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