src/mesa/main/buffers.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.1
   4  *
   5  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  21  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  22  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  23  * OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26
  27 /**
  28  * \file buffers.c
  29  * glReadBuffer, DrawBuffer functions.
  30  */
  31
  32
  33
  34 #include "glheader.h"
  35 #include "buffers.h"
  36 #include "colormac.h"
  37 #include "context.h"
  38 #include "enums.h"
  39 #include "fbobject.h"
  40 #include "mtypes.h"
  41
  42
  43 #define BAD_MASK ~0u
  44
  45
  46 /**
  47  * Return bitmask of BUFFER_BIT_* flags indicating which color buffers are
  48  * available to the rendering context (for drawing or reading).
  49  * This depends on the type of framebuffer.  For window system framebuffers
  50  * we look at the framebuffer's visual.  But for user-create framebuffers we
  51  * look at the number of supported color attachments.
  52  * \param fb  the framebuffer to draw to, or read from
  53  * \return  bitmask of BUFFER_BIT_* flags
  54  */
  55 static GLbitfield
  56 supported_buffer_bitmask(const struct gl_context *ctx,
  57                          const struct gl_framebuffer *fb)
  58 {
  59    GLbitfield mask = 0x0;
  60
  61    if (_mesa_is_user_fbo(fb)) {
  62       /* A user-created renderbuffer */
  63       GLuint i;
  64       ASSERT(ctx->Extensions.EXT_framebuffer_object);
  65       for (i = 0; i < ctx->Const.MaxColorAttachments; i++) {
  66          mask |= (BUFFER_BIT_COLOR0 << i);
  67       }
  68    }
  69    else {
  70       /* A window system framebuffer */
  71       GLint i;
  72       mask = BUFFER_BIT_FRONT_LEFT; /* always have this */
  73       if (fb->Visual.stereoMode) {
  74          mask |= BUFFER_BIT_FRONT_RIGHT;
  75          if (fb->Visual.doubleBufferMode) {
  76             mask |= BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
  77          }
  78       }
  79       else if (fb->Visual.doubleBufferMode) {
  80          mask |= BUFFER_BIT_BACK_LEFT;
  81       }
  82
  83       for (i = 0; i < fb->Visual.numAuxBuffers; i++) {
  84          mask |= (BUFFER_BIT_AUX0 << i);
  85       }
  86    }
  87
  88    return mask;
  89 }
  90
  91
  92 /**
  93  * Helper routine used by glDrawBuffer and glDrawBuffersARB.
  94  * Given a GLenum naming one or more color buffers (such as
  95  * GL_FRONT_AND_BACK), return the corresponding bitmask of BUFFER_BIT_* flags.
  96  */
  97 static GLbitfield
  98 draw_buffer_enum_to_bitmask(const struct gl_context *ctx, GLenum buffer)
  99 {
 100    switch (buffer) {
 101       case GL_NONE:
 102          return 0;
 103       case GL_FRONT:
 104          return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_FRONT_RIGHT;
 105       case GL_BACK:
 106          if (_mesa_is_gles3(ctx)) {
 107             /* Page 181 (page 192 of the PDF) in section 4.2.1 of the OpenGL
 108              * ES 3.0.1 specification says:
 109              *
 110              *     "When draw buffer zero is BACK, color values are written
 111              *     into the sole buffer for single-buffered contexts, or into
 112              *     the back buffer for double-buffered contexts."
 113              *
 114              * Since there is no stereo rendering in ES 3.0, only return the
 115              * LEFT bits.  This also satisfies the "n must be 1" requirement.
 116              */
 117             if (ctx->DrawBuffer->Visual.doubleBufferMode)
 118                return BUFFER_BIT_BACK_LEFT;
 119             return BUFFER_BIT_FRONT_LEFT;
 120          }
 121          return BUFFER_BIT_BACK_LEFT | BUFFER_BIT_BACK_RIGHT;
 122       case GL_RIGHT:
 123          return BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
 124       case GL_FRONT_RIGHT:
 125          return BUFFER_BIT_FRONT_RIGHT;
 126       case GL_BACK_RIGHT:
 127          return BUFFER_BIT_BACK_RIGHT;
 128       case GL_BACK_LEFT:
 129          return BUFFER_BIT_BACK_LEFT;
 130       case GL_FRONT_AND_BACK:
 131          return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT
 132               | BUFFER_BIT_FRONT_RIGHT | BUFFER_BIT_BACK_RIGHT;
 133       case GL_LEFT:
 134          return BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT;
 135       case GL_FRONT_LEFT:
 136          return BUFFER_BIT_FRONT_LEFT;
 137       case GL_AUX0:
 138          return BUFFER_BIT_AUX0;
 139       case GL_AUX1:
 140       case GL_AUX2:
 141       case GL_AUX3:
 142          return 1 << BUFFER_COUNT; /* invalid, but not BAD_MASK */
 143       case GL_COLOR_ATTACHMENT0_EXT:
 144          return BUFFER_BIT_COLOR0;
 145       case GL_COLOR_ATTACHMENT1_EXT:
 146          return BUFFER_BIT_COLOR1;
 147       case GL_COLOR_ATTACHMENT2_EXT:
 148          return BUFFER_BIT_COLOR2;
 149       case GL_COLOR_ATTACHMENT3_EXT:
 150          return BUFFER_BIT_COLOR3;
 151       case GL_COLOR_ATTACHMENT4_EXT:
 152          return BUFFER_BIT_COLOR4;
 153       case GL_COLOR_ATTACHMENT5_EXT:
 154          return BUFFER_BIT_COLOR5;
 155       case GL_COLOR_ATTACHMENT6_EXT:
 156          return BUFFER_BIT_COLOR6;
 157       case GL_COLOR_ATTACHMENT7_EXT:
 158          return BUFFER_BIT_COLOR7;
 159       default:
 160          /* error */
 161          return BAD_MASK;
 162    }
 163 }
 164
 165
 166 /**
 167  * Helper routine used by glReadBuffer.
 168  * Given a GLenum naming a color buffer, return the index of the corresponding
 169  * renderbuffer (a BUFFER_* value).
 170  * return -1 for an invalid buffer.
 171  */
 172 static GLint
 173 read_buffer_enum_to_index(GLenum buffer)
 174 {
 175    switch (buffer) {
 176       case GL_FRONT:
 177          return BUFFER_FRONT_LEFT;
 178       case GL_BACK:
 179          return BUFFER_BACK_LEFT;
 180       case GL_RIGHT:
 181          return BUFFER_FRONT_RIGHT;
 182       case GL_FRONT_RIGHT:
 183          return BUFFER_FRONT_RIGHT;
 184       case GL_BACK_RIGHT:
 185          return BUFFER_BACK_RIGHT;
 186       case GL_BACK_LEFT:
 187          return BUFFER_BACK_LEFT;
 188       case GL_LEFT:
 189          return BUFFER_FRONT_LEFT;
 190       case GL_FRONT_LEFT:
 191          return BUFFER_FRONT_LEFT;
 192       case GL_AUX0:
 193          return BUFFER_AUX0;
 194       case GL_AUX1:
 195       case GL_AUX2:
 196       case GL_AUX3:
 197          return BUFFER_COUNT; /* invalid, but not -1 */
 198       case GL_COLOR_ATTACHMENT0_EXT:
 199          return BUFFER_COLOR0;
 200       case GL_COLOR_ATTACHMENT1_EXT:
 201          return BUFFER_COLOR1;
 202       case GL_COLOR_ATTACHMENT2_EXT:
 203          return BUFFER_COLOR2;
 204       case GL_COLOR_ATTACHMENT3_EXT:
 205          return BUFFER_COLOR3;
 206       case GL_COLOR_ATTACHMENT4_EXT:
 207          return BUFFER_COLOR4;
 208       case GL_COLOR_ATTACHMENT5_EXT:
 209          return BUFFER_COLOR5;
 210       case GL_COLOR_ATTACHMENT6_EXT:
 211          return BUFFER_COLOR6;
 212       case GL_COLOR_ATTACHMENT7_EXT:
 213          return BUFFER_COLOR7;
 214       default:
 215          /* error */
 216          return -1;
 217    }
 218 }
 219
 220
 221 /**
 222  * Called by glDrawBuffer().
 223  * Specify which renderbuffer(s) to draw into for the first color output.
 224  * <buffer> can name zero, one, two or four renderbuffers!
 225  * \sa _mesa_DrawBuffers
 226  *
 227  * \param buffer  buffer token such as GL_LEFT or GL_FRONT_AND_BACK, etc.
 228  *
 229  * Note that the behaviour of this function depends on whether the
 230  * current ctx->DrawBuffer is a window-system framebuffer (Name=0) or
 231  * a user-created framebuffer object (Name!=0).
 232  *   In the former case, we update the per-context ctx->Color.DrawBuffer
 233  *   state var _and_ the FB's ColorDrawBuffer state.
 234  *   In the later case, we update the FB's ColorDrawBuffer state only.
 235  *
 236  * Furthermore, upon a MakeCurrent() or BindFramebuffer() call, if the
 237  * new FB is a window system FB, we need to re-update the FB's
 238  * ColorDrawBuffer state to match the context.  This is handled in
 239  * _mesa_update_framebuffer().
 240  *
 241  * See the GL_EXT_framebuffer_object spec for more info.
 242  */
 243 void GLAPIENTRY
 244 _mesa_DrawBuffer(GLenum buffer)
 245 {
 246    GLbitfield destMask;
 247    GET_CURRENT_CONTEXT(ctx);
 248
 249    FLUSH_VERTICES(ctx, 0);
 250
 251    if (MESA_VERBOSE & VERBOSE_API) {
 252       _mesa_debug(ctx, "glDrawBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 253    }
 254
 255    if (buffer == GL_NONE) {
 256       destMask = 0x0;
 257    }
 258    else {
 259       const GLbitfield supportedMask
 260          = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
 261       destMask = draw_buffer_enum_to_bitmask(ctx, buffer);
 262       if (destMask == BAD_MASK) {
 263          /* totally bogus buffer */
 264          _mesa_error(ctx, GL_INVALID_ENUM,
 265                      "glDrawBuffer(buffer=0x%x)", buffer);
 266          return;
 267       }
 268       destMask &= supportedMask;
 269       if (destMask == 0x0) {
 270          /* none of the named color buffers exist! */
 271          _mesa_error(ctx, GL_INVALID_OPERATION,
 272                      "glDrawBuffer(buffer=0x%x)", buffer);
 273          return;
 274       }
 275    }
 276
 277    /* if we get here, there's no error so set new state */
 278    _mesa_drawbuffers(ctx, 1, &buffer, &destMask);
 279
 280    /*
 281     * Call device driver function.
 282     */
 283    if (ctx->Driver.DrawBuffers)
 284       ctx->Driver.DrawBuffers(ctx, 1, &buffer);
 285    else if (ctx->Driver.DrawBuffer)
 286       ctx->Driver.DrawBuffer(ctx, buffer);
 287 }
 288
 289
 290 /**
 291  * Called by glDrawBuffersARB; specifies the destination color renderbuffers
 292  * for N fragment program color outputs.
 293  * \sa _mesa_DrawBuffer
 294  * \param n  number of outputs
 295  * \param buffers  array [n] of renderbuffer names.  Unlike glDrawBuffer, the
 296  *                 names cannot specify more than one buffer.  For example,
 297  *                 GL_FRONT_AND_BACK is illegal.
 298  */
 299 void GLAPIENTRY
 300 _mesa_DrawBuffers(GLsizei n, const GLenum *buffers)
 301 {
 302    GLint output;
 303    GLbitfield usedBufferMask, supportedMask;
 304    GLbitfield destMask[MAX_DRAW_BUFFERS];
 305    GET_CURRENT_CONTEXT(ctx);
 306
 307    FLUSH_VERTICES(ctx, 0);
 308
 309    /* Turns out n==0 is a valid input that should not produce an error.
 310     * The remaining code below correctly handles the n==0 case.
 311     *
 312     * From the OpenGL 3.0 specification, page 258:
 313     * "An INVALID_VALUE error is generated if n is greater than
 314     *  MAX_DRAW_BUFFERS."
 315     */
 316    if (n < 0 || n > (GLsizei) ctx->Const.MaxDrawBuffers) {
 317       _mesa_error(ctx, GL_INVALID_VALUE, "glDrawBuffersARB(n)");
 318       return;
 319    }
 320
 321    supportedMask = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
 322    usedBufferMask = 0x0;
 323
 324    /* From the ES 3.0 specification, page 180:
 325     * "If the GL is bound to the default framebuffer, then n must be 1
 326     *  and the constant must be BACK or NONE."
 327     */
 328    if (_mesa_is_gles3(ctx) && _mesa_is_winsys_fbo(ctx->DrawBuffer) &&
 329        (n != 1 || (buffers[0] != GL_NONE && buffers[0] != GL_BACK))) {
 330       _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffers(buffer)");
 331       return;
 332    }
 333
 334    /* complicated error checking... */
 335    for (output = 0; output < n; output++) {
 336       if (buffers[output] == GL_NONE) {
 337          destMask[output] = 0x0;
 338       }
 339       else {
 340          /* Page 259 (page 275 of the PDF) in section 4.2.1 of the OpenGL 3.0
 341           * spec (20080923) says:
 342           *
 343           *     "If the GL is bound to a framebuffer object and DrawBuffers is
 344           *     supplied with [...] COLOR_ATTACHMENTm where m is greater than
 345           *     or equal to the value of MAX_COLOR_ATTACHMENTS, then the error
 346           *     INVALID_OPERATION results."
 347           */
 348          if (_mesa_is_user_fbo(ctx->DrawBuffer) && buffers[output] >=
 349              GL_COLOR_ATTACHMENT0 + ctx->Const.MaxDrawBuffers) {
 350             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB(buffer)");
 351             return;
 352          }
 353
 354          destMask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
 355
 356          /* From the OpenGL 3.0 specification, page 258:
 357           * "Each buffer listed in bufs must be one of the values from tables
 358           *  4.5 or 4.6.  Otherwise, an INVALID_ENUM error is generated.
 359           */
 360          if (destMask[output] == BAD_MASK) {
 361             _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffersARB(buffer)");
 362             return;
 363          }
 364
 365          /* From the OpenGL 3.0 specification, page 259:
 366           * "For both the default framebuffer and framebuffer objects, the
 367           *  constants FRONT, BACK, LEFT, RIGHT, and FRONT_AND_BACK are not
 368           *  valid in the bufs array passed to DrawBuffers, and will result in
 369           *  the error INVALID_OPERATION.  This restriction is because these
 370           *  constants may themselves refer to multiple buffers, as shown in
 371           *  table 4.4."
 372           */
 373          if (_mesa_bitcount(destMask[output]) > 1) {
 374             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB(buffer)");
 375             return;
 376          }
 377
 378          /* From the OpenGL 3.0 specification, page 259:
 379           * "If the GL is bound to the default framebuffer and DrawBuffers is
 380           *  supplied with a constant (other than NONE) that does not indicate
 381           *  any of the color buffers allocated to the GL context by the window
 382           *  system, the error INVALID_OPERATION will be generated.
 383           *
 384           *  If the GL is bound to a framebuffer object and DrawBuffers is
 385           *  supplied with a constant from table 4.6 [...] then the error
 386           *  INVALID_OPERATION results."
 387           */
 388          destMask[output] &= supportedMask;
 389          if (destMask[output] == 0) {
 390             _mesa_error(ctx, GL_INVALID_OPERATION,
 391                         "glDrawBuffersARB(unsupported buffer)");
 392             return;
 393          }
 394
 395          /* ES 3.0 is even more restrictive.  From the ES 3.0 spec, page 180:
 396           * "If the GL is bound to a framebuffer object, the ith buffer listed
 397           *  in bufs must be COLOR_ATTACHMENTi or NONE. [...] INVALID_OPERATION."
 398           */
 399          if (_mesa_is_gles3(ctx) && _mesa_is_user_fbo(ctx->DrawBuffer) &&
 400              buffers[output] != GL_NONE &&
 401              buffers[output] != GL_COLOR_ATTACHMENT0 + output) {
 402             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffers(buffer)");
 403             return;
 404          }
 405
 406          /* From the OpenGL 3.0 specification, page 258:
 407           * "Except for NONE, a buffer may not appear more than once in the
 408           *  array pointed to by bufs.  Specifying a buffer more then once will
 409           *  result in the error INVALID_OPERATION."
 410           */
 411          if (destMask[output] & usedBufferMask) {
 412             _mesa_error(ctx, GL_INVALID_OPERATION,
 413                         "glDrawBuffersARB(duplicated buffer)");
 414             return;
 415          }
 416
 417          /* update bitmask */
 418          usedBufferMask |= destMask[output];
 419       }
 420    }
 421
 422    /* OK, if we get here, there were no errors so set the new state */
 423    _mesa_drawbuffers(ctx, n, buffers, destMask);
 424
 425    /*
 426     * Call device driver function.  Note that n can be equal to 0,
 427     * in which case we don't want to reference buffers[0], which
 428     * may not be valid.
 429     */
 430    if (ctx->Driver.DrawBuffers)
 431       ctx->Driver.DrawBuffers(ctx, n, buffers);
 432    else if (ctx->Driver.DrawBuffer)
 433       ctx->Driver.DrawBuffer(ctx, n > 0 ? buffers[0] : GL_NONE);
 434 }
 435
 436
 437 /**
 438  * Performs necessary state updates when _mesa_drawbuffers makes an
 439  * actual change.
 440  */
 441 static void
 442 updated_drawbuffers(struct gl_context *ctx)
 443 {
 444    FLUSH_VERTICES(ctx, _NEW_BUFFERS);
 445
 446    if (ctx->API == API_OPENGL_COMPAT && !ctx->Extensions.ARB_ES2_compatibility) {
 447       struct gl_framebuffer *fb = ctx->DrawBuffer;
 448
 449       /* Flag the FBO as requiring validation. */
 450       if (_mesa_is_user_fbo(fb)) {
 451          fb->_Status = 0;
 452       }
 453    }
 454 }
 455
 456
 457 /**
 458  * Helper function to set the GL_DRAW_BUFFER state in the context and
 459  * current FBO.  Called via glDrawBuffer(), glDrawBuffersARB()
 460  *
 461  * All error checking will have been done prior to calling this function
 462  * so nothing should go wrong at this point.
 463  *
 464  * \param ctx  current context
 465  * \param n    number of color outputs to set
 466  * \param buffers  array[n] of colorbuffer names, like GL_LEFT.
 467  * \param destMask  array[n] of BUFFER_BIT_* bitmasks which correspond to the
 468  *                  colorbuffer names.  (i.e. GL_FRONT_AND_BACK =>
 469  *                  BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT).
 470  */
 471 void
 472 _mesa_drawbuffers(struct gl_context *ctx, GLuint n, const GLenum *buffers,
 473                   const GLbitfield *destMask)
 474 {
 475    struct gl_framebuffer *fb = ctx->DrawBuffer;
 476    GLbitfield mask[MAX_DRAW_BUFFERS];
 477    GLuint buf;
 478
 479    if (!destMask) {
 480       /* compute destMask values now */
 481       const GLbitfield supportedMask = supported_buffer_bitmask(ctx, fb);
 482       GLuint output;
 483       for (output = 0; output < n; output++) {
 484          mask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
 485          ASSERT(mask[output] != BAD_MASK);
 486          mask[output] &= supportedMask;
 487       }
 488       destMask = mask;
 489    }
 490
 491    /*
 492     * If n==1, destMask[0] may have up to four bits set.
 493     * Otherwise, destMask[x] can only have one bit set.
 494     */
 495    if (n == 1) {
 496       GLuint count = 0, destMask0 = destMask[0];
 497       while (destMask0) {
 498          GLint bufIndex = ffs(destMask0) - 1;
 499          if (fb->_ColorDrawBufferIndexes[count] != bufIndex) {
 500             updated_drawbuffers(ctx);
 501             fb->_ColorDrawBufferIndexes[count] = bufIndex;
 502          }
 503          count++;
 504          destMask0 &= ~(1 << bufIndex);
 505       }
 506       fb->ColorDrawBuffer[0] = buffers[0];
 507       fb->_NumColorDrawBuffers = count;
 508    }
 509    else {
 510       GLuint count = 0;
 511       for (buf = 0; buf < n; buf++ ) {
 512          if (destMask[buf]) {
 513             GLint bufIndex = ffs(destMask[buf]) - 1;
 514             /* only one bit should be set in the destMask[buf] field */
 515             ASSERT(_mesa_bitcount(destMask[buf]) == 1);
 516             if (fb->_ColorDrawBufferIndexes[buf] != bufIndex) {
 517                updated_drawbuffers(ctx);
 518                fb->_ColorDrawBufferIndexes[buf] = bufIndex;
 519             }
 520             count = buf + 1;
 521          }
 522          else {
 523             if (fb->_ColorDrawBufferIndexes[buf] != -1) {
 524                updated_drawbuffers(ctx);
 525                fb->_ColorDrawBufferIndexes[buf] = -1;
 526             }
 527          }
 528          fb->ColorDrawBuffer[buf] = buffers[buf];
 529       }
 530       fb->_NumColorDrawBuffers = count;
 531    }
 532
 533    /* set remaining outputs to -1 (GL_NONE) */
 534    for (buf = fb->_NumColorDrawBuffers; buf < ctx->Const.MaxDrawBuffers; buf++) {
 535       if (fb->_ColorDrawBufferIndexes[buf] != -1) {
 536          updated_drawbuffers(ctx);
 537          fb->_ColorDrawBufferIndexes[buf] = -1;
 538       }
 539    }
 540    for (buf = n; buf < ctx->Const.MaxDrawBuffers; buf++) {
 541       fb->ColorDrawBuffer[buf] = GL_NONE;
 542    }
 543
 544    if (_mesa_is_winsys_fbo(fb)) {
 545       /* also set context drawbuffer state */
 546       for (buf = 0; buf < ctx->Const.MaxDrawBuffers; buf++) {
 547          if (ctx->Color.DrawBuffer[buf] != fb->ColorDrawBuffer[buf]) {
 548             updated_drawbuffers(ctx);
 549             ctx->Color.DrawBuffer[buf] = fb->ColorDrawBuffer[buf];
 550          }
 551       }
 552    }
 553 }
 554
 555
 556 /**
 557  * Update the current drawbuffer's _ColorDrawBufferIndex[] list, etc.
 558  * from the context's Color.DrawBuffer[] state.
 559  * Use when changing contexts.
 560  */
 561 void
 562 _mesa_update_draw_buffers(struct gl_context *ctx)
 563 {
 564    GLenum buffers[MAX_DRAW_BUFFERS];
 565    GLuint i;
 566
 567    /* should be a window system FBO */
 568    assert(_mesa_is_winsys_fbo(ctx->DrawBuffer));
 569
 570    for (i = 0; i < ctx->Const.MaxDrawBuffers; i++)
 571       buffers[i] = ctx->Color.DrawBuffer[i];
 572
 573    _mesa_drawbuffers(ctx, ctx->Const.MaxDrawBuffers, buffers, NULL);
 574 }
 575
 576
 577 /**
 578  * Like \sa _mesa_drawbuffers(), this is a helper function for setting
 579  * GL_READ_BUFFER state in the context and current FBO.
 580  * \param ctx  the rendering context
 581  * \param buffer  GL_FRONT, GL_BACK, GL_COLOR_ATTACHMENT0, etc.
 582  * \param bufferIndex  the numerical index corresponding to 'buffer'
 583  */
 584 void
 585 _mesa_readbuffer(struct gl_context *ctx, GLenum buffer, GLint bufferIndex)
 586 {
 587    struct gl_framebuffer *fb = ctx->ReadBuffer;
 588
 589    if (_mesa_is_winsys_fbo(fb)) {
 590       /* Only update the per-context READ_BUFFER state if we're bound to
 591        * a window-system framebuffer.
 592        */
 593       ctx->Pixel.ReadBuffer = buffer;
 594    }
 595
 596    fb->ColorReadBuffer = buffer;
 597    fb->_ColorReadBufferIndex = bufferIndex;
 598
 599    ctx->NewState |= _NEW_BUFFERS;
 600 }
 601
 602
 603
 604 /**
 605  * Called by glReadBuffer to set the source renderbuffer for reading pixels.
 606  * \param mode color buffer such as GL_FRONT, GL_BACK, etc.
 607  */
 608 void GLAPIENTRY
 609 _mesa_ReadBuffer(GLenum buffer)
 610 {
 611    struct gl_framebuffer *fb;
 612    GLbitfield supportedMask;
 613    GLint srcBuffer;
 614    GET_CURRENT_CONTEXT(ctx);
 615
 616    FLUSH_VERTICES(ctx, 0);
 617
 618    if (MESA_VERBOSE & VERBOSE_API)
 619       _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 620
 621    fb = ctx->ReadBuffer;
 622
 623    if (MESA_VERBOSE & VERBOSE_API)
 624       _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 625
 626    if (buffer == GL_NONE) {
 627       /* This is legal--it means that no buffer should be bound for reading. */
 628       srcBuffer = -1;
 629    }
 630    else {
 631       /* general case / window-system framebuffer */
 632       srcBuffer = read_buffer_enum_to_index(buffer);
 633       if (srcBuffer == -1) {
 634          _mesa_error(ctx, GL_INVALID_ENUM,
 635                      "glReadBuffer(buffer=0x%x)", buffer);
 636          return;
 637       }
 638       supportedMask = supported_buffer_bitmask(ctx, fb);
 639       if (((1 << srcBuffer) & supportedMask) == 0) {
 640          _mesa_error(ctx, GL_INVALID_OPERATION,
 641                      "glReadBuffer(buffer=0x%x)", buffer);
 642          return;
 643       }
 644    }
 645
 646    /* OK, all error checking has been completed now */
 647
 648    _mesa_readbuffer(ctx, buffer, srcBuffer);
 649
 650    /*
 651     * Call device driver function.
 652     */
 653    if (ctx->Driver.ReadBuffer)
 654       (*ctx->Driver.ReadBuffer)(ctx, buffer);
 655 }