/*
 * Mesa 3-D graphics library
 * Version:  6.3
 *
 * Copyright (C) 1999-2004  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "glxheader.h"
#include "main/context.h"
#include "main/macros.h"
#include "main/imports.h"
#include "main/mtypes.h"
#include "xmesaP.h"

#include "swrast/swrast.h"


/*
 * The following functions are used to trap XGetImage() calls which
 * generate BadMatch errors if the drawable isn't mapped.
 */

static int caught_xgetimage_error = 0;
static int (*old_xerror_handler)( XMesaDisplay *dpy, XErrorEvent *ev );
static unsigned long xgetimage_serial;

/*
 * This is the error handler which will be called if XGetImage fails.
 */
static int xgetimage_error_handler( XMesaDisplay *dpy, XErrorEvent *ev )
{
   if (ev->serial==xgetimage_serial && ev->error_code==BadMatch) {
      /* caught the expected error */
      caught_xgetimage_error = 0;
   }
   else {
      /* call the original X error handler, if any.  otherwise ignore */
      if (old_xerror_handler) {
         (*old_xerror_handler)( dpy, ev );
      }
   }
   return 0;
}


/*
 * Call this right before XGetImage to setup error trap.
 */
static void catch_xgetimage_errors( XMesaDisplay *dpy )
{
   xgetimage_serial = NextRequest( dpy );
   old_xerror_handler = XSetErrorHandler( xgetimage_error_handler );
   caught_xgetimage_error = 0;
}


/*
 * Call this right after XGetImage to check if an error occured.
 */
static int check_xgetimage_errors( void )
{
   /* restore old handler */
   (void) XSetErrorHandler( old_xerror_handler );
   /* return 0=no error, 1=error caught */
   return caught_xgetimage_error;
}


/*
 * Read a pixel from an X drawable.
 */
static unsigned long read_pixel( XMesaDisplay *dpy,
                                 XMesaDrawable d, int x, int y )
{
   unsigned long p;
   XMesaImage *pixel = NULL;
   int error;

   catch_xgetimage_errors( dpy );
   pixel = XGetImage( dpy, d, x, y, 1, 1, AllPlanes, ZPixmap );
   error = check_xgetimage_errors();
   if (pixel && !error) {
      p = XMesaGetPixel( pixel, 0, 0 );
   }
   else {
      p = 0;
   }
   if (pixel) {
      XMesaDestroyImage( pixel );
   }
   return p;
}



/*
 * The Mesa library needs to be able to draw pixels in a number of ways:
 *   1. RGB vs Color Index
 *   2. as horizontal spans (polygons, images) vs random locations (points,
 *      lines)
 *   3. different color per-pixel or same color for all pixels
 *
 * Furthermore, the X driver needs to support rendering to 3 possible
 * "buffers", usually one, but sometimes two at a time:
 *   1. The front buffer as an X window
 *   2. The back buffer as a Pixmap
 *   3. The back buffer as an XImage
 *
 * Finally, if the back buffer is an XImage, we can avoid using XPutPixel and
 * optimize common cases such as 24-bit and 8-bit modes.
 *
 * By multiplication, there's at least 48 possible combinations of the above.
 *
 * Below are implementations of the most commonly used combinations.  They are
 * accessed through function pointers which get initialized here and are used
 * directly from the Mesa library.  The 8 function pointers directly correspond
 * to the first 3 cases listed above.
 *
 *
 * The function naming convention is:
 *
 *   [put|get]_[row|values]_[format]_[pixmap|ximage]
 *
 * New functions optimized for specific cases can be added without too much
 * trouble.  An example might be the 24-bit TrueColor mode 8A8R8G8B which is
 * found on IBM RS/6000 X servers.
 */




/**********************************************************************/
/*** Write COLOR SPAN functions                                     ***/
/**********************************************************************/


#define PUT_ROW_ARGS \
	struct gl_context *ctx,					\
	struct gl_renderbuffer *rb,			\
	GLuint n, GLint x, GLint y,			\
	const void *values, const GLubyte mask[]

#define RGB_SPAN_ARGS \
	struct gl_context *ctx,					\
	struct gl_renderbuffer *rb,			\
	GLuint n, GLint x, GLint y,			\
	const void *values, const GLubyte mask[]


#define GET_XRB(XRB) \
   struct xmesa_renderbuffer *XRB = xmesa_renderbuffer(rb)


/*
 * Write a span of PF_TRUECOLOR pixels to a pixmap.
 */
static void put_row_TRUECOLOR_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = XMESA_BUFFER(ctx->DrawBuffer)->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;

   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            unsigned long p;
            PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
            XMesaSetForeground( dpy, gc, p );
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      for (i=0;i<n;i++) {
         unsigned long p;
         PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
         XMesaPutPixel( rowimg, i, 0, p );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_TRUEDITHER pixels to a pixmap.
 */
static void put_row_TRUEDITHER_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            unsigned long p;
            PACK_TRUEDITHER(p, x, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
            XMesaSetForeground( dpy, gc, p );
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      for (i=0;i<n;i++) {
         unsigned long p;
         PACK_TRUEDITHER(p, x+i, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
         XMesaPutPixel( rowimg, i, 0, p );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_8A8B8G8R pixels to a pixmap.
 */
static void put_row_8A8B8G8R_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            XMesaSetForeground( dpy, gc,
                         PACK_8A8B8G8R(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP]) );
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLuint *ptr4 = (GLuint *) rowimg->data;
      for (i=0;i<n;i++) {
         *ptr4++ = PACK_8A8B8G8R( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_8A8R8G8B pixels to a pixmap.
 */
static void put_row_8A8R8G8B_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            XMesaSetForeground( dpy, gc,
                         PACK_8A8R8G8B(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP]) );
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLuint *ptr4 = (GLuint *) rowimg->data;
      for (i=0;i<n;i++) {
         *ptr4++ = PACK_8A8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}



/*
 * Write a span of PF_8R8G8B pixels to a pixmap.
 */
static void put_row_8R8G8B_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
#if 1
            /*
             * XXX Something funny is going on here.
             * If we're drawing into a window that uses a depth 32 TrueColor
             * visual, we see the right pixels on screen, but when we read
             * them back with XGetImage() we get random colors.
             * The alternative code below which uses XPutImage() instead
             * seems to mostly fix the problem, but not always.
             * We don't normally create windows with this visual, but glean
             * does and we're seeing some failures there.
             */
            XMesaSetForeground( dpy, gc, PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ));
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
#else
            /* This code works more often, but not always */
            XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
            GLuint *ptr4 = (GLuint *) rowimg->data;
            *ptr4 = PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
            XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, 1, 1 );
#endif
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLuint *ptr4 = (GLuint *) rowimg->data;
      for (i=0;i<n;i++) {
         *ptr4++ = PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_8R8G8B24 pixels to a pixmap.
 */
static void put_row_8R8G8B24_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   y = YFLIP(xrb, y);
   if (mask) {
      register GLuint i;
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            XMesaSetForeground( dpy, gc,
               PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ));
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLuint *ptr4 = (GLuint *) rowimg->data;
      register GLuint pixel;
      static const GLuint shift[4] = {0, 8, 16, 24};
      register GLuint i = 0;
      int w = n;
      while (w > 3) {
         pixel  = rgba[i][BCOMP] /* << shift[0]*/;
         pixel |= rgba[i][GCOMP]    << shift[1];
         pixel |= rgba[i++][RCOMP]  << shift[2];
         pixel |= rgba[i][BCOMP]    << shift[3];
         *ptr4++ = pixel;

         pixel  = rgba[i][GCOMP] /* << shift[0]*/;
         pixel |= rgba[i++][RCOMP]  << shift[1];
         pixel |= rgba[i][BCOMP]    << shift[2];
         pixel |= rgba[i][GCOMP]    << shift[3];
         *ptr4++ = pixel;

         pixel  = rgba[i++][RCOMP]/* << shift[0]*/;
         pixel |= rgba[i][BCOMP]     << shift[1];
         pixel |= rgba[i][GCOMP]     << shift[2];
         pixel |= rgba[i++][RCOMP]   << shift[3];
         *ptr4++ = pixel;

         w -= 4;
      }
      switch (w) {
         case 3:
            pixel = 0;
            pixel |= rgba[i][BCOMP] /*<< shift[0]*/;
            pixel |= rgba[i][GCOMP]   << shift[1];
            pixel |= rgba[i++][RCOMP] << shift[2];
            pixel |= rgba[i][BCOMP]   << shift[3];
            *ptr4++ = pixel;
            pixel = 0;
            pixel |= rgba[i][GCOMP] /*<< shift[0]*/;
            pixel |= rgba[i++][RCOMP] << shift[1];
            pixel |= rgba[i][BCOMP]   << shift[2];
            pixel |= rgba[i][GCOMP]   << shift[3];
            *ptr4++ = pixel;
            pixel = 0xffffff00 & *ptr4;
            pixel |= rgba[i][RCOMP] /*<< shift[0]*/;
            *ptr4 = pixel;
            break;
         case 2:
            pixel = 0;
            pixel |= rgba[i][BCOMP] /*<< shift[0]*/;
            pixel |= rgba[i][GCOMP]   << shift[1];
            pixel |= rgba[i++][RCOMP] << shift[2];
            pixel |= rgba[i][BCOMP]   << shift[3];
            *ptr4++ = pixel;
            pixel = 0xffff0000 & *ptr4;
            pixel |= rgba[i][GCOMP] /*<< shift[0]*/;
            pixel |= rgba[i][RCOMP]   << shift[1];
            *ptr4 = pixel;
            break;
         case 1:
            pixel = 0xff000000 & *ptr4;
            pixel |= rgba[i][BCOMP] /*<< shift[0]*/;
            pixel |= rgba[i][GCOMP] << shift[1];
            pixel |= rgba[i][RCOMP] << shift[2];
            *ptr4 = pixel;
            break;
         case 0:
            break;
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}



/*
 * Write a span of PF_5R6G5B pixels to a pixmap.
 */
static void put_row_5R6G5B_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            XMesaSetForeground( dpy, gc, PACK_5R6G5B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ));
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLushort *ptr2 = (GLushort *) rowimg->data;
      for (i=0;i<n;i++) {
         ptr2[i] = PACK_5R6G5B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_DITHER_5R6G5B pixels to a pixmap.
 */
static void put_row_DITHER_5R6G5B_pixmap( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            unsigned long p;
            PACK_TRUEDITHER(p, x, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
            XMesaSetForeground( dpy, gc, p );
            XMesaDrawPoint( dpy, buffer, gc, (int) x, (int) y );
         }
      }
   }
   else {
      /* draw all pixels */
      XMesaImage *rowimg = XMESA_BUFFER(ctx->DrawBuffer)->rowimage;
      register GLushort *ptr2 = (GLushort *) rowimg->data;
      for (i=0;i<n;i++) {
         PACK_TRUEDITHER( ptr2[i], x+i, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
      XMesaPutImage( dpy, buffer, gc, rowimg, 0, 0, x, y, n, 1 );
   }
}


/*
 * Write a span of PF_TRUECOLOR pixels to an XImage.
 */
static void put_row_TRUECOLOR_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaImage *img = xrb->ximage;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            unsigned long p;
            PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
            XMesaPutPixel( img, x, y, p );
         }
      }
   }
   else {
      /* draw all pixels */
      for (i=0;i<n;i++,x++) {
         unsigned long p;
         PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
         XMesaPutPixel( img, x, y, p );
      }
   }
}


/*
 * Write a span of PF_TRUEDITHER pixels to an XImage.
 */
static void put_row_TRUEDITHER_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaImage *img = xrb->ximage;
   register GLuint i;
   y = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            unsigned long p;
            PACK_TRUEDITHER(p, x, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
            XMesaPutPixel( img, x, y, p );
         }
      }
   }
   else {
      /* draw all pixels */
      for (i=0;i<n;i++,x++) {
         unsigned long p;
         PACK_TRUEDITHER(p, x, y, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
         XMesaPutPixel( img, x, y, p );
      }
   }
}


/*
 * Write a span of PF_8A8B8G8R-format pixels to an ximage.
 */
static void put_row_8A8B8G8R_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   register GLuint *ptr = PIXEL_ADDR4(xrb, x, y);
   (void) ctx;
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            ptr[i] = PACK_8A8B8G8R( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
         }
      }
   }
   else {
      /* draw all pixels */
      for (i=0;i<n;i++) {
         ptr[i] = PACK_8A8B8G8R( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}


/*
 * Write a span of PF_8A8R8G8B-format pixels to an ximage.
 */
static void put_row_8A8R8G8B_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   register GLuint *ptr = PIXEL_ADDR4(xrb, x, y);
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            ptr[i] = PACK_8A8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
         }
      }
   }
   else {
      /* draw all pixels */
      for (i=0;i<n;i++) {
         ptr[i] = PACK_8A8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}


/*
 * Write a span of PF_8R8G8B-format pixels to an ximage.
 */
static void put_row_8R8G8B_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   register GLuint *ptr = PIXEL_ADDR4(xrb, x, y);
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            ptr[i] = PACK_8R8G8B(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
         }
      }
   }
   else {
      for (i=0;i<n;i++) {
         ptr[i] = PACK_8R8G8B(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
      }
   }
}


/*
 * Write a span of PF_8R8G8B24-format pixels to an ximage.
 */
static void put_row_8R8G8B24_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   register GLubyte *ptr = (GLubyte *) PIXEL_ADDR3(xrb, x, y );
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            GLuint *ptr4 = (GLuint *) ptr;
            register GLuint pixel = *ptr4;
            switch (3 & (int)(ptr - (GLubyte*)ptr4)) {
               case 0:
                  pixel &= 0xff000000;
                  pixel |= rgba[i][BCOMP];
                  pixel |= rgba[i][GCOMP] << 8;
                  pixel |= rgba[i][RCOMP] << 16;
                  *ptr4 = pixel;
                  break;
               case 3:
                  pixel &= 0x00ffffff;
                  pixel |= rgba[i][BCOMP] << 24;
                  *ptr4++ = pixel;
                  pixel = *ptr4 & 0xffff0000;
                  pixel |= rgba[i][GCOMP];
                  pixel |= rgba[i][RCOMP] << 8;
                  *ptr4 = pixel;
                  break;
               case 2:
                  pixel &= 0x0000ffff;
                  pixel |= rgba[i][BCOMP] << 16;
                  pixel |= rgba[i][GCOMP] << 24;
                  *ptr4++ = pixel;
                  pixel = *ptr4 & 0xffffff00;
                  pixel |= rgba[i][RCOMP];
                  *ptr4 = pixel;
                  break;
               case 1:
                  pixel &= 0x000000ff;
                  pixel |= rgba[i][BCOMP] << 8;
                  pixel |= rgba[i][GCOMP] << 16;
                  pixel |= rgba[i][RCOMP] << 24;
                  *ptr4 = pixel;
                  break;
            }
         }
	 ptr += 3;
      }
   }
   else {
      /* write all pixels */
      int w = n;
      GLuint *ptr4 = (GLuint *) ptr;
      register GLuint pixel = *ptr4;
      int index = (int)(ptr - (GLubyte *)ptr4);
      register GLuint i = 0;
      switch (index) {
         case 0:
            break;
         case 1:
            pixel &= 0x00ffffff;
            pixel |= rgba[i][BCOMP] << 24;
            *ptr4++ = pixel;
            pixel = *ptr4 & 0xffff0000;
            pixel |= rgba[i][GCOMP];
            pixel |= rgba[i++][RCOMP] << 8;
            *ptr4 = pixel;
            if (0 == --w)
               break;
         case 2:
            pixel &= 0x0000ffff;
            pixel |= rgba[i][BCOMP] << 16;
            pixel |= rgba[i][GCOMP] << 24;
            *ptr4++ = pixel;
            pixel = *ptr4 & 0xffffff00;
            pixel |= rgba[i++][RCOMP];
            *ptr4 = pixel;
            if (0 == --w)
               break;
         case 3:
            pixel &= 0x000000ff;
            pixel |= rgba[i][BCOMP] << 8;
            pixel |= rgba[i][GCOMP] << 16;
            pixel |= rgba[i++][RCOMP] << 24;
            *ptr4++ = pixel;
            if (0 == --w)
               break;
            break;
      }
      while (w > 3) {
         pixel = rgba[i][BCOMP];
         pixel |= rgba[i][GCOMP] << 8;
         pixel |= rgba[i++][RCOMP] << 16;
         pixel |= rgba[i][BCOMP] << 24;
         *ptr4++ = pixel;
         pixel = rgba[i][GCOMP];
         pixel |= rgba[i++][RCOMP] << 8;
         pixel |= rgba[i][BCOMP] << 16;
         pixel |= rgba[i][GCOMP] << 24;
         *ptr4++ = pixel;
         pixel = rgba[i++][RCOMP];
         pixel |= rgba[i][BCOMP] << 8;
         pixel |= rgba[i][GCOMP] << 16;
         pixel |= rgba[i++][RCOMP] << 24;
         *ptr4++ = pixel;
         w -= 4;
      }
      switch (w) {
         case 0:
            break;
         case 1:
            pixel = *ptr4 & 0xff000000;
            pixel |= rgba[i][BCOMP];
            pixel |= rgba[i][GCOMP] << 8;
            pixel |= rgba[i][RCOMP] << 16;
            *ptr4 = pixel;
            break;
         case 2:
            pixel = rgba[i][BCOMP];
            pixel |= rgba[i][GCOMP] << 8;
            pixel |= rgba[i++][RCOMP] << 16;
            pixel |= rgba[i][BCOMP] << 24;
            *ptr4++ = pixel;
            pixel = *ptr4 & 0xffff0000;
            pixel |= rgba[i][GCOMP];
            pixel |= rgba[i][RCOMP] << 8;
            *ptr4 = pixel;
            break;
         case 3:
            pixel = rgba[i][BCOMP];
            pixel |= rgba[i][GCOMP] << 8;
            pixel |= rgba[i++][RCOMP] << 16;
            pixel |= rgba[i][BCOMP] << 24;
            *ptr4++ = pixel;
            pixel = rgba[i][GCOMP];
            pixel |= rgba[i++][RCOMP] << 8;
            pixel |= rgba[i][BCOMP] << 16;
            pixel |= rgba[i][GCOMP] << 24;
            *ptr4++ = pixel;
            pixel = *ptr4 & 0xffffff00;
            pixel |= rgba[i][RCOMP];
            *ptr4 = pixel;
            break;
      }
   }
}


/*
 * Write a span of PF_5R6G5B-format pixels to an ximage.
 */
static void put_row_5R6G5B_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   register GLushort *ptr = PIXEL_ADDR2(xrb, x, y);
   if (mask) {
      for (i=0;i<n;i++) {
         if (mask[i]) {
            ptr[i] = PACK_5R6G5B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
         }
      }
   }
   else {
      /* draw all pixels */
#if defined(__i386__) /* word stores don't have to be on 4-byte boundaries */
      GLuint *ptr32 = (GLuint *) ptr;
      GLuint extraPixel = (n & 1);
      n -= extraPixel;
      for (i = 0; i < n; i += 2) {
         GLuint p0, p1;
         p0 = PACK_5R6G5B(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
         p1 = PACK_5R6G5B(rgba[i+1][RCOMP], rgba[i+1][GCOMP], rgba[i+1][BCOMP]);
         *ptr32++ = (p1 << 16) | p0;
      }
      if (extraPixel) {
         ptr[n] = PACK_5R6G5B(rgba[n][RCOMP], rgba[n][GCOMP], rgba[n][BCOMP]);
      }
#else
      for (i = 0; i < n; i++) {
         ptr[i] = PACK_5R6G5B(rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
      }
#endif
   }
}


/*
 * Write a span of PF_DITHER_5R6G5B-format pixels to an ximage.
 */
static void put_row_DITHER_5R6G5B_ximage( PUT_ROW_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   register GLuint i;
   register GLushort *ptr = PIXEL_ADDR2(xrb, x, y);
   const GLint y2 = YFLIP(xrb, y);
   if (mask) {
      for (i=0;i<n;i++,x++) {
         if (mask[i]) {
            PACK_TRUEDITHER( ptr[i], x, y2, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
         }
      }
   }
   else {
      /* draw all pixels */
#if defined(__i386__) /* word stores don't have to be on 4-byte boundaries */
      GLuint *ptr32 = (GLuint *) ptr;
      GLuint extraPixel = (n & 1);
      n -= extraPixel;
      for (i = 0; i < n; i += 2, x += 2) {
         GLuint p0, p1;
         PACK_TRUEDITHER( p0, x, y2, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
         PACK_TRUEDITHER( p1, x+1, y2, rgba[i+1][RCOMP], rgba[i+1][GCOMP], rgba[i+1][BCOMP] );
         *ptr32++ = (p1 << 16) | p0;
      }
      if (extraPixel) {
         PACK_TRUEDITHER( ptr[n], x+n, y2, rgba[n][RCOMP], rgba[n][GCOMP], rgba[n][BCOMP]);
      }
#else
      for (i = 0; i < n; i++, x++) {
         PACK_TRUEDITHER( ptr[i], x, y2, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
      }
#endif
   }
}


/**********************************************************************/
/*** Write COLOR PIXEL functions                                    ***/
/**********************************************************************/


#define PUT_VALUES_ARGS \
	struct gl_context *ctx, struct gl_renderbuffer *rb,	\
	GLuint n, const GLint x[], const GLint y[],	\
	const void *values, const GLubyte mask[]


/*
 * Write an array of PF_TRUECOLOR pixels to a pixmap.
 */
static void put_values_TRUECOLOR_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         unsigned long p;
         PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
	 XMesaSetForeground( dpy, gc, p );
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_TRUEDITHER pixels to a pixmap.
 */
static void put_values_TRUEDITHER_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         unsigned long p;
         PACK_TRUEDITHER(p, x[i], y[i], rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
         XMesaSetForeground( dpy, gc, p );
         XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_8A8B8G8R pixels to a pixmap.
 */
static void put_values_8A8B8G8R_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 XMesaSetForeground( dpy, gc,
                         PACK_8A8B8G8R( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] ));
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}

/*
 * Write an array of PF_8A8R8G8B pixels to a pixmap.
 */
static void put_values_8A8R8G8B_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 XMesaSetForeground( dpy, gc,
                         PACK_8A8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] ));
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}

/*
 * Write an array of PF_8R8G8B pixels to a pixmap.
 */
static void put_values_8R8G8B_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 XMesaSetForeground( dpy, gc, PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ) );
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_8R8G8B24 pixels to a pixmap.
 */
static void put_values_8R8G8B24_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 XMesaSetForeground( dpy, gc, PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ) );
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_5R6G5B pixels to a pixmap.
 */
static void put_values_5R6G5B_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 XMesaSetForeground( dpy, gc, PACK_5R6G5B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] ) );
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_DITHER_5R6G5B pixels to a pixmap.
 */
static void put_values_DITHER_5R6G5B_pixmap( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   XMesaDrawable buffer = xrb->drawable;
   XMesaGC gc = XMESA_BUFFER(ctx->DrawBuffer)->gc;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         unsigned long p;
         PACK_TRUEDITHER(p, x[i], y[i], rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
	 XMesaSetForeground( dpy, gc, p );
	 XMesaDrawPoint( dpy, buffer, gc, (int) x[i], (int) YFLIP(xrb, y[i]) );
      }
   }
}


/*
 * Write an array of PF_TRUECOLOR pixels to an ximage.
 */
static void put_values_TRUECOLOR_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaImage *img = xrb->ximage;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         unsigned long p;
         PACK_TRUECOLOR( p, rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
	 XMesaPutPixel( img, x[i], YFLIP(xrb, y[i]), p );
      }
   }
}


/*
 * Write an array of PF_TRUEDITHER pixels to an XImage.
 */
static void put_values_TRUEDITHER_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);
   XMesaImage *img = xrb->ximage;
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
         unsigned long p;
         PACK_TRUEDITHER(p, x[i], y[i], rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP]);
	 XMesaPutPixel( img, x[i], YFLIP(xrb, y[i]), p );
      }
   }
}


/*
 * Write an array of PF_8A8B8G8R pixels to an ximage.
 */
static void put_values_8A8B8G8R_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 GLuint *ptr = PIXEL_ADDR4(xrb, x[i], y[i] );
         *ptr = PACK_8A8B8G8R( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}

/*
 * Write an array of PF_8A8R8G8B pixels to an ximage.
 */
static void put_values_8A8R8G8B_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 GLuint *ptr = PIXEL_ADDR4(xrb, x[i], y[i]);
         *ptr = PACK_8A8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP], rgba[i][ACOMP] );
      }
   }
}


/*
 * Write an array of PF_8R8G8B pixels to an ximage.
 */
static void put_values_8R8G8B_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 GLuint *ptr = PIXEL_ADDR4(xrb, x[i], y[i]);
         *ptr = PACK_8R8G8B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
   }
}


/*
 * Write an array of PF_8R8G8B24 pixels to an ximage.
 */
static void put_values_8R8G8B24_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 bgr_t *ptr = PIXEL_ADDR3(xrb, x[i], y[i] );
         ptr->r = rgba[i][RCOMP];
         ptr->g = rgba[i][GCOMP];
         ptr->b = rgba[i][BCOMP];
      }
   }
}


/*
 * Write an array of PF_5R6G5B pixels to an ximage.
 */
static void put_values_5R6G5B_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 GLushort *ptr = PIXEL_ADDR2(xrb, x[i], y[i] );
         *ptr = PACK_5R6G5B( rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
   }
}


/*
 * Write an array of PF_DITHER_5R6G5B pixels to an ximage.
 */
static void put_values_DITHER_5R6G5B_ximage( PUT_VALUES_ARGS )
{
   const GLubyte (*rgba)[4] = (const GLubyte (*)[4]) values;
   GET_XRB(xrb);
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   register GLuint i;
   for (i=0;i<n;i++) {
      if (mask[i]) {
	 GLushort *ptr = PIXEL_ADDR2(xrb, x[i], y[i] );
         PACK_TRUEDITHER( *ptr, x[i], y[i], rgba[i][RCOMP], rgba[i][GCOMP], rgba[i][BCOMP] );
      }
   }
}



/**********************************************************************/
/*****                      Pixel reading                         *****/
/**********************************************************************/

/**
 * Do clip testing prior to calling XGetImage.  If any of the region lies
 * outside the screen's bounds, XGetImage will return NULL.
 * We use XTranslateCoordinates() to check if that's the case and
 * adjust the x, y and length parameters accordingly.
 * \return  -1 if span is totally clipped away,
 *          else return number of pixels to skip in the destination array.
 */
static int
clip_for_xgetimage(struct gl_context *ctx, XMesaPixmap pixmap, GLuint *n, GLint *x, GLint *y)
{
   XMesaContext xmesa = XMESA_CONTEXT(ctx);
   XMesaBuffer source = XMESA_BUFFER(ctx->DrawBuffer);
   Window rootWin = RootWindow(xmesa->display, 0);
   Window child;
   GLint screenWidth = WidthOfScreen(DefaultScreenOfDisplay(xmesa->display));
   GLint dx, dy;
   if (source->type == PBUFFER || source->type == PIXMAP)
      return 0;
   XTranslateCoordinates(xmesa->display, pixmap, rootWin,
                         *x, *y, &dx, &dy, &child);
   if (dx >= screenWidth) {
      /* totally clipped on right */
      return -1;
   }
   if (dx < 0) {
      /* clipped on left */
      GLint clip = -dx;
      if (clip >= (GLint) *n)
         return -1;  /* totally clipped on left */
      *x += clip;
      *n -= clip;
      dx = 0;
      return clip;
   }
   if ((GLint) (dx + *n) > screenWidth) {
      /* clipped on right */
      GLint clip = dx + *n - screenWidth;
      *n -= clip;
   }
   return 0;
}


/*
 * Read a horizontal span of color pixels.
 */
static void
get_row_rgba(struct gl_context *ctx, struct gl_renderbuffer *rb,
             GLuint n, GLint x, GLint y, void *values)
{
   GLubyte (*rgba)[4] = (GLubyte (*)[4]) values;
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   GET_XRB(xrb);

   if (xrb->pixmap) {
      /* Read from Pixmap or Window */
      XMesaImage *span = NULL;
      int error;
      int k;
      y = YFLIP(xrb, y);
      k = clip_for_xgetimage(ctx, xrb->pixmap, &n, &x, &y);
      if (k < 0)
         return;
      rgba += k;
      catch_xgetimage_errors( xmesa->display );
      span = XGetImage( xmesa->display, xrb->pixmap,
		        x, y, n, 1, AllPlanes, ZPixmap );
      error = check_xgetimage_errors();
      if (span && !error) {
	 switch (xmesa->pixelformat) {
	    case PF_Truecolor:
	    case PF_Dither_True:
               {
                  const GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
                  const GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
                  const GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
                  unsigned long rMask = GET_REDMASK(xmesa->xm_visual);
                  unsigned long gMask = GET_GREENMASK(xmesa->xm_visual);
                  unsigned long bMask = GET_BLUEMASK(xmesa->xm_visual);
                  GLint rShift = xmesa->xm_visual->rshift;
                  GLint gShift = xmesa->xm_visual->gshift;
                  GLint bShift = xmesa->xm_visual->bshift;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     unsigned long p;
                     p = XMesaGetPixel( span, i, 0 );
                     rgba[i][RCOMP] = pixelToR[(p & rMask) >> rShift];
                     rgba[i][GCOMP] = pixelToG[(p & gMask) >> gShift];
                     rgba[i][BCOMP] = pixelToB[(p & bMask) >> bShift];
                     rgba[i][ACOMP] = 255;
                  }
               }
	       break;
            case PF_5R6G5B:
            case PF_Dither_5R6G5B:
               {
                  const GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
                  const GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
                  const GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     unsigned long p = XMesaGetPixel( span, i, 0 );
                     /* fast, but not quite accurate
                     rgba[i][RCOMP] = ((p >> 8) & 0xf8);
                     rgba[i][GCOMP] = ((p >> 3) & 0xfc);
                     rgba[i][BCOMP] = ((p << 3) & 0xff);
                     */
                     rgba[i][RCOMP] = pixelToR[p >> 11];
                     rgba[i][GCOMP] = pixelToG[(p >> 5) & 0x3f];
                     rgba[i][BCOMP] = pixelToB[p & 0x1f];
                     rgba[i][ACOMP] = 255;
                  }
               }
	       break;
	    case PF_8A8B8G8R:
               {
                  const GLuint *ptr4 = (GLuint *) span->data;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     GLuint p4 = *ptr4++;
                     rgba[i][RCOMP] = (GLubyte) ( p4        & 0xff);
                     rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                     rgba[i][BCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                     rgba[i][ACOMP] = (GLubyte) ((p4 >> 24) & 0xff);
                  }
	       }
	       break;
            case PF_8A8R8G8B:
               {
                  const GLuint *ptr4 = (GLuint *) span->data;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     GLuint p4 = *ptr4++;
                     rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                     rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                     rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
                     rgba[i][ACOMP] = (GLubyte) ((p4 >> 24) & 0xff);
                  }
	       }
	       break;
            case PF_8R8G8B:
               {
                  const GLuint *ptr4 = (GLuint *) span->data;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     GLuint p4 = *ptr4++;
                     rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                     rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                     rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
                     rgba[i][ACOMP] = 255;
                  }
	       }
	       break;
            case PF_8R8G8B24:
               {
                  const bgr_t *ptr3 = (bgr_t *) span->data;
                  GLuint i;
                  for (i=0;i<n;i++) {
                     rgba[i][RCOMP] = ptr3[i].r;
                     rgba[i][GCOMP] = ptr3[i].g;
                     rgba[i][BCOMP] = ptr3[i].b;
                     rgba[i][ACOMP] = 255;
                  }
	       }
	       break;
	    default:
	       _mesa_problem(NULL,"Problem in DD.read_color_span (1)");
               return;
	 }
      }
      else {
	 /* return black pixels */
         GLuint i;
	 for (i=0;i<n;i++) {
	    rgba[i][RCOMP] = rgba[i][GCOMP] = rgba[i][BCOMP] = rgba[i][ACOMP] = 0;
	 }
      }
      if (span) {
	 XMesaDestroyImage( span );
      }
   }
   else if (xrb->ximage) {
      /* Read from XImage back buffer */
      switch (xmesa->pixelformat) {
         case PF_Truecolor:
         case PF_Dither_True:
            {
               const GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
               const GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
               const GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
               unsigned long rMask = GET_REDMASK(xmesa->xm_visual);
               unsigned long gMask = GET_GREENMASK(xmesa->xm_visual);
               unsigned long bMask = GET_BLUEMASK(xmesa->xm_visual);
               GLint rShift = xmesa->xm_visual->rshift;
               GLint gShift = xmesa->xm_visual->gshift;
               GLint bShift = xmesa->xm_visual->bshift;
               XMesaImage *img = xrb->ximage;
               GLuint i;
               y = YFLIP(xrb, y);
               for (i=0;i<n;i++) {
                  unsigned long p;
		  p = XMesaGetPixel( img, x+i, y );
                  rgba[i][RCOMP] = pixelToR[(p & rMask) >> rShift];
                  rgba[i][GCOMP] = pixelToG[(p & gMask) >> gShift];
                  rgba[i][BCOMP] = pixelToB[(p & bMask) >> bShift];
                  rgba[i][ACOMP] = 255;
               }
            }
            break;
         case PF_5R6G5B:
         case PF_Dither_5R6G5B:
            {
               const GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
               const GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
               const GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
               const GLushort *ptr2 = PIXEL_ADDR2(xrb, x, y);
               GLuint i;
#if defined(__i386__) /* word stores don't have to be on 4-byte boundaries */
               const GLuint *ptr4 = (const GLuint *) ptr2;
               GLuint extraPixel = (n & 1);
               n -= extraPixel;
               for (i = 0; i < n; i += 2) {
                  const GLuint p = *ptr4++;
                  const GLuint p0 = p & 0xffff;
                  const GLuint p1 = p >> 16;
                  /* fast, but not quite accurate
                  rgba[i][RCOMP] = ((p >> 8) & 0xf8);
                  rgba[i][GCOMP] = ((p >> 3) & 0xfc);
                  rgba[i][BCOMP] = ((p << 3) & 0xff);
                  */
                  rgba[i][RCOMP] = pixelToR[p0 >> 11];
                  rgba[i][GCOMP] = pixelToG[(p0 >> 5) & 0x3f];
                  rgba[i][BCOMP] = pixelToB[p0 & 0x1f];
                  rgba[i][ACOMP] = 255;
                  rgba[i+1][RCOMP] = pixelToR[p1 >> 11];
                  rgba[i+1][GCOMP] = pixelToG[(p1 >> 5) & 0x3f];
                  rgba[i+1][BCOMP] = pixelToB[p1 & 0x1f];
                  rgba[i+1][ACOMP] = 255;
               }
               if (extraPixel) {
                  GLushort p = ptr2[n];
                  rgba[n][RCOMP] = pixelToR[p >> 11];
                  rgba[n][GCOMP] = pixelToG[(p >> 5) & 0x3f];
                  rgba[n][BCOMP] = pixelToB[p & 0x1f];
                  rgba[n][ACOMP] = 255;
               }
#else
               for (i = 0; i < n; i++) {
                  const GLushort p = ptr2[i];
                  rgba[i][RCOMP] = pixelToR[p >> 11];
                  rgba[i][GCOMP] = pixelToG[(p >> 5) & 0x3f];
                  rgba[i][BCOMP] = pixelToB[p & 0x1f];
                  rgba[i][ACOMP] = 255;
               }
#endif
            }
            break;
	 case PF_8A8B8G8R:
            {
               const GLuint *ptr4 = PIXEL_ADDR4(xrb, x, y);
               GLuint i;
               for (i=0;i<n;i++) {
                  GLuint p4 = *ptr4++;
                  rgba[i][RCOMP] = (GLubyte) ( p4        & 0xff);
                  rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                  rgba[i][BCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                  rgba[i][ACOMP] = (GLint)   ((p4 >> 24) & 0xff);
               }
            }
	    break;
	 case PF_8A8R8G8B:
            {
               const GLuint *ptr4 = PIXEL_ADDR4(xrb, x, y);
               GLuint i;
               for (i=0;i<n;i++) {
                  GLuint p4 = *ptr4++;
                  rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                  rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                  rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
                  rgba[i][ACOMP] = (GLint)   ((p4 >> 24) & 0xff);
               }
            }
	    break;
	 case PF_8R8G8B:
            {
               const GLuint *ptr4 = PIXEL_ADDR4(xrb, x, y);
               GLuint i;
               for (i=0;i<n;i++) {
                  GLuint p4 = *ptr4++;
                  rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
                  rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
                  rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
                  rgba[i][ACOMP] = 255;
               }
            }
	    break;
	 case PF_8R8G8B24:
            {
               const bgr_t *ptr3 = PIXEL_ADDR3(xrb, x, y);
               GLuint i;
               for (i=0;i<n;i++) {
                  rgba[i][RCOMP] = ptr3[i].r;
                  rgba[i][GCOMP] = ptr3[i].g;
                  rgba[i][BCOMP] = ptr3[i].b;
                  rgba[i][ACOMP] = 255;
               }
            }
	    break;
	 default:
	    _mesa_problem(NULL,"Problem in DD.read_color_span (2)");
            return;
      }
   }
}



static void
get_values_rgba(struct gl_context *ctx, struct gl_renderbuffer *rb,
                GLuint n, const GLint x[], const GLint y[], void *values)
{
   GLubyte (*rgba)[4] = (GLubyte (*)[4]) values;
   GET_XRB(xrb);
   const XMesaContext xmesa = XMESA_CONTEXT(ctx);
   XMesaDisplay *dpy = xmesa->xm_visual->display;
   register GLuint i;

   if (xrb->pixmap) {
      XMesaDrawable buffer = xrb->drawable;
      switch (xmesa->pixelformat) {
	 case PF_Truecolor:
         case PF_Dither_True:
         case PF_5R6G5B:
         case PF_Dither_5R6G5B:
            {
               unsigned long rMask = GET_REDMASK(xmesa->xm_visual);
               unsigned long gMask = GET_GREENMASK(xmesa->xm_visual);
               unsigned long bMask = GET_BLUEMASK(xmesa->xm_visual);
               GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
               GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
               GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
               GLint rShift = xmesa->xm_visual->rshift;
               GLint gShift = xmesa->xm_visual->gshift;
               GLint bShift = xmesa->xm_visual->bshift;
               for (i=0;i<n;i++) {
                  unsigned long p = read_pixel( dpy, buffer,
                                                x[i], YFLIP(xrb, y[i]) );
                  rgba[i][RCOMP] = pixelToR[(p & rMask) >> rShift];
                  rgba[i][GCOMP] = pixelToG[(p & gMask) >> gShift];
                  rgba[i][BCOMP] = pixelToB[(p & bMask) >> bShift];
                  rgba[i][ACOMP] = 255;
               }
            }
            break;
	 case PF_8A8B8G8R:
	    for (i=0;i<n;i++) {
               unsigned long p = read_pixel( dpy, buffer,
                                             x[i], YFLIP(xrb, y[i]) );
               rgba[i][RCOMP] = (GLubyte) ( p        & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ((p >> 16) & 0xff);
               rgba[i][ACOMP] = (GLubyte) ((p >> 24) & 0xff);
	    }
	    break;
	 case PF_8A8R8G8B:
	    for (i=0;i<n;i++) {
               unsigned long p = read_pixel( dpy, buffer,
                                             x[i], YFLIP(xrb, y[i]) );
               rgba[i][RCOMP] = (GLubyte) ((p >> 16) & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ( p        & 0xff);
               rgba[i][ACOMP] = (GLubyte) ((p >> 24) & 0xff);
	    }
	    break;
	 case PF_8R8G8B:
	    for (i=0;i<n;i++) {
               unsigned long p = read_pixel( dpy, buffer,
                                             x[i], YFLIP(xrb, y[i]) );
               rgba[i][RCOMP] = (GLubyte) ((p >> 16) & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ( p        & 0xff);
               rgba[i][ACOMP] = 255;
	    }
	    break;
	 case PF_8R8G8B24:
	    for (i=0;i<n;i++) {
               unsigned long p = read_pixel( dpy, buffer,
                                             x[i], YFLIP(xrb, y[i]) );
               rgba[i][RCOMP] = (GLubyte) ((p >> 16) & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ( p        & 0xff);
               rgba[i][ACOMP] = 255;
	    }
	    break;
	 default:
	    _mesa_problem(NULL,"Problem in DD.read_color_pixels (1)");
            return;
      }
   }
   else if (xrb->ximage) {
      /* Read from XImage back buffer */
      switch (xmesa->pixelformat) {
	 case PF_Truecolor:
         case PF_Dither_True:
         case PF_5R6G5B:
         case PF_Dither_5R6G5B:
            {
               unsigned long rMask = GET_REDMASK(xmesa->xm_visual);
               unsigned long gMask = GET_GREENMASK(xmesa->xm_visual);
               unsigned long bMask = GET_BLUEMASK(xmesa->xm_visual);
               GLubyte *pixelToR = xmesa->xm_visual->PixelToR;
               GLubyte *pixelToG = xmesa->xm_visual->PixelToG;
               GLubyte *pixelToB = xmesa->xm_visual->PixelToB;
               GLint rShift = xmesa->xm_visual->rshift;
               GLint gShift = xmesa->xm_visual->gshift;
               GLint bShift = xmesa->xm_visual->bshift;
               XMesaImage *img = xrb->ximage;
               for (i=0;i<n;i++) {
                  unsigned long p;
                  p = XMesaGetPixel( img, x[i], YFLIP(xrb, y[i]) );
                  rgba[i][RCOMP] = pixelToR[(p & rMask) >> rShift];
                  rgba[i][GCOMP] = pixelToG[(p & gMask) >> gShift];
                  rgba[i][BCOMP] = pixelToB[(p & bMask) >> bShift];
                  rgba[i][ACOMP] = 255;
               }
            }
            break;
	 case PF_8A8B8G8R:
	    for (i=0;i<n;i++) {
               GLuint *ptr4 = PIXEL_ADDR4(xrb, x[i], y[i]);
               GLuint p4 = *ptr4;
               rgba[i][RCOMP] = (GLubyte) ( p4        & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
               rgba[i][ACOMP] = (GLubyte) ((p4 >> 24) & 0xff);
	    }
	    break;
	 case PF_8A8R8G8B:
	    for (i=0;i<n;i++) {
               GLuint *ptr4 = PIXEL_ADDR4(xrb, x[i], y[i]);
               GLuint p4 = *ptr4;
               rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
               rgba[i][ACOMP] = (GLubyte) ((p4 >> 24) & 0xff);
	    }
	    break;
	 case PF_8R8G8B:
	    for (i=0;i<n;i++) {
               GLuint *ptr4 = PIXEL_ADDR4(xrb, x[i], y[i]);
               GLuint p4 = *ptr4;
               rgba[i][RCOMP] = (GLubyte) ((p4 >> 16) & 0xff);
               rgba[i][GCOMP] = (GLubyte) ((p4 >> 8)  & 0xff);
               rgba[i][BCOMP] = (GLubyte) ( p4        & 0xff);
               rgba[i][ACOMP] = 255;
	    }
	    break;
	 case PF_8R8G8B24:
	    for (i=0;i<n;i++) {
               bgr_t *ptr3 = PIXEL_ADDR3(xrb, x[i], y[i]);
               rgba[i][RCOMP] = ptr3->r;
               rgba[i][GCOMP] = ptr3->g;
               rgba[i][BCOMP] = ptr3->b;
               rgba[i][ACOMP] = 255;
	    }
	    break;
	 default:
	    _mesa_problem(NULL,"Problem in DD.read_color_pixels (1)");
            return;
      }
   }
}


/**
 * Initialize the renderbuffer's PutRow, GetRow, etc. functions.
 * This would generally only need to be called once when the renderbuffer
 * is created.  However, we can change pixel formats on the fly if dithering
 * is enabled/disabled.  Therefore, we may call this more often than that.
 */
void
xmesa_set_renderbuffer_funcs(struct xmesa_renderbuffer *xrb,
                             enum pixel_format pixelformat, GLint depth)
{
   const GLboolean pixmap = xrb->pixmap ? GL_TRUE : GL_FALSE;

   switch (pixelformat) {
   case PF_Truecolor:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_TRUECOLOR_pixmap;
         xrb->Base.PutValues     = put_values_TRUECOLOR_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_TRUECOLOR_ximage;
         xrb->Base.PutValues     = put_values_TRUECOLOR_ximage;
      }
      break;
   case PF_Dither_True:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_TRUEDITHER_pixmap;
         xrb->Base.PutValues     = put_values_TRUEDITHER_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_TRUEDITHER_ximage;
         xrb->Base.PutValues     = put_values_TRUEDITHER_ximage;
      }
      break;
   case PF_8A8B8G8R:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_8A8B8G8R_pixmap;
         xrb->Base.PutValues     = put_values_8A8B8G8R_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_8A8B8G8R_ximage;
         xrb->Base.PutValues     = put_values_8A8B8G8R_ximage;
      }
      break;
   case PF_8A8R8G8B:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_8A8R8G8B_pixmap;
         xrb->Base.PutValues     = put_values_8A8R8G8B_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_8A8R8G8B_ximage;
         xrb->Base.PutValues     = put_values_8A8R8G8B_ximage;
      }
      break;
   case PF_8R8G8B:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_8R8G8B_pixmap;
         xrb->Base.PutValues     = put_values_8R8G8B_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_8R8G8B_ximage;
         xrb->Base.PutValues     = put_values_8R8G8B_ximage;
      }
      break;
   case PF_8R8G8B24:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_8R8G8B24_pixmap;
         xrb->Base.PutValues     = put_values_8R8G8B24_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_8R8G8B24_ximage;
         xrb->Base.PutValues     = put_values_8R8G8B24_ximage;
      }
      break;
   case PF_5R6G5B:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_5R6G5B_pixmap;
         xrb->Base.PutValues     = put_values_5R6G5B_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_5R6G5B_ximage;
         xrb->Base.PutValues     = put_values_5R6G5B_ximage;
      }
      break;
   case PF_Dither_5R6G5B:
      if (pixmap) {
         xrb->Base.PutRow        = put_row_DITHER_5R6G5B_pixmap;
         xrb->Base.PutValues     = put_values_DITHER_5R6G5B_pixmap;
      }
      else {
         xrb->Base.PutRow        = put_row_DITHER_5R6G5B_ximage;
         xrb->Base.PutValues     = put_values_DITHER_5R6G5B_ximage;
      }
      break;
   default:
      _mesa_problem(NULL, "Bad pixel format in xmesa_update_state (1)");
      return;
   }


   /* Get functions */
   xrb->Base.GetRow = get_row_rgba;
   xrb->Base.GetValues = get_values_rgba;
}