summaryrefslogtreecommitdiffstats
path: root/src/mesa/main/buffers.c
blob: 5424f442feb1209ac7599597c22a8c14213359de (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
/*
 * Mesa 3-D graphics library
 * Version:  7.1
 *
 * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


/**
 * \file buffers.c
 * General framebuffer-related functions, like glClear, glScissor, etc.
 */



#include "glheader.h"
#include "buffers.h"
#include "colormac.h"
#include "context.h"
#include "enums.h"
#include "fbobject.h"
#include "state.h"


#define BAD_MASK ~0u


#if _HAVE_FULL_GL
void GLAPIENTRY
_mesa_ClearIndex( GLfloat c )
{
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END(ctx);

   if (ctx->Color.ClearIndex == (GLuint) c)
      return;

   FLUSH_VERTICES(ctx, _NEW_COLOR);
   ctx->Color.ClearIndex = (GLuint) c;

   if (!ctx->Visual.rgbMode && ctx->Driver.ClearIndex) {
      /* it's OK to call glClearIndex in RGBA mode but it should be a NOP */
      (*ctx->Driver.ClearIndex)( ctx, ctx->Color.ClearIndex );
   }
}
#endif


/**
 * Specify the clear values for the color buffers.
 *
 * \param red red color component.
 * \param green green color component.
 * \param blue blue color component.
 * \param alpha alpha component.
 *
 * \sa glClearColor().
 *
 * Clamps the parameters and updates gl_colorbuffer_attrib::ClearColor.  On a
 * change, flushes the vertices and notifies the driver via the
 * dd_function_table::ClearColor callback.
 */
void GLAPIENTRY
_mesa_ClearColor( GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha )
{
   GLfloat tmp[4];
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END(ctx);

   tmp[0] = CLAMP(red,   0.0F, 1.0F);
   tmp[1] = CLAMP(green, 0.0F, 1.0F);
   tmp[2] = CLAMP(blue,  0.0F, 1.0F);
   tmp[3] = CLAMP(alpha, 0.0F, 1.0F);

   if (TEST_EQ_4V(tmp, ctx->Color.ClearColor))
      return; /* no change */

   FLUSH_VERTICES(ctx, _NEW_COLOR);
   COPY_4V(ctx->Color.ClearColor, tmp);

   if (ctx->Visual.rgbMode && ctx->Driver.ClearColor) {
      /* it's OK to call glClearColor in CI mode but it should be a NOP */
      (*ctx->Driver.ClearColor)(ctx, ctx->Color.ClearColor);
   }
}


/**
 * Clear buffers.
 * 
 * \param mask bit-mask indicating the buffers to be cleared.
 *
 * Flushes the vertices and verifies the parameter. If __GLcontextRec::NewState
 * is set then calls _mesa_update_state() to update gl_frame_buffer::_Xmin,
 * etc. If the rasterization mode is set to GL_RENDER then requests the driver
 * to clear the buffers, via the dd_function_table::Clear callback.
 */ 
void GLAPIENTRY
_mesa_Clear( GLbitfield mask )
{
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);

   FLUSH_CURRENT(ctx, 0);

   if (MESA_VERBOSE & VERBOSE_API)
      _mesa_debug(ctx, "glClear 0x%x\n", mask);

   if (mask & ~(GL_COLOR_BUFFER_BIT |
                GL_DEPTH_BUFFER_BIT |
                GL_STENCIL_BUFFER_BIT |
                GL_ACCUM_BUFFER_BIT)) {
      /* invalid bit set */
      _mesa_error( ctx, GL_INVALID_VALUE, "glClear(0x%x)", mask);
      return;
   }

   if (ctx->NewState) {
      _mesa_update_state( ctx );	/* update _Xmin, etc */
   }

   if (ctx->DrawBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
      _mesa_error(ctx, GL_INVALID_FRAMEBUFFER_OPERATION_EXT,
                  "glClear(incomplete framebuffer)");
      return;
   }

   if (ctx->DrawBuffer->Width == 0 || ctx->DrawBuffer->Height == 0)
      return;

   if (ctx->RenderMode == GL_RENDER) {
      GLbitfield bufferMask;

      /* don't clear depth buffer if depth writing disabled */
      if (!ctx->Depth.Mask)
         mask &= ~GL_DEPTH_BUFFER_BIT;

      /* Build the bitmask to send to device driver's Clear function.
       * Note that the GL_COLOR_BUFFER_BIT flag will expand to 0, 1, 2 or 4
       * of the BUFFER_BIT_FRONT/BACK_LEFT/RIGHT flags, or one of the
       * BUFFER_BIT_COLORn flags.
       */
      bufferMask = 0;
      if (mask & GL_COLOR_BUFFER_BIT) {
         bufferMask |= ctx->DrawBuffer->_ColorDrawBufferMask[0];
      }

      if ((mask & GL_DEPTH_BUFFER_BIT)
          && ctx->DrawBuffer->Visual.haveDepthBuffer) {
         bufferMask |= BUFFER_BIT_DEPTH;
      }

      if ((mask & GL_STENCIL_BUFFER_BIT)
          && ctx->DrawBuffer->Visual.haveStencilBuffer) {
         bufferMask |= BUFFER_BIT_STENCIL;
      }

      if ((mask & GL_ACCUM_BUFFER_BIT)
          && ctx->DrawBuffer->Visual.haveAccumBuffer) {
         bufferMask |= BUFFER_BIT_ACCUM;
      }

      ASSERT(ctx->Driver.Clear);
      ctx->Driver.Clear(ctx, bufferMask);
   }
}



/**
 * Return bitmask of BUFFER_BIT_* flags indicating which color buffers are
 * available to the rendering context (for drawing or reading).
 * This depends on the type of framebuffer.  For window system framebuffers
 * we look at the framebuffer's visual.  But for user-create framebuffers we
 * look at the number of supported color attachments.
 * \param fb  the framebuffer to draw to, or read from
 * \return  bitmask of BUFFER_BIT_* flags
 */
static GLbitfield
supported_buffer_bitmask(const GLcontext *ctx, const struct gl_framebuffer *fb)
{
   GLbitfield mask = 0x0;

   if (fb->Name > 0) {
      /* A user-created renderbuffer */
      GLuint i;
      ASSERT(ctx->Extensions.EXT_framebuffer_object);
      for (i = 0; i < ctx->Const.MaxColorAttachments; i++) {
         mask |= (BUFFER_BIT_COLOR0 << i);
      }
   }
   else {
      /* A window system framebuffer */
      GLint i;
      mask = BUFFER_BIT_FRONT_LEFT; /* always have this */
      if (fb->Visual.stereoMode) {
         mask |= BUFFER_BIT_FRONT_RIGHT;
         if (fb->Visual.doubleBufferMode) {
            mask |= BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
         }
      }
      else if (fb->Visual.doubleBufferMode) {
         mask |= BUFFER_BIT_BACK_LEFT;
      }

      for (i = 0; i < fb->Visual.numAuxBuffers; i++) {
         mask |= (BUFFER_BIT_AUX0 << i);
      }
   }

   return mask;
}


/**
 * Helper routine used by glDrawBuffer and glDrawBuffersARB.
 * Given a GLenum naming one or more color buffers (such as
 * GL_FRONT_AND_BACK), return the corresponding bitmask of BUFFER_BIT_* flags.
 */
static GLbitfield
draw_buffer_enum_to_bitmask(GLenum buffer)
{
   switch (buffer) {
      case GL_NONE:
         return 0;
      case GL_FRONT:
         return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_FRONT_RIGHT;
      case GL_BACK:
         return BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
      case GL_RIGHT:
         return BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
      case GL_FRONT_RIGHT:
         return BUFFER_BIT_FRONT_RIGHT;
      case GL_BACK_RIGHT:
         return BUFFER_BIT_BACK_RIGHT;
      case GL_BACK_LEFT:
         return BUFFER_BIT_BACK_LEFT;
      case GL_FRONT_AND_BACK:
         return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT
              | BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
      case GL_LEFT:
         return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT;
      case GL_FRONT_LEFT:
         return BUFFER_BIT_FRONT_LEFT;
      case GL_AUX0:
         return BUFFER_BIT_AUX0;
      case GL_AUX1:
         return BUFFER_BIT_AUX1;
      case GL_AUX2:
         return BUFFER_BIT_AUX2;
      case GL_AUX3:
         return BUFFER_BIT_AUX3;
      case GL_COLOR_ATTACHMENT0_EXT:
         return BUFFER_BIT_COLOR0;
      case GL_COLOR_ATTACHMENT1_EXT:
         return BUFFER_BIT_COLOR1;
      case GL_COLOR_ATTACHMENT2_EXT:
         return BUFFER_BIT_COLOR2;
      case GL_COLOR_ATTACHMENT3_EXT:
         return BUFFER_BIT_COLOR3;
      default:
         /* error */
         return BAD_MASK;
   }
}


/**
 * Helper routine used by glReadBuffer.
 * Given a GLenum naming a color buffer, return the index of the corresponding
 * renderbuffer (a BUFFER_* value).
 * return -1 for an invalid buffer.
 */
static GLint
read_buffer_enum_to_index(GLenum buffer)
{
   switch (buffer) {
      case GL_FRONT:
         return BUFFER_FRONT_LEFT;
      case GL_BACK:
         return BUFFER_BACK_LEFT;
      case GL_RIGHT:
         return BUFFER_FRONT_RIGHT;
      case GL_FRONT_RIGHT:
         return BUFFER_FRONT_RIGHT;
      case GL_BACK_RIGHT:
         return BUFFER_BACK_RIGHT;
      case GL_BACK_LEFT:
         return BUFFER_BACK_LEFT;
      case GL_LEFT:
         return BUFFER_FRONT_LEFT;
      case GL_FRONT_LEFT:
         return BUFFER_FRONT_LEFT;
      case GL_AUX0:
         return BUFFER_AUX0;
      case GL_AUX1:
         return BUFFER_AUX1;
      case GL_AUX2:
         return BUFFER_AUX2;
      case GL_AUX3:
         return BUFFER_AUX3;
      case GL_COLOR_ATTACHMENT0_EXT:
         return BUFFER_COLOR0;
      case GL_COLOR_ATTACHMENT1_EXT:
         return BUFFER_COLOR1;
      case GL_COLOR_ATTACHMENT2_EXT:
         return BUFFER_COLOR2;
      case GL_COLOR_ATTACHMENT3_EXT:
         return BUFFER_COLOR3;
      default:
         /* error */
         return -1;
   }
}


/**
 * Called by glDrawBuffer().
 * Specify which renderbuffer(s) to draw into for the first color output.
 * <buffer> can name zero, one, two or four renderbuffers!
 * \sa _mesa_DrawBuffersARB
 *
 * \param buffer  buffer token such as GL_LEFT or GL_FRONT_AND_BACK, etc.
 */
void GLAPIENTRY
_mesa_DrawBuffer(GLenum buffer)
{
   GLbitfield destMask;
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx); /* too complex... */

   if (MESA_VERBOSE & VERBOSE_API) {
      _mesa_debug(ctx, "glDrawBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
   }

   if (buffer == GL_NONE) {
      destMask = 0x0;
   }
   else {
      const GLbitfield supportedMask
         = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
      destMask = draw_buffer_enum_to_bitmask(buffer);
      if (destMask == BAD_MASK) {
         /* totally bogus buffer */
         _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffer(buffer)");
         return;
      }
      destMask &= supportedMask;
      if (destMask == 0x0) {
         /* none of the named color buffers exist! */
         _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffer(buffer)");
         return;
      }
   }

   /* if we get here, there's no error so set new state */
   _mesa_drawbuffers(ctx, 1, &buffer, &destMask);

   /*
    * Call device driver function.
    */
   if (ctx->Driver.DrawBuffers)
      ctx->Driver.DrawBuffers(ctx, 1, &buffer);
   else if (ctx->Driver.DrawBuffer)
      ctx->Driver.DrawBuffer(ctx, buffer);
}


/**
 * Called by glDrawBuffersARB; specifies the destination color renderbuffers
 * for N fragment program color outputs.
 * \sa _mesa_DrawBuffer
 * \param n  number of outputs
 * \param buffers  array [n] of renderbuffer names.  Unlike glDrawBuffer, the
 *                 names cannot specify more than one buffer.  For example,
 *                 GL_FRONT_AND_BACK is illegal.
 */
void GLAPIENTRY
_mesa_DrawBuffersARB(GLsizei n, const GLenum *buffers)
{
   GLint output;
   GLbitfield usedBufferMask, supportedMask;
   GLbitfield destMask[MAX_DRAW_BUFFERS];
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);

   if (!ctx->Extensions.ARB_draw_buffers) {
      _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB");
      return;
   }
   if (n < 1 || n > (GLsizei) ctx->Const.MaxDrawBuffers) {
      _mesa_error(ctx, GL_INVALID_VALUE, "glDrawBuffersARB(n)");
      return;
   }

   supportedMask = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
   usedBufferMask = 0x0;

   /* complicated error checking... */
   for (output = 0; output < n; output++) {
      if (buffers[output] == GL_NONE) {
         destMask[output] = 0x0;
      }
      else {
         destMask[output] = draw_buffer_enum_to_bitmask(buffers[output]);
         if (destMask[output] == BAD_MASK
             || _mesa_bitcount(destMask[output]) > 1) {
            _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffersARB(buffer)");
            return;
         }         
         destMask[output] &= supportedMask;
         if (destMask[output] == 0) {
            _mesa_error(ctx, GL_INVALID_OPERATION,
                        "glDrawBuffersARB(unsupported buffer)");
            return;
         }
         if (destMask[output] & usedBufferMask) {
            /* can't specify a dest buffer more than once! */
            _mesa_error(ctx, GL_INVALID_OPERATION,
                        "glDrawBuffersARB(duplicated buffer)");
            return;
         }

         /* update bitmask */
         usedBufferMask |= destMask[output];
      }
   }

   /* OK, if we get here, there were no errors so set the new state */
   _mesa_drawbuffers(ctx, n, buffers, destMask);

   /*
    * Call device driver function.
    */
   if (ctx->Driver.DrawBuffers)
      ctx->Driver.DrawBuffers(ctx, n, buffers);
   else if (ctx->Driver.DrawBuffer)
      ctx->Driver.DrawBuffer(ctx, buffers[0]);
}


/**
 * Set color output state.  Traditionally, there was only one color
 * output, but fragment programs can now have several distinct color
 * outputs (see GL_ARB_draw_buffers).  This function sets the state
 * for one such color output.
 * \param ctx  current context
 * \param output  which fragment program output
 * \param buffer  buffer to write to (like GL_LEFT)
 * \param destMask  BUFFER_* bitmask
 *                  (like BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT).
 */
static void
set_color_output(GLcontext *ctx, GLuint output, GLenum buffer,
                 GLbitfield destMask)
{
   struct gl_framebuffer *fb = ctx->DrawBuffer;

   ASSERT(output < ctx->Const.MaxDrawBuffers);

   /* Set per-FBO state */
   fb->ColorDrawBuffer[output] = buffer;
   fb->_ColorDrawBufferMask[output] = destMask;
   /* not really needed, will be set later */
   fb->_NumColorDrawBuffers[output] = 0;

   if (fb->Name == 0)
   /* Set traditional state var */
      ctx->Color.DrawBuffer[output] = buffer;
}


/**
 * Helper routine used by _mesa_DrawBuffer, _mesa_DrawBuffersARB and
 * other places (window fbo fixup) to set fbo (and the old ctx) fields.
 * All error checking will have been done prior to calling this function
 * so nothing should go wrong at this point.
 * \param ctx  current context
 * \param n    number of color outputs to set
 * \param buffers  array[n] of colorbuffer names, like GL_LEFT.
 * \param destMask  array[n] of BUFFER_* bitmasks which correspond to the
 *                  colorbuffer names.  (i.e. GL_FRONT_AND_BACK =>
 *                  BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT).
 */
void
_mesa_drawbuffers(GLcontext *ctx, GLuint n, const GLenum *buffers,
                  const GLbitfield *destMask)
{
   GLbitfield mask[MAX_DRAW_BUFFERS];
   GLuint output;

   if (!destMask) {
      /* compute destMask values now */
      const GLbitfield supportedMask
         = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
      for (output = 0; output < n; output++) {
         mask[output] = draw_buffer_enum_to_bitmask(buffers[output]);
         ASSERT(mask[output] != BAD_MASK);
         mask[output] &= supportedMask;
      }
      destMask = mask;
   }

   for (output = 0; output < n; output++) {
      set_color_output(ctx, output, buffers[output], destMask[output]);
   }

   /* set remaining color outputs to NONE */
   for (output = n; output < ctx->Const.MaxDrawBuffers; output++) {
      set_color_output(ctx, output, GL_NONE, 0x0);
   }

   ctx->NewState |= _NEW_BUFFERS;
}


GLboolean
_mesa_readbuffer_update_fields(GLcontext *ctx, GLenum buffer)
{
   struct gl_framebuffer *fb;
   GLbitfield supportedMask;
   GLint srcBuffer;

   fb = ctx->ReadBuffer;

   if (MESA_VERBOSE & VERBOSE_API)
      _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));

   if (fb->Name > 0 && buffer == GL_NONE) {
      /* This is legal for user-created framebuffer objects */
      srcBuffer = -1;
   }
   else {
      /* general case / window-system framebuffer */
      srcBuffer = read_buffer_enum_to_index(buffer);
      if (srcBuffer == -1) {
         _mesa_error(ctx, GL_INVALID_ENUM, "glReadBuffer(buffer=0x%x)", buffer);
         return GL_FALSE;
      }
      supportedMask = supported_buffer_bitmask(ctx, fb);
      if (((1 << srcBuffer) & supportedMask) == 0) {
         _mesa_error(ctx, GL_INVALID_OPERATION, "glReadBuffer(buffer=0x%x)", buffer);
         return GL_FALSE;
      }
   }

   if (fb->Name == 0) {
      ctx->Pixel.ReadBuffer = buffer;
   }
   fb->ColorReadBuffer = buffer;
   fb->_ColorReadBufferIndex = srcBuffer;

   return GL_TRUE;
}



/**
 * Called by glReadBuffer to set the source renderbuffer for reading pixels.
 * \param mode color buffer such as GL_FRONT, GL_BACK, etc.
 */
void GLAPIENTRY
_mesa_ReadBuffer(GLenum buffer)
{
   GET_CURRENT_CONTEXT(ctx);
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);

   if (MESA_VERBOSE & VERBOSE_API)
      _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));

   if (!_mesa_readbuffer_update_fields(ctx, buffer))
      return;

   ctx->NewState |= _NEW_BUFFERS;

   /*
    * Call device driver function.
    */
   if (ctx->Driver.ReadBuffer)
      (*ctx->Driver.ReadBuffer)(ctx, buffer);
}


#if _HAVE_FULL_GL

/**
 * XXX THIS IS OBSOLETE - drivers should take care of detecting window
 * size changes and act accordingly, likely calling _mesa_resize_framebuffer().
 *
 * GL_MESA_resize_buffers extension.
 *
 * When this function is called, we'll ask the window system how large
 * the current window is.  If it's a new size, we'll call the driver's
 * ResizeBuffers function.  The driver will then resize its color buffers
 * as needed, and maybe call the swrast's routine for reallocating
 * swrast-managed depth/stencil/accum/etc buffers.
 * \note This function should only be called through the GL API, not
 * from device drivers (as was done in the past).
 */

void _mesa_resizebuffers( GLcontext *ctx )
{
   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH( ctx );

   if (MESA_VERBOSE & VERBOSE_API)
      _mesa_debug(ctx, "glResizeBuffersMESA\n");

   if (!ctx->Driver.GetBufferSize) {
      return;
   }

   if (ctx->WinSysDrawBuffer) {
      GLuint newWidth, newHeight;
      GLframebuffer *buffer = ctx->WinSysDrawBuffer;

      assert(buffer->Name == 0);

      /* ask device driver for size of output buffer */
      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );

      /* see if size of device driver's color buffer (window) has changed */
      if (buffer->Width != newWidth || buffer->Height != newHeight) {
         if (ctx->Driver.ResizeBuffers)
            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
      }
   }

   if (ctx->WinSysReadBuffer
       && ctx->WinSysReadBuffer != ctx->WinSysDrawBuffer) {
      GLuint newWidth, newHeight;
      GLframebuffer *buffer = ctx->WinSysReadBuffer;

      assert(buffer->Name == 0);

      /* ask device driver for size of read buffer */
      ctx->Driver.GetBufferSize( buffer, &newWidth, &newHeight );

      /* see if size of device driver's color buffer (window) has changed */
      if (buffer->Width != newWidth || buffer->Height != newHeight) {
         if (ctx->Driver.ResizeBuffers)
            ctx->Driver.ResizeBuffers(ctx, buffer, newWidth, newHeight );
      }
   }

   ctx->NewState |= _NEW_BUFFERS;  /* to update scissor / window bounds */
}


/*
 * XXX THIS IS OBSOLETE
 */
void GLAPIENTRY
_mesa_ResizeBuffersMESA( void )
{
   GET_CURRENT_CONTEXT(ctx);

   if (ctx->Extensions.MESA_resize_buffers)
      _mesa_resizebuffers( ctx );
}


/*
 * XXX move somewhere else someday?
 */
void GLAPIENTRY
_mesa_SampleCoverageARB(GLclampf value, GLboolean invert)
{
   GET_CURRENT_CONTEXT(ctx);

   if (!ctx->Extensions.ARB_multisample) {
      _mesa_error(ctx, GL_INVALID_OPERATION, "glSampleCoverageARB");
      return;
   }

   ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH( ctx );
   ctx->Multisample.SampleCoverageValue = (GLfloat) CLAMP(value, 0.0, 1.0);
   ctx->Multisample.SampleCoverageInvert = invert;
   ctx->NewState |= _NEW_MULTISAMPLE;
}

#endif /* _HAVE_FULL_GL */



/**
 * Initialize the context's multisample state.
 * \param ctx  the GL context.
 */
void
_mesa_init_multisample(GLcontext *ctx)
{
   ctx->Multisample.Enabled = GL_FALSE;
   ctx->Multisample.SampleAlphaToCoverage = GL_FALSE;
   ctx->Multisample.SampleAlphaToOne = GL_FALSE;
   ctx->Multisample.SampleCoverage = GL_FALSE;
   ctx->Multisample.SampleCoverageValue = 1.0;
   ctx->Multisample.SampleCoverageInvert = GL_FALSE;
}