xref: /external/mesa3d/src/mesa/drivers/osmesa/osmesa.c

/* $Id: osmesa.c,v 1.29 2000/11/14 17:40:14 brianp Exp $ */

/*
 * Mesa 3-D graphics library
 * Version:  3.3
 *
 * Copyright (C) 1999-2000  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.
 */


/*
 * Off-Screen Mesa rendering / Rendering into client memory space
 *
 * Note on thread safety:  this driver is thread safe.  All
 * functions are reentrant.  The notion of current context is
 * managed by the core _mesa_make_current() and _mesa_get_current_context()
 * functions.  Those functions are thread-safe.
 */


#ifdef PC_HEADER
#include "all.h"
#else
#include "glheader.h"
#include "GL/osmesa.h"
#include "context.h"
#include "depth.h"
#include "macros.h"
#include "mem.h"
#include "matrix.h"
#include "types.h"
#include "extensions.h"
#include "swrast/swrast.h"
#include "swrast_setup/swrast_setup.h"
#include "swrast/s_context.h"
#include "swrast/s_depth.h"
#include "swrast/s_lines.h"
#include "swrast/s_triangle.h"
#endif




/*
 * This is the OS/Mesa context struct.
 * Notice how it includes a GLcontext.  By doing this we're mimicking
 * C++ inheritance/derivation.
 * Later, we can cast a GLcontext pointer into an OSMesaContext pointer
 * or vice versa.
 */
struct osmesa_context {
   GLcontext gl_ctx;		/* The core GL/Mesa context */
   GLvisual *gl_visual;		/* Describes the buffers */
   GLframebuffer *gl_buffer;	/* Depth, stencil, accum, etc buffers */
   GLenum format;		/* either GL_RGBA or GL_COLOR_INDEX */
   void *buffer;		/* the image buffer */
   GLint width, height;		/* size of image buffer */
   GLuint pixel;		/* current color index or RGBA pixel value */
   GLuint clearpixel;		/* pixel for clearing the color buffer */
   GLint rowlength;		/* number of pixels per row */
   GLint userRowLength;		/* user-specified number of pixels per row */
   GLint rshift, gshift;	/* bit shifts for RGBA formats */
   GLint bshift, ashift;
   GLint rind, gind, bind;	/* index offsets for RGBA formats */
   void *rowaddr[MAX_HEIGHT];	/* address of first pixel in each image row */
   GLboolean yup;		/* TRUE  -> Y increases upward */
				/* FALSE -> Y increases downward */
};



/* A forward declaration: */
static void osmesa_update_state( GLcontext *ctx );
static void osmesa_register_swrast_functions( GLcontext *ctx );



#define OSMESA_CONTEXT(ctx)  ((OSMesaContext) (ctx->DriverCtx))



/**********************************************************************/
/*****                    Public Functions                        *****/
/**********************************************************************/


/*
 * Create an Off-Screen Mesa rendering context.  The only attribute needed is
 * an RGBA vs Color-Index mode flag.
 *
 * Input:  format - either GL_RGBA or GL_COLOR_INDEX
 *         sharelist - specifies another OSMesaContext with which to share
 *                     display lists.  NULL indicates no sharing.
 * Return:  an OSMesaContext or 0 if error
 */
OSMesaContext GLAPIENTRY
OSMesaCreateContext( GLenum format, OSMesaContext sharelist )
{
   return OSMesaCreateContextExt(format, DEFAULT_SOFTWARE_DEPTH_BITS,
                                 8, 16, sharelist);
}



/*
 * New in Mesa 3.5
 *
 * Create context and specify size of ancillary buffers.
 */
OSMesaContext GLAPIENTRY
OSMesaCreateContextExt( GLenum format, GLint depthBits, GLint stencilBits,
                        GLint accumBits, OSMesaContext sharelist )
{
   OSMesaContext osmesa;
   GLint rshift, gshift, bshift, ashift;
   GLint rind, gind, bind;
   GLint indexBits, redBits, greenBits, blueBits, alphaBits;
   GLboolean rgbmode;
   GLboolean swalpha;
   GLuint i4 = 1;
   GLubyte *i1 = (GLubyte *) &i4;
   GLint little_endian = *i1;

   swalpha = GL_FALSE;
   rind = gind = bind = 0;
   if (format==OSMESA_COLOR_INDEX) {
      indexBits = 8;
      rshift = gshift = bshift = ashift = 0;
      rgbmode = GL_FALSE;
   }
   else if (format==OSMESA_RGBA) {
      indexBits = 0;
      redBits = 8;
      greenBits = 8;
      blueBits = 8;
      alphaBits = 8;
      if (little_endian) {
         rshift = 0;
         gshift = 8;
         bshift = 16;
         ashift = 24;
      }
      else {
         rshift = 24;
         gshift = 16;
         bshift = 8;
         ashift = 0;
      }
      rgbmode = GL_TRUE;
   }
   else if (format==OSMESA_BGRA) {
      indexBits = 0;
      redBits = 8;
      greenBits = 8;
      blueBits = 8;
      alphaBits = 8;
      if (little_endian) {
         ashift = 0;
         rshift = 8;
         gshift = 16;
         bshift = 24;
      }
      else {
         bshift = 24;
         gshift = 16;
         rshift = 8;
         ashift = 0;
      }
      rgbmode = GL_TRUE;
   }
   else if (format==OSMESA_ARGB) {
      indexBits = 0;
      redBits = 8;
      greenBits = 8;
      blueBits = 8;
      alphaBits = 8;
      if (little_endian) {
         bshift = 0;
         gshift = 8;
         rshift = 16;
         ashift = 24;
      }
      else {
         ashift = 24;
         rshift = 16;
         gshift = 8;
         bshift = 0;
      }
      rgbmode = GL_TRUE;
   }
   else if (format==OSMESA_RGB) {
      indexBits = 0;
      redBits = 8;
      greenBits = 8;
      blueBits = 8;
      alphaBits = 0;
      bshift = 0;
      gshift = 8;
      rshift = 16;
      ashift = 24;
      bind = 2;
      gind = 1;
      rind = 0;
      rgbmode = GL_TRUE;
      swalpha = GL_TRUE;
   }
   else if (format==OSMESA_BGR) {
      indexBits = 0;
      redBits = 8;
      greenBits = 8;
      blueBits = 8;
      alphaBits = 0;
      bshift = 0;
      gshift = 8;
      rshift = 16;
      ashift = 24;
      bind = 0;
      gind = 1;
      rind = 2;
      rgbmode = GL_TRUE;
      swalpha = GL_TRUE;
   }
   else {
      return NULL;
   }


   osmesa = (OSMesaContext) CALLOC_STRUCT(osmesa_context);
   if (osmesa) {
      osmesa->gl_visual = _mesa_create_visual( rgbmode,
                                               GL_FALSE,    /* double buffer */
                                               GL_FALSE,    /* stereo */
                                               redBits,
                                               greenBits,
                                               blueBits,
                                               alphaBits,
                                               indexBits,
                                               depthBits,
                                               stencilBits,
                                               accumBits,
                                               accumBits,
                                               accumBits,
                                               alphaBits ? accumBits : 0,
                                               1            /* num samples */
                                               );
      if (!osmesa->gl_visual) {
         FREE(osmesa);
         return NULL;
      }

      if (!_mesa_initialize_context(&osmesa->gl_ctx,
                                    osmesa->gl_visual,
                                    sharelist ? &sharelist->gl_ctx
                                              : (GLcontext *) NULL,
                                    (void *) osmesa, GL_TRUE )) {
         _mesa_destroy_visual( osmesa->gl_visual );
         FREE(osmesa);
         return NULL;
      }
      gl_extensions_enable(&(osmesa->gl_ctx),"GL_HP_occlusion_test");
      gl_extensions_enable(&(osmesa->gl_ctx), "GL_ARB_texture_cube_map");
      gl_extensions_enable(&(osmesa->gl_ctx), "GL_EXT_texture_env_combine");

      osmesa->gl_buffer = _mesa_create_framebuffer( osmesa->gl_visual,
                                          osmesa->gl_visual->DepthBits > 0,
                                          osmesa->gl_visual->StencilBits > 0,
                                          osmesa->gl_visual->AccumRedBits > 0,
                                          osmesa->gl_visual->AlphaBits > 0 );

      if (!osmesa->gl_buffer) {
         _mesa_destroy_visual( osmesa->gl_visual );
         _mesa_free_context_data( &osmesa->gl_ctx );
         FREE(osmesa);
         return NULL;
      }
      osmesa->format = format;
      osmesa->buffer = NULL;
      osmesa->width = 0;
      osmesa->height = 0;
      osmesa->pixel = 0;
      osmesa->clearpixel = 0;
      osmesa->userRowLength = 0;
      osmesa->rowlength = 0;
      osmesa->yup = GL_TRUE;
      osmesa->rshift = rshift;
      osmesa->gshift = gshift;
      osmesa->bshift = bshift;
      osmesa->ashift = ashift;
      osmesa->rind = rind;
      osmesa->gind = gind;
      osmesa->bind = bind;


      /* Initialize the software rasterizer and helper modules.
       */
      {
	 GLcontext *ctx = &osmesa->gl_ctx;

	 _swrast_CreateContext( ctx );
	 _swsetup_CreateContext( ctx );

	 if (ctx->VB)
	    _swsetup_RegisterVB( ctx->VB );

	 osmesa_register_swrast_functions( ctx );
      }
   }
   return osmesa;
}




/*
 * Destroy an Off-Screen Mesa rendering context.
 *
 * Input:  ctx - the context to destroy
 */
void GLAPIENTRY OSMesaDestroyContext( OSMesaContext ctx )
{
   if (ctx) {
      _mesa_destroy_visual( ctx->gl_visual );
      _mesa_destroy_framebuffer( ctx->gl_buffer );
      _mesa_free_context_data( &ctx->gl_ctx );
      FREE( ctx );
   }
}



/*
 * Recompute the values of the context's rowaddr array.
 */
static void compute_row_addresses( OSMesaContext ctx )
{
   GLint i;

   if (ctx->yup) {
      /* Y=0 is bottom line of window */
      if (ctx->format==OSMESA_COLOR_INDEX) {
         /* 1-byte CI mode */
         GLubyte *origin = (GLubyte *) ctx->buffer;
         for (i=0;i<MAX_HEIGHT;i++) {
            ctx->rowaddr[i] = origin + i * ctx->rowlength;
         }
      }
      else {
         if ((ctx->format==OSMESA_RGB) || (ctx->format==OSMESA_BGR)) {
            /* 3-byte RGB mode */
            GLubyte *origin = (GLubyte *) ctx->buffer;
            for (i=0;i<MAX_HEIGHT;i++) {
               ctx->rowaddr[i] = origin + (i * (ctx->rowlength*3));
            }
         } else {
            /* 4-byte RGBA mode */
            GLuint *origin = (GLuint *) ctx->buffer;
            for (i=0;i<MAX_HEIGHT;i++) {
               ctx->rowaddr[i] = origin + i * ctx->rowlength;
            }
         }
      }
   }
   else {
      /* Y=0 is top line of window */
      if (ctx->format==OSMESA_COLOR_INDEX) {
         /* 1-byte CI mode */
         GLubyte *origin = (GLubyte *) ctx->buffer;
         for (i=0;i<MAX_HEIGHT;i++) {
            ctx->rowaddr[i] = origin + (ctx->height-i-1) * ctx->rowlength;
         }
      }
      else {
         if ((ctx->format==OSMESA_RGB) || (ctx->format==OSMESA_BGR)) {
            /* 3-byte RGB mode */
            GLubyte *origin = (GLubyte *) ctx->buffer;
            for (i=0;i<MAX_HEIGHT;i++) {
               ctx->rowaddr[i] = origin + ((ctx->height-i-1) * (ctx->rowlength*3));
            }
         } else {
            /* 4-byte RGBA mode */
            GLuint *origin = (GLuint *) ctx->buffer;
            for (i=0;i<MAX_HEIGHT;i++) {
               ctx->rowaddr[i] = origin + (ctx->height-i-1) * ctx->rowlength;
            }
         }
      }
   }
}


/*
 * Bind an OSMesaContext to an image buffer.  The image buffer is just a
 * block of memory which the client provides.  Its size must be at least
 * as large as width*height*sizeof(type).  Its address should be a multiple
 * of 4 if using RGBA mode.
 *
 * Image data is stored in the order of glDrawPixels:  row-major order
 * with the lower-left image pixel stored in the first array position
 * (ie. bottom-to-top).
 *
 * Since the only type initially supported is GL_UNSIGNED_BYTE, if the
 * context is in RGBA mode, each pixel will be stored as a 4-byte RGBA
 * value.  If the context is in color indexed mode, each pixel will be
 * stored as a 1-byte value.
 *
 * If the context's viewport hasn't been initialized yet, it will now be
 * initialized to (0,0,width,height).
 *
 * Input:  ctx - the rendering context
 *         buffer - the image buffer memory
 *         type - data type for pixel components, only GL_UNSIGNED_BYTE
 *                supported now
 *         width, height - size of image buffer in pixels, at least 1
 * Return:  GL_TRUE if success, GL_FALSE if error because of invalid ctx,
 *          invalid buffer address, type!=GL_UNSIGNED_BYTE, width<1, height<1,
 *          width>internal limit or height>internal limit.
 */
GLboolean GLAPIENTRY
OSMesaMakeCurrent( OSMesaContext ctx, void *buffer, GLenum type,
                   GLsizei width, GLsizei height )
{
   if (!ctx || !buffer || type!=GL_UNSIGNED_BYTE
       || width<1 || height<1 || width>MAX_WIDTH || height>MAX_HEIGHT) {
      return GL_FALSE;
   }

   osmesa_update_state( &ctx->gl_ctx );
   _mesa_make_current( &ctx->gl_ctx, ctx->gl_buffer );

   ctx->buffer = buffer;
   ctx->width = width;
   ctx->height = height;
   if (ctx->userRowLength)
      ctx->rowlength = ctx->userRowLength;
   else
      ctx->rowlength = width;

   compute_row_addresses( ctx );

   /* init viewport */
   if (ctx->gl_ctx.Viewport.Width==0) {
      /* initialize viewport and scissor box to buffer size */
      _mesa_Viewport( 0, 0, width, height );
      ctx->gl_ctx.Scissor.Width = width;
      ctx->gl_ctx.Scissor.Height = height;
   }

   return GL_TRUE;
}



OSMesaContext GLAPIENTRY OSMesaGetCurrentContext( void )
{
   GLcontext *ctx = _mesa_get_current_context();
   if (ctx)
      return (OSMesaContext) ctx;
   else
      return NULL;
}



void GLAPIENTRY OSMesaPixelStore( GLint pname, GLint value )
{
   OSMesaContext ctx = OSMesaGetCurrentContext();

   switch (pname) {
      case OSMESA_ROW_LENGTH:
         if (value<0) {
            gl_error( &ctx->gl_ctx, GL_INVALID_VALUE,
                      "OSMesaPixelStore(value)" );
            return;
         }
         ctx->userRowLength = value;
         ctx->rowlength = value;
         break;
      case OSMESA_Y_UP:
         ctx->yup = value ? GL_TRUE : GL_FALSE;
         break;
      default:
         gl_error( &ctx->gl_ctx, GL_INVALID_ENUM, "OSMesaPixelStore(pname)" );
         return;
   }

   compute_row_addresses( ctx );
}


void GLAPIENTRY OSMesaGetIntegerv( GLint pname, GLint *value )
{
   OSMesaContext ctx = OSMesaGetCurrentContext();

   switch (pname) {
      case OSMESA_WIDTH:
         *value = ctx->width;
         return;
      case OSMESA_HEIGHT:
         *value = ctx->height;
         return;
      case OSMESA_FORMAT:
         *value = ctx->format;
         return;
      case OSMESA_TYPE:
         *value = GL_UNSIGNED_BYTE;
         return;
      case OSMESA_ROW_LENGTH:
         *value = ctx->rowlength;
         return;
      case OSMESA_Y_UP:
         *value = ctx->yup;
         return;
      default:
         gl_error(&ctx->gl_ctx, GL_INVALID_ENUM, "OSMesaGetIntergerv(pname)");
         return;
   }
}

/*
 * Return the depth buffer associated with an OSMesa context.
 * Input:  c - the OSMesa context
 * Output:  width, height - size of buffer in pixels
 *          bytesPerValue - bytes per depth value (2 or 4)
 *          buffer - pointer to depth buffer values
 * Return:  GL_TRUE or GL_FALSE to indicate success or failure.
 */
GLboolean GLAPIENTRY
OSMesaGetDepthBuffer( OSMesaContext c, GLint *width, GLint *height,
                      GLint *bytesPerValue, void **buffer )
{
   if ((!c->gl_buffer) || (!c->gl_buffer->DepthBuffer)) {
      *width = 0;
      *height = 0;
      *bytesPerValue = 0;
      *buffer = 0;
      return GL_FALSE;
   }
   else {
      *width = c->gl_buffer->Width;
      *height = c->gl_buffer->Height;
      *bytesPerValue = sizeof(GLdepth);
      *buffer = c->gl_buffer->DepthBuffer;
      return GL_TRUE;
   }
}

/*
 * Return the color buffer associated with an OSMesa context.
 * Input:  c - the OSMesa context
 * Output:  width, height - size of buffer in pixels
 *          format - the pixel format (OSMESA_FORMAT)
 *          buffer - pointer to color buffer values
 * Return:  GL_TRUE or GL_FALSE to indicate success or failure.
 */
GLboolean GLAPIENTRY
OSMesaGetColorBuffer( OSMesaContext c, GLint *width,
                      GLint *height, GLint *format, void **buffer )
{
   if (!c->buffer) {
      *width = 0;
      *height = 0;
      *format = 0;
      *buffer = 0;
      return GL_FALSE;
   }
   else {
      *width = c->width;
      *height = c->height;
      *format = c->format;
      *buffer = c->buffer;
      return GL_TRUE;
   }
}

/**********************************************************************/
/*** Device Driver Functions                                        ***/
/**********************************************************************/


/*
 * Useful macros:
 */
#define PACK_RGBA(R,G,B,A)  (  ((R) << osmesa->rshift) \
                             | ((G) << osmesa->gshift) \
                             | ((B) << osmesa->bshift) \
                             | ((A) << osmesa->ashift) )

#define PACK_RGBA2(R,G,B,A)  (  ((R) << rshift) \
                              | ((G) << gshift) \
                              | ((B) << bshift) \
                              | ((A) << ashift) )

#define UNPACK_RED(P)      (((P) >> osmesa->rshift) & 0xff)
#define UNPACK_GREEN(P)    (((P) >> osmesa->gshift) & 0xff)
#define UNPACK_BLUE(P)     (((P) >> osmesa->bshift) & 0xff)
#define UNPACK_ALPHA(P)    (((P) >> osmesa->ashift) & 0xff)

#define PIXELADDR1(X,Y)  ((GLubyte *) osmesa->rowaddr[Y] + (X))
#define PIXELADDR3(X,Y)  ((GLubyte *) osmesa->rowaddr[Y] + ((X)*3))
#define PIXELADDR4(X,Y)  ((GLuint *)  osmesa->rowaddr[Y] + (X))




static GLboolean set_draw_buffer( GLcontext *ctx, GLenum mode )
{
   (void) ctx;
   if (mode==GL_FRONT_LEFT) {
      return GL_TRUE;
   }
   else {
      return GL_FALSE;
   }
}


static void set_read_buffer( GLcontext *ctx, GLframebuffer *buffer, GLenum mode )
{
   /* separate read buffer not supported */
   ASSERT(buffer == ctx->DrawBuffer);
   ASSERT(mode == GL_FRONT_LEFT);
}


static void clear_index( GLcontext *ctx, GLuint index )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   osmesa->clearpixel = index;
}



static void clear_color( GLcontext *ctx,
                         GLchan r, GLchan g, GLchan b, GLchan a )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   osmesa->clearpixel = PACK_RGBA( r, g, b, a );
}



static GLbitfield clear( GLcontext *ctx, GLbitfield mask, GLboolean all,
                         GLint x, GLint y, GLint width, GLint height )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLuint *colorMask = (GLuint *) &ctx->Color.ColorMask;

   /* we can't handle color or index masking */
   if (*colorMask != 0xffffffff || ctx->Color.IndexMask != 0xffffffff)
      return mask;

   /* sanity check - we only have a front-left buffer */
   ASSERT((mask & (DD_FRONT_RIGHT_BIT | DD_BACK_LEFT_BIT | DD_BACK_RIGHT_BIT)) == 0);

   if (mask & DD_FRONT_LEFT_BIT) {
      if (osmesa->format==OSMESA_COLOR_INDEX) {
         if (all) {
            /* Clear whole CI buffer */
            MEMSET(osmesa->buffer, osmesa->clearpixel,
                   osmesa->rowlength * osmesa->height);
         }
         else {
            /* Clear part of CI buffer */
            GLint i, j;
            for (i=0;i<height;i++) {
               GLubyte *ptr1 = PIXELADDR1( x, (y+i) );
               for (j=0;j<width;j++) {
                  *ptr1++ = osmesa->clearpixel;
               }
            }
         }
      }
      else if ((osmesa->format==OSMESA_RGB)||(osmesa->format==OSMESA_BGR)) {
         GLubyte rval = UNPACK_RED(osmesa->clearpixel);
         GLubyte gval = UNPACK_GREEN(osmesa->clearpixel);
         GLubyte bval = UNPACK_BLUE(osmesa->clearpixel);
         GLint   rind = osmesa->rind;
         GLint   gind = osmesa->gind;
         GLint   bind = osmesa->bind;
         if (all) {
            GLuint  i, n;
            GLubyte *ptr3 = (GLubyte *) osmesa->buffer;
            /* Clear whole RGB buffer */
            n = osmesa->rowlength * osmesa->height;
            for (i=0;i<n;i++) {
               ptr3[rind] = rval;
               ptr3[gind] = gval;
               ptr3[bind] = bval;
               ptr3 += 3;
            }
         }
         else {
            /* Clear part of RGB buffer */
            GLint i, j;
            for (i=0;i<height;i++) {
               GLubyte *ptr3 = PIXELADDR3( x, (y+i) );
               for (j=0;j<width;j++) {
                  ptr3[rind] = rval;
                  ptr3[gind] = gval;
                  ptr3[bind] = bval;
                  ptr3 += 3;
               }
            }
         }
      }
      else {
         if (all) {
            /* Clear whole RGBA buffer */
            GLuint i, n, *ptr4;
            n = osmesa->rowlength * osmesa->height;
            ptr4 = (GLuint *) osmesa->buffer;
            if (osmesa->clearpixel) {
               for (i=0;i<n;i++) {
                  *ptr4++ = osmesa->clearpixel;
               }
            }
            else {
               BZERO(ptr4, n * sizeof(GLuint));
            }
         }
         else {
            /* Clear part of RGBA buffer */
            GLint i, j;
            for (i=0;i<height;i++) {
               GLuint *ptr4 = PIXELADDR4( x, (y+i) );
               for (j=0;j<width;j++) {
                  *ptr4++ = osmesa->clearpixel;
               }
            }
         }
      }
   }
   /* have Mesa clear all other buffers */
   return mask & (~DD_FRONT_LEFT_BIT);
}



static void set_index( GLcontext *ctx, GLuint index )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   osmesa->pixel = index;
}



static void set_color( GLcontext *ctx,
                       GLchan r, GLchan g, GLchan b, GLchan a )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   osmesa->pixel = PACK_RGBA( r, g, b, a );
}



static void buffer_size( GLcontext *ctx, GLuint *width, GLuint *height )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   *width = osmesa->width;
   *height = osmesa->height;
}


/**********************************************************************/
/*****        Read/write spans/arrays of RGBA pixels              *****/
/**********************************************************************/

/* Write RGBA pixels to an RGBA (or permuted) buffer. */
static void write_rgba_span( const GLcontext *ctx,
                             GLuint n, GLint x, GLint y,
                             CONST GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint *ptr4 = PIXELADDR4( x, y );
   GLuint i;
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint ashift = osmesa->ashift;
   if (mask) {
      for (i=0;i<n;i++,ptr4++) {
         if (mask[i]) {
            *ptr4 = PACK_RGBA2( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
         }
      }
   }
   else {
      for (i=0;i<n;i++,ptr4++) {
         *ptr4 = PACK_RGBA2( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}


/* Write RGBA pixels to an RGBA buffer.  This is the fastest span-writer. */
static void write_rgba_span_rgba( const GLcontext *ctx,
                                  GLuint n, GLint x, GLint y,
                                  CONST GLchan rgba[][4],
                                  const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint *ptr4 = PIXELADDR4( x, y );
   const GLuint *rgba4 = (const GLuint *) rgba;
   GLuint i;
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            ptr4[i] = rgba4[i];
         }
      }
   }
   else {
      MEMCPY( ptr4, rgba4, n * 4 );
   }
}


/* Write RGB pixels to an RGBA (or permuted) buffer. */
static void write_rgb_span( const GLcontext *ctx,
                            GLuint n, GLint x, GLint y,
                            CONST GLchan rgb[][3], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint *ptr4 = PIXELADDR4( x, y );
   GLuint i;
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint ashift = osmesa->ashift;
   if (mask) {
      for (i=0;i<n;i++,ptr4++) {
         if (mask[i]) {
            *ptr4 = PACK_RGBA2( rgb[i][RCOMP], rgb[i][GCOMP], rgb[i][BCOMP], 255 );
         }
      }
   }
   else {
      for (i=0;i<n;i++,ptr4++) {
         *ptr4 = PACK_RGBA2( rgb[i][RCOMP], rgb[i][GCOMP], rgb[i][BCOMP], 255);
      }
   }
}



static void write_monocolor_span( const GLcontext *ctx,
                                  GLuint n, GLint x, GLint y,
				  const GLchan color[4], const GLubyte mask[] )
{
   const OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLuint pixel = PACK_RGBA(color[RCOMP], color[GCOMP],
                                  color[BCOMP], color[ACOMP]);
   GLuint *ptr4 = PIXELADDR4(x,y);
   GLuint i;
   for (i=0;i<n;i++,ptr4++) {
      if (mask[i]) {
         *ptr4 = pixel;
      }
   }
}



static void write_rgba_pixels( const GLcontext *ctx,
                               GLuint n, const GLint x[], const GLint y[],
                               CONST GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint ashift = osmesa->ashift;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLuint *ptr4 = PIXELADDR4(x[i],y[i]);
         *ptr4 = PACK_RGBA2( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}



static void write_monocolor_pixels( const GLcontext *ctx,
                                    GLuint n, const GLint x[], const GLint y[],
				    const GLchan color[4],
                                    const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLuint pixel = PACK_RGBA(color[RCOMP], color[GCOMP],
                                  color[BCOMP], color[ACOMP]);
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLuint *ptr4 = PIXELADDR4(x[i],y[i]);
         *ptr4 = pixel;
      }
   }
}


static void read_rgba_span( const GLcontext *ctx, GLuint n, GLint x, GLint y,
                             GLchan rgba[][4] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   GLuint *ptr4 = PIXELADDR4(x,y);
   for (i=0;i<n;i++) {
      GLuint pixel = *ptr4++;
      rgba[i][RCOMP] = UNPACK_RED(pixel);
      rgba[i][GCOMP] = UNPACK_GREEN(pixel);
      rgba[i][BCOMP] = UNPACK_BLUE(pixel);
      rgba[i][ACOMP] = UNPACK_ALPHA(pixel);
   }
}


/* Read RGBA pixels from an RGBA buffer */
static void read_rgba_span_rgba( const GLcontext *ctx,
                                 GLuint n, GLint x, GLint y,
                                 GLchan rgba[][4] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint *ptr4 = PIXELADDR4(x,y);
   MEMCPY( rgba, ptr4, n * 4 * sizeof(GLchan) );
}


static void read_rgba_pixels( const GLcontext *ctx,
                               GLuint n, const GLint x[], const GLint y[],
			       GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLuint *ptr4 = PIXELADDR4(x[i],y[i]);
         GLuint pixel = *ptr4;
         rgba[i][RCOMP] = UNPACK_RED(pixel);
         rgba[i][GCOMP] = UNPACK_GREEN(pixel);
         rgba[i][BCOMP] = UNPACK_BLUE(pixel);
         rgba[i][ACOMP] = UNPACK_ALPHA(pixel);
      }
   }
}

/**********************************************************************/
/*****                3 byte RGB pixel support funcs              *****/
/**********************************************************************/

/* Write RGBA pixels to an RGB or BGR buffer. */
static void write_rgba_span3( const GLcontext *ctx,
                              GLuint n, GLint x, GLint y,
                              CONST GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *ptr3 = PIXELADDR3( x, y);
   GLuint i;
   GLint rind = osmesa->rind;
   GLint gind = osmesa->gind;
   GLint bind = osmesa->bind;
   if (mask) {
      for (i=0;i<n;i++,ptr3+=3) {
         if (mask[i]) {
            ptr3[rind] = rgba[i][RCOMP];
            ptr3[gind] = rgba[i][GCOMP];
            ptr3[bind] = rgba[i][BCOMP];
         }
      }
   }
   else {
      for (i=0;i<n;i++,ptr3+=3) {
         ptr3[rind] = rgba[i][RCOMP];
         ptr3[gind] = rgba[i][GCOMP];
         ptr3[bind] = rgba[i][BCOMP];
      }
   }
}

/* Write RGB pixels to an RGB or BGR buffer. */
static void write_rgb_span3( const GLcontext *ctx,
                             GLuint n, GLint x, GLint y,
                             CONST GLchan rgb[][3], const GLubyte mask[] )
{
   const OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLint rind = osmesa->rind;
   const GLint gind = osmesa->gind;
   const GLint bind = osmesa->bind;
   GLubyte *ptr3 = PIXELADDR3( x, y);
   GLuint i;
   if (mask) {
      for (i=0;i<n;i++,ptr3+=3) {
         if (mask[i]) {
            ptr3[rind] = rgb[i][RCOMP];
            ptr3[gind] = rgb[i][GCOMP];
            ptr3[bind] = rgb[i][BCOMP];
         }
      }
   }
   else {
      for (i=0;i<n;i++,ptr3+=3) {
         ptr3[rind] = rgb[i][RCOMP];
         ptr3[gind] = rgb[i][GCOMP];
         ptr3[bind] = rgb[i][BCOMP];
      }
   }
}


static void write_monocolor_span3( const GLcontext *ctx,
                                   GLuint n, GLint x, GLint y,
                                   const GLchan color[4], const GLubyte mask[] )
{
   const OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLubyte rval = color[RCOMP];
   const GLubyte gval = color[GCOMP];
   const GLubyte bval = color[BCOMP];
   const GLint   rind = osmesa->rind;
   const GLint   gind = osmesa->gind;
   const GLint   bind = osmesa->bind;
   GLubyte *ptr3 = PIXELADDR3( x, y);
   GLuint i;
   for (i=0;i<n;i++,ptr3+=3) {
      if (mask[i]) {
         ptr3[rind] = rval;
         ptr3[gind] = gval;
         ptr3[bind] = bval;
      }
   }
}

static void write_rgba_pixels3( const GLcontext *ctx,
                                GLuint n, const GLint x[], const GLint y[],
                                CONST GLchan rgba[][4], const GLubyte mask[] )
{
   const OSMesaContext osmesa = (const OSMesaContext) ctx;
   GLuint i;
   GLint rind = osmesa->rind;
   GLint gind = osmesa->gind;
   GLint bind = osmesa->bind;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLubyte *ptr3 = PIXELADDR3(x[i],y[i]);
         ptr3[rind] = rgba[i][RCOMP];
         ptr3[gind] = rgba[i][GCOMP];
         ptr3[bind] = rgba[i][BCOMP];
      }
   }
}

static void write_monocolor_pixels3( const GLcontext *ctx,
                                     GLuint n, const GLint x[],
                                     const GLint y[],
                                     const GLchan color[4],
                                     const GLubyte mask[] )
{
   const OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   const GLint rind = osmesa->rind;
   const GLint gind = osmesa->gind;
   const GLint bind = osmesa->bind;
   const GLubyte rval = color[RCOMP];
   const GLubyte gval = color[GCOMP];
   const GLubyte bval = color[BCOMP];
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLubyte *ptr3 = PIXELADDR3(x[i],y[i]);
         ptr3[rind] = rval;
         ptr3[gind] = gval;
         ptr3[bind] = bval;
      }
   }
}

static void read_rgba_span3( const GLcontext *ctx,
                             GLuint n, GLint x, GLint y,
                             GLchan rgba[][4] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   GLint rind = osmesa->rind;
   GLint gind = osmesa->gind;
   GLint bind = osmesa->bind;
   const GLubyte *ptr3 = PIXELADDR3( x, y);
   for (i=0;i<n;i++,ptr3+=3) {
      rgba[i][RCOMP] = ptr3[rind];
      rgba[i][GCOMP] = ptr3[gind];
      rgba[i][BCOMP] = ptr3[bind];
      rgba[i][ACOMP] = 0;
   }
}

static void read_rgba_pixels3( const GLcontext *ctx,
                               GLuint n, const GLint x[], const GLint y[],
			       GLchan rgba[][4], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   GLint rind = osmesa->rind;
   GLint gind = osmesa->gind;
   GLint bind = osmesa->bind;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         const GLubyte *ptr3 = PIXELADDR3(x[i],y[i]);
         rgba[i][RCOMP] = ptr3[rind];
         rgba[i][GCOMP] = ptr3[gind];
         rgba[i][BCOMP] = ptr3[bind];
         rgba[i][ACOMP] = 0;
      }
   }
}


/**********************************************************************/
/*****        Read/write spans/arrays of CI pixels                *****/
/**********************************************************************/

/* Write 32-bit color index to buffer */
static void write_index32_span( const GLcontext *ctx,
                                GLuint n, GLint x, GLint y,
                                const GLuint index[], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *ptr1 = PIXELADDR1(x,y);
   GLuint i;
   if (mask) {
      for (i=0;i<n;i++,ptr1++) {
         if (mask[i]) {
            *ptr1 = (GLubyte) index[i];
         }
      }
   }
   else {
      for (i=0;i<n;i++,ptr1++) {
         *ptr1 = (GLubyte) index[i];
      }
   }
}


/* Write 8-bit color index to buffer */
static void write_index8_span( const GLcontext *ctx,
                               GLuint n, GLint x, GLint y,
                               const GLubyte index[], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *ptr1 = PIXELADDR1(x,y);
   GLuint i;
   if (mask) {
      for (i=0;i<n;i++,ptr1++) {
         if (mask[i]) {
            *ptr1 = (GLubyte) index[i];
         }
      }
   }
   else {
      MEMCPY( ptr1, index, n );
   }
}


static void write_monoindex_span( const GLcontext *ctx,
                                  GLuint n, GLint x, GLint y,
				  GLuint colorIndex, const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *ptr1 = PIXELADDR1(x,y);
   GLuint i;
   for (i=0;i<n;i++,ptr1++) {
      if (mask[i]) {
         *ptr1 = (GLubyte) colorIndex;
      }
   }
}


static void write_index_pixels( const GLcontext *ctx,
                                GLuint n, const GLint x[], const GLint y[],
			        const GLuint index[], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLubyte *ptr1 = PIXELADDR1(x[i],y[i]);
         *ptr1 = (GLubyte) index[i];
      }
   }
}


static void write_monoindex_pixels( const GLcontext *ctx,
                                    GLuint n, const GLint x[], const GLint y[],
				    GLuint colorIndex, const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         GLubyte *ptr1 = PIXELADDR1(x[i],y[i]);
         *ptr1 = (GLubyte) colorIndex;
      }
   }
}


static void read_index_span( const GLcontext *ctx,
                             GLuint n, GLint x, GLint y, GLuint index[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   const GLubyte *ptr1 = PIXELADDR1(x,y);
   for (i=0;i<n;i++,ptr1++) {
      index[i] = (GLuint) *ptr1;
   }
}


static void read_index_pixels( const GLcontext *ctx,
                               GLuint n, const GLint x[], const GLint y[],
			       GLuint index[], const GLubyte mask[] )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i] ) {
         const GLubyte *ptr1 = PIXELADDR1(x[i],y[i]);
         index[i] = (GLuint) *ptr1;
      }
   }
}



/**********************************************************************/
/*****                   Optimized line rendering                 *****/
/**********************************************************************/


/*
 * Draw a flat-shaded, RGB line into an osmesa buffer.
 */
static void flat_rgba_line( GLcontext *ctx,
                            SWvertex *vert0, SWvertex *vert1 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *color = vert0->color;
   unsigned long pixel = PACK_RGBA( color[0], color[1], color[2], color[3] );

#define INTERP_XY 1
#define CLIP_HACK 1
#define PLOT(X,Y) { GLuint *ptr4 = PIXELADDR4(X,Y); *ptr4 = pixel; }

#ifdef WIN32
#include "..\swrast\s_linetemp.h"
#else
#include "swrast/s_linetemp.h"
#endif
}


/*
 * Draw a flat-shaded, Z-less, RGB line into an osmesa buffer.
 */
static void flat_rgba_z_line( GLcontext *ctx,
			      SWvertex *vert0, SWvertex *vert1 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLubyte *color = vert0->color;
   unsigned long pixel = PACK_RGBA( color[0], color[1], color[2], color[3] );

#define INTERP_XY 1
#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define CLIP_HACK 1
#define PLOT(X,Y)				\
	if (Z < *zPtr) {			\
	   GLuint *ptr4 = PIXELADDR4(X,Y);	\
	   *ptr4 = pixel;			\
	   *zPtr = Z;				\
	}

#ifdef WIN32
#include "..\swrast\s_linetemp.h"
#else
#include "swrast/s_linetemp.h"
#endif
}


/*
 * Draw a flat-shaded, alpha-blended, RGB line into an osmesa buffer.
 */
static void flat_blend_rgba_line( GLcontext *ctx,
				  SWvertex *vert0, SWvertex *vert1 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint avalue = vert0->color[3];
   GLint msavalue = 255 - avalue;
   GLint rvalue = vert0->color[0]*avalue;
   GLint gvalue = vert0->color[1]*avalue;
   GLint bvalue = vert0->color[2]*avalue;

#define INTERP_XY 1
#define CLIP_HACK 1
#define PLOT(X,Y)					\
   { GLuint *ptr4 = PIXELADDR4(X,Y);			\
     GLuint  pixel = 0;					\
     pixel |=((((((*ptr4) >> rshift) & 0xff)*msavalue+rvalue)>>8) << rshift);\
     pixel |=((((((*ptr4) >> gshift) & 0xff)*msavalue+gvalue)>>8) << gshift);\
     pixel |=((((((*ptr4) >> bshift) & 0xff)*msavalue+bvalue)>>8) << bshift);\
     *ptr4 = pixel;					\
   }

#ifdef WIN32
#include "..\swrast\s_linetemp.h"
#else
#include "swrast/s_linetemp.h"
#endif
}


/*
 * Draw a flat-shaded, Z-less, alpha-blended, RGB line into an osmesa buffer.
 */
static void flat_blend_rgba_z_line( GLcontext *ctx,
				    SWvertex *vert0, SWvertex *vert1 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint avalue = vert0->color[3];
   GLint msavalue = 256 - avalue;
   GLint rvalue = vert0->color[0]*avalue;
   GLint gvalue = vert0->color[1]*avalue;
   GLint bvalue = vert0->color[2]*avalue;

#define INTERP_XY 1
#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define CLIP_HACK 1
#define PLOT(X,Y)							\
	if (Z < *zPtr) {						\
	   GLuint *ptr4 = PIXELADDR4(X,Y);				\
	   GLuint  pixel = 0;						\
	   pixel |=((((((*ptr4) >> rshift) & 0xff)*msavalue+rvalue)>>8) << rshift);	\
	   pixel |=((((((*ptr4) >> gshift) & 0xff)*msavalue+gvalue)>>8) << gshift);	\
	   pixel |=((((((*ptr4) >> bshift) & 0xff)*msavalue+bvalue)>>8) << bshift);	\
	   *ptr4 = pixel; 						\
	}

#ifdef WIN32
#include "..\swrast\s_linetemp.h"
#else
#include "swrast/s_linetemp.h"
#endif
}


/*
 * Draw a flat-shaded, Z-less, alpha-blended, RGB line into an osmesa buffer.
 */
static void flat_blend_rgba_z_line_write( GLcontext *ctx,
					  SWvertex *vert0, SWvertex *vert1 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint avalue = vert0->color[3];
   GLint msavalue = 256 - avalue;
   GLint rvalue = vert0->color[0]*avalue;
   GLint gvalue = vert0->color[1]*avalue;
   GLint bvalue = vert0->color[2]*avalue;

#define INTERP_XY 1
#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define CLIP_HACK 1
#define PLOT(X,Y)							\
	if (Z < *zPtr) {						\
	   GLuint *ptr4 = PIXELADDR4(X,Y);				\
	   GLuint  pixel = 0;						\
	   pixel |=((((((*ptr4) >> rshift) & 0xff)*msavalue+rvalue)>>8) << rshift);	\
	   pixel |=((((((*ptr4) >> gshift) & 0xff)*msavalue+gvalue)>>8) << gshift);	\
	   pixel |=((((((*ptr4) >> bshift) & 0xff)*msavalue+bvalue)>>8) << bshift);	\
	   *ptr4 = pixel;						\
	   *zPtr = Z;							\
	}

#ifdef WIN32
#include "..\swrast\s_linetemp.h"
#else
#include "swrast/s_linetemp.h"
#endif
}


/*
 * Analyze context state to see if we can provide a fast line drawing
 * function, like those in lines.c.  Otherwise, return NULL.
 */
static swrast_line_func
osmesa_choose_line_function( GLcontext *ctx )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   if (ctx->RenderMode != GL_RENDER)      return NULL;
   if (ctx->Line.SmoothFlag)              return NULL;
   if (ctx->Texture._ReallyEnabled)       return NULL;
   if (ctx->Light.ShadeModel!=GL_FLAT)    return NULL;

   if (ctx->Line.Width==1.0F
       && ctx->Line.StippleFlag==GL_FALSE) {

       if (swrast->_RasterMask==DEPTH_BIT
           && ctx->Depth.Func==GL_LESS
           && ctx->Depth.Mask==GL_TRUE
           && ctx->Visual.DepthBits == DEFAULT_SOFTWARE_DEPTH_BITS) {
           switch(osmesa->format) {
       		case OSMESA_RGBA:
       		case OSMESA_BGRA:
       		case OSMESA_ARGB:
       			return flat_rgba_z_line;
       		default:
       			return NULL;
           }
       }

       if (swrast->_RasterMask==0) {
           switch(osmesa->format) {
       		case OSMESA_RGBA:
       		case OSMESA_BGRA:
       		case OSMESA_ARGB:
       			return flat_rgba_line;
       		default:
       			return NULL;
           }
       }

       if (swrast->_RasterMask==(DEPTH_BIT|BLEND_BIT)
           && ctx->Depth.Func==GL_LESS
           && ctx->Depth.Mask==GL_TRUE
           && ctx->Visual.DepthBits == DEFAULT_SOFTWARE_DEPTH_BITS
           && ctx->Color.BlendSrcRGB==GL_SRC_ALPHA
           && ctx->Color.BlendDstRGB==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendSrcA==GL_SRC_ALPHA
           && ctx->Color.BlendDstA==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendEquation==GL_FUNC_ADD_EXT) {
           switch(osmesa->format) {
       		case OSMESA_RGBA:
       		case OSMESA_BGRA:
       		case OSMESA_ARGB:
       			return flat_blend_rgba_z_line_write;
       		default:
       			return NULL;
           }
       }

       if (swrast->_RasterMask==(DEPTH_BIT|BLEND_BIT)
           && ctx->Depth.Func==GL_LESS
           && ctx->Depth.Mask==GL_FALSE
           && ctx->Visual.DepthBits == DEFAULT_SOFTWARE_DEPTH_BITS
           && ctx->Color.BlendSrcRGB==GL_SRC_ALPHA
           && ctx->Color.BlendDstRGB==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendSrcA==GL_SRC_ALPHA
           && ctx->Color.BlendDstA==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendEquation==GL_FUNC_ADD_EXT) {
           switch(osmesa->format) {
       		case OSMESA_RGBA:
       		case OSMESA_BGRA:
       		case OSMESA_ARGB:
       			return flat_blend_rgba_z_line;
       		default:
       			return NULL;
           }
       }

       if (swrast->_RasterMask==BLEND_BIT
           && ctx->Color.BlendSrcRGB==GL_SRC_ALPHA
           && ctx->Color.BlendDstRGB==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendSrcA==GL_SRC_ALPHA
           && ctx->Color.BlendDstA==GL_ONE_MINUS_SRC_ALPHA
           && ctx->Color.BlendEquation==GL_FUNC_ADD_EXT) {
           switch(osmesa->format) {
       		case OSMESA_RGBA:
       		case OSMESA_BGRA:
       		case OSMESA_ARGB:
       			return flat_blend_rgba_line;
       		default:
       			return NULL;
           }
       }

   }
   return NULL;
}


/**********************************************************************/
/*****                 Optimized triangle rendering               *****/
/**********************************************************************/


/*
 * Smooth-shaded, z-less triangle, RGBA color.
 */
static void smooth_rgba_z_triangle( GLcontext *ctx,
				    SWvertex *v0, SWvertex *v1, SWvertex *v2 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   GLint rshift = osmesa->rshift;
   GLint gshift = osmesa->gshift;
   GLint bshift = osmesa->bshift;
   GLint ashift = osmesa->ashift;

#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define INTERP_RGB 1
#define INTERP_ALPHA 1
#define INNER_LOOP( LEFT, RIGHT, Y )				\
{								\
   GLint i, len = RIGHT-LEFT;					\
   GLuint *img = PIXELADDR4(LEFT,Y);   				\
   (void) fffog;                        \
   for (i=0;i<len;i++,img++) {					\
      GLdepth z = FixedToDepth(ffz);				\
      if (z < zRow[i]) {					\
         *img = PACK_RGBA2( FixedToInt(ffr), FixedToInt(ffg),	\
		            FixedToInt(ffb), FixedToInt(ffa) );	\
         zRow[i] = z;						\
      }								\
      ffr += fdrdx;  ffg += fdgdx;  ffb += fdbdx;  ffa += fdadx;\
      ffz += fdzdx;						\
   }								\
}
#ifdef WIN32
#include "..\swrast\s_tritemp.h"
#else
#include "swrast/s_tritemp.h"
#endif
}




/*
 * Flat-shaded, z-less triangle, RGBA color.
 */
static void flat_rgba_z_triangle( GLcontext *ctx,
				  SWvertex *v0, SWvertex *v1, SWvertex *v2 )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
#define INTERP_Z 1
#define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
#define SETUP_CODE			\
   GLubyte r = v0->color[0];	\
   GLubyte g = v0->color[1];	\
   GLubyte b = v0->color[2];	\
   GLubyte a = v0->color[3];	\
   GLuint pixel = PACK_RGBA(r,g,b,a);

#define INNER_LOOP( LEFT, RIGHT, Y )	\
{					\
   GLint i, len = RIGHT-LEFT;		\
   GLuint *img = PIXELADDR4(LEFT,Y);   	\
   (void) fffog;                        \
   for (i=0;i<len;i++,img++) {		\
      GLdepth z = FixedToDepth(ffz);	\
      if (z < zRow[i]) {		\
         *img = pixel;			\
         zRow[i] = z;			\
      }					\
      ffz += fdzdx;			\
   }					\
}
#ifdef WIN32
#include "..\swrast\s_tritemp.h"
#else
#include "swrast/s_tritemp.h"
#endif
}



/*
 * Return pointer to an accelerated triangle function if possible.
 */
static swrast_tri_func
osmesa_choose_triangle_function( GLcontext *ctx )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   if ((osmesa->format==OSMESA_RGB)||(osmesa->format==OSMESA_BGR))
      return (swrast_tri_func)NULL;

   if (ctx->RenderMode != GL_RENDER)  return (swrast_tri_func) NULL;
   if (ctx->Polygon.SmoothFlag)       return (swrast_tri_func) NULL;
   if (ctx->Polygon.StippleFlag)      return (swrast_tri_func) NULL;
   if (ctx->Texture._ReallyEnabled)   return (swrast_tri_func) NULL;

   if (swrast->_RasterMask==DEPTH_BIT
       && ctx->Depth.Func==GL_LESS
       && ctx->Depth.Mask==GL_TRUE
       && ctx->Visual.DepthBits == DEFAULT_SOFTWARE_DEPTH_BITS
       && osmesa->format!=OSMESA_COLOR_INDEX) {
      if (ctx->Light.ShadeModel==GL_SMOOTH) {
         return smooth_rgba_z_triangle;
      }
      else {
         return flat_rgba_z_triangle;
      }
   }
   return (swrast_tri_func)NULL;
}

/* Override for the swrast triangle-selection function.  Try to use one
 * of our internal triangle functions, otherwise fall back to the
 * standard swrast functions.
 */
static void osmesa_choose_triangle( GLcontext *ctx )
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   swrast->Triangle = osmesa_choose_triangle_function( ctx );
   if (!swrast->Triangle)
      _swrast_choose_triangle( ctx );
}

static void osmesa_choose_line( GLcontext *ctx )
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);

   swrast->Line = osmesa_choose_line_function( ctx );
   if (!swrast->Line)
      _swrast_choose_line( ctx );
}


#define OSMESA_NEW_LINE   (_NEW_LINE | \
                           _NEW_TEXTURE | \
                           _NEW_LIGHT | \
                           _NEW_DEPTH | \
                           _NEW_RENDERMODE | \
                           _SWRAST_NEW_RASTERMASK)

#define OSMESA_NEW_TRIANGLE (_NEW_POLYGON | \
                             _NEW_TEXTURE | \
                             _NEW_LIGHT | \
                             _NEW_DEPTH | \
                             _NEW_RENDERMODE | \
                             _SWRAST_NEW_RASTERMASK)


/* Extend the software rasterizer with our line and triangle
 * functions.
 */
static void osmesa_register_swrast_functions( GLcontext *ctx )
{
   SWcontext *swrast = SWRAST_CONTEXT( ctx );

   swrast->choose_line = osmesa_choose_line;
   swrast->choose_triangle = osmesa_choose_triangle;

   swrast->invalidate_line |= OSMESA_NEW_LINE;
   swrast->invalidate_triangle |= OSMESA_NEW_TRIANGLE;
}


static const GLubyte *get_string( GLcontext *ctx, GLenum name )
{
   (void) ctx;
   switch (name) {
      case GL_RENDERER:
         return (const GLubyte *) "Mesa OffScreen";
      default:
         return NULL;
   }
}


static void osmesa_update_state( GLcontext *ctx )
{
   OSMesaContext osmesa = OSMESA_CONTEXT(ctx);

   ASSERT((void *) osmesa == (void *) ctx->DriverCtx);

   ctx->Driver.GetString = get_string;
   ctx->Driver.UpdateStateNotify = ~0;
   ctx->Driver.UpdateState = osmesa_update_state;

   ctx->Driver.SetDrawBuffer = set_draw_buffer;
   ctx->Driver.SetReadBuffer = set_read_buffer;
#if 000
   ctx->Driver.Color = set_color;
   ctx->Driver.Index = set_index;
#endif
   ctx->Driver.ClearIndex = clear_index;
   ctx->Driver.ClearColor = clear_color;
   ctx->Driver.Clear = clear;

   ctx->Driver.GetBufferSize = buffer_size;

   ctx->Driver.PointsFunc = _swsetup_Points;
   ctx->Driver.LineFunc = _swsetup_Line;
   ctx->Driver.TriangleFunc = _swsetup_Triangle;
   ctx->Driver.QuadFunc = _swsetup_Quad;
   ctx->Driver.RasterSetup = _swsetup_RasterSetup;


   /* RGB(A) span/pixel functions */
   if ((osmesa->format==OSMESA_RGB) || (osmesa->format==OSMESA_BGR)) {
      /* 3 bytes / pixel in frame buffer */
      ctx->Driver.WriteRGBASpan = write_rgba_span3;
      ctx->Driver.WriteRGBSpan = write_rgb_span3;
      ctx->Driver.WriteRGBAPixels = write_rgba_pixels3;
      ctx->Driver.WriteMonoRGBASpan = write_monocolor_span3;
      ctx->Driver.WriteMonoRGBAPixels = write_monocolor_pixels3;
      ctx->Driver.ReadRGBASpan = read_rgba_span3;
      ctx->Driver.ReadRGBAPixels = read_rgba_pixels3;
   }
   else {
      /* 4 bytes / pixel in frame buffer */
      if (osmesa->format==OSMESA_RGBA
          && RCOMP==0 && GCOMP==1 && BCOMP==2 && ACOMP==3)
         ctx->Driver.WriteRGBASpan = write_rgba_span_rgba;
      else
         ctx->Driver.WriteRGBASpan = write_rgba_span;
      ctx->Driver.WriteRGBSpan = write_rgb_span;
      ctx->Driver.WriteRGBAPixels = write_rgba_pixels;
      ctx->Driver.WriteMonoRGBASpan = write_monocolor_span;
      ctx->Driver.WriteMonoRGBAPixels = write_monocolor_pixels;
      if (osmesa->format==OSMESA_RGBA
          && RCOMP==0 && GCOMP==1 && BCOMP==2 && ACOMP==3)
         ctx->Driver.ReadRGBASpan = read_rgba_span_rgba;
      else
         ctx->Driver.ReadRGBASpan = read_rgba_span;
      ctx->Driver.ReadRGBAPixels = read_rgba_pixels;
   }

   /* CI span/pixel functions */
   ctx->Driver.WriteCI32Span = write_index32_span;
   ctx->Driver.WriteCI8Span = write_index8_span;
   ctx->Driver.WriteMonoCISpan = write_monoindex_span;
   ctx->Driver.WriteCI32Pixels = write_index_pixels;
   ctx->Driver.WriteMonoCIPixels = write_monoindex_pixels;
   ctx->Driver.ReadCI32Span = read_index_span;
   ctx->Driver.ReadCI32Pixels = read_index_pixels;
}