Overhaul of glRead/DrawBuffer() code. Now, swrast->Driver.SetBuffer()

indicates the read AND draw color buffer for all software rasterization.
Lots of related clean-ups.  See RELNOTES-4.1 for details.

11 files changed, 177 insertions, 293 deletions

diff --git a/src/mesa/drivers/dos/dmesa.c b/src/mesa/drivers/dos/dmesa.c
index c9bc898dcb..5855f04f3e 100644
--- a/src/mesa/drivers/dos/dmesa.c
+++ b/src/mesa/drivers/dos/dmesa.c
@@ -512,8 +512,7 @@ static void clear (GLcontext *ctx, GLbitfield mask, GLboolean all,
 /*

  * Set the current reading buffer.

  */

-static void set_read_buffer (GLcontext *ctx, GLframebuffer *buffer,

-                             GLenum mode)

+static void set_buffer (GLcontext *ctx, GLframebuffer *buffer, GLenum mode)

 {

 /*

  DMesaContext c = (DMesaContext)ctx->DriverCtx;

@@ -524,18 +523,6 @@ static void set_read_buffer (GLcontext *ctx, GLframebuffer *buffer,
 

 

 /*

- * Set the destination/draw buffer.

- */

-static void set_draw_buffer (GLcontext *ctx, GLenum mode)

-{

-   /*

-     XXX this has to be fixed

-   */

-}

-

-

-

-/*

  * Return the width and height of the current buffer.

  * If anything special has to been done when the buffer/window is

  * resized, do it now.

@@ -640,6 +627,7 @@ void dmesa_init_pointers (GLcontext *ctx)
  ctx->Driver.CopyPixels = _swrast_CopyPixels;

  ctx->Driver.DrawPixels = _swrast_DrawPixels;

  ctx->Driver.ReadPixels = _swrast_ReadPixels;

+ ctx->Driver.DrawBuffer = _swrast_DrawBuffer;

 

  /* Software texture functions:

   */

@@ -671,7 +659,6 @@ void dmesa_init_pointers (GLcontext *ctx)
 

  /* Statechange callbacks:

   */

- ctx->Driver.SetDrawBuffer = set_draw_buffer;

  ctx->Driver.ClearColor = clear_color;

 

  /* Initialize the TNL driver interface:

@@ -699,7 +686,7 @@ static void dmesa_update_state (GLcontext *ctx, GLuint new_state)
  _ac_InvalidateState(ctx, new_state);

  _tnl_InvalidateState(ctx, new_state);

 

- swdd->SetReadBuffer = set_read_buffer;

+ swdd->SetBuffer = set_buffer;

 

  /* RGB(A) span/pixel functions */

  swdd->WriteRGBASpan = write_rgba_span;

diff --git a/src/mesa/drivers/ggi/ggimesa.c b/src/mesa/drivers/ggi/ggimesa.c
index 97ab159558..86de850e91 100644
--- a/src/mesa/drivers/ggi/ggimesa.c
+++ b/src/mesa/drivers/ggi/ggimesa.c
@@ -143,50 +143,30 @@ static void gl_ggiClear(GLcontext *ctx, GLbitfield mask, GLboolean all,
 	
 }
 
-/* Set the buffer used for drawing */
-static void gl_ggiSetDrawBuffer(GLcontext *ctx, GLenum mode)
-{
-	ggi_mesa_context_t ggi_ctx = (ggi_mesa_context_t)ctx->DriverCtx;
-
-	printf("set draw %d\n", mode);
-	GGIMESADPRINT_CORE("gl_ggiSetDrawBuffer() called\n");
-	
-	if (mode == GL_FRONT_LEFT) 
-	{
-		ggiSetWriteFrame(ggi_ctx->ggi_visual,
-				 ggiGetDisplayFrame(ggi_ctx->ggi_visual));
-	}
-	else if (mode == GL_BACK_LEFT) 
-	{
-		ggiSetWriteFrame(ggi_ctx->ggi_visual,
-				 ggiGetDisplayFrame(ggi_ctx->ggi_visual)?0 : 1);
-	}
-	else 
-	{
-		/* nothing since we don't have any point/line/triangle functions. */
-	}
-}
-
 
 /* Set the buffer used for reading */
 /* XXX support for separate read/draw buffers hasn't been tested */
-static GLboolean gl_ggiSetReadBuffer(GLcontext *ctx, GLframebuffer *buffer, GLenum mode)
+static GLboolean gl_ggiSetBuffer(GLcontext *ctx, GLframebuffer *buffer, GLenum mode)
 {
 	ggi_mesa_context_t ggi_ctx = (ggi_mesa_context_t)ctx->DriverCtx;
 	
 	printf("set read %d\n", mode);
-	GGIMESADPRINT_CORE("gl_ggiSetReadBuffer() called\n");
+	GGIMESADPRINT_CORE("gl_ggiSetBuffer() called\n");
 
 	if (mode == GL_FRONT_LEFT) 
 	{
 		ggiSetReadFrame(ggi_ctx->ggi_visual,
 				ggiGetDisplayFrame(ggi_ctx->ggi_visual));
+		ggiSetWriteFrame(ggi_ctx->ggi_visual,
+				 ggiGetDisplayFrame(ggi_ctx->ggi_visual));
 		return GL_TRUE;
 	}
 	else if (mode == GL_BACK_LEFT) 
 	{
 		ggiSetReadFrame(ggi_ctx->ggi_visual,
 				ggiGetDisplayFrame(ggi_ctx->ggi_visual)?0 : 1);
+		ggiSetWriteFrame(ggi_ctx->ggi_visual,
+				 ggiGetDisplayFrame(ggi_ctx->ggi_visual)?0 : 1);
 		return GL_TRUE;
 	}
 	else
@@ -249,6 +229,7 @@ static void gl_ggiSetupPointers(GLcontext *ctx)
 	ctx->Driver.CopyPixels = _swrast_CopyPixels;
 	ctx->Driver.DrawPixels = _swrast_DrawPixels;
 	ctx->Driver.ReadPixels = _swrast_ReadPixels;
+        ctx->Driver.DrawBuffer = _swrast_DrawBuffer;
 
 	/* Software texturing */
 	ctx->Driver.ChooseTextureFormat = _mesa_choose_tex_format;
@@ -277,7 +258,6 @@ static void gl_ggiSetupPointers(GLcontext *ctx)
 	ctx->Driver.CopyConvolutionFilter2D = _swrast_CopyConvolutionFilter2D;
 	
 	/* State change callbacks */
-	ctx->Driver.SetDrawBuffer = gl_ggiSetDrawBuffer;
 	ctx->Driver.ClearIndex = gl_ggiSetClearIndex; 
 	ctx->Driver.ClearColor = gl_ggiSetClearColor;
 	ctx->Driver.IndexMask = gl_ggiIndexMask;
diff --git a/src/mesa/drivers/glide/fxdd.c b/src/mesa/drivers/glide/fxdd.c
index 2fb1a2ada4..9b7cd306b2 100644
--- a/src/mesa/drivers/glide/fxdd.c
+++ b/src/mesa/drivers/glide/fxdd.c
@@ -1,4 +1,4 @@
-/* $Id: fxdd.c,v 1.88 2002/06/15 03:03:10 brianp Exp $ */
+/* $Id: fxdd.c,v 1.89 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -288,6 +288,9 @@ fxDDSetDrawBuffer(GLcontext * ctx, GLenum mode)
       /* we'll need a software fallback */
       /* XXX not implemented */
    }
+
+   /* update s/w fallback state */
+   _swrast_DrawBuffer(ctx, mode);
 }
 
 
@@ -991,7 +994,7 @@ fxSetupDDPointers(GLcontext * ctx)
    ctx->Driver.ClearIndex = NULL;
    ctx->Driver.ClearColor = fxDDClearColor;
    ctx->Driver.Clear = fxDDClear;
-   ctx->Driver.SetDrawBuffer = fxDDSetDrawBuffer;
+   ctx->Driver.DrawBuffer = fxDDSetDrawBuffer;
    ctx->Driver.GetBufferSize = fxDDBufferSize;
    ctx->Driver.Accum = _swrast_Accum;
    ctx->Driver.Bitmap = fxDDDrawBitmap;
diff --git a/src/mesa/drivers/glide/fxddspan.c b/src/mesa/drivers/glide/fxddspan.c
index 1ee7873efa..98aabc5c0d 100644
--- a/src/mesa/drivers/glide/fxddspan.c
+++ b/src/mesa/drivers/glide/fxddspan.c
@@ -1,4 +1,4 @@
-/* $Id: fxddspan.c,v 1.19 2001/09/23 16:50:01 brianp Exp $ */
+/* $Id: fxddspan.c,v 1.20 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -536,7 +536,7 @@ fxDDReadDepthPixels(GLcontext * ctx, GLuint n,
 /* Set the buffer used for reading */
 /* XXX support for separate read/draw buffers hasn't been tested */
 static void
-fxDDSetReadBuffer(GLcontext * ctx, GLframebuffer * buffer, GLenum mode)
+fxDDSetBuffer(GLcontext * ctx, GLframebuffer * buffer, GLenum mode)
 {
    fxMesaContext fxMesa = (fxMesaContext) ctx->DriverCtx;
    (void) buffer;
@@ -565,7 +565,7 @@ fxSetupDDSpanPointers(GLcontext * ctx)
 {
    struct swrast_device_driver *swdd = _swrast_GetDeviceDriverReference( ctx );
 
-   swdd->SetReadBuffer = fxDDSetReadBuffer;
+   swdd->SetBuffer = fxDDSetBuffer;
 
    swdd->WriteRGBASpan = fxDDWriteRGBASpan;
    swdd->WriteRGBSpan = fxDDWriteRGBSpan;
diff --git a/src/mesa/drivers/osmesa/osmesa.c b/src/mesa/drivers/osmesa/osmesa.c
index 20847f6286..8a80ab7597 100644
--- a/src/mesa/drivers/osmesa/osmesa.c
+++ b/src/mesa/drivers/osmesa/osmesa.c
@@ -1,4 +1,4 @@
-/* $Id: osmesa.c,v 1.85 2002/06/30 16:07:18 brianp Exp $ */
+/* $Id: osmesa.c,v 1.86 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -721,14 +721,7 @@ do {									\
 
 
 
-static void set_draw_buffer( GLcontext *ctx, GLenum mode )
-{
-   (void) ctx;
-   (void) mode;
-}
-
-
-static void set_read_buffer( GLcontext *ctx, GLframebuffer *buffer, GLenum mode )
+static void set_buffer( GLcontext *ctx, GLframebuffer *buffer, GLenum mode )
 {
    /* separate read buffer not supported */
    ASSERT(buffer == ctx->DrawBuffer);
@@ -1887,7 +1880,6 @@ static void smooth_rgba_z_triangle( GLcontext *ctx,
                                     const SWvertex *v2 )
 {
    const OSMesaContext osmesa = OSMESA_CONTEXT(ctx);
-
 #define INTERP_Z 1
 #define DEPTH_TYPE DEFAULT_SOFTWARE_DEPTH_TYPE
 #define INTERP_RGB 1
@@ -1903,7 +1895,7 @@ static void smooth_rgba_z_triangle( GLcontext *ctx,
             FixedToChan(span->alpha));				\
          zRow[i] = z;						\
       }								\
-      span->red += span->redStep;					\
+      span->red += span->redStep;				\
       span->green += span->greenStep;				\
       span->blue += span->blueStep;				\
       span->alpha += span->alphaStep;				\
@@ -2080,7 +2072,6 @@ static void osmesa_update_state( GLcontext *ctx, GLuint new_state )
 
    ctx->Driver.GetString = get_string;
    ctx->Driver.UpdateState = osmesa_update_state;
-   ctx->Driver.SetDrawBuffer = set_draw_buffer;
    ctx->Driver.ResizeBuffers = _swrast_alloc_buffers;
    ctx->Driver.GetBufferSize = buffer_size;
 
@@ -2090,6 +2081,7 @@ static void osmesa_update_state( GLcontext *ctx, GLuint new_state )
    ctx->Driver.CopyPixels = _swrast_CopyPixels;
    ctx->Driver.DrawPixels = _swrast_DrawPixels;
    ctx->Driver.ReadPixels = _swrast_ReadPixels;
+   ctx->Driver.DrawBuffer = _swrast_DrawBuffer;
 
    ctx->Driver.ChooseTextureFormat = _mesa_choose_tex_format;
    ctx->Driver.TexImage1D = _mesa_store_teximage1d;
@@ -2114,6 +2106,8 @@ static void osmesa_update_state( GLcontext *ctx, GLuint new_state )
    ctx->Driver.CompressedTextureSize = _mesa_compressed_texture_size;
    ctx->Driver.GetCompressedTexImage = _mesa_get_compressed_teximage;
 
+   swdd->SetBuffer = set_buffer;
+
    /* RGB(A) span/pixel functions */
    if (osmesa->format == OSMESA_RGB) {
       swdd->WriteRGBASpan = write_rgba_span_RGB;
@@ -2171,8 +2165,6 @@ static void osmesa_update_state( GLcontext *ctx, GLuint new_state )
    swdd->ReadCI32Span = read_index_span;
    swdd->ReadCI32Pixels = read_index_pixels;
 
-   swdd->SetReadBuffer = set_read_buffer;
-
    tnl->Driver.RunPipeline = _tnl_run_pipeline;
 
    _swrast_InvalidateState( ctx, new_state );
diff --git a/src/mesa/drivers/svga/svgamesa.c b/src/mesa/drivers/svga/svgamesa.c
index 5d2e3d55a2..270455ee69 100644
--- a/src/mesa/drivers/svga/svgamesa.c
+++ b/src/mesa/drivers/svga/svgamesa.c
@@ -1,4 +1,4 @@
-/* $Id: svgamesa.c,v 1.19 2002/06/15 02:38:17 brianp Exp $ */
+/* $Id: svgamesa.c,v 1.20 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -217,34 +217,9 @@ static void get_buffer_size( GLframebuffer *buffer, GLuint *width, GLuint *heigh
    *height = SVGAMesa->height = vga_getydim();
 }
 
-static void set_draw_buffer( GLcontext *ctx, GLenum buffer )
-{
-   if (buffer == GL_FRONT_LEFT) {
-      SVGABuffer.DrawBuffer = SVGABuffer.FrontBuffer;
-#if 0
-      /*    vga_waitretrace(); */
-      void * tmpptr;
-      copy_buffer(SVGABuffer.FrontBuffer);
-      tmpptr=SVGABuffer.BackBuffer;
-      SVGABuffer.BackBuffer=SVGABuffer.FrontBuffer;
-      SVGABuffer.FrontBuffer=tmpptr;
-#endif
-   }
-   else if (buffer == GL_BACK_LEFT) {
-      SVGABuffer.DrawBuffer = SVGABuffer.BackBuffer;
-#if 0
-      /*    vga_waitretrace(); */
-      copy_buffer(SVGABuffer.BackBuffer);
-#endif
-   }
-   else {
-      /* nothing since we don't have any point/line/triangle functions. */
-   }
-}
 
-
-static void set_read_buffer( GLcontext *ctx, GLframebuffer *colorBuffer,
-                             GLenum buffer )
+static void set_buffer( GLcontext *ctx, GLframebuffer *colorBuffer,
+                        GLenum buffer )
 {
    /* We can ignore colorBuffer since we don't support a MakeCurrentRead()
     * function.
@@ -253,6 +228,7 @@ static void set_read_buffer( GLcontext *ctx, GLframebuffer *colorBuffer,
 
    if (buffer == GL_FRONT_LEFT) {
       SVGABuffer.ReadBuffer = SVGABuffer.FrontBuffer;
+      SVGABuffer.DrawBuffer = SVGABuffer.FrontBuffer;
 #if 0
       void * tmpptr;
       /*    vga_waitretrace(); */
@@ -264,6 +240,7 @@ static void set_read_buffer( GLcontext *ctx, GLframebuffer *colorBuffer,
    }
    else if (buffer == GL_BACK_LEFT) {
       SVGABuffer.ReadBuffer = SVGABuffer.BackBuffer;
+      SVGABuffer.DrawBuffer = SVGABuffer.BackBuffer;
 #if 0
       /*    vga_waitretrace(); */
       copy_buffer(SVGABuffer.BackBuffer);
@@ -285,7 +262,6 @@ static void svgamesa_update_state( GLcontext *ctx, GLuint new_state )
    ctx->Driver.UpdateState = svgamesa_update_state;
 
    ctx->Driver.GetBufferSize = get_buffer_size;
-   ctx->Driver.SetDrawBuffer = set_draw_buffer;
    ctx->Driver.ResizeBuffers = _swrast_alloc_buffers;
 
    /* Software rasterizer pixel paths:
@@ -295,10 +271,11 @@ static void svgamesa_update_state( GLcontext *ctx, GLuint new_state )
    ctx->Driver.CopyPixels = _swrast_CopyPixels;
    ctx->Driver.DrawPixels = _swrast_DrawPixels;
    ctx->Driver.ReadPixels = _swrast_ReadPixels;
+   ctx->Driver.DrawBuffer = _swrast_DrawBuffer;
 
    /* Fill in the swrast driver interface:
     */
-   swdd->SetReadBuffer = set_read_buffer;
+   swdd->SetBuffer = set_buffer;
 
    switch (SVGABuffer.Depth) {
     case  8: ctx->Driver.ClearIndex = __clear_index8;
diff --git a/src/mesa/drivers/windows/wmesa.c b/src/mesa/drivers/windows/wmesa.c
index 09fa23737f..35a670096a 100644
--- a/src/mesa/drivers/windows/wmesa.c
+++ b/src/mesa/drivers/windows/wmesa.c
@@ -1,4 +1,4 @@
-/* $Id: wmesa.c,v 1.31 2002/06/15 03:03:10 brianp Exp $ */
+/* $Id: wmesa.c,v 1.32 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Windows (Win32) device driver for Mesa 3.4
@@ -569,20 +569,12 @@ static void enable( GLcontext* ctx, GLenum pname, GLboolean enable )
   }
 }
 
-static void set_draw_buffer( GLcontext* ctx, GLenum mode )
-{
-   /* XXX doing nothing for now */
-   /* if front buffer, fine */
-   /* if back buffer, fine */
-   /* else, check swrast->_RasterMask & MULTI_DRAW_BIT, if true, */
-   /* use a swrast fallback function */
-}
 
 
-static void set_read_buffer(GLcontext *ctx, GLframebuffer *colorBuffer,
-                            GLenum buffer )
+static void set_buffer(GLcontext *ctx, GLframebuffer *colorBuffer,
+                       GLenum buffer )
 {
-  /* XXX todo */
+  /* XXX todo - examine buffer and set read/write pointers */
   return;
 }
 
@@ -1027,7 +1019,6 @@ static void SetFunctionPointers(GLcontext *ctx)
   struct swrast_device_driver *swdd = _swrast_GetDeviceDriverReference( ctx );
   ctx->Driver.GetString = get_string;
   ctx->Driver.UpdateState = wmesa_update_state;
-  ctx->Driver.SetDrawBuffer = set_draw_buffer;
   ctx->Driver.ResizeBuffers = _swrast_alloc_buffers;
   ctx->Driver.GetBufferSize = buffer_size;
   
@@ -1043,6 +1034,7 @@ static void SetFunctionPointers(GLcontext *ctx)
   ctx->Driver.CopyPixels = _swrast_CopyPixels;
   ctx->Driver.DrawPixels = _swrast_DrawPixels;
   ctx->Driver.ReadPixels = _swrast_ReadPixels;
+  ctx->Driver.DrawBuffer = _swrast_DrawBuffer;
   
   ctx->Driver.ChooseTextureFormat = _mesa_choose_tex_format;
   ctx->Driver.TexImage1D = _mesa_store_teximage1d;
@@ -1068,7 +1060,7 @@ static void SetFunctionPointers(GLcontext *ctx)
   ctx->Driver.GetCompressedTexImage = _mesa_get_compressed_teximage;
   
   
-  swdd->SetReadBuffer = set_read_buffer;
+  swdd->SetBuffer = set_buffer;
   
   
   /* Pixel/span writing functions: */
@@ -1106,7 +1098,6 @@ static void wmesa_update_state( GLcontext *ctx, GLuint new_state )
 #if 0
   ctx->Driver.GetString = get_string;
   ctx->Driver.UpdateState = wmesa_update_state;
-  ctx->Driver.SetDrawBuffer = set_draw_buffer;
   ctx->Driver.ResizeBuffers = _swrast_alloc_buffers;
   ctx->Driver.GetBufferSize = buffer_size;
   
@@ -1145,10 +1136,8 @@ static void wmesa_update_state( GLcontext *ctx, GLuint new_state )
   ctx->Driver.BaseCompressedTexFormat = _mesa_base_compressed_texformat;
   ctx->Driver.CompressedTextureSize = _mesa_compressed_texture_size;
   ctx->Driver.GetCompressedTexImage = _mesa_get_compressed_teximage;
-  
-  
-  swdd->SetReadBuffer = set_read_buffer;
-  
+    
+  swdd->SetBuffer = set_buffer;
   
   /* Pixel/span writing functions: */
   swdd->WriteRGBASpan        = write_rgba_span;
diff --git a/src/mesa/drivers/x11/xm_api.c b/src/mesa/drivers/x11/xm_api.c
index 1ef83c12cf..4d74281bf9 100644
--- a/src/mesa/drivers/x11/xm_api.c
+++ b/src/mesa/drivers/x11/xm_api.c
@@ -1,4 +1,4 @@
-/* $Id: xm_api.c,v 1.39 2002/06/17 23:38:14 brianp Exp $ */
+/* $Id: xm_api.c,v 1.40 2002/07/09 01:22:51 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -1654,6 +1654,8 @@ XMesaContext XMesaCreateContext( XMesaVisual v, XMesaContext share_list )
    }
 
    c->xm_visual = v;
+   c->xm_draw_buffer = NULL;   /* set later by XMesaMakeCurrent */
+   c->xm_read_buffer = NULL;   /* set later by XMesaMakeCurrent */
    c->xm_buffer = NULL;   /* set later by XMesaMakeCurrent */
    c->display = v->display;
    c->pixelformat = v->dithered_pf;      /* Dithering is enabled by default */
@@ -1682,8 +1684,8 @@ XMesaContext XMesaCreateContext( XMesaVisual v, XMesaContext share_list )
 void XMesaDestroyContext( XMesaContext c )
 {
 #ifdef FX
-   if (c->xm_buffer && c->xm_buffer->FXctx)
-      fxMesaDestroyContext(c->xm_buffer->FXctx);
+   if (c->xm_draw_buffer && c->xm_buffer->FXctx)
+      fxMesaDestroyContext(c->xm_draw_buffer->FXctx);
 #endif
    if (c->gl_ctx) {
       _swsetup_DestroyContext( c->gl_ctx );
@@ -2045,24 +2047,24 @@ GLboolean XMesaMakeCurrent2( XMesaContext c, XMesaBuffer drawBuffer,
       if (drawBuffer->FXctx) {
          fxMesaMakeCurrent(drawBuffer->FXctx);
 
-         c->xm_buffer = drawBuffer;
+         c->xm_draw_buffer = drawBuffer;
          c->xm_read_buffer = readBuffer;
-         c->use_read_buffer = (drawBuffer != readBuffer);
+         c->xm_buffer = drawBuffer;
 
          return GL_TRUE;
       }
 #endif
       if (c->gl_ctx == _mesa_get_current_context()
-          && c->xm_buffer == drawBuffer
+          && c->xm_draw_buffer == drawBuffer
           && c->xm_read_buffer == readBuffer
-          && c->xm_buffer->wasCurrent) {
+          && c->xm_draw_buffer->wasCurrent) {
          /* same context and buffer, do nothing */
          return GL_TRUE;
       }
 
-      c->xm_buffer = drawBuffer;
+      c->xm_draw_buffer = drawBuffer;
       c->xm_read_buffer = readBuffer;
-      c->use_read_buffer = (drawBuffer != readBuffer);
+      c->xm_buffer = drawBuffer;
 
       _mesa_make_current2(c->gl_ctx,
                           &drawBuffer->mesa_buffer,
@@ -2086,11 +2088,11 @@ GLboolean XMesaMakeCurrent2( XMesaContext c, XMesaBuffer drawBuffer,
                                                c->clearcolor[2],
                                                c->clearcolor[3],
                                                c->xm_visual->undithered_pf);
-         XMesaSetForeground(c->display, c->xm_buffer->cleargc, c->clearpixel);
+         XMesaSetForeground(c->display, c->xm_draw_buffer->cleargc, c->clearpixel);
       }
 
       /* Solution to Stephane Rehel's problem with glXReleaseBuffersMESA(): */
-      c->xm_buffer->wasCurrent = GL_TRUE;
+      c->xm_draw_buffer->wasCurrent = GL_TRUE;
    }
    else {
       /* Detach */
@@ -2128,7 +2130,7 @@ XMesaBuffer XMesaGetCurrentBuffer( void )
    GET_CURRENT_CONTEXT(ctx);
    if (ctx) {
       XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-      return xmesa->xm_buffer;
+      return xmesa->xm_draw_buffer;
    }
    else {
       return 0;
@@ -2142,7 +2144,7 @@ XMesaBuffer XMesaGetCurrentReadBuffer( void )
    GET_CURRENT_CONTEXT(ctx);
    if (ctx) {
       XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-      return xmesa->xm_buffer;
+      return xmesa->xm_read_buffer;
    }
    else {
       return 0;
@@ -2154,7 +2156,7 @@ GLboolean XMesaForceCurrent(XMesaContext c)
 {
    if (c) {
       if (c->gl_ctx != _mesa_get_current_context()) {
-	 _mesa_make_current(c->gl_ctx, &c->xm_buffer->mesa_buffer);
+	 _mesa_make_current(c->gl_ctx, &c->xm_draw_buffer->mesa_buffer);
       }
    }
    else {
@@ -2193,15 +2195,15 @@ GLboolean XMesaSetFXmode( GLint mode )
       if (ctx) {
          XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
          if (mode == XMESA_FX_WINDOW) {
-	    if (xmesa->xm_buffer->FXisHackUsable) {
+	    if (xmesa->xm_draw_buffer->FXisHackUsable) {
 	       FX_grSstControl(GR_CONTROL_DEACTIVATE);
-	       xmesa->xm_buffer->FXwindowHack = GL_TRUE;
+	       xmesa->xm_draw_buffer->FXwindowHack = GL_TRUE;
 	       return GL_TRUE;
 	    }
 	 }
 	 else if (mode == XMESA_FX_FULLSCREEN) {
 	    FX_grSstControl(GR_CONTROL_ACTIVATE);
-	    xmesa->xm_buffer->FXwindowHack = GL_FALSE;
+	    xmesa->xm_draw_buffer->FXwindowHack = GL_FALSE;
 	    return GL_TRUE;
 	 }
 	 else {
@@ -2232,7 +2234,7 @@ static void FXgetImage( XMesaBuffer b )
    unsigned int bw, depth, width, height;
    XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
 
-   assert(xmesa->xm_buffer->FXctx);
+   assert(xmesa->xm_draw_buffer->FXctx);
 
 #ifdef XFree86Server
    x = b->frontbuffer->x;
@@ -2245,8 +2247,8 @@ static void FXgetImage( XMesaBuffer b )
                  &root, &xpos, &ypos, &width, &height, &bw, &depth);
 #endif
    if (b->width != width || b->height != height) {
-      b->width = MIN2((int)width, xmesa->xm_buffer->FXctx->width);
-      b->height = MIN2((int)height, xmesa->xm_buffer->FXctx->height);
+      b->width = MIN2((int)width, xmesa->xm_draw_buffer->FXctx->width);
+      b->height = MIN2((int)height, xmesa->xm_draw_buffer->FXctx->height);
       if (b->width & 1)
          b->width--;  /* prevent odd width */
       xmesa_alloc_back_buffer( b );
@@ -2256,7 +2258,7 @@ static void FXgetImage( XMesaBuffer b )
    if (xmesa->xm_visual->undithered_pf==PF_5R6G5B) {
       /* Special case: 16bpp RGB */
       grLfbReadRegion( GR_BUFFER_FRONTBUFFER,       /* src buffer */
-                       0, xmesa->xm_buffer->FXctx->height - b->height,  /*pos*/
+                       0, xmesa->xm_draw_buffer->FXctx->height - b->height,  /*pos*/
                        b->width, b->height,         /* size */
                        b->width * sizeof(GLushort), /* stride */
                        b->backimage->data);         /* dest buffer */
@@ -2265,13 +2267,13 @@ static void FXgetImage( XMesaBuffer b )
 	    && GET_VISUAL_DEPTH(xmesa->xm_visual)==8) {
       /* Special case: 8bpp RGB */
       for (y=0;y<b->height;y++) {
-         GLubyte *ptr = (GLubyte*) xmesa->xm_buffer->backimage->data
-                        + xmesa->xm_buffer->backimage->bytes_per_line * y;
+         GLubyte *ptr = (GLubyte*) xmesa->xm_draw_buffer->backimage->data
+                        + xmesa->xm_draw_buffer->backimage->bytes_per_line * y;
          XDITHER_SETUP(y);
 
          /* read row from 3Dfx frame buffer */
          grLfbReadRegion( GR_BUFFER_FRONTBUFFER,
-                          0, xmesa->xm_buffer->FXctx->height-(b->height-y),
+                          0, xmesa->xm_draw_buffer->FXctx->height-(b->height-y),
                           b->width, 1,
                           0,
                           pixbuf );
@@ -2290,7 +2292,7 @@ static void FXgetImage( XMesaBuffer b )
       for (y=0;y<b->height;y++) {
          /* read row from 3Dfx frame buffer */
          grLfbReadRegion( GR_BUFFER_FRONTBUFFER,
-                          0, xmesa->xm_buffer->FXctx->height-(b->height-y),
+                          0, xmesa->xm_draw_buffer->FXctx->height-(b->height-y),
                           b->width, 1,
                           0,
                           pixbuf );
diff --git a/src/mesa/drivers/x11/xm_dd.c b/src/mesa/drivers/x11/xm_dd.c
index c10afede92..8aa10ae805 100644
--- a/src/mesa/drivers/x11/xm_dd.c
+++ b/src/mesa/drivers/x11/xm_dd.c
@@ -1,4 +1,4 @@
-/* $Id: xm_dd.c,v 1.33 2002/06/19 21:49:37 brianp Exp $ */
+/* $Id: xm_dd.c,v 1.34 2002/07/09 01:22:52 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -116,74 +116,51 @@ flush( GLcontext *ctx )
 }
 
 
-static void
-set_draw_buffer( GLcontext *ctx, GLenum mode )
-{
-   const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-   if (mode == GL_FRONT_LEFT) {
-      /* write to front buffer */
-      xmesa->xm_buffer->buffer = xmesa->xm_buffer->frontbuffer;
-      xmesa_update_span_funcs(ctx);
-   }
-   else if (mode==GL_BACK_LEFT && xmesa->xm_buffer->db_state) {
-      /* write to back buffer */
-      if (xmesa->xm_buffer->backpixmap) {
-         xmesa->xm_buffer->buffer =
-	     (XMesaDrawable)xmesa->xm_buffer->backpixmap;
-      }
-      else if (xmesa->xm_buffer->backimage) {
-         xmesa->xm_buffer->buffer = None;
-      }
-      else {
-         /* just in case there wasn't enough memory for back buffer */
-         xmesa->xm_buffer->buffer = xmesa->xm_buffer->frontbuffer;
-      }
-      xmesa_update_span_funcs(ctx);
-   }
-   else {
-      /* the swrast->_RasterMask MULTI_DRAW_BIT will be set and
-       * we'll fall back to swrast to draw points/lines/triangles.
-       */
-   }
-}
 
-
-void
-xmesa_set_read_buffer( GLcontext *ctx, GLframebuffer *buffer, GLenum mode )
+/*
+ * This chooses the color buffer for reading and writing spans, points,
+ * lines, and triangles.
+ */
+static void
+set_buffer( GLcontext *ctx, GLframebuffer *buffer, GLenum mode )
 {
-   XMesaBuffer target;
+   /* We can make this cast since the XMesaBuffer wraps GLframebuffer.
+    * GLframebuffer is the first member in a XMesaBuffer struct.
+    */
+   XMesaBuffer target = (XMesaBuffer) buffer;
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
 
-   if (buffer == ctx->DrawBuffer) {
-      target = xmesa->xm_buffer;
-      xmesa->use_read_buffer = GL_FALSE;
-   }
-   else {
-      ASSERT(buffer == ctx->ReadBuffer);
-      target = xmesa->xm_read_buffer;
-      xmesa->use_read_buffer = GL_TRUE;
-   }
+   /* This assignment tells the span/point/line/triangle functions
+    * which XMesaBuffer to use.
+    */
+   xmesa->xm_buffer = target;
 
+   /*
+    * Now determine front vs back color buffer.
+    */
    if (mode == GL_FRONT_LEFT) {
       target->buffer = target->frontbuffer;
-      xmesa_update_span_funcs(ctx);
    }
-   else if (mode==GL_BACK_LEFT && xmesa->xm_read_buffer->db_state) {
+   else if (mode == GL_BACK_LEFT) {
+      ASSERT(target->db_state);
       if (target->backpixmap) {
-         target->buffer = (XMesaDrawable)xmesa->xm_buffer->backpixmap;
+         /* back buffer is a pixmape */
+         target->buffer = target->backpixmap;
       }
       else if (target->backimage) {
+         /* back buffer is an XImage */
          target->buffer = None;
       }
       else {
-         /* just in case there wasn't enough memory for back buffer */
+         /* No back buffer!!!!  Must be out of memory, use front buffer */
          target->buffer = target->frontbuffer;
       }
-      xmesa_update_span_funcs(ctx);
    }
    else {
-      _mesa_problem(ctx, "invalid buffer in set_read_buffer() in xmesa2.c");
+      _mesa_problem(ctx, "invalid buffer in set_buffer() in xmesa2.c");
+      return;
    }
+   xmesa_update_span_funcs(ctx);
 }
 
 
@@ -193,7 +170,7 @@ clear_index( GLcontext *ctx, GLuint index )
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    xmesa->clearpixel = (unsigned long) index;
-   XMesaSetForeground( xmesa->display, xmesa->xm_buffer->cleargc,
+   XMesaSetForeground( xmesa->display, xmesa->xm_draw_buffer->cleargc,
                        (unsigned long) index );
 }
 
@@ -210,7 +187,7 @@ clear_color( GLcontext *ctx, const GLchan color[4] )
                                              color[2], color[3],
                                              xmesa->xm_visual->undithered_pf );
    _glthread_LOCK_MUTEX(_xmesa_lock);
-   XMesaSetForeground( xmesa->display, xmesa->xm_buffer->cleargc,
+   XMesaSetForeground( xmesa->display, xmesa->xm_draw_buffer->cleargc,
                        xmesa->clearpixel );
    _glthread_UNLOCK_MUTEX(_xmesa_lock);
 }
@@ -222,7 +199,7 @@ static void
 index_mask( GLcontext *ctx, GLuint mask )
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-   if (xmesa->xm_buffer->buffer != XIMAGE) {
+   if (xmesa->xm_draw_buffer->buffer != XIMAGE) {
       unsigned long m;
       if (mask==0xffffffff) {
 	 m = ((unsigned long)~0L);
@@ -230,7 +207,7 @@ index_mask( GLcontext *ctx, GLuint mask )
       else {
          m = (unsigned long) mask;
       }
-      XMesaSetPlaneMask( xmesa->display, xmesa->xm_buffer->cleargc, m );
+      XMesaSetPlaneMask( xmesa->display, xmesa->xm_draw_buffer->cleargc, m );
    }
 }
 
@@ -255,7 +232,7 @@ color_mask(GLcontext *ctx,
          if (gmask)   m |= GET_GREENMASK(xmesa->xm_visual);
          if (bmask)   m |= GET_BLUEMASK(xmesa->xm_visual);
       }
-      XMesaSetPlaneMask( xmesa->display, xmesa->xm_buffer->cleargc, m );
+      XMesaSetPlaneMask( xmesa->display, xmesa->xm_draw_buffer->cleargc, m );
    }
 }
 
@@ -272,16 +249,16 @@ clear_front_pixmap( GLcontext *ctx, GLboolean all,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    if (all) {
-      XMesaFillRectangle( xmesa->display, xmesa->xm_buffer->frontbuffer,
-                          xmesa->xm_buffer->cleargc,
+      XMesaFillRectangle( xmesa->display, xmesa->xm_draw_buffer->frontbuffer,
+                          xmesa->xm_draw_buffer->cleargc,
                           0, 0,
-                          xmesa->xm_buffer->width+1,
-                          xmesa->xm_buffer->height+1 );
+                          xmesa->xm_draw_buffer->width+1,
+                          xmesa->xm_draw_buffer->height+1 );
    }
    else {
-      XMesaFillRectangle( xmesa->display, xmesa->xm_buffer->frontbuffer,
-                          xmesa->xm_buffer->cleargc,
-                          x, xmesa->xm_buffer->height - y - height,
+      XMesaFillRectangle( xmesa->display, xmesa->xm_draw_buffer->frontbuffer,
+                          xmesa->xm_draw_buffer->cleargc,
+                          x, xmesa->xm_draw_buffer->height - y - height,
                           width, height );
    }
 }
@@ -293,16 +270,16 @@ clear_back_pixmap( GLcontext *ctx, GLboolean all,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    if (all) {
-      XMesaFillRectangle( xmesa->display, xmesa->xm_buffer->backpixmap,
-                          xmesa->xm_buffer->cleargc,
+      XMesaFillRectangle( xmesa->display, xmesa->xm_draw_buffer->backpixmap,
+                          xmesa->xm_draw_buffer->cleargc,
                           0, 0,
-                          xmesa->xm_buffer->width+1,
-                          xmesa->xm_buffer->height+1 );
+                          xmesa->xm_draw_buffer->width+1,
+                          xmesa->xm_draw_buffer->height+1 );
    }
    else {
-      XMesaFillRectangle( xmesa->display, xmesa->xm_buffer->backpixmap,
-                          xmesa->xm_buffer->cleargc,
-                          x, xmesa->xm_buffer->height - y - height,
+      XMesaFillRectangle( xmesa->display, xmesa->xm_draw_buffer->backpixmap,
+                          xmesa->xm_draw_buffer->cleargc,
+                          x, xmesa->xm_draw_buffer->height - y - height,
                           width, height );
    }
 }
@@ -314,14 +291,14 @@ clear_8bit_ximage( GLcontext *ctx, GLboolean all,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    if (all) {
-      size_t n = xmesa->xm_buffer->backimage->bytes_per_line
-         * xmesa->xm_buffer->backimage->height;
-      MEMSET( xmesa->xm_buffer->backimage->data, xmesa->clearpixel, n );
+      size_t n = xmesa->xm_draw_buffer->backimage->bytes_per_line
+         * xmesa->xm_draw_buffer->backimage->height;
+      MEMSET( xmesa->xm_draw_buffer->backimage->data, xmesa->clearpixel, n );
    }
    else {
       GLint i;
       for (i=0;i<height;i++) {
-         GLubyte *ptr = PIXELADDR1( xmesa->xm_buffer, x, y+i );
+         GLubyte *ptr = PIXELADDR1( xmesa->xm_draw_buffer, x, y+i );
          MEMSET( ptr, xmesa->clearpixel, width );
       }
    }
@@ -334,9 +311,9 @@ clear_HPCR_ximage( GLcontext *ctx, GLboolean all,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    if (all) {
-      GLint i, c16 = (xmesa->xm_buffer->backimage->bytes_per_line>>4)<<4;
-      GLubyte *ptr  = (GLubyte *)xmesa->xm_buffer->backimage->data;
-      for (i=0; i<xmesa->xm_buffer->backimage->height; i++) {
+      GLint i, c16 = (xmesa->xm_draw_buffer->backimage->bytes_per_line>>4)<<4;
+      GLubyte *ptr  = (GLubyte *)xmesa->xm_draw_buffer->backimage->data;
+      for (i=0; i<xmesa->xm_draw_buffer->backimage->height; i++) {
          GLint j;
          GLubyte *sptr = xmesa->xm_visual->hpcr_clear_ximage_pattern[0];
          if (i&1) {
@@ -361,7 +338,7 @@ clear_HPCR_ximage( GLcontext *ctx, GLboolean all,
             ptr[15] = sptr[15];
             ptr += 16;
          }
-         for (; j<xmesa->xm_buffer->backimage->bytes_per_line; j++) {
+         for (; j<xmesa->xm_draw_buffer->backimage->bytes_per_line; j++) {
             *ptr = sptr[j&15];
             ptr++;
          }
@@ -370,7 +347,7 @@ clear_HPCR_ximage( GLcontext *ctx, GLboolean all,
    else {
       GLint i;
       for (i=y; i<y+height; i++) {
-         GLubyte *ptr = PIXELADDR1( xmesa->xm_buffer, x, i );
+         GLubyte *ptr = PIXELADDR1( xmesa->xm_draw_buffer, x, i );
          int j;
          GLubyte *sptr = xmesa->xm_visual->hpcr_clear_ximage_pattern[0];
          if (i&1) {
@@ -396,31 +373,31 @@ clear_16bit_ximage( GLcontext *ctx, GLboolean all,
    }
    if (all) {
       register GLuint n;
-      register GLuint *ptr4 = (GLuint *) xmesa->xm_buffer->backimage->data;
+      register GLuint *ptr4 = (GLuint *) xmesa->xm_draw_buffer->backimage->data;
       if ((pixel & 0xff) == ((pixel >> 8) & 0xff)) {
          /* low and high bytes are equal so use memset() */
-         n = xmesa->xm_buffer->backimage->bytes_per_line
-            * xmesa->xm_buffer->height;
+         n = xmesa->xm_draw_buffer->backimage->bytes_per_line
+            * xmesa->xm_draw_buffer->height;
          MEMSET( ptr4, pixel & 0xff, n );
       }
       else {
          pixel = pixel | (pixel<<16);
-         n = xmesa->xm_buffer->backimage->bytes_per_line
-            * xmesa->xm_buffer->height / 4;
+         n = xmesa->xm_draw_buffer->backimage->bytes_per_line
+            * xmesa->xm_draw_buffer->height / 4;
          do {
             *ptr4++ = pixel;
                n--;
          } while (n!=0);
 
-         if ((xmesa->xm_buffer->backimage->bytes_per_line *
-              xmesa->xm_buffer->height) & 0x2)
+         if ((xmesa->xm_draw_buffer->backimage->bytes_per_line *
+              xmesa->xm_draw_buffer->height) & 0x2)
             *(GLushort *)ptr4 = pixel & 0xffff;
       }
    }
    else {
       register int i, j;
       for (j=0;j<height;j++) {
-         register GLushort *ptr2 = PIXELADDR2( xmesa->xm_buffer, x, y+j );
+         register GLushort *ptr2 = PIXELADDR2( xmesa->xm_draw_buffer, x, y+j );
          for (i=0;i<width;i++) {
             *ptr2++ = pixel;
          }
@@ -449,21 +426,21 @@ clear_24bit_ximage( GLcontext *ctx, GLboolean all,
    if (all) {
       if (r==g && g==b) {
          /* same value for all three components (gray) */
-         const GLint w3 = xmesa->xm_buffer->width * 3;
-         const GLint h = xmesa->xm_buffer->height;
+         const GLint w3 = xmesa->xm_draw_buffer->width * 3;
+         const GLint h = xmesa->xm_draw_buffer->height;
          GLint i;
          for (i = 0; i < h; i++) {
-            bgr_t *ptr3 = PIXELADDR3(xmesa->xm_buffer, 0, i);
+            bgr_t *ptr3 = PIXELADDR3(xmesa->xm_draw_buffer, 0, i);
             MEMSET(ptr3, r, w3);
          }
       }
       else {
          /* the usual case */
-         const GLint w = xmesa->xm_buffer->width;
-         const GLint h = xmesa->xm_buffer->height;
+         const GLint w = xmesa->xm_draw_buffer->width;
+         const GLint h = xmesa->xm_draw_buffer->height;
          GLint i, j;
          for (i = 0; i < h; i++) {
-            bgr_t *ptr3 = PIXELADDR3(xmesa->xm_buffer, 0, i);
+            bgr_t *ptr3 = PIXELADDR3(xmesa->xm_draw_buffer, 0, i);
             for (j = 0; j < w; j++) {
                ptr3->r = r;
                ptr3->g = g;
@@ -547,7 +524,7 @@ clear_24bit_ximage( GLcontext *ctx, GLboolean all,
          /* same value for all three components (gray) */
          GLint j;
          for (j=0;j<height;j++) {
-            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_buffer, x, y+j );
+            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_draw_buffer, x, y+j );
             MEMSET(ptr3, r, 3 * width);
          }
       }
@@ -555,7 +532,7 @@ clear_24bit_ximage( GLcontext *ctx, GLboolean all,
          /* non-gray clear color */
          GLint i, j;
          for (j = 0; j < height; j++) {
-            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_buffer, x, y+j );
+            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_draw_buffer, x, y+j );
             for (i = 0; i < width; i++) {
                ptr3->r = r;
                ptr3->g = g;
@@ -570,7 +547,7 @@ clear_24bit_ximage( GLcontext *ctx, GLboolean all,
          pixel4[1] = (clearPixel << 16) | (clearPixel >> 8);
          pixel4[2] = (clearPixel << 8) | (clearPixel >>  16);
          for (j=0;j<height;j++) {
-            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_buffer, x, y+j );
+            bgr_t *ptr3 = PIXELADDR3( xmesa->xm_draw_buffer, x, y+j );
             register GLuint *ptr4 = (GLuint *)ptr3;
             register GLuint *p, px;
             GLuint w = width;
@@ -653,8 +630,8 @@ clear_32bit_ximage( GLcontext *ctx, GLboolean all,
             | ((pixel << 24) & 0xff000000);
    }
    if (all) {
-      register GLint n = xmesa->xm_buffer->width * xmesa->xm_buffer->height;
-      register GLuint *ptr4 = (GLuint *) xmesa->xm_buffer->backimage->data;
+      register GLint n = xmesa->xm_draw_buffer->width * xmesa->xm_draw_buffer->height;
+      register GLuint *ptr4 = (GLuint *) xmesa->xm_draw_buffer->backimage->data;
       if (pixel==0) {
          MEMSET( ptr4, pixel, 4*n );
       }
@@ -668,7 +645,7 @@ clear_32bit_ximage( GLcontext *ctx, GLboolean all,
    else {
       register int i, j;
       for (j=0;j<height;j++) {
-         register GLuint *ptr4 = PIXELADDR4( xmesa->xm_buffer, x, y+j );
+         register GLuint *ptr4 = PIXELADDR4( xmesa->xm_draw_buffer, x, y+j );
          for (i=0;i<width;i++) {
             *ptr4++ = pixel;
          }
@@ -682,11 +659,11 @@ clear_nbit_ximage( GLcontext *ctx, GLboolean all,
                    GLint x, GLint y, GLint width, GLint height )
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-   XMesaImage *img = xmesa->xm_buffer->backimage;
+   XMesaImage *img = xmesa->xm_draw_buffer->backimage;
    if (all) {
       register int i, j;
-      width = xmesa->xm_buffer->width;
-      height = xmesa->xm_buffer->height;
+      width = xmesa->xm_draw_buffer->width;
+      height = xmesa->xm_draw_buffer->height;
       for (j=0;j<height;j++) {
          for (i=0;i<width;i++) {
             XMesaPutPixel( img, i, j, xmesa->clearpixel );
@@ -696,7 +673,7 @@ clear_nbit_ximage( GLcontext *ctx, GLboolean all,
    else {
       /* TODO: optimize this */
       register int i, j;
-      y = FLIP(xmesa->xm_buffer, y);
+      y = FLIP(xmesa->xm_draw_buffer, y);
       for (j=0;j<height;j++) {
          for (i=0;i<width;i++) {
             XMesaPutPixel( img, x+i, y-j, xmesa->clearpixel );
@@ -715,7 +692,7 @@ clear_buffers( GLcontext *ctx, GLbitfield mask,
    const GLuint *colorMask = (GLuint *) &ctx->Color.ColorMask;
 
    if ((mask & (DD_FRONT_LEFT_BIT | DD_BACK_LEFT_BIT)) &&
-       xmesa->xm_buffer->mesa_buffer.UseSoftwareAlphaBuffers &&
+       xmesa->xm_draw_buffer->mesa_buffer.UseSoftwareAlphaBuffers &&
        ctx->Color.ColorMask[ACOMP]) {
       _mesa_clear_alpha_buffers(ctx);
    }
@@ -723,13 +700,13 @@ clear_buffers( GLcontext *ctx, GLbitfield mask,
    /* we can't handle color or index masking */
    if (*colorMask == 0xffffffff && ctx->Color.IndexMask == 0xffffffff) {
       if (mask & DD_FRONT_LEFT_BIT) {
-	 ASSERT(xmesa->xm_buffer->front_clear_func);
-	 (*xmesa->xm_buffer->front_clear_func)( ctx, all, x, y, width, height );
+	 ASSERT(xmesa->xm_draw_buffer->front_clear_func);
+	 (*xmesa->xm_draw_buffer->front_clear_func)( ctx, all, x, y, width, height );
 	 mask &= ~DD_FRONT_LEFT_BIT;
       }
       if (mask & DD_BACK_LEFT_BIT) {
-	 ASSERT(xmesa->xm_buffer->back_clear_func);
-	 (*xmesa->xm_buffer->back_clear_func)( ctx, all, x, y, width, height );
+	 ASSERT(xmesa->xm_draw_buffer->back_clear_func);
+	 (*xmesa->xm_draw_buffer->back_clear_func)( ctx, all, x, y, width, height );
 	 mask &= ~DD_BACK_LEFT_BIT;
       }
    }
@@ -802,8 +779,8 @@ drawpixels_8R8G8B( GLcontext *ctx,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    XMesaDisplay *dpy = xmesa->xm_visual->display;
-   XMesaDrawable buffer = xmesa->xm_buffer->buffer;
-   XMesaGC gc = xmesa->xm_buffer->gc;
+   XMesaDrawable buffer = xmesa->xm_draw_buffer->buffer;
+   XMesaGC gc = xmesa->xm_draw_buffer->gc;
    assert(dpy);
    assert(buffer);
    assert(gc);
@@ -833,7 +810,7 @@ drawpixels_8R8G8B( GLcontext *ctx,
          ximage.red_mask   = 0xff0000;
          ximage.green_mask = 0x00ff00;
          ximage.blue_mask  = 0x0000ff;
-         dstY = FLIP(xmesa->xm_buffer,dstY) - height + 1;
+         dstY = FLIP(xmesa->xm_draw_buffer,dstY) - height + 1;
          XPutImage(dpy, buffer, gc, &ximage, srcX, srcY, dstX, dstY, w, h);
          return GL_TRUE;
       }
@@ -899,33 +876,33 @@ void xmesa_update_state( GLcontext *ctx, GLuint new_state )
 
 
    /* setup pointers to front and back buffer clear functions */
-   xmesa->xm_buffer->front_clear_func = clear_front_pixmap;
-   if (xmesa->xm_buffer->backpixmap != XIMAGE) {
-      xmesa->xm_buffer->back_clear_func = clear_back_pixmap;
+   xmesa->xm_draw_buffer->front_clear_func = clear_front_pixmap;
+   if (xmesa->xm_draw_buffer->backpixmap != XIMAGE) {
+      xmesa->xm_draw_buffer->back_clear_func = clear_back_pixmap;
    }
    else if (sizeof(GLushort)!=2 || sizeof(GLuint)!=4) {
-      xmesa->xm_buffer->back_clear_func = clear_nbit_ximage;
+      xmesa->xm_draw_buffer->back_clear_func = clear_nbit_ximage;
    }
    else switch (xmesa->xm_visual->BitsPerPixel) {
    case 8:
       if (xmesa->xm_visual->hpcr_clear_flag) {
-	 xmesa->xm_buffer->back_clear_func = clear_HPCR_ximage;
+	 xmesa->xm_draw_buffer->back_clear_func = clear_HPCR_ximage;
       }
       else {
-	 xmesa->xm_buffer->back_clear_func = clear_8bit_ximage;
+	 xmesa->xm_draw_buffer->back_clear_func = clear_8bit_ximage;
       }
       break;
    case 16:
-      xmesa->xm_buffer->back_clear_func = clear_16bit_ximage;
+      xmesa->xm_draw_buffer->back_clear_func = clear_16bit_ximage;
       break;
    case 24:
-      xmesa->xm_buffer->back_clear_func = clear_24bit_ximage;
+      xmesa->xm_draw_buffer->back_clear_func = clear_24bit_ximage;
       break;
    case 32:
-      xmesa->xm_buffer->back_clear_func = clear_32bit_ximage;
+      xmesa->xm_draw_buffer->back_clear_func = clear_32bit_ximage;
       break;
    default:
-      xmesa->xm_buffer->back_clear_func = clear_nbit_ximage;
+      xmesa->xm_draw_buffer->back_clear_func = clear_nbit_ximage;
       break;
    }
 
@@ -940,6 +917,7 @@ void xmesa_update_state( GLcontext *ctx, GLuint new_state )
 void xmesa_init_pointers( GLcontext *ctx )
 {
    TNLcontext *tnl;
+   struct swrast_device_driver *dd = _swrast_GetDeviceDriverReference( ctx );
 
    ctx->Driver.GetString = get_string;
    ctx->Driver.GetBufferSize = get_buffer_size;
@@ -955,6 +933,7 @@ void xmesa_init_pointers( GLcontext *ctx )
    ctx->Driver.CopyPixels = _swrast_CopyPixels;
    ctx->Driver.DrawPixels = _swrast_DrawPixels;
    ctx->Driver.ReadPixels = _swrast_ReadPixels;
+   ctx->Driver.DrawBuffer = _swrast_DrawBuffer;
 
    /* Software texture functions:
     */
@@ -987,7 +966,6 @@ void xmesa_init_pointers( GLcontext *ctx )
 
    /* Statechange callbacks:
     */
-   ctx->Driver.SetDrawBuffer = set_draw_buffer;
    ctx->Driver.ClearIndex = clear_index;
    ctx->Driver.ClearColor = clear_color;
    ctx->Driver.IndexMask = index_mask;
@@ -1000,6 +978,8 @@ void xmesa_init_pointers( GLcontext *ctx )
    tnl = TNL_CONTEXT(ctx);
    tnl->Driver.RunPipeline = _tnl_run_pipeline;
    
+   dd->SetBuffer = set_buffer;
+
    /* Install swsetup for tnl->Driver.Render.*:
     */
    _swsetup_Wakeup(ctx);
diff --git a/src/mesa/drivers/x11/xm_span.c b/src/mesa/drivers/x11/xm_span.c
index cbb138a0b3..eed8c91a96 100644
--- a/src/mesa/drivers/x11/xm_span.c
+++ b/src/mesa/drivers/x11/xm_span.c
@@ -1,4 +1,4 @@
-/* $Id: xm_span.c,v 1.14 2002/03/01 04:28:32 brianp Exp $ */
+/* $Id: xm_span.c,v 1.15 2002/07/09 01:22:52 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -3472,14 +3472,9 @@ static void read_index_span( const GLcontext *ctx,
 			     GLuint n, GLint x, GLint y, GLuint index[] )
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-   XMesaBuffer source;
+   XMesaBuffer source = xmesa->xm_buffer;
    GLuint i;
 
-   if (xmesa->use_read_buffer)
-      source = xmesa->xm_read_buffer;
-   else
-      source = xmesa->xm_buffer;
-
    y = FLIP(source, y);
 
    if (source->buffer) {
@@ -3528,12 +3523,7 @@ static void read_color_span( const GLcontext *ctx,
                              GLubyte rgba[][4] )
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
-   XMesaBuffer source;
-
-   if (xmesa->use_read_buffer)
-      source = xmesa->xm_read_buffer;
-   else
-      source = xmesa->xm_buffer;
+   XMesaBuffer source = xmesa->xm_buffer;
 
    if (source->buffer) {
       /* Read from Pixmap or Window */
@@ -3902,12 +3892,7 @@ static void read_index_pixels( const GLcontext *ctx,
 {
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    register GLuint i;
-   XMesaBuffer source;
-
-   if (xmesa->use_read_buffer)
-      source = xmesa->xm_read_buffer;
-   else
-      source = xmesa->xm_buffer;
+   XMesaBuffer source = xmesa->xm_buffer;
 
    if (source->buffer) {
       for (i=0;i<n;i++) {
@@ -3937,15 +3922,8 @@ static void read_color_pixels( const GLcontext *ctx,
    const XMesaContext xmesa = (XMesaContext) ctx->DriverCtx;
    XMesaDisplay *dpy = xmesa->xm_visual->display;
    register GLuint i;
-   XMesaBuffer source;
-   XMesaDrawable buffer;
-
-   if (xmesa->use_read_buffer)
-      source = xmesa->xm_read_buffer;
-   else
-      source = xmesa->xm_buffer;
-
-   buffer = source->buffer;  /* the X drawable */
+   XMesaBuffer source = xmesa->xm_buffer;
+   XMesaDrawable buffer = source->buffer;  /* the X drawable */
 
    if (source->buffer) {
       switch (xmesa->pixelformat) {
@@ -4491,6 +4469,4 @@ void xmesa_update_span_funcs( GLcontext *ctx )
    dd->ReadRGBASpan = read_color_span;
    dd->ReadCI32Pixels = read_index_pixels;
    dd->ReadRGBAPixels = read_color_pixels;
-
-   dd->SetReadBuffer = xmesa_set_read_buffer;
 }
diff --git a/src/mesa/drivers/x11/xmesaP.h b/src/mesa/drivers/x11/xmesaP.h
index ae90d99573..5e3ef9e8d9 100644
--- a/src/mesa/drivers/x11/xmesaP.h
+++ b/src/mesa/drivers/x11/xmesaP.h
@@ -1,4 +1,4 @@
-/* $Id: xmesaP.h,v 1.28 2002/05/27 17:06:59 brianp Exp $ */
+/* $Id: xmesaP.h,v 1.29 2002/07/09 01:22:52 brianp Exp $ */
 
 /*
  * Mesa 3-D graphics library
@@ -120,9 +120,9 @@ struct xmesa_visual {
 struct xmesa_context {
    GLcontext *gl_ctx;		/* the core library context */
    XMesaVisual xm_visual;	/* Describes the buffers */
-   XMesaBuffer xm_buffer;	/* current draw framebuffer */
+   XMesaBuffer xm_draw_buffer;	/* current draw framebuffer */
    XMesaBuffer xm_read_buffer;	/* current read framebuffer */
-   GLboolean use_read_buffer;	/* read from the xm_read_buffer/ */
+   XMesaBuffer xm_buffer;	/* current span/point/line/triangle buffer */
 
    XMesaDisplay *display;	/* == xm_visual->display */
    GLboolean swapbytes;		/* Host byte order != display byte order? */
@@ -149,6 +149,7 @@ typedef enum {
  */
 struct xmesa_buffer {
    GLframebuffer mesa_buffer;	/* depth, stencil, accum, etc buffers */
+				/* This MUST BE FIRST! */
    GLboolean wasCurrent;	/* was ever the current buffer? */
    XMesaVisual xm_visual;	/* the X/Mesa visual */
 
@@ -536,9 +537,6 @@ extern GLboolean XMesaForceCurrent(XMesaContext c);
 extern GLboolean XMesaLoseCurrent(XMesaContext c);
 extern void XMesaReset( void );
 
-extern void xmesa_set_read_buffer( GLcontext *ctx, 
-				   GLframebuffer *buffer, GLenum mode );
-
 extern void xmesa_resize_buffers( GLframebuffer *buffer );
 
 #endif