text: /*
   * Mesa 3-D graphics library
   * Version:  7.3
   *
   * 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.
   */
  
  
  /*
   * When the device driver doesn't implement triangle rasterization it
   * can hook in _swrast_Triangle, which eventually calls one of these
   * functions to draw triangles.
   */
  
  #include "main/glheader.h"
  #include "main/context.h"
  #include "main/colormac.h"
  #include "main/imports.h"
  #include "main/macros.h"
  #include "main/texformat.h"
  #include "program/prog_instruction.h"
  
  #include "s_aatriangle.h"
  #include "s_context.h"
  #include "s_feedback.h"
  #include "s_span.h"
  #include "s_triangle.h"
  
  
  /**
   * Test if a triangle should be culled.  Used for feedback and selection mode.
   * \return GL_TRUE if the triangle is to be culled, GL_FALSE otherwise.
   */
  GLboolean
  _swrast_culltriangle( GLcontext *ctx,
                        const SWvertex *v0,
                        const SWvertex *v1,
                        const SWvertex *v2 )
  {
     SWcontext *swrast = SWRAST_CONTEXT(ctx);
     GLfloat ex = v1->attrib[FRAG_ATTRIB_WPOS][0] - v0->attrib[FRAG_ATTRIB_WPOS][0];
     GLfloat ey = v1->attrib[FRAG_ATTRIB_WPOS][1] - v0->attrib[FRAG_ATTRIB_WPOS][1];
     GLfloat fx = v2->attrib[FRAG_ATTRIB_WPOS][0] - v0->attrib[FRAG_ATTRIB_WPOS][0];
     GLfloat fy = v2->attrib[FRAG_ATTRIB_WPOS][1] - v0->attrib[FRAG_ATTRIB_WPOS][1];
     GLfloat c = ex*fy-ey*fx;
  
     if (c * swrast->_BackfaceSign * swrast->_BackfaceCullSign <= 0.0F)
        return GL_FALSE;
  
     return GL_TRUE;
  }
  
  
  
  /*
   * Render a flat-shaded RGBA triangle.
   */
  #define NAME flat_rgba_triangle
  #define INTERP_Z 1
  #define SETUP_CODE				\
     ASSERT(ctx->Texture._EnabledCoordUnits == 0);\
     ASSERT(ctx->Light.ShadeModel==GL_FLAT);	\
     span.interpMask |= SPAN_RGBA;		\
     span.red = ChanToFixed(v2->color[0]);	\
     span.green = ChanToFixed(v2->color[1]);	\
     span.blue = ChanToFixed(v2->color[2]);	\
     span.alpha = ChanToFixed(v2->color[3]);	\
     span.redStep = 0;				\
     span.greenStep = 0;				\
     span.blueStep = 0;				\
     span.alphaStep = 0;
  #define RENDER_SPAN( span )  _swrast_write_rgba_span(ctx, &span);
  #include "s_tritemp.h"
  
  
  
  /*
   * Render a smooth-shaded RGBA triangle.
   */
  #define NAME smooth_rgba_triangle
  #define INTERP_Z 1
  #define INTERP_RGB 1
  #define INTERP_ALPHA 1
  #define SETUP_CODE				\
     {						\
        /* texturing must be off */		\
        ASSERT(ctx->Texture._EnabledCoordUnits == 0);	\
        ASSERT(ctx->Light.ShadeModel==GL_SMOOTH);	\
     }
  #define RENDER_SPAN( span )  _swrast_write_rgba_span(ctx, &span);
  #include "s_tritemp.h"
  
  
  
  /*
   * Render an RGB, GL_DECAL, textured triangle.
   * Interpolate S,T only w/out mipmapping or perspective correction.
   *
   * No fog.  No depth testing.
   */
  #define NAME simple_textured_triangle
  #define INTERP_INT_TEX 1
  #define S_SCALE twidth
  #define T_SCALE theight
  
  #define SETUP_CODE							\
     struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[0];	\
     const struct gl_texture_object *obj = 				\
        ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];		\
     const struct gl_texture_image *texImg =				\
        obj->Image[0][obj->BaseLevel];					\
     const GLfloat twidth = (GLfloat) texImg->Width;			\
     const GLfloat theight = (GLfloat) texImg->Height;			\
     const GLint twidth_log2 = texImg->WidthLog2;				\
     const GLubyte *texture = (const GLubyte *) texImg->Data;		\
     const GLint smask = texImg->Width - 1;				\
     const GLint tmask = texImg->Height - 1;				\
     ASSERT(texImg->TexFormat == MESA_FORMAT_RGB888);			\
     if (!rb || !texture) {						\
        return;								\
     }
  
  #define RENDER_SPAN( span )						\
     GLuint i;								\
     GLubyte rgb[MAX_WIDTH][3];						\
     span.intTex[0] -= FIXED_HALF; /* off-by-one error? */		\
     span.intTex[1] -= FIXED_HALF;					\
     for (i = 0; i < span.end; i++) {					\
        GLint s = FixedToInt(span.intTex[0]) & smask;			\
        GLint t = FixedToInt(span.intTex[1]) & tmask;			\
        GLint pos = (t << twidth_log2) + s;				\
        pos = pos + pos + pos;  /* multiply by 3 */			\
        rgb[i][RCOMP] = texture[pos+2];					\
        rgb[i][GCOMP] = texture[pos+1];					\
        rgb[i][BCOMP] = texture[pos+0];					\
        span.intTex[0] += span.intTexStep[0];				\
        span.intTex[1] += span.intTexStep[1];				\
     }									\
     rb->PutRowRGB(ctx, rb, span.end, span.x, span.y, rgb, NULL);
  
  #include "s_tritemp.h"
  
  
  
  /*
   * Render an RGB, GL_DECAL, textured triangle.
   * Interpolate S,T, GL_LESS depth test, w/out mipmapping or
   * perspective correction.
   * Depth buffer bits must be <= sizeof(DEFAULT_SOFTWARE_DEPTH_TYPE)
   *
   * No fog.
   */
  #define NAME simple_z_textured_triangle
  #define INTERP_Z 1
  #define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
  #define INTERP_INT_TEX 1
  #define S_SCALE twidth
  #define T_SCALE theight
  
  #define SETUP_CODE							\
     struct gl_renderbuffer *rb = ctx->DrawBuffer->_ColorDrawBuffers[0];	\
     const struct gl_texture_object *obj = 				\
        ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];		\
     const struct gl_texture_image *texImg = 				\
         obj->Image[0][obj->BaseLevel]; 					\
     const GLfloat twidth = (GLfloat) texImg->Width;			\
     const GLfloat theight = (GLfloat) texImg->Height;			\
     const GLint twidth_log2 = texImg->WidthLog2;				\
     const GLubyte *texture = (const GLubyte *) texImg->Data;		\
     const GLint smask = texImg->Width - 1;				\
     const GLint tmask = texImg->Height - 1;				\
     ASSERT(texImg->TexFormat == MESA_FORMAT_RGB888);			\
     if (!rb || !texture) {						\
        return;								\
     }
  
  #define RENDER_SPAN( span )						\
     GLuint i;				    				\
     GLubyte rgb[MAX_WIDTH][3];						\
     span.intTex[0] -= FIXED_HALF; /* off-by-one error? */		\
     span.intTex[1] -= FIXED_HALF;					\
     for (i = 0; i < span.end; i++) {					\
        const GLuint z = FixedToDepth(span.z);				\
        if (z < zRow[i]) {						\
           GLint s = FixedToInt(span.intTex[0]) & smask;			\
           GLint t = FixedToInt(span.intTex[1]) & tmask;			\
           GLint pos = (t << twidth_log2) + s;				\
           pos = pos + pos + pos;  /* multiply by 3 */			\
           rgb[i][RCOMP] = texture[pos+2];				\
           rgb[i][GCOMP] = texture[pos+1];				\
           rgb[i][BCOMP] = texture[pos+0];				\
           zRow[i] = z;							\
           span.array->mask[i] = 1;					\
        }									\
        else {								\
           span.array->mask[i] = 0;					\
        }									\
        span.intTex[0] += span.intTexStep[0];				\
        span.intTex[1] += span.intTexStep[1];				\
        span.z += span.zStep;						\
     }									\
     rb->PutRowRGB(ctx, rb, span.end, span.x, span.y, rgb, span.array->mask);
  
  #include "s_tritemp.h"
  
  
  #if CHAN_TYPE != GL_FLOAT
  
  struct affine_info
  {
     GLenum filter;
     GLenum format;
     GLenum envmode;
     GLint smask, tmask;
     GLint twidth_log2;
     const GLchan *texture;
     GLfixed er, eg, eb, ea;
     GLint tbytesline, tsize;
  };
  
  
  static INLINE GLint
  ilerp(GLint t, GLint a, GLint b)
  {
     return a + ((t * (b - a)) >> FIXED_SHIFT);
  }
  
  static INLINE GLint
  ilerp_2d(GLint ia, GLint ib, GLint v00, GLint v10, GLint v01, GLint v11)
  {
     const GLint temp0 = ilerp(ia, v00, v10);
     const GLint temp1 = ilerp(ia, v01, v11);
     return ilerp(ib, temp0, temp1);
  }
  
  
  /* This function can handle GL_NEAREST or GL_LINEAR sampling of 2D RGB or RGBA
   * textures with GL_REPLACE, GL_MODULATE, GL_BLEND, GL_DECAL or GL_ADD
   * texture env modes.
   */
  static INLINE void
  affine_span(GLcontext *ctx, SWspan *span,
              struct affine_info *info)
  {
     GLchan sample[4];  /* the filtered texture sample */
     const GLuint texEnableSave = ctx->Texture._EnabledCoordUnits;
  
     /* Instead of defining a function for each mode, a test is done
      * between the outer and inner loops. This is to reduce code size
      * and complexity. Observe that an optimizing compiler kills
      * unused variables (for instance tf,sf,ti,si in case of GL_NEAREST).
      */
  
  #define NEAREST_RGB		\
     sample[RCOMP] = tex00[2];	\
     sample[GCOMP] = tex00[1];	\
     sample[BCOMP] = tex00[0];	\
     sample[ACOMP] = CHAN_MAX;
  
  #define LINEAR_RGB							\
     sample[RCOMP] = ilerp_2d(sf, tf, tex00[2], tex01[2], tex10[2], tex11[2]);\
     sample[GCOMP] = ilerp_2d(sf, tf, tex00[1], tex01[1], tex10[1], tex11[1]);\
     sample[BCOMP] = ilerp_2d(sf, tf, tex00[0], tex01[0], tex10[0], tex11[0]);\
     sample[ACOMP] = CHAN_MAX;
  
  #define NEAREST_RGBA  \
     sample[RCOMP] = tex00[3];	\
     sample[GCOMP] = tex00[2];	\
     sample[BCOMP] = tex00[1];	\
     sample[ACOMP] = tex00[0];
  
  #define LINEAR_RGBA							\
     sample[RCOMP] = ilerp_2d(sf, tf, tex00[3], tex01[3], tex10[3], tex11[3]);\
     sample[GCOMP] = ilerp_2d(sf, tf, tex00[2], tex01[2], tex10[2], tex11[2]);\
     sample[BCOMP] = ilerp_2d(sf, tf, tex00[1], tex01[1], tex10[1], tex11[1]);\
     sample[ACOMP] = ilerp_2d(sf, tf, tex00[0], tex01[0], tex10[0], tex11[0])
  
  #define MODULATE							  \
     dest[RCOMP] = span->red   * (sample[RCOMP] + 1u) >> (FIXED_SHIFT + 8); \
     dest[GCOMP] = span->green * (sample[GCOMP] + 1u) >> (FIXED_SHIFT + 8); \
     dest[BCOMP] = span->blue  * (sample[BCOMP] + 1u) >> (FIXED_SHIFT + 8); \
     dest[ACOMP] = span->alpha * (sample[ACOMP] + 1u) >> (FIXED_SHIFT + 8)
  
  #define DECAL								\
     dest[RCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->red +		\
                 ((sample[ACOMP] + 1) * sample[RCOMP] << FIXED_SHIFT))	\
                 >> (FIXED_SHIFT + 8);					\
     dest[GCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->green +		\
                 ((sample[ACOMP] + 1) * sample[GCOMP] << FIXED_SHIFT))	\
                 >> (FIXED_SHIFT + 8);					\
     dest[BCOMP] = ((CHAN_MAX - sample[ACOMP]) * span->blue +		\
                 ((sample[ACOMP] + 1) * sample[BCOMP] << FIXED_SHIFT))	\
                 >> (FIXED_SHIFT + 8);					\
     dest[ACOMP] = FixedToInt(span->alpha)
  
  #define BLEND								\
     dest[RCOMP] = ((CHAN_MAX - sample[RCOMP]) * span->red		\
                 + (sample[RCOMP] + 1) * info->er) >> (FIXED_SHIFT + 8);	\
     dest[GCOMP] = ((CHAN_MAX - sample[GCOMP]) * span->green		\
                 + (sample[GCOMP] + 1) * info->eg) >> (FIXED_SHIFT + 8);	\
     dest[BCOMP] = ((CHAN_MAX - sample[BCOMP]) * span->blue		\
                 + (sample[BCOMP] + 1) * info->eb) >> (FIXED_SHIFT + 8);	\
     dest[ACOMP] = span->alpha * (sample[ACOMP] + 1) >> (FIXED_SHIFT + 8)
  
  #define REPLACE  COPY_CHAN4(dest, sample)
  
  #define ADD								\
     {									\
        GLint rSum = FixedToInt(span->red)   + (GLint) sample[RCOMP];	\
        GLint gSum = FixedToInt(span->green) + (GLint) sample[GCOMP];	\
        GLint bSum = FixedToInt(span->blue)  + (GLint) sample[BCOMP];	\
        dest[RCOMP] = MIN2(rSum, CHAN_MAX);				\
        dest[GCOMP] = MIN2(gSum, CHAN_MAX);				\
        dest[BCOMP] = MIN2(bSum, CHAN_MAX);				\
        dest[ACOMP] = span->alpha * (sample[ACOMP] + 1) >> (FIXED_SHIFT + 8); \
    }
  
  /* shortcuts */
  
  #define NEAREST_RGB_REPLACE		\
     NEAREST_RGB;				\
     dest[0] = sample[0];			\
     dest[1] = sample[1];			\
     dest[2] = sample[2];			\
     dest[3] = FixedToInt(span->alpha);
  
  #define NEAREST_RGBA_REPLACE  \
     dest[RCOMP] = tex00[3]; \
     dest[GCOMP] = tex00[2]; \
     dest[BCOMP] = tex00[1]; \
     dest[ACOMP] = tex00[0]
  
  #define SPAN_NEAREST(DO_TEX, COMPS)					\
  	for (i = 0; i < span->end; i++) {				\
             /* Isn't it necessary to use FixedFloor below?? */		\
             GLint s = FixedToInt(span->intTex[0]) & info->smask;		\
             GLint t = FixedToInt(span->intTex[1]) & info->tmask;		\
             GLint pos = (t << info->twidth_log2) + s;			\
             const GLchan *tex00 = info->texture + COMPS * pos;		\
             DO_TEX;							\
             span->red += span->redStep;					\
  	   span->green += span->greenStep;				\
             span->blue += span->blueStep;				\
  	   span->alpha += span->alphaStep;				\
  	   span->intTex[0] += span->intTexStep[0];			\
  	   span->intTex[1] += span->intTexStep[1];			\
             dest += 4;							\
  	}
  
  #define SPAN_LINEAR(DO_TEX, COMPS)					\
  	for (i = 0; i < span->end; i++) {				\
             /* Isn't it necessary to use FixedFloor below?? */		\
             const GLint s = FixedToInt(span->intTex[0]) & info->smask;	\
             const GLint t = FixedToInt(span->intTex[1]) & info->tmask;	\
             const GLfixed sf = span->intTex[0] & FIXED_FRAC_MASK;	\
             const GLfixed tf = span->intTex[1] & FIXED_FRAC_MASK;	\
             const GLint pos = (t << info->twidth_log2) + s;		\
             const GLchan *tex00 = info->texture + COMPS * pos;		\
             const GLchan *tex10 = tex00 + info->tbytesline;		\
             const GLchan *tex01 = tex00 + COMPS;				\
             const GLchan *tex11 = tex10 + COMPS;				\
             if (t == info->tmask) {					\
                tex10 -= info->tsize;					\
                tex11 -= info->tsize;					\
             }								\
             if (s == info->smask) {					\
                tex01 -= info->tbytesline;				\
                tex11 -= info->tbytesline;				\
             }								\
             DO_TEX;							\
             span->red += span->redStep;					\
  	   span->green += span->greenStep;				\
             span->blue += span->blueStep;				\
  	   span->alpha += span->alphaStep;				\
  	   span->intTex[0] += span->intTexStep[0];			\
  	   span->intTex[1] += span->intTexStep[1];			\
             dest += 4;							\
  	}
  
  
     GLuint i;
     GLchan *dest = span->array->rgba[0];
  
     /* Disable tex units so they're not re-applied in swrast_write_rgba_span */
     ctx->Texture._EnabledCoordUnits = 0x0;
  
     span->intTex[0] -= FIXED_HALF;
     span->intTex[1] -= FIXED_HALF;
     switch (info->filter) {
     case GL_NEAREST:
        switch (info->format) {
        case MESA_FORMAT_RGB888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_NEAREST(NEAREST_RGB;MODULATE,3);
              break;
           case GL_DECAL:
           case GL_REPLACE:
              SPAN_NEAREST(NEAREST_RGB_REPLACE,3);
              break;
           case GL_BLEND:
              SPAN_NEAREST(NEAREST_RGB;BLEND,3);
              break;
           case GL_ADD:
              SPAN_NEAREST(NEAREST_RGB;ADD,3);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode in SPAN_LINEAR");
              return;
           }
           break;
        case MESA_FORMAT_RGBA8888:
           switch(info->envmode) {
           case GL_MODULATE:
              SPAN_NEAREST(NEAREST_RGBA;MODULATE,4);
              break;
           case GL_DECAL:
              SPAN_NEAREST(NEAREST_RGBA;DECAL,4);
              break;
           case GL_BLEND:
              SPAN_NEAREST(NEAREST_RGBA;BLEND,4);
              break;
           case GL_ADD:
              SPAN_NEAREST(NEAREST_RGBA;ADD,4);
              break;
           case GL_REPLACE:
              SPAN_NEAREST(NEAREST_RGBA_REPLACE,4);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (2) in SPAN_LINEAR");
              return;
           }
           break;
        }
        break;
  
     case GL_LINEAR:
        span->intTex[0] -= FIXED_HALF;
        span->intTex[1] -= FIXED_HALF;
        switch (info->format) {
        case MESA_FORMAT_RGB888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_LINEAR(LINEAR_RGB;MODULATE,3);
              break;
           case GL_DECAL:
           case GL_REPLACE:
              SPAN_LINEAR(LINEAR_RGB;REPLACE,3);
              break;
           case GL_BLEND:
              SPAN_LINEAR(LINEAR_RGB;BLEND,3);
              break;
           case GL_ADD:
              SPAN_LINEAR(LINEAR_RGB;ADD,3);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (3) in SPAN_LINEAR");
              return;
           }
           break;
        case MESA_FORMAT_RGBA8888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_LINEAR(LINEAR_RGBA;MODULATE,4);
              break;
           case GL_DECAL:
              SPAN_LINEAR(LINEAR_RGBA;DECAL,4);
              break;
           case GL_BLEND:
              SPAN_LINEAR(LINEAR_RGBA;BLEND,4);
              break;
           case GL_ADD:
              SPAN_LINEAR(LINEAR_RGBA;ADD,4);
              break;
           case GL_REPLACE:
              SPAN_LINEAR(LINEAR_RGBA;REPLACE,4);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (4) in SPAN_LINEAR");
              return;
           }
           break;
        }
        break;
     }
     span->interpMask &= ~SPAN_RGBA;
     ASSERT(span->arrayMask & SPAN_RGBA);
  
     _swrast_write_rgba_span(ctx, span);
  
     /* re-enable texture units */
     ctx->Texture._EnabledCoordUnits = texEnableSave;
  
  #undef SPAN_NEAREST
  #undef SPAN_LINEAR
  }
  
  
  
  /*
   * Render an RGB/RGBA textured triangle without perspective correction.
   */
  #define NAME affine_textured_triangle
  #define INTERP_Z 1
  #define INTERP_RGB 1
  #define INTERP_ALPHA 1
  #define INTERP_INT_TEX 1
  #define S_SCALE twidth
  #define T_SCALE theight
  
  #define SETUP_CODE							\
     struct affine_info info;						\
     struct gl_texture_unit *unit = ctx->Texture.Unit+0;			\
     const struct gl_texture_object *obj = 				\
        ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];		\
     const struct gl_texture_image *texImg = 				\
        obj->Image[0][obj->BaseLevel]; 					\
     const GLfloat twidth = (GLfloat) texImg->Width;			\
     const GLfloat theight = (GLfloat) texImg->Height;			\
     info.texture = (const GLchan *) texImg->Data;			\
     info.twidth_log2 = texImg->WidthLog2;				\
     info.smask = texImg->Width - 1;					\
     info.tmask = texImg->Height - 1;					\
     info.format = texImg->TexFormat;					\
     info.filter = obj->MinFilter;					\
     info.envmode = unit->EnvMode;					\
     info.er = 0;					\
     info.eg = 0;					\
     info.eb = 0;					\
     span.arrayMask |= SPAN_RGBA;						\
  									\
     if (info.envmode == GL_BLEND) {					\
        /* potential off-by-one error here? (1.0f -> 2048 -> 0) */	\
        info.er = FloatToFixed(unit->EnvColor[RCOMP] * CHAN_MAXF);	\
        info.eg = FloatToFixed(unit->EnvColor[GCOMP] * CHAN_MAXF);	\
        info.eb = FloatToFixed(unit->EnvColor[BCOMP] * CHAN_MAXF);	\
        info.ea = FloatToFixed(unit->EnvColor[ACOMP] * CHAN_MAXF);	\
     }									\
     if (!info.texture) {							\
        /* this shouldn't happen */					\
        return;								\
     }									\
  									\
     switch (info.format) {						\
     case MESA_FORMAT_RGB888:						\
        info.tbytesline = texImg->Width * 3;				\
        break;								\
     case MESA_FORMAT_RGBA8888:						\
        info.tbytesline = texImg->Width * 4;				\
        break;								\
     default:								\
        _mesa_problem(NULL, "Bad texture format in affine_texture_triangle");\
        return;								\
     }									\
     info.tsize = texImg->Height * info.tbytesline;
  
  #define RENDER_SPAN( span )   affine_span(ctx, &span, &info);
  
  #include "s_tritemp.h"
  
  
  
  struct persp_info
  {
     GLenum filter;
     GLenum format;
     GLenum envmode;
     GLint smask, tmask;
     GLint twidth_log2;
     const GLchan *texture;
     GLfixed er, eg, eb, ea;   /* texture env color */
     GLint tbytesline, tsize;
  };
  
  
  static INLINE void
  fast_persp_span(GLcontext *ctx, SWspan *span,
  		struct persp_info *info)
  {
     GLchan sample[4];  /* the filtered texture sample */
  
    /* Instead of defining a function for each mode, a test is done
     * between the outer and inner loops. This is to reduce code size
     * and complexity. Observe that an optimizing compiler kills
     * unused variables (for instance tf,sf,ti,si in case of GL_NEAREST).
     */
  #define SPAN_NEAREST(DO_TEX,COMP)					\
  	for (i = 0; i < span->end; i++) {				\
             GLdouble invQ = tex_coord[2] ?				\
                                   (1.0 / tex_coord[2]) : 1.0;            \
             GLfloat s_tmp = (GLfloat) (tex_coord[0] * invQ);		\
             GLfloat t_tmp = (GLfloat) (tex_coord[1] * invQ);		\
             GLint s = IFLOOR(s_tmp) & info->smask;	        	\
             GLint t = IFLOOR(t_tmp) & info->tmask;	        	\
             GLint pos = (t << info->twidth_log2) + s;			\
             const GLchan *tex00 = info->texture + COMP * pos;		\
             DO_TEX;							\
             span->red += span->redStep;					\
  	   span->green += span->greenStep;				\
             span->blue += span->blueStep;				\
  	   span->alpha += span->alphaStep;				\
  	   tex_coord[0] += tex_step[0];					\
  	   tex_coord[1] += tex_step[1];					\
  	   tex_coord[2] += tex_step[2];					\
             dest += 4;							\
  	}
  
  #define SPAN_LINEAR(DO_TEX,COMP)					\
  	for (i = 0; i < span->end; i++) {				\
             GLdouble invQ = tex_coord[2] ?				\
                                   (1.0 / tex_coord[2]) : 1.0;            \
             const GLfloat s_tmp = (GLfloat) (tex_coord[0] * invQ);	\
             const GLfloat t_tmp = (GLfloat) (tex_coord[1] * invQ);	\
             const GLfixed s_fix = FloatToFixed(s_tmp) - FIXED_HALF;	\
             const GLfixed t_fix = FloatToFixed(t_tmp) - FIXED_HALF;      \
             const GLint s = FixedToInt(FixedFloor(s_fix)) & info->smask;	\
             const GLint t = FixedToInt(FixedFloor(t_fix)) & info->tmask;	\
             const GLfixed sf = s_fix & FIXED_FRAC_MASK;			\
             const GLfixed tf = t_fix & FIXED_FRAC_MASK;			\
             const GLint pos = (t << info->twidth_log2) + s;		\
             const GLchan *tex00 = info->texture + COMP * pos;		\
             const GLchan *tex10 = tex00 + info->tbytesline;		\
             const GLchan *tex01 = tex00 + COMP;				\
             const GLchan *tex11 = tex10 + COMP;				\
             if (t == info->tmask) {					\
                tex10 -= info->tsize;					\
                tex11 -= info->tsize;					\
             }								\
             if (s == info->smask) {					\
                tex01 -= info->tbytesline;				\
                tex11 -= info->tbytesline;				\
             }								\
             DO_TEX;							\
             span->red   += span->redStep;				\
  	   span->green += span->greenStep;				\
             span->blue  += span->blueStep;				\
  	   span->alpha += span->alphaStep;				\
  	   tex_coord[0] += tex_step[0];					\
  	   tex_coord[1] += tex_step[1];					\
  	   tex_coord[2] += tex_step[2];					\
             dest += 4;							\
  	}
  
     GLuint i;
     GLfloat tex_coord[3], tex_step[3];
     GLchan *dest = span->array->rgba[0];
  
     const GLuint texEnableSave = ctx->Texture._EnabledCoordUnits;
     ctx->Texture._EnabledCoordUnits = 0;
  
     tex_coord[0] = span->attrStart[FRAG_ATTRIB_TEX0][0]  * (info->smask + 1);
     tex_step[0] = span->attrStepX[FRAG_ATTRIB_TEX0][0] * (info->smask + 1);
     tex_coord[1] = span->attrStart[FRAG_ATTRIB_TEX0][1] * (info->tmask + 1);
     tex_step[1] = span->attrStepX[FRAG_ATTRIB_TEX0][1] * (info->tmask + 1);
     /* span->attrStart[FRAG_ATTRIB_TEX0][2] only if 3D-texturing, here only 2D */
     tex_coord[2] = span->attrStart[FRAG_ATTRIB_TEX0][3];
     tex_step[2] = span->attrStepX[FRAG_ATTRIB_TEX0][3];
  
     switch (info->filter) {
     case GL_NEAREST:
        switch (info->format) {
        case MESA_FORMAT_RGB888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_NEAREST(NEAREST_RGB;MODULATE,3);
              break;
           case GL_DECAL:
           case GL_REPLACE:
              SPAN_NEAREST(NEAREST_RGB_REPLACE,3);
              break;
           case GL_BLEND:
              SPAN_NEAREST(NEAREST_RGB;BLEND,3);
              break;
           case GL_ADD:
              SPAN_NEAREST(NEAREST_RGB;ADD,3);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (5) in SPAN_LINEAR");
              return;
           }
           break;
        case MESA_FORMAT_RGBA8888:
           switch(info->envmode) {
           case GL_MODULATE:
              SPAN_NEAREST(NEAREST_RGBA;MODULATE,4);
              break;
           case GL_DECAL:
              SPAN_NEAREST(NEAREST_RGBA;DECAL,4);
              break;
           case GL_BLEND:
              SPAN_NEAREST(NEAREST_RGBA;BLEND,4);
              break;
           case GL_ADD:
              SPAN_NEAREST(NEAREST_RGBA;ADD,4);
              break;
           case GL_REPLACE:
              SPAN_NEAREST(NEAREST_RGBA_REPLACE,4);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (6) in SPAN_LINEAR");
              return;
           }
           break;
        }
        break;
  
     case GL_LINEAR:
        switch (info->format) {
        case MESA_FORMAT_RGB888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_LINEAR(LINEAR_RGB;MODULATE,3);
              break;
           case GL_DECAL:
           case GL_REPLACE:
              SPAN_LINEAR(LINEAR_RGB;REPLACE,3);
              break;
           case GL_BLEND:
              SPAN_LINEAR(LINEAR_RGB;BLEND,3);
              break;
           case GL_ADD:
              SPAN_LINEAR(LINEAR_RGB;ADD,3);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (7) in SPAN_LINEAR");
              return;
           }
           break;
        case MESA_FORMAT_RGBA8888:
           switch (info->envmode) {
           case GL_MODULATE:
              SPAN_LINEAR(LINEAR_RGBA;MODULATE,4);
              break;
           case GL_DECAL:
              SPAN_LINEAR(LINEAR_RGBA;DECAL,4);
              break;
           case GL_BLEND:
              SPAN_LINEAR(LINEAR_RGBA;BLEND,4);
              break;
           case GL_ADD:
              SPAN_LINEAR(LINEAR_RGBA;ADD,4);
              break;
           case GL_REPLACE:
              SPAN_LINEAR(LINEAR_RGBA;REPLACE,4);
              break;
           default:
              _mesa_problem(ctx, "bad tex env mode (8) in SPAN_LINEAR");
              return;
           }
           break;
        }
        break;
     }
     
     ASSERT(span->arrayMask & SPAN_RGBA);
     _swrast_write_rgba_span(ctx, span);
  
  #undef SPAN_NEAREST
  #undef SPAN_LINEAR
  
     /* restore state */
     ctx->Texture._EnabledCoordUnits = texEnableSave;
  }
  
  
  /*
   * Render an perspective corrected RGB/RGBA textured triangle.
   * The Q (aka V in Mesa) coordinate must be zero such that the divide
   * by interpolated Q/W comes out right.
   *
   */
  #define NAME persp_textured_triangle
  #define INTERP_Z 1
  #define INTERP_RGB 1
  #define INTERP_ALPHA 1
  #define INTERP_ATTRIBS 1
  
  #define SETUP_CODE							\
     struct persp_info info;						\
     const struct gl_texture_unit *unit = ctx->Texture.Unit+0;		\
     const struct gl_texture_object *obj = 				\
        ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];		\
     const struct gl_texture_image *texImg = 				\
        obj->Image[0][obj->BaseLevel];			 		\
     info.texture = (const GLchan *) texImg->Data;			\
     info.twidth_log2 = texImg->WidthLog2;				\
     info.smask = texImg->Width - 1;					\
     info.tmask = texImg->Height - 1;					\
     info.format = texImg->TexFormat;					\
     info.filter = obj->MinFilter;					\
     info.envmode = unit->EnvMode;					\
     info.er = 0;					\
     info.eg = 0;					\
     info.eb = 0;					\
  									\
     if (info.envmode == GL_BLEND) {					\
        /* potential off-by-one error here? (1.0f -> 2048 -> 0) */	\
        info.er = FloatToFixed(unit->EnvColor[RCOMP] * CHAN_MAXF);	\
        info.eg = FloatToFixed(unit->EnvColor[GCOMP] * CHAN_MAXF);	\
        info.eb = FloatToFixed(unit->EnvColor[BCOMP] * CHAN_MAXF);	\
        info.ea = FloatToFixed(unit->EnvColor[ACOMP] * CHAN_MAXF);	\
     }									\
     if (!info.texture) {							\
        /* this shouldn't happen */					\
        return;								\
     }									\
  									\
     switch (info.format) {						\
     case MESA_FORMAT_RGB888:						\
        info.tbytesline = texImg->Width * 3;				\
        break;								\
     case MESA_FORMAT_RGBA8888:						\
        info.tbytesline = texImg->Width * 4;				\
        break;								\
     default:								\
        _mesa_problem(NULL, "Bad texture format in persp_textured_triangle");\
        return;								\
     }									\
     info.tsize = texImg->Height * info.tbytesline;
  
  #define RENDER_SPAN( span )			\
     span.interpMask &= ~SPAN_RGBA;		\
     span.arrayMask |= SPAN_RGBA;			\
     fast_persp_span(ctx, &span, &info);
  
  #include "s_tritemp.h"
  
  #endif /*CHAN_TYPE != GL_FLOAT*/
  
  
  
  /*
   * Render an RGBA triangle with arbitrary attributes.
   */
  #define NAME general_triangle
  #define INTERP_Z 1
  #define INTERP_RGB 1
  #define INTERP_ALPHA 1
  #define INTERP_ATTRIBS 1
  #define RENDER_SPAN( span )   _swrast_write_rgba_span(ctx, &span);
  #include "s_tritemp.h"
  
  
  
  
  /*
   * Special tri function for occlusion testing
   */
  #define NAME occlusion_zless_triangle
  #define INTERP_Z 1
  #define SETUP_CODE							\
     struct gl_renderbuffer *rb = ctx->DrawBuffer->_DepthBuffer;		\
     struct gl_query_object *q = ctx->Query.CurrentOcclusionObject;	\
     ASSERT(ctx->Depth.Test);						\
     ASSERT(!ctx->Depth.Mask);						\
     ASSERT(ctx->Depth.Func == GL_LESS);					\
     if (!q) {								\
        return;								\
     }
  #define RENDER_SPAN( span )						\
     if (rb->Format == MESA_FORMAT_Z16) {					\
        GLuint i;								\
        const GLushort *zRow = (const GLushort *)				\
           rb->GetPointer(ctx, rb, span.x, span.y);			\
        for (i = 0; i < span.end; i++) {					\
           GLuint z = FixedToDepth(span.z);				\
           if (z < zRow[i]) {						\
              q->Result++;						\
           }								\
           span.z += span.zStep;						\
        }									\
     }									\
     else {								\
        GLuint i;								\
        const GLuint *zRow = (const GLuint *)				\
           rb->GetPointer(ctx, rb, span.x, span.y);			\
        for (i = 0; i < span.end; i++) {					\
           if ((GLuint)span.z < zRow[i]) {				\
              q->Result++;						\
           }								\
           span.z += span.zStep;						\
        }									\
     }
  #include "s_tritemp.h"
  
  
  
  static void
  nodraw_triangle( GLcontext *ctx,
                   const SWvertex *v0,
                   const SWvertex *v1,
                   const SWvertex *v2 )
  {
     (void) (ctx && v0 && v1 && v2);
  }
  
  
  /*
   * This is used when separate specular color is enabled, but not
   * texturing.  We add the specular color to the primary color,
   * draw the triangle, then restore the original primary color.
   * Inefficient, but seldom needed.
   */
  void
  _swrast_add_spec_terms_triangle(GLcontext *ctx, const SWvertex *v0,
                                  const SWvertex *v1, const SWvertex *v2)
  {
     SWvertex *ncv0 = (SWvertex *)v0; /* drop const qualifier */
     SWvertex *ncv1 = (SWvertex *)v1;
     SWvertex *ncv2 = (SWvertex *)v2;
     GLfloat rSum, gSum, bSum;
     GLchan cSave[3][4];
  
     /* save original colors */
     COPY_CHAN4( cSave[0], ncv0->color );
     COPY_CHAN4( cSave[1], ncv1->color );
     COPY_CHAN4( cSave[2], ncv2->color );
     /* sum v0 */
     rSum = CHAN_TO_FLOAT(ncv0->color[0]) + ncv0->attrib[FRAG_ATTRIB_COL1][0];
     gSum = CHAN_TO_FLOAT(ncv0->color[1]) + ncv0->attrib[FRAG_ATTRIB_COL1][1];
     bSum = CHAN_TO_FLOAT(ncv0->color[2]) + ncv0->attrib[FRAG_ATTRIB_COL1][2];
     UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[0], rSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[1], gSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv0->color[2], bSum);
     /* sum v1 */
     rSum = CHAN_TO_FLOAT(ncv1->color[0]) + ncv1->attrib[FRAG_ATTRIB_COL1][0];
     gSum = CHAN_TO_FLOAT(ncv1->color[1]) + ncv1->attrib[FRAG_ATTRIB_COL1][1];
     bSum = CHAN_TO_FLOAT(ncv1->color[2]) + ncv1->attrib[FRAG_ATTRIB_COL1][2];
     UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[0], rSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[1], gSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv1->color[2], bSum);
     /* sum v2 */
     rSum = CHAN_TO_FLOAT(ncv2->color[0]) + ncv2->attrib[FRAG_ATTRIB_COL1][0];
     gSum = CHAN_TO_FLOAT(ncv2->color[1]) + ncv2->attrib[FRAG_ATTRIB_COL1][1];
     bSum = CHAN_TO_FLOAT(ncv2->color[2]) + ncv2->attrib[FRAG_ATTRIB_COL1][2];
     UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[0], rSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[1], gSum);
     UNCLAMPED_FLOAT_TO_CHAN(ncv2->color[2], bSum);
     /* draw */
     SWRAST_CONTEXT(ctx)->SpecTriangle( ctx, ncv0, ncv1, ncv2 );
     /* restore original colors */
     COPY_CHAN4( ncv0->color, cSave[0] );
     COPY_CHAN4( ncv1->color, cSave[1] );
     COPY_CHAN4( ncv2->color, cSave[2] );
  }
  
  
  
  #ifdef DEBUG
  
  /* record the current triangle function name */
  const char *_mesa_triFuncName = NULL;
  
  #define USE(triFunc)				\
  do {						\
      _mesa_triFuncName = #triFunc;		\
      /*printf("%s\n", _mesa_triFuncName);*/	\
      swrast->Triangle = triFunc;			\
  } while (0)
  
  #else
  
  #define USE(triFunc)  swrast->Triangle = triFunc;
  
  #endif
  
  
  
  
  /*
   * Determine which triangle rendering function to use given the current
   * rendering context.
   *
   * Please update the summary flag _SWRAST_NEW_TRIANGLE if you add or
   * remove tests to this code.
   */
  void
  _swrast_choose_triangle( GLcontext *ctx )
  {
     SWcontext *swrast = SWRAST_CONTEXT(ctx);
  
     if (ctx->Polygon.CullFlag &&
         ctx->Polygon.CullFaceMode == GL_FRONT_AND_BACK) {
        USE(nodraw_triangle);
        return;
     }
  
     if (ctx->RenderMode==GL_RENDER) {
  
        if (ctx->Polygon.SmoothFlag) {
           _swrast_set_aa_triangle_function(ctx);
           ASSERT(swrast->Triangle);
           return;
        }
  
        /* special case for occlusion testing */
        if (ctx->Query.CurrentOcclusionObject &&
            ctx->Depth.Test &&
            ctx->Depth.Mask == GL_FALSE &&
            ctx->Depth.Func == GL_LESS &&
            !ctx->Stencil._Enabled) {
           if (ctx->Color.ColorMask[0][0] == 0 &&
  	     ctx->Color.ColorMask[0][1] == 0 &&
  	     ctx->Color.ColorMask[0][2] == 0 &&
  	     ctx->Color.ColorMask[0][3] == 0) {
              USE(occlusion_zless_triangle);
              return;
           }
        }
  
        /*
         * XXX should examine swrast->_ActiveAttribMask to determine what
         * needs to be interpolated.
         */
        if (ctx->Texture._EnabledCoordUnits ||
            ctx->FragmentProgram._Current ||
            ctx->ATIFragmentShader._Enabled ||
            NEED_SECONDARY_COLOR(ctx) ||
            swrast->_FogEnabled) {
           /* Ugh, we do a _lot_ of tests to pick the best textured tri func */
           const struct gl_texture_object *texObj2D;
           const struct gl_texture_image *texImg;
           GLenum minFilter, magFilter, envMode;
           gl_format format;
           texObj2D = ctx->Texture.Unit[0].CurrentTex[TEXTURE_2D_INDEX];
  
           texImg = texObj2D ? texObj2D->Image[0][texObj2D->BaseLevel] : NULL;
           format = texImg ? texImg->TexFormat : MESA_FORMAT_NONE;
           minFilter = texObj2D ? texObj2D->MinFilter : GL_NONE;
           magFilter = texObj2D ? texObj2D->MagFilter : GL_NONE;
           envMode = ctx->Texture.Unit[0].EnvMode;
  
           /* First see if we can use an optimized 2-D texture function */
           if (ctx->Texture._EnabledCoordUnits == 0x1
               && !ctx->FragmentProgram._Current
               && !ctx->ATIFragmentShader._Enabled
               && ctx->Texture._EnabledUnits == 0x1
               && ctx->Texture.Unit[0]._ReallyEnabled == TEXTURE_2D_BIT
               && texObj2D->WrapS == GL_REPEAT
               && texObj2D->WrapT == GL_REPEAT
               && texObj2D->_Swizzle == SWIZZLE_NOOP
               && texImg->_IsPowerOfTwo
               && texImg->Border == 0
               && texImg->Width == texImg->RowStride
               && (format == MESA_FORMAT_RGB888 || format == MESA_FORMAT_RGBA8888)
               && minFilter == magFilter
               && ctx->Light.Model.ColorControl == GL_SINGLE_COLOR
               && !swrast->_FogEnabled
               && ctx->Texture.Unit[0].EnvMode != GL_COMBINE_EXT
               && ctx->Texture.Unit[0].EnvMode != GL_COMBINE4_NV) {
  	    if (ctx->Hint.PerspectiveCorrection==GL_FASTEST) {
  	       if (minFilter == GL_NEAREST
  		   && format == MESA_FORMAT_RGB888
  		   && (envMode == GL_REPLACE || envMode == GL_DECAL)
  		   && ((swrast->_RasterMask == (DEPTH_BIT | TEXTURE_BIT)
  			&& ctx->Depth.Func == GL_LESS
  			&& ctx->Depth.Mask == GL_TRUE)
  		       || swrast->_RasterMask == TEXTURE_BIT)
  		   && ctx->Polygon.StippleFlag == GL_FALSE
                     && ctx->DrawBuffer->Visual.depthBits <= 16) {
  		  if (swrast->_RasterMask == (DEPTH_BIT | TEXTURE_BIT)) {
  		     USE(simple_z_textured_triangle);
  		  }
  		  else {
  		     USE(simple_textured_triangle);
  		  }
  	       }
  	       else {
  #if CHAN_BITS != 8
                    USE(general_triangle);
  #else
                    if (format == MESA_FORMAT_RGBA8888 && !_mesa_little_endian()) {
                       /* We only handle RGBA8888 correctly on little endian
                        * in the optimized code above.
                        */
                       USE(general_triangle);
                    }
                    else {
                       USE(affine_textured_triangle);
                   }
  #endif
  	       }
  	    }
  	    else {
  #if CHAN_BITS != 8
                 USE(general_triangle);
  #else
                 USE(persp_textured_triangle);
  #endif
  	    }
  	 }
           else {
              /* general case textured triangles */
              USE(general_triangle);
           }
        }
        else {
           ASSERT(!swrast->_FogEnabled);
           ASSERT(!NEED_SECONDARY_COLOR(ctx));
  	 if (ctx->Light.ShadeModel==GL_SMOOTH) {
  	    /* smooth shaded, no texturing, stippled or some raster ops */
  #if CHAN_BITS != 8
                 USE(general_triangle);
  #else
                 USE(smooth_rgba_triangle);
  #endif
  	 }
  	 else {
  	    /* flat shaded, no texturing, stippled or some raster ops */
  #if CHAN_BITS != 8
              USE(general_triangle);
  #else
              USE(flat_rgba_triangle);
  #endif
  	 }
        }
     }
     else if (ctx->RenderMode==GL_FEEDBACK) {
        USE(_swrast_feedback_triangle);
     }
     else {
        /* GL_SELECT mode */
        USE(_swrast_select_triangle);
     }
  }
  