
-         GLint aLeft = 0, fdaOuter = 0, fdaInner;
-#endif
-#ifdef INTERP_INT_TEX
-         GLfixed sLeft=0, dsOuter=0, dsInner;
-         GLfixed tLeft=0, dtOuter=0, dtInner;
-#endif
-#ifdef INTERP_ATTRIBS
-         GLfloat wLeft = 0, dwOuter = 0, dwInner;
-         GLfloat attrLeft[FRAG_ATTRIB_MAX][4];
-         GLfloat daOuter[FRAG_ATTRIB_MAX][4], daInner[FRAG_ATTRIB_MAX][4];
-#endif
-
-         for (subTriangle=0; subTriangle<=1; subTriangle++) {
-            EdgeT *eLeft, *eRight;
-            int setupLeft, setupRight;
-            int lines;
-
-            if (subTriangle==0) {
-               /* bottom half */
-               if (scan_from_left_to_right) {
-                  eLeft = &eMaj;
-                  eRight = &eBot;
-                  lines = eRight->lines;
-                  setupLeft = 1;
-                  setupRight = 1;
-               }
-               else {
-                  eLeft = &eBot;
-                  eRight = &eMaj;
-                  lines = eLeft->lines;
-                  setupLeft = 1;
-                  setupRight = 1;
-               }
-            }
-            else {
-               /* top half */
-               if (scan_from_left_to_right) {
-                  eLeft = &eMaj;
-                  eRight = &eTop;
-                  lines = eRight->lines;
-                  setupLeft = 0;
-                  setupRight = 1;
-               }
-               else {
-                  eLeft = &eTop;
-                  eRight = &eMaj;
-                  lines = eLeft->lines;
-                  setupLeft = 1;
-                  setupRight = 0;
-               }
-               if (lines == 0)
-                  return;
-            }
-
-            if (setupLeft && eLeft->lines > 0) {
-               const SWvertex *vLower = eLeft->v0;
-               const GLfixed fsy = eLeft->fsy;
-               const GLfixed fsx = eLeft->fsx;  /* no fractional part */
-               const GLfixed fx = FixedCeil(fsx);  /* no fractional part */
-               const GLfixed adjx = (GLfixed) (fx - eLeft->fx0); /* SCALED! */
-               const GLfixed adjy = (GLfixed) eLeft->adjy;      /* SCALED! */
-               GLint idxOuter;
-               GLfloat dxOuter;
-               GLfixed fdxOuter;
-
-               fError = fx - fsx - FIXED_ONE;
-               fxLeftEdge = fsx - FIXED_EPSILON;
-               fdxLeftEdge = eLeft->fdxdy;
-               fdxOuter = FixedFloor(fdxLeftEdge - FIXED_EPSILON);
-               fdError = fdxOuter - fdxLeftEdge + FIXED_ONE;
-               idxOuter = FixedToInt(fdxOuter);
-               dxOuter = (GLfloat) idxOuter;
-               span.y = FixedToInt(fsy);
-
-               /* silence warnings on some compilers */
-               (void) dxOuter;
-               (void) adjx;
-               (void) adjy;
-               (void) vLower;
-
-#ifdef PIXEL_ADDRESS
-               {
-                  pRow = (PIXEL_TYPE *) PIXEL_ADDRESS(FixedToInt(fxLeftEdge), span.y);
-                  dPRowOuter = -((int)BYTES_PER_ROW) + idxOuter * sizeof(PIXEL_TYPE);
-                  /* negative because Y=0 at bottom and increases upward */
-               }
-#endif
-               /*
-                * Now we need the set of parameter (z, color, etc.) values at
-                * the point (fx, fsy).  This gives us properly-sampled parameter
-                * values that we can step from pixel to pixel.  Furthermore,
-                * although we might have intermediate results that overflow
-                * the normal parameter range when we step temporarily outside
-                * the triangle, we shouldn't overflow or underflow for any
-                * pixel that's actually inside the triangle.
-                */
-
-#ifdef INTERP_Z
-               {
-                  GLfloat z0 = vLower->attrib[FRAG_ATTRIB_WPOS][2];
-                  if (depthBits <= 16) {
-                     /* interpolate fixed-pt values */
-                     GLfloat tmp = (z0 * FIXED_SCALE
-                                    + span.attrStepX[FRAG_ATTRIB_WPOS][2] * adjx
-                                    + span.attrStepY[FRAG_ATTRIB_WPOS][2] * adjy) + FIXED_HALF;
-                     if (tmp < MAX_GLUINT / 2)
-                        zLeft = (GLfixed) tmp;
-                     else
-                        zLeft = MAX_GLUINT / 2;
-                     fdzOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_WPOS][2] +
-                                                   dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);
-                  }
-                  else {
-                     /* interpolate depth values w/out scaling */
-                     zLeft = (GLuint) (z0 + span.attrStepX[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjx)
-                                          + span.attrStepY[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjy));
-                     fdzOuter = (GLint) (span.attrStepY[FRAG_ATTRIB_WPOS][2] +
-                                         dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);
-                  }
-#  ifdef DEPTH_TYPE
-                  zRow = (DEPTH_TYPE *)
-                    zrb->GetPointer(ctx, zrb, FixedToInt(fxLeftEdge), span.y);
-                  dZRowOuter = (ctx->DrawBuffer->Width + idxOuter) * sizeof(DEPTH_TYPE);
-#  endif
-               }
-#endif
-#ifdef INTERP_RGB
-               if (ctx->Light.ShadeModel == GL_SMOOTH) {
-                  rLeft = (GLint)(ChanToFixed(vLower->color[RCOMP])
-                                  + span.attrStepX[FRAG_ATTRIB_COL0][0] * adjx
-                                  + span.attrStepY[FRAG_ATTRIB_COL0][0] * adjy) + FIXED_HALF;
-                  gLeft = (GLint)(ChanToFixed(vLower->color[GCOMP])
-                                  + span.attrStepX[FRAG_ATTRIB_COL0][1] * adjx
-                                  + span.attrStepY[FRAG_ATTRIB_COL0][1] * adjy) + FIXED_HALF;
-                  bLeft = (GLint)(ChanToFixed(vLower->color[BCOMP])
-                                  + span.attrStepX[FRAG_ATTRIB_COL0][2] * adjx
-                                  + span.attrStepY[FRAG_ATTRIB_COL0][2] * adjy) + FIXED_HALF;
-                  fdrOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][0]
-                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][0]);
-                  fdgOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][1]
-                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][1]);
-                  fdbOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][2]
-                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][2]);
-#  ifdef INTERP_ALPHA
-                  aLeft = (GLint)(ChanToFixed(vLower->color[ACOMP])
-                                  + span.attrStepX[FRAG_ATTRIB_COL0][3] * adjx
-                                  + span.attrStepY[FRAG_ATTRIB_COL0][3] * adjy) + FIXED_HALF;
-                  fdaOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][3]
-                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][3]);
-#  endif
-               }
-               else {
-                  ASSERT(ctx->Light.ShadeModel == GL_FLAT);
-                  rLeft = ChanToFixed(v2->color[RCOMP]);
-                  gLeft = ChanToFixed(v2->color[GCOMP]);
-                  bLeft = ChanToFixed(v2->color[BCOMP]);
-                  fdrOuter = fdgOuter = fdbOuter = 0;
-#  ifdef INTERP_ALPHA
-                  aLeft = ChanToFixed(v2->color[ACOMP]);
-                  fdaOuter = 0;
-#  endif
-               }
-#endif /* INTERP_RGB */
-
-
-#ifdef INTERP_INT_TEX
-               {
-                  GLfloat s0, t0;
-                  s0 = vLower->attrib[FRAG_ATTRIB_TEX0][0] * S_SCALE;
-                  sLeft = (GLfixed)(s0 * FIXED_SCALE + span.attrStepX[FRAG_ATTRIB_TEX0][0] * adjx
-                                 + span.attrStepY[FRAG_ATTRIB_TEX0][0] * adjy) + FIXED_HALF;
-                  dsOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_TEX0][0]
-                                               + dxOuter * span.attrStepX[FRAG_ATTRIB_TEX0][0]);
-
-                  t0 = vLower->attrib[FRAG_ATTRIB_TEX0][1] * T_SCALE;
-                  tLeft = (GLfixed)(t0 * FIXED_SCALE + span.attrStepX[FRAG_ATTRIB_TEX0][1] * adjx
-                                 + span.attrStepY[FRAG_ATTRIB_TEX0][1] * adjy) + FIXED_HALF;
-                  dtOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_TEX0][1]
-                                               + dxOuter * span.attrStepX[FRAG_ATTRIB_TEX0][1]);
-               }
-#endif
-#ifdef INTERP_ATTRIBS
-               {
-                  const GLuint attr = FRAG_ATTRIB_WPOS;
-                  wLeft = vLower->attrib[FRAG_ATTRIB_WPOS][3]
-                        + (span.attrStepX[attr][3] * adjx
-                           + span.attrStepY[attr][3] * adjy) * (1.0F/FIXED_SCALE);
-                  dwOuter = span.attrStepY[attr][3] + dxOuter * span.attrStepX[attr][3];
-               }
-               ATTRIB_LOOP_BEGIN
-                  const GLfloat invW = vLower->attrib[FRAG_ATTRIB_WPOS][3];
-                  if (swrast->_InterpMode[attr] == GL_FLAT) {
-                     GLuint c;
-                     for (c = 0; c < 4; c++) {
-                        attrLeft[attr][c] = v2->attrib[attr][c] * invW;
-                        daOuter[attr][c] = 0.0;
-                     }
-                  }
-                  else {
-                     GLuint c;
-                     for (c = 0; c < 4; c++) {
-                        const GLfloat a = vLower->attrib[attr][c] * invW;
-                        attrLeft[attr][c] = a + (  span.attrStepX[attr][c] * adjx
-                                                 + span.attrStepY[attr][c] * adjy) * (1.0F/FIXED_SCALE);
-                        daOuter[attr][c] = span.attrStepY[attr][c] + dxOuter * span.attrStepX[attr][c];
-                     }
-                  }
-               ATTRIB_LOOP_END
-#endif
-            } /*if setupLeft*/
-
-
-            if (setupRight && eRight->lines>0) {
-               fxRightEdge = eRight->fsx - FIXED_EPSILON;
-               fdxRightEdge = eRight->fdxdy;
-            }
-
-            if (lines==0) {
-               continue;
-            }
-
-
-            /* Rasterize setup */
-#ifdef PIXEL_ADDRESS
-            dPRowInner = dPRowOuter + sizeof(PIXEL_TYPE);
-#endif
-#ifdef INTERP_Z
-#  ifdef DEPTH_TYPE
-            dZRowInner = dZRowOuter + sizeof(DEPTH_TYPE);
-#  endif
-            fdzInner = fdzOuter + span.zStep;
-#endif
-#ifdef INTERP_RGB
-            fdrInner = fdrOuter + span.redStep;
-            fdgInner = fdgOuter + span.greenStep;
-            fdbInner = fdbOuter + span.blueStep;
-#endif
-#ifdef INTERP_ALPHA
-            fdaInner = fdaOuter + span.alphaStep;
-#endif
-#ifdef INTERP_INT_TEX
-            dsInner = dsOuter + span.intTexStep[0];
-            dtInner = dtOuter + span.intTexStep[1];
-#endif
-#ifdef INTERP_ATTRIBS
-            dwInner = dwOuter + span.attrStepX[FRAG_ATTRIB_WPOS][3];
-            ATTRIB_LOOP_BEGIN
-               GLuint c;
-               for (c = 0; c < 4; c++) {
-                  daInner[attr][c] = daOuter[attr][c] + span.attrStepX[attr][c];
-               }
-            ATTRIB_LOOP_END
-#endif
-
-            while (lines > 0) {
-               /* initialize the span interpolants to the leftmost value */
-               /* ff = fixed-pt fragment */
-               const GLint right = FixedToInt(fxRightEdge);
-               span.x = FixedToInt(fxLeftEdge);
-               if (right <= span.x)
-                  span.end = 0;
-               else
-                  span.end = right - span.x;
-
-#ifdef INTERP_Z
-               span.z = zLeft;
-#endif
-#ifdef INTERP_RGB
-               span.red = rLeft;
-               span.green = gLeft;
-               span.blue = bLeft;
-#endif
-#ifdef INTERP_ALPHA
-               span.alpha = aLeft;
-#endif
-#ifdef INTERP_INT_TEX
-               span.intTex[0] = sLeft;
-               span.intTex[1] = tLeft;
-#endif
-
-#ifdef INTERP_ATTRIBS
-               span.attrStart[FRAG_ATTRIB_WPOS][3] = wLeft;
-               ATTRIB_LOOP_BEGIN
-                  GLuint c;
-                  for (c = 0; c < 4; c++) {
-                     span.attrStart[attr][c] = attrLeft[attr][c];
-                  }
-               ATTRIB_LOOP_END
-#endif
-
-               /* This is where we actually generate fragments */
-               /* XXX the test for span.y > 0 _shouldn't_ be needed but
-                * it fixes a problem on 64-bit Opterons (bug 4842).
-                */
-               if (span.end > 0 && span.y >= 0) {
-                  const GLint len = span.end - 1;
-                  (void) len;
-#ifdef INTERP_RGB
-                  CLAMP_INTERPOLANT(red, redStep, len);
-                  CLAMP_INTERPOLANT(green, greenStep, len);
-                  CLAMP_INTERPOLANT(blue, blueStep, len);
-#endif
-#ifdef INTERP_ALPHA
-                  CLAMP_INTERPOLANT(alpha, alphaStep, len);
-#endif
-                  {
-                     RENDER_SPAN( span );
-                  }
-               }
-
-               /*
-                * Advance to the next scan line.  Compute the
-                * new edge coordinates, and adjust the
-                * pixel-center x coordinate so that it stays
-                * on or inside the major edge.
-                */
-               span.y++;
-               lines--;
-
-               fxLeftEdge += fdxLeftEdge;
-               fxRightEdge += fdxRightEdge;
-
-               fError += fdError;
-               if (fError >= 0) {
-                  fError -= FIXED_ONE;
-
-#ifdef PIXEL_ADDRESS
-                  pRow = (PIXEL_TYPE *) ((GLubyte *) pRow + dPRowOuter);
-#endif
-#ifdef INTERP_Z
-#  ifdef DEPTH_TYPE
-                  zRow = (DEPTH_TYPE *) ((GLubyte *) zRow + dZRowOuter);
-#  endif
-                  zLeft += fdzOuter;
-#endif
-#ifdef INTERP_RGB
-                  rLeft += fdrOuter;
-                  gLeft += fdgOuter;
-                  bLeft += fdbOuter;
-#endif
-#ifdef INTERP_ALPHA
-                  aLeft += fdaOuter;
-#endif
-#ifdef INTERP_INT_TEX
-                  sLeft += dsOuter;
-                  tLeft += dtOuter;
-#endif
-#ifdef INTERP_ATTRIBS
-                  wLeft += dwOuter;
-                  ATTRIB_LOOP_BEGIN
-                     GLuint c;
-                     for (c = 0; c < 4; c++) {
-                        attrLeft[attr][c] += daOuter[attr][c];
-                     }
-                  ATTRIB_LOOP_END
-#endif
-               }
-               else {
-#ifdef PIXEL_ADDRESS
-                  pRow = (PIXEL_TYPE *) ((GLubyte *) pRow + dPRowInner);
-#endif
-#ifdef INTERP_Z
-#  ifdef DEPTH_TYPE
-                  zRow = (DEPTH_TYPE *) ((GLubyte *) zRow + dZRowInner);
-#  endif
-                  zLeft += fdzInner;
-#endif
-#ifdef INTERP_RGB
-                  rLeft += fdrInner;
-                  gLeft += fdgInner;
-                  bLeft += fdbInner;
-#endif
-#ifdef INTERP_ALPHA
-                  aLeft += fdaInner;
-#endif
-#ifdef INTERP_INT_TEX
-                  sLeft += dsInner;
-                  tLeft += dtInner;
-#endif
-#ifdef INTERP_ATTRIBS
-                  wLeft += dwInner;
-                  ATTRIB_LOOP_BEGIN
-                     GLuint c;
-                     for (c = 0; c < 4; c++) {
-                        attrLeft[attr][c] += daInner[attr][c];
-                     }
-                  ATTRIB_LOOP_END
-#endif
-               }
-            } /*while lines>0*/
-
-         } /* for subTriangle */
-
-      }
-   }
-}
-
-#undef SETUP_CODE
-#undef RENDER_SPAN
-
-#undef PIXEL_TYPE
-#undef BYTES_PER_ROW
-#undef PIXEL_ADDRESS
-#undef DEPTH_TYPE
-
-#undef INTERP_Z
-#undef INTERP_RGB
-#undef INTERP_ALPHA
-#undef INTERP_INT_TEX
-#undef INTERP_ATTRIBS
-
-#undef S_SCALE
-#undef T_SCALE
-
-#undef FixedToDepth
-
-#undef NAME
+/*

+ * Mesa 3-D graphics library

+ * Version:  7.0

+ *

+ * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.

+ *

+ * Permission is hereby granted, free of charge, to any person obtaining a

+ * copy of this software and associated documentation files (the "Software"),

+ * to deal in the Software without restriction, including without limitation

+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,

+ * and/or sell copies of the Software, and to permit persons to whom the

+ * Software is furnished to do so, subject to the following conditions:

+ *

+ * The above copyright notice and this permission notice shall be included

+ * in all copies or substantial portions of the Software.

+ *

+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS

+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

+ * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN

+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

+ */

+

+/*

+ * Triangle Rasterizer Template

+ *

+ * This file is #include'd to generate custom triangle rasterizers.

+ *

+ * The following macros may be defined to indicate what auxillary information

+ * must be interpolated across the triangle:

+ *    INTERP_Z        - if defined, interpolate integer Z values

+ *    INTERP_RGB      - if defined, interpolate integer RGB values

+ *    INTERP_ALPHA    - if defined, interpolate integer Alpha values

+ *    INTERP_INT_TEX  - if defined, interpolate integer ST texcoords

+ *                         (fast, simple 2-D texture mapping, without

+ *                         perspective correction)

+ *    INTERP_ATTRIBS  - if defined, interpolate arbitrary attribs (texcoords,

+ *                         varying vars, etc)  This also causes W to be

+ *                         computed for perspective correction).

+ *

+ * When one can directly address pixels in the color buffer the following

+ * macros can be defined and used to compute pixel addresses during

+ * rasterization (see pRow):

+ *    PIXEL_TYPE          - the datatype of a pixel (GLubyte, GLushort, GLuint)

+ *    BYTES_PER_ROW       - number of bytes per row in the color buffer

+ *    PIXEL_ADDRESS(X,Y)  - returns the address of pixel at (X,Y) where

+ *                          Y==0 at bottom of screen and increases upward.

+ *

+ * Similarly, for direct depth buffer access, this type is used for depth

+ * buffer addressing (see zRow):

+ *    DEPTH_TYPE          - either GLushort or GLuint

+ *

+ * Optionally, one may provide one-time setup code per triangle:

+ *    SETUP_CODE    - code which is to be executed once per triangle

+ *

+ * The following macro MUST be defined:

+ *    RENDER_SPAN(span) - code to write a span of pixels.

+ *

+ * This code was designed for the origin to be in the lower-left corner.

+ *

+ * Inspired by triangle rasterizer code written by Allen Akin.  Thanks Allen!

+ *

+ *

+ * Some notes on rasterization accuracy:

+ *

+ * This code uses fixed point arithmetic (the GLfixed type) to iterate

+ * over the triangle edges and interpolate ancillary data (such as Z,

+ * color, secondary color, etc).  The number of fractional bits in

+ * GLfixed and the value of SUB_PIXEL_BITS has a direct bearing on the

+ * accuracy of rasterization.

+ *

+ * If SUB_PIXEL_BITS=4 then we'll snap the vertices to the nearest

+ * 1/16 of a pixel.  If we're walking up a long, nearly vertical edge

+ * (dx=1/16, dy=1024) we'll need 4 + 10 = 14 fractional bits in

+ * GLfixed to walk the edge without error.  If the maximum viewport

+ * height is 4K pixels, then we'll need 4 + 12 = 16 fractional bits.

+ *

+ * Historically, Mesa has used 11 fractional bits in GLfixed, snaps

+ * vertices to 1/16 pixel and allowed a maximum viewport height of 2K

+ * pixels.  11 fractional bits is actually insufficient for accurately

+ * rasterizing some triangles.  More recently, the maximum viewport

+ * height was increased to 4K pixels.  Thus, Mesa should be using 16

+ * fractional bits in GLfixed.  Unfortunately, there may be some issues

+ * with setting FIXED_FRAC_BITS=16, such as multiplication overflow.

+ * This will have to be examined in some detail...

+ *

+ * For now, if you find rasterization errors, particularly with tall,

+ * sliver triangles, try increasing FIXED_FRAC_BITS and/or decreasing

+ * SUB_PIXEL_BITS.

+ */

+

+

+/*

+ * Some code we unfortunately need to prevent negative interpolated colors.

+ */

+#ifndef CLAMP_INTERPOLANT

+#define CLAMP_INTERPOLANT(CHANNEL, CHANNELSTEP, LEN)		\

+do {								\

+   GLfixed endVal = span.CHANNEL + (LEN) * span.CHANNELSTEP;	\

+   if (endVal < 0) {						\

+      span.CHANNEL -= endVal;					\

+   }								\

+   if (span.CHANNEL < 0) {					\

+      span.CHANNEL = 0;						\

+   }								\

+} while (0)

+#endif

+

+

+static void NAME(struct gl_context *ctx, const SWvertex *v0,

+                                 const SWvertex *v1,

+                                 const SWvertex *v2 )

+{

+   typedef struct {

+      const SWvertex *v0, *v1;   /* Y(v0) < Y(v1) */

+      GLfloat dx;	/* X(v1) - X(v0) */

+      GLfloat dy;	/* Y(v1) - Y(v0) */

+      GLfloat dxdy;	/* dx/dy */

+      GLfixed fdxdy;	/* dx/dy in fixed-point */

+      GLfloat adjy;	/* adjust from v[0]->fy to fsy, scaled */

+      GLfixed fsx;	/* first sample point x coord */

+      GLfixed fsy;

+      GLfixed fx0;	/* fixed pt X of lower endpoint */

+      GLint lines;	/* number of lines to be sampled on this edge */

+   } EdgeT;

+

+   const SWcontext *swrast = SWRAST_CONTEXT(ctx);

+#ifdef INTERP_Z

+   const GLint depthBits = ctx->DrawBuffer->Visual.depthBits;

+   const GLint fixedToDepthShift = depthBits <= 16 ? FIXED_SHIFT : 0;

+   const GLfloat maxDepth = ctx->DrawBuffer->_DepthMaxF;

+#define FixedToDepth(F)  ((F) >> fixedToDepthShift)

+#endif

+   EdgeT eMaj, eTop, eBot;

+   GLfloat oneOverArea;

+   const SWvertex *vMin, *vMid, *vMax;  /* Y(vMin)<=Y(vMid)<=Y(vMax) */

+   GLfloat bf = SWRAST_CONTEXT(ctx)->_BackfaceSign;

+   const GLint snapMask = ~((FIXED_ONE / (1 << SUB_PIXEL_BITS)) - 1); /* for x/y coord snapping */

+   GLfixed vMin_fx, vMin_fy, vMid_fx, vMid_fy, vMax_fx, vMax_fy;

+

+   SWspan span;

+

+   (void) swrast;

+

+   INIT_SPAN(span, GL_POLYGON);

+   span.y = 0; /* silence warnings */

+

+#ifdef INTERP_Z

+   (void) fixedToDepthShift;

+#endif

+

+   /*

+   printf("%s()\n", __FUNCTION__);

+   printf("  %g, %g, %g\n",

+          v0->attrib[FRAG_ATTRIB_WPOS][0],

+          v0->attrib[FRAG_ATTRIB_WPOS][1],

+          v0->attrib[FRAG_ATTRIB_WPOS][2]);

+   printf("  %g, %g, %g\n",

+          v1->attrib[FRAG_ATTRIB_WPOS][0],

+          v1->attrib[FRAG_ATTRIB_WPOS][1],

+          v1->attrib[FRAG_ATTRIB_WPOS][2]);

+   printf("  %g, %g, %g\n",

+          v2->attrib[FRAG_ATTRIB_WPOS][0],

+          v2->attrib[FRAG_ATTRIB_WPOS][1],

+          v2->attrib[FRAG_ATTRIB_WPOS][2]);

+   */

+

+   /* Compute fixed point x,y coords w/ half-pixel offsets and snapping.

+    * And find the order of the 3 vertices along the Y axis.

+    */

+   {

+      const GLfixed fy0 = FloatToFixed(v0->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;

+      const GLfixed fy1 = FloatToFixed(v1->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;

+      const GLfixed fy2 = FloatToFixed(v2->attrib[FRAG_ATTRIB_WPOS][1] - 0.5F) & snapMask;

+      if (fy0 <= fy1) {

+         if (fy1 <= fy2) {

+            /* y0 <= y1 <= y2 */

+            vMin = v0;   vMid = v1;   vMax = v2;

+            vMin_fy = fy0;  vMid_fy = fy1;  vMax_fy = fy2;

+         }

+         else if (fy2 <= fy0) {

+            /* y2 <= y0 <= y1 */

+            vMin = v2;   vMid = v0;   vMax = v1;

+            vMin_fy = fy2;  vMid_fy = fy0;  vMax_fy = fy1;

+         }

+         else {

+            /* y0 <= y2 <= y1 */

+            vMin = v0;   vMid = v2;   vMax = v1;

+            vMin_fy = fy0;  vMid_fy = fy2;  vMax_fy = fy1;

+            bf = -bf;

+         }

+      }

+      else {

+         if (fy0 <= fy2) {

+            /* y1 <= y0 <= y2 */

+            vMin = v1;   vMid = v0;   vMax = v2;

+            vMin_fy = fy1;  vMid_fy = fy0;  vMax_fy = fy2;

+            bf = -bf;

+         }

+         else if (fy2 <= fy1) {

+            /* y2 <= y1 <= y0 */

+            vMin = v2;   vMid = v1;   vMax = v0;

+            vMin_fy = fy2;  vMid_fy = fy1;  vMax_fy = fy0;

+            bf = -bf;

+         }

+         else {

+            /* y1 <= y2 <= y0 */

+            vMin = v1;   vMid = v2;   vMax = v0;

+            vMin_fy = fy1;  vMid_fy = fy2;  vMax_fy = fy0;

+         }

+      }

+

+      /* fixed point X coords */

+      vMin_fx = FloatToFixed(vMin->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;

+      vMid_fx = FloatToFixed(vMid->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;

+      vMax_fx = FloatToFixed(vMax->attrib[FRAG_ATTRIB_WPOS][0] + 0.5F) & snapMask;

+   }

+

+   /* vertex/edge relationship */

+   eMaj.v0 = vMin;   eMaj.v1 = vMax;   /*TODO: .v1's not needed */

+   eTop.v0 = vMid;   eTop.v1 = vMax;

+   eBot.v0 = vMin;   eBot.v1 = vMid;

+

+   /* compute deltas for each edge:  vertex[upper] - vertex[lower] */

+   eMaj.dx = FixedToFloat(vMax_fx - vMin_fx);

+   eMaj.dy = FixedToFloat(vMax_fy - vMin_fy);

+   eTop.dx = FixedToFloat(vMax_fx - vMid_fx);

+   eTop.dy = FixedToFloat(vMax_fy - vMid_fy);

+   eBot.dx = FixedToFloat(vMid_fx - vMin_fx);

+   eBot.dy = FixedToFloat(vMid_fy - vMin_fy);

+

+   /* compute area, oneOverArea and perform backface culling */

+   {

+      const GLfloat area = eMaj.dx * eBot.dy - eBot.dx * eMaj.dy;

+

+      if (IS_INF_OR_NAN(area) || area == 0.0F)

+         return;

+

+      if (area * bf * swrast->_BackfaceCullSign < 0.0)

+         return;

+

+      oneOverArea = 1.0F / area;

+

+      /* 0 = front, 1 = back */

+      span.facing = oneOverArea * bf > 0.0F;

+   }

+

+   /* Edge setup.  For a triangle strip these could be reused... */

+   {

+      eMaj.fsy = FixedCeil(vMin_fy);

+      eMaj.lines = FixedToInt(FixedCeil(vMax_fy - eMaj.fsy));

+      if (eMaj.lines > 0) {

+         eMaj.dxdy = eMaj.dx / eMaj.dy;

+         eMaj.fdxdy = SignedFloatToFixed(eMaj.dxdy);

+         eMaj.adjy = (GLfloat) (eMaj.fsy - vMin_fy);  /* SCALED! */

+         eMaj.fx0 = vMin_fx;

+         eMaj.fsx = eMaj.fx0 + (GLfixed) (eMaj.adjy * eMaj.dxdy);

+      }

+      else {

+         return;  /*CULLED*/

+      }

+

+      eTop.fsy = FixedCeil(vMid_fy);

+      eTop.lines = FixedToInt(FixedCeil(vMax_fy - eTop.fsy));

+      if (eTop.lines > 0) {

+         eTop.dxdy = eTop.dx / eTop.dy;

+         eTop.fdxdy = SignedFloatToFixed(eTop.dxdy);

+         eTop.adjy = (GLfloat) (eTop.fsy - vMid_fy); /* SCALED! */

+         eTop.fx0 = vMid_fx;

+         eTop.fsx = eTop.fx0 + (GLfixed) (eTop.adjy * eTop.dxdy);

+      }

+

+      eBot.fsy = FixedCeil(vMin_fy);

+      eBot.lines = FixedToInt(FixedCeil(vMid_fy - eBot.fsy));

+      if (eBot.lines > 0) {

+         eBot.dxdy = eBot.dx / eBot.dy;

+         eBot.fdxdy = SignedFloatToFixed(eBot.dxdy);

+         eBot.adjy = (GLfloat) (eBot.fsy - vMin_fy);  /* SCALED! */

+         eBot.fx0 = vMin_fx;

+         eBot.fsx = eBot.fx0 + (GLfixed) (eBot.adjy * eBot.dxdy);

+      }

+   }

+

+   /*

+    * Conceptually, we view a triangle as two subtriangles

+    * separated by a perfectly horizontal line.  The edge that is

+    * intersected by this line is one with maximal absolute dy; we

+    * call it a ``major'' edge.  The other two edges are the

+    * ``top'' edge (for the upper subtriangle) and the ``bottom''

+    * edge (for the lower subtriangle).  If either of these two

+    * edges is horizontal or very close to horizontal, the

+    * corresponding subtriangle might cover zero sample points;

+    * we take care to handle such cases, for performance as well

+    * as correctness.

+    *

+    * By stepping rasterization parameters along the major edge,

+    * we can avoid recomputing them at the discontinuity where

+    * the top and bottom edges meet.  However, this forces us to

+    * be able to scan both left-to-right and right-to-left.

+    * Also, we must determine whether the major edge is at the

+    * left or right side of the triangle.  We do this by

+    * computing the magnitude of the cross-product of the major

+    * and top edges.  Since this magnitude depends on the sine of

+    * the angle between the two edges, its sign tells us whether

+    * we turn to the left or to the right when travelling along

+    * the major edge to the top edge, and from this we infer

+    * whether the major edge is on the left or the right.

+    *

+    * Serendipitously, this cross-product magnitude is also a

+    * value we need to compute the iteration parameter

+    * derivatives for the triangle, and it can be used to perform

+    * backface culling because its sign tells us whether the

+    * triangle is clockwise or counterclockwise.  In this code we

+    * refer to it as ``area'' because it's also proportional to

+    * the pixel area of the triangle.

+    */

+

+   {

+      GLint scan_from_left_to_right;  /* true if scanning left-to-right */

+

+      /*

+       * Execute user-supplied setup code

+       */

+#ifdef SETUP_CODE

+      SETUP_CODE

+#endif

+

+      scan_from_left_to_right = (oneOverArea < 0.0F);

+

+

+      /* compute d?/dx and d?/dy derivatives */

+#ifdef INTERP_Z

+      span.interpMask |= SPAN_Z;

+      {

+         GLfloat eMaj_dz = vMax->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];

+         GLfloat eBot_dz = vMid->attrib[FRAG_ATTRIB_WPOS][2] - vMin->attrib[FRAG_ATTRIB_WPOS][2];

+         span.attrStepX[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj_dz * eBot.dy - eMaj.dy * eBot_dz);

+         if (span.attrStepX[FRAG_ATTRIB_WPOS][2] > maxDepth ||

+             span.attrStepX[FRAG_ATTRIB_WPOS][2] < -maxDepth) {

+            /* probably a sliver triangle */

+            span.attrStepX[FRAG_ATTRIB_WPOS][2] = 0.0;

+            span.attrStepY[FRAG_ATTRIB_WPOS][2] = 0.0;

+         }

+         else {

+            span.attrStepY[FRAG_ATTRIB_WPOS][2] = oneOverArea * (eMaj.dx * eBot_dz - eMaj_dz * eBot.dx);

+         }

+         if (depthBits <= 16)

+            span.zStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_WPOS][2]);

+         else

+            span.zStep = (GLint) span.attrStepX[FRAG_ATTRIB_WPOS][2];

+      }

+#endif

+#ifdef INTERP_RGB

+      span.interpMask |= SPAN_RGBA;

+      if (ctx->Light.ShadeModel == GL_SMOOTH) {

+         GLfloat eMaj_dr = (GLfloat) (vMax->color[RCOMP] - vMin->color[RCOMP]);

+         GLfloat eBot_dr = (GLfloat) (vMid->color[RCOMP] - vMin->color[RCOMP]);

+         GLfloat eMaj_dg = (GLfloat) (vMax->color[GCOMP] - vMin->color[GCOMP]);

+         GLfloat eBot_dg = (GLfloat) (vMid->color[GCOMP] - vMin->color[GCOMP]);

+         GLfloat eMaj_db = (GLfloat) (vMax->color[BCOMP] - vMin->color[BCOMP]);

+         GLfloat eBot_db = (GLfloat) (vMid->color[BCOMP] - vMin->color[BCOMP]);

+#  ifdef INTERP_ALPHA

+         GLfloat eMaj_da = (GLfloat) (vMax->color[ACOMP] - vMin->color[ACOMP]);

+         GLfloat eBot_da = (GLfloat) (vMid->color[ACOMP] - vMin->color[ACOMP]);

+#  endif

+         span.attrStepX[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj_dr * eBot.dy - eMaj.dy * eBot_dr);

+         span.attrStepY[FRAG_ATTRIB_COL0][0] = oneOverArea * (eMaj.dx * eBot_dr - eMaj_dr * eBot.dx);

+         span.attrStepX[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj_dg * eBot.dy - eMaj.dy * eBot_dg);

+         span.attrStepY[FRAG_ATTRIB_COL0][1] = oneOverArea * (eMaj.dx * eBot_dg - eMaj_dg * eBot.dx);

+         span.attrStepX[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj_db * eBot.dy - eMaj.dy * eBot_db);

+         span.attrStepY[FRAG_ATTRIB_COL0][2] = oneOverArea * (eMaj.dx * eBot_db - eMaj_db * eBot.dx);

+         span.redStep   = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][0]);

+         span.greenStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][1]);

+         span.blueStep  = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][2]);

+#  ifdef INTERP_ALPHA

+         span.attrStepX[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);

+         span.attrStepY[FRAG_ATTRIB_COL0][3] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);

+         span.alphaStep = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_COL0][3]);

+#  endif /* INTERP_ALPHA */

+      }

+      else {

+         ASSERT(ctx->Light.ShadeModel == GL_FLAT);

+         span.interpMask |= SPAN_FLAT;

+         span.attrStepX[FRAG_ATTRIB_COL0][0] = span.attrStepY[FRAG_ATTRIB_COL0][0] = 0.0F;

+         span.attrStepX[FRAG_ATTRIB_COL0][1] = span.attrStepY[FRAG_ATTRIB_COL0][1] = 0.0F;

+         span.attrStepX[FRAG_ATTRIB_COL0][2] = span.attrStepY[FRAG_ATTRIB_COL0][2] = 0.0F;

+	 span.redStep   = 0;

+	 span.greenStep = 0;

+	 span.blueStep  = 0;

+#  ifdef INTERP_ALPHA

+         span.attrStepX[FRAG_ATTRIB_COL0][3] = span.attrStepY[FRAG_ATTRIB_COL0][3] = 0.0F;

+	 span.alphaStep = 0;

+#  endif

+      }

+#endif /* INTERP_RGB */

+#ifdef INTERP_INT_TEX

+      {

+         GLfloat eMaj_ds = (vMax->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;

+         GLfloat eBot_ds = (vMid->attrib[FRAG_ATTRIB_TEX0][0] - vMin->attrib[FRAG_ATTRIB_TEX0][0]) * S_SCALE;

+         GLfloat eMaj_dt = (vMax->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;

+         GLfloat eBot_dt = (vMid->attrib[FRAG_ATTRIB_TEX0][1] - vMin->attrib[FRAG_ATTRIB_TEX0][1]) * T_SCALE;

+         span.attrStepX[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj_ds * eBot.dy - eMaj.dy * eBot_ds);

+         span.attrStepY[FRAG_ATTRIB_TEX0][0] = oneOverArea * (eMaj.dx * eBot_ds - eMaj_ds * eBot.dx);

+         span.attrStepX[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj_dt * eBot.dy - eMaj.dy * eBot_dt);

+         span.attrStepY[FRAG_ATTRIB_TEX0][1] = oneOverArea * (eMaj.dx * eBot_dt - eMaj_dt * eBot.dx);

+         span.intTexStep[0] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][0]);

+         span.intTexStep[1] = SignedFloatToFixed(span.attrStepX[FRAG_ATTRIB_TEX0][1]);

+      }

+#endif

+#ifdef INTERP_ATTRIBS

+      {

+         /* attrib[FRAG_ATTRIB_WPOS][3] is 1/W */

+         const GLfloat wMax = vMax->attrib[FRAG_ATTRIB_WPOS][3];

+         const GLfloat wMin = vMin->attrib[FRAG_ATTRIB_WPOS][3];

+         const GLfloat wMid = vMid->attrib[FRAG_ATTRIB_WPOS][3];

+         {

+            const GLfloat eMaj_dw = wMax - wMin;

+            const GLfloat eBot_dw = wMid - wMin;

+            span.attrStepX[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj_dw * eBot.dy - eMaj.dy * eBot_dw);

+            span.attrStepY[FRAG_ATTRIB_WPOS][3] = oneOverArea * (eMaj.dx * eBot_dw - eMaj_dw * eBot.dx);

+         }

+         ATTRIB_LOOP_BEGIN

+            if (swrast->_InterpMode[attr] == GL_FLAT) {

+               ASSIGN_4V(span.attrStepX[attr], 0.0, 0.0, 0.0, 0.0);

+               ASSIGN_4V(span.attrStepY[attr], 0.0, 0.0, 0.0, 0.0);

+            }

+            else {

+               GLuint c;

+               for (c = 0; c < 4; c++) {

+                  GLfloat eMaj_da = vMax->attrib[attr][c] * wMax - vMin->attrib[attr][c] * wMin;

+                  GLfloat eBot_da = vMid->attrib[attr][c] * wMid - vMin->attrib[attr][c] * wMin;

+                  span.attrStepX[attr][c] = oneOverArea * (eMaj_da * eBot.dy - eMaj.dy * eBot_da);

+                  span.attrStepY[attr][c] = oneOverArea * (eMaj.dx * eBot_da - eMaj_da * eBot.dx);

+               }

+            }

+         ATTRIB_LOOP_END

+      }

+#endif

+

+      /*

+       * We always sample at pixel centers.  However, we avoid

+       * explicit half-pixel offsets in this code by incorporating

+       * the proper offset in each of x and y during the

+       * transformation to window coordinates.

+       *

+       * We also apply the usual rasterization rules to prevent

+       * cracks and overlaps.  A pixel is considered inside a

+       * subtriangle if it meets all of four conditions: it is on or

+       * to the right of the left edge, strictly to the left of the

+       * right edge, on or below the top edge, and strictly above

+       * the bottom edge.  (Some edges may be degenerate.)

+       *

+       * The following discussion assumes left-to-right scanning

+       * (that is, the major edge is on the left); the right-to-left

+       * case is a straightforward variation.

+       *

+       * We start by finding the half-integral y coordinate that is

+       * at or below the top of the triangle.  This gives us the

+       * first scan line that could possibly contain pixels that are

+       * inside the triangle.

+       *

+       * Next we creep down the major edge until we reach that y,

+       * and compute the corresponding x coordinate on the edge.

+       * Then we find the half-integral x that lies on or just

+       * inside the edge.  This is the first pixel that might lie in

+       * the interior of the triangle.  (We won't know for sure

+       * until we check the other edges.)

+       *

+       * As we rasterize the triangle, we'll step down the major

+       * edge.  For each step in y, we'll move an integer number

+       * of steps in x.  There are two possible x step sizes, which

+       * we'll call the ``inner'' step (guaranteed to land on the

+       * edge or inside it) and the ``outer'' step (guaranteed to

+       * land on the edge or outside it).  The inner and outer steps

+       * differ by one.  During rasterization we maintain an error

+       * term that indicates our distance from the true edge, and

+       * select either the inner step or the outer step, whichever

+       * gets us to the first pixel that falls inside the triangle.

+       *

+       * All parameters (z, red, etc.) as well as the buffer

+       * addresses for color and z have inner and outer step values,

+       * so that we can increment them appropriately.  This method

+       * eliminates the need to adjust parameters by creeping a

+       * sub-pixel amount into the triangle at each scanline.

+       */

+

+      {

+         GLint subTriangle;

+         GLfixed fxLeftEdge = 0, fxRightEdge = 0;

+         GLfixed fdxLeftEdge = 0, fdxRightEdge = 0;

+         GLfixed fError = 0, fdError = 0;

+#ifdef PIXEL_ADDRESS

+         PIXEL_TYPE *pRow = NULL;

+         GLint dPRowOuter = 0, dPRowInner;  /* offset in bytes */

+#endif

+#ifdef INTERP_Z

+#  ifdef DEPTH_TYPE

+         struct gl_renderbuffer *zrb

+            = ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;

+         DEPTH_TYPE *zRow = NULL;

+         GLint dZRowOuter = 0, dZRowInner;  /* offset in bytes */

+#  endif

+         GLuint zLeft = 0;

+         GLfixed fdzOuter = 0, fdzInner;

+#endif

+#ifdef INTERP_RGB

+         GLint rLeft = 0, fdrOuter = 0, fdrInner;

+         GLint gLeft = 0, fdgOuter = 0, fdgInner;

+         GLint bLeft = 0, fdbOuter = 0, fdbInner;

+#endif

+#ifdef INTERP_ALPHA

+         GLint aLeft = 0, fdaOuter = 0, fdaInner;

+#endif

+#ifdef INTERP_INT_TEX

+         GLfixed sLeft=0, dsOuter=0, dsInner;

+         GLfixed tLeft=0, dtOuter=0, dtInner;

+#endif

+#ifdef INTERP_ATTRIBS

+         GLfloat wLeft = 0, dwOuter = 0, dwInner;

+         GLfloat attrLeft[FRAG_ATTRIB_MAX][4];

+         GLfloat daOuter[FRAG_ATTRIB_MAX][4], daInner[FRAG_ATTRIB_MAX][4];

+#endif

+

+         for (subTriangle=0; subTriangle<=1; subTriangle++) {

+            EdgeT *eLeft, *eRight;

+            int setupLeft, setupRight;

+            int lines;

+

+            if (subTriangle==0) {

+               /* bottom half */

+               if (scan_from_left_to_right) {

+                  eLeft = &eMaj;

+                  eRight = &eBot;

+                  lines = eRight->lines;

+                  setupLeft = 1;

+                  setupRight = 1;

+               }

+               else {

+                  eLeft = &eBot;

+                  eRight = &eMaj;

+                  lines = eLeft->lines;

+                  setupLeft = 1;

+                  setupRight = 1;

+               }

+            }

+            else {

+               /* top half */

+               if (scan_from_left_to_right) {

+                  eLeft = &eMaj;

+                  eRight = &eTop;

+                  lines = eRight->lines;

+                  setupLeft = 0;

+                  setupRight = 1;

+               }

+               else {

+                  eLeft = &eTop;

+                  eRight = &eMaj;

+                  lines = eLeft->lines;

+                  setupLeft = 1;

+                  setupRight = 0;

+               }

+               if (lines == 0)

+                  return;

+            }

+

+            if (setupLeft && eLeft->lines > 0) {

+               const SWvertex *vLower = eLeft->v0;

+               const GLfixed fsy = eLeft->fsy;

+               const GLfixed fsx = eLeft->fsx;  /* no fractional part */

+               const GLfixed fx = FixedCeil(fsx);  /* no fractional part */

+               const GLfixed adjx = (GLfixed) (fx - eLeft->fx0); /* SCALED! */

+               const GLfixed adjy = (GLfixed) eLeft->adjy;      /* SCALED! */

+               GLint idxOuter;

+               GLfloat dxOuter;

+               GLfixed fdxOuter;

+

+               fError = fx - fsx - FIXED_ONE;

+               fxLeftEdge = fsx - FIXED_EPSILON;

+               fdxLeftEdge = eLeft->fdxdy;

+               fdxOuter = FixedFloor(fdxLeftEdge - FIXED_EPSILON);

+               fdError = fdxOuter - fdxLeftEdge + FIXED_ONE;

+               idxOuter = FixedToInt(fdxOuter);

+               dxOuter = (GLfloat) idxOuter;

+               span.y = FixedToInt(fsy);

+

+               /* silence warnings on some compilers */

+               (void) dxOuter;

+               (void) adjx;

+               (void) adjy;

+               (void) vLower;

+

+#ifdef PIXEL_ADDRESS

+               {

+                  pRow = (PIXEL_TYPE *) PIXEL_ADDRESS(FixedToInt(fxLeftEdge), span.y);

+                  dPRowOuter = -((int)BYTES_PER_ROW) + idxOuter * sizeof(PIXEL_TYPE);

+                  /* negative because Y=0 at bottom and increases upward */

+               }

+#endif

+               /*

+                * Now we need the set of parameter (z, color, etc.) values at

+                * the point (fx, fsy).  This gives us properly-sampled parameter

+                * values that we can step from pixel to pixel.  Furthermore,

+                * although we might have intermediate results that overflow

+                * the normal parameter range when we step temporarily outside

+                * the triangle, we shouldn't overflow or underflow for any

+                * pixel that's actually inside the triangle.

+                */

+

+#ifdef INTERP_Z

+               {

+                  GLfloat z0 = vLower->attrib[FRAG_ATTRIB_WPOS][2];

+                  if (depthBits <= 16) {

+                     /* interpolate fixed-pt values */

+                     GLfloat tmp = (z0 * FIXED_SCALE

+                                    + span.attrStepX[FRAG_ATTRIB_WPOS][2] * adjx

+                                    + span.attrStepY[FRAG_ATTRIB_WPOS][2] * adjy) + FIXED_HALF;

+                     if (tmp < MAX_GLUINT / 2)

+                        zLeft = (GLfixed) tmp;

+                     else

+                        zLeft = MAX_GLUINT / 2;

+                     fdzOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_WPOS][2] +

+                                                   dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);

+                  }

+                  else {

+                     /* interpolate depth values w/out scaling */

+                     zLeft = (GLuint) (z0 + span.attrStepX[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjx)

+                                          + span.attrStepY[FRAG_ATTRIB_WPOS][2] * FixedToFloat(adjy));

+                     fdzOuter = (GLint) (span.attrStepY[FRAG_ATTRIB_WPOS][2] +

+                                         dxOuter * span.attrStepX[FRAG_ATTRIB_WPOS][2]);

+                  }

+#  ifdef DEPTH_TYPE

+                  zRow = (DEPTH_TYPE *)

+                    zrb->GetPointer(ctx, zrb, FixedToInt(fxLeftEdge), span.y);

+                  dZRowOuter = (ctx->DrawBuffer->Width + idxOuter) * sizeof(DEPTH_TYPE);

+#  endif

+               }

+#endif

+#ifdef INTERP_RGB

+               if (ctx->Light.ShadeModel == GL_SMOOTH) {

+                  rLeft = (GLint)(ChanToFixed(vLower->color[RCOMP])

+                                  + span.attrStepX[FRAG_ATTRIB_COL0][0] * adjx

+                                  + span.attrStepY[FRAG_ATTRIB_COL0][0] * adjy) + FIXED_HALF;

+                  gLeft = (GLint)(ChanToFixed(vLower->color[GCOMP])

+                                  + span.attrStepX[FRAG_ATTRIB_COL0][1] * adjx

+                                  + span.attrStepY[FRAG_ATTRIB_COL0][1] * adjy) + FIXED_HALF;

+                  bLeft = (GLint)(ChanToFixed(vLower->color[BCOMP])

+                                  + span.attrStepX[FRAG_ATTRIB_COL0][2] * adjx

+                                  + span.attrStepY[FRAG_ATTRIB_COL0][2] * adjy) + FIXED_HALF;

+                  fdrOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][0]

+                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][0]);

+                  fdgOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][1]

+                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][1]);

+                  fdbOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][2]

+                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][2]);

+#  ifdef INTERP_ALPHA

+                  aLeft = (GLint)(ChanToFixed(vLower->color[ACOMP])

+                                  + span.attrStepX[FRAG_ATTRIB_COL0][3] * adjx

+                                  + span.attrStepY[FRAG_ATTRIB_COL0][3] * adjy) + FIXED_HALF;

+                  fdaOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_COL0][3]

+                                                + dxOuter * span.attrStepX[FRAG_ATTRIB_COL0][3]);

+#  endif

+               }

+               else {

+                  ASSERT(ctx->Light.ShadeModel == GL_FLAT);

+                  rLeft = ChanToFixed(v2->color[RCOMP]);

+                  gLeft = ChanToFixed(v2->color[GCOMP]);

+                  bLeft = ChanToFixed(v2->color[BCOMP]);

+                  fdrOuter = fdgOuter = fdbOuter = 0;

+#  ifdef INTERP_ALPHA

+                  aLeft = ChanToFixed(v2->color[ACOMP]);

+                  fdaOuter = 0;

+#  endif

+               }

+#endif /* INTERP_RGB */

+

+

+#ifdef INTERP_INT_TEX

+               {

+                  GLfloat s0, t0;

+                  s0 = vLower->attrib[FRAG_ATTRIB_TEX0][0] * S_SCALE;

+                  sLeft = (GLfixed)(s0 * FIXED_SCALE + span.attrStepX[FRAG_ATTRIB_TEX0][0] * adjx

+                                 + span.attrStepY[FRAG_ATTRIB_TEX0][0] * adjy) + FIXED_HALF;

+                  dsOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_TEX0][0]

+                                               + dxOuter * span.attrStepX[FRAG_ATTRIB_TEX0][0]);

+

+                  t0 = vLower->attrib[FRAG_ATTRIB_TEX0][1] * T_SCALE;

+                  tLeft = (GLfixed)(t0 * FIXED_SCALE + span.attrStepX[FRAG_ATTRIB_TEX0][1] * adjx

+                                 + span.attrStepY[FRAG_ATTRIB_TEX0][1] * adjy) + FIXED_HALF;

+                  dtOuter = SignedFloatToFixed(span.attrStepY[FRAG_ATTRIB_TEX0][1]

+                                               + dxOuter * span.attrStepX[FRAG_ATTRIB_TEX0][1]);

+               }

+#endif

+#ifdef INTERP_ATTRIBS

+               {

+                  const GLuint attr = FRAG_ATTRIB_WPOS;

+                  wLeft = vLower->attrib[FRAG_ATTRIB_WPOS][3]

+                        + (span.attrStepX[attr][3] * adjx

+                           + span.attrStepY[attr][3] * adjy) * (1.0F/FIXED_SCALE);

+                  dwOuter = span.attrStepY[attr][3] + dxOuter * span.attrStepX[attr][3];

+               }

+               ATTRIB_LOOP_BEGIN

+                  const GLfloat invW = vLower->attrib[FRAG_ATTRIB_WPOS][3];

+                  if (swrast->_InterpMode[attr] == GL_FLAT) {

+                     GLuint c;

+                     for (c = 0; c < 4; c++) {

+                        attrLeft[attr][c] = v2->attrib[attr][c] * invW;

+                        daOuter[attr][c] = 0.0;

+                     }

+                  }

+                  else {

+                     GLuint c;

+                     for (c = 0; c < 4; c++) {

+                        const GLfloat a = vLower->attrib[attr][c] * invW;

+                        attrLeft[attr][c] = a + (  span.attrStepX[attr][c] * adjx

+                                                 + span.attrStepY[attr][c] * adjy) * (1.0F/FIXED_SCALE);

+                        daOuter[attr][c] = span.attrStepY[attr][c] + dxOuter * span.attrStepX[attr][c];

+                     }

+                  }

+               ATTRIB_LOOP_END

+#endif

+            } /*if setupLeft*/

+

+

+            if (setupRight && eRight->lines>0) {

+               fxRightEdge = eRight->fsx - FIXED_EPSILON;

+               fdxRightEdge = eRight->fdxdy;

+            }

+

+            if (lines==0) {

+               continue;

+            }

+

+

+            /* Rasterize setup */

+#ifdef PIXEL_ADDRESS

+            dPRowInner = dPRowOuter + sizeof(PIXEL_TYPE);

+#endif

+#ifdef INTERP_Z

+#  ifdef DEPTH_TYPE

+            dZRowInner = dZRowOuter + sizeof(DEPTH_TYPE);

+#  endif

+            fdzInner = fdzOuter + span.zStep;

+#endif

+#ifdef INTERP_RGB

+            fdrInner = fdrOuter + span.redStep;

+            fdgInner = fdgOuter + span.greenStep;

+            fdbInner = fdbOuter + span.blueStep;

+#endif

+#ifdef INTERP_ALPHA

+            fdaInner = fdaOuter + span.alphaStep;

+#endif

+#ifdef INTERP_INT_TEX

+            dsInner = dsOuter + span.intTexStep[0];

+            dtInner = dtOuter + span.intTexStep[1];

+#endif

+#ifdef INTERP_ATTRIBS

+            dwInner = dwOuter + span.attrStepX[FRAG_ATTRIB_WPOS][3];

+            ATTRIB_LOOP_BEGIN

+               GLuint c;

+               for (c = 0; c < 4; c++) {

+                  daInner[attr][c] = daOuter[attr][c] + span.attrStepX[attr][c];

+               }

+            ATTRIB_LOOP_END

+#endif

+

+            while (lines > 0) {

+               /* initialize the span interpolants to the leftmost value */

+               /* ff = fixed-pt fragment */

+               const GLint right = FixedToInt(fxRightEdge);

+               span.x = FixedToInt(fxLeftEdge);

+               if (right <= span.x)

+                  span.end = 0;

+               else

+                  span.end = right - span.x;

+

+#ifdef INTERP_Z

+               span.z = zLeft;

+#endif

+#ifdef INTERP_RGB

+               span.red = rLeft;

+               span.green = gLeft;

+               span.blue = bLeft;

+#endif

+#ifdef INTERP_ALPHA

+               span.alpha = aLeft;

+#endif

+#ifdef INTERP_INT_TEX

+               span.intTex[0] = sLeft;

+               span.intTex[1] = tLeft;

+#endif

+

+#ifdef INTERP_ATTRIBS

+               span.attrStart[FRAG_ATTRIB_WPOS][3] = wLeft;

+               ATTRIB_LOOP_BEGIN

+                  GLuint c;

+                  for (c = 0; c < 4; c++) {

+                     span.attrStart[attr][c] = attrLeft[attr][c];

+                  }

+               ATTRIB_LOOP_END

+#endif

+

+               /* This is where we actually generate fragments */

+               /* XXX the test for span.y > 0 _shouldn't_ be needed but

+                * it fixes a problem on 64-bit Opterons (bug 4842).

+                */

+               if (span.end > 0 && span.y >= 0) {

+                  const GLint len = span.end - 1;

+                  (void) len;

+#ifdef INTERP_RGB

+                  CLAMP_INTERPOLANT(red, redStep, len);

+                  CLAMP_INTERPOLANT(green, greenStep, len);

+                  CLAMP_INTERPOLANT(blue, blueStep, len);

+#endif

+#ifdef INTERP_ALPHA

+                  CLAMP_INTERPOLANT(alpha, alphaStep, len);

+#endif

+                  {

+                     RENDER_SPAN( span );

+                  }

+               }

+

+               /*

+                * Advance to the next scan line.  Compute the

+                * new edge coordinates, and adjust the

+                * pixel-center x coordinate so that it stays

+                * on or inside the major edge.

+                */

+               span.y++;

+               lines--;

+

+               fxLeftEdge += fdxLeftEdge;

+               fxRightEdge += fdxRightEdge;

+

+               fError += fdError;

+               if (fError >= 0) {

+                  fError -= FIXED_ONE;

+

+#ifdef PIXEL_ADDRESS

+                  pRow = (PIXEL_TYPE *) ((GLubyte *) pRow + dPRowOuter);

+#endif

+#ifdef INTERP_Z

+#  ifdef DEPTH_TYPE

+                  zRow = (DEPTH_TYPE *) ((GLubyte *) zRow + dZRowOuter);

+#  endif

+                  zLeft += fdzOuter;

+#endif

+#ifdef INTERP_RGB

+                  rLeft += fdrOuter;

+                  gLeft += fdgOuter;

+                  bLeft += fdbOuter;

+#endif

+#ifdef INTERP_ALPHA

+                  aLeft += fdaOuter;

+#endif

+#ifdef INTERP_INT_TEX

+                  sLeft += dsOuter;

+                  tLeft += dtOuter;

+#endif

+#ifdef INTERP_ATTRIBS

+                  wLeft += dwOuter;

+                  ATTRIB_LOOP_BEGIN

+                     GLuint c;

+                     for (c = 0; c < 4; c++) {

+                        attrLeft[attr][c] += daOuter[attr][c];

+                     }

+                  ATTRIB_LOOP_END

+#endif

+               }

+               else {

+#ifdef PIXEL_ADDRESS

+                  pRow = (PIXEL_TYPE *) ((GLubyte *) pRow + dPRowInner);

+#endif

+#ifdef INTERP_Z

+#  ifdef DEPTH_TYPE

+                  zRow = (DEPTH_TYPE *) ((GLubyte *) zRow + dZRowInner);

+#  endif

+                  zLeft += fdzInner;

+#endif

+#ifdef INTERP_RGB

+                  rLeft += fdrInner;

+                  gLeft += fdgInner;

+                  bLeft += fdbInner;

+#endif

+#ifdef INTERP_ALPHA

+                  aLeft += fdaInner;

+#endif

+#ifdef INTERP_INT_TEX

+                  sLeft += dsInner;

+                  tLeft += dtInner;

+#endif

+#ifdef INTERP_ATTRIBS

+                  wLeft += dwInner;

+                  ATTRIB_LOOP_BEGIN

+                     GLuint c;

+                     for (c = 0; c < 4; c++) {

+                        attrLeft[attr][c] += daInner[attr][c];

+                     }

+                  ATTRIB_LOOP_END

+#endif

+               }

+            } /*while lines>0*/

+

+         } /* for subTriangle */

+

+      }

+   }

+}

+

+#undef SETUP_CODE

+#undef RENDER_SPAN

+

+#undef PIXEL_TYPE

+#undef BYTES_PER_ROW

+#undef PIXEL_ADDRESS

+#undef DEPTH_TYPE

+

+#undef INTERP_Z

+#undef INTERP_RGB

+#undef INTERP_ALPHA

+#undef INTERP_INT_TEX

+#undef INTERP_ATTRIBS

+

+#undef S_SCALE

+#undef T_SCALE

+

+#undef FixedToDepth

+

+#undef NAME