src/mesa/main/buffers.c

   1 /*
   2  * Mesa 3-D graphics library
   3  *
   4  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included
  14  * in all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  17  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  22  * 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 or a user-created
 230  * framebuffer object.
 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
 248    FLUSH_VERTICES(ctx, 0);
 249
 250    if (MESA_VERBOSE & VERBOSE_API) {
 251       _mesa_debug(ctx, "glDrawBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 252    }
 253
 254    if (buffer == GL_NONE) {
 255       destMask = 0x0;
 256    }
 257    else {
 258       const GLbitfield supportedMask
 259          = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
 260       destMask = draw_buffer_enum_to_bitmask(ctx, buffer);
 261       if (destMask == BAD_MASK) {
 262          /* totally bogus buffer */
 263          _mesa_error(ctx, GL_INVALID_ENUM,
 264                      "glDrawBuffer(buffer=0x%x)", buffer);
 265          return;
 266       }
 267       destMask &= supportedMask;
 268       if (destMask == 0x0) {
 269          /* none of the named color buffers exist! */
 270          _mesa_error(ctx, GL_INVALID_OPERATION,
 271                      "glDrawBuffer(buffer=0x%x)", buffer);
 272          return;
 273       }
 274    }
 275
 276    /* if we get here, there's no error so set new state */
 277    _mesa_drawbuffers(ctx, 1, &buffer, &destMask);
 278
 279    /*
 280     * Call device driver function.
 281     */
 282    if (ctx->Driver.DrawBuffers)
 283       ctx->Driver.DrawBuffers(ctx, 1, &buffer);
 284    else if (ctx->Driver.DrawBuffer)
 285       ctx->Driver.DrawBuffer(ctx, buffer);
 286 }
 287
 288
 289 /**
 290  * Called by glDrawBuffersARB; specifies the destination color renderbuffers
 291  * for N fragment program color outputs.
 292  * \sa _mesa_DrawBuffer
 293  * \param n  number of outputs
 294  * \param buffers  array [n] of renderbuffer names.  Unlike glDrawBuffer, the
 295  *                 names cannot specify more than one buffer.  For example,
 296  *                 GL_FRONT_AND_BACK is illegal.
 297  */
 298 void GLAPIENTRY
 299 _mesa_DrawBuffers(GLsizei n, const GLenum *buffers)
 300 {
 301    GLint output;
 302    GLbitfield usedBufferMask, supportedMask;
 303    GLbitfield destMask[MAX_DRAW_BUFFERS];
 304    GET_CURRENT_CONTEXT(ctx);
 305
 306    FLUSH_VERTICES(ctx, 0);
 307
 308    /* Turns out n==0 is a valid input that should not produce an error.
 309     * The remaining code below correctly handles the n==0 case.
 310     *
 311     * From the OpenGL 3.0 specification, page 258:
 312     * "An INVALID_VALUE error is generated if n is greater than
 313     *  MAX_DRAW_BUFFERS."
 314     */
 315    if (n < 0 || n > (GLsizei) ctx->Const.MaxDrawBuffers) {
 316       _mesa_error(ctx, GL_INVALID_VALUE, "glDrawBuffersARB(n)");
 317       return;
 318    }
 319
 320    supportedMask = supported_buffer_bitmask(ctx, ctx->DrawBuffer);
 321    usedBufferMask = 0x0;
 322
 323    /* From the ES 3.0 specification, page 180:
 324     * "If the GL is bound to the default framebuffer, then n must be 1
 325     *  and the constant must be BACK or NONE."
 326     */
 327    if (_mesa_is_gles3(ctx) && _mesa_is_winsys_fbo(ctx->DrawBuffer) &&
 328        (n != 1 || (buffers[0] != GL_NONE && buffers[0] != GL_BACK))) {
 329       _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffers(buffer)");
 330       return;
 331    }
 332
 333    /* complicated error checking... */
 334    for (output = 0; output < n; output++) {
 335       if (buffers[output] == GL_NONE) {
 336          destMask[output] = 0x0;
 337       }
 338       else {
 339          /* Page 259 (page 275 of the PDF) in section 4.2.1 of the OpenGL 3.0
 340           * spec (20080923) says:
 341           *
 342           *     "If the GL is bound to a framebuffer object and DrawBuffers is
 343           *     supplied with [...] COLOR_ATTACHMENTm where m is greater than
 344           *     or equal to the value of MAX_COLOR_ATTACHMENTS, then the error
 345           *     INVALID_OPERATION results."
 346           */
 347          if (_mesa_is_user_fbo(ctx->DrawBuffer) && buffers[output] >=
 348              GL_COLOR_ATTACHMENT0 + ctx->Const.MaxDrawBuffers) {
 349             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB(buffer)");
 350             return;
 351          }
 352
 353          destMask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
 354
 355          /* From the OpenGL 3.0 specification, page 258:
 356           * "Each buffer listed in bufs must be one of the values from tables
 357           *  4.5 or 4.6.  Otherwise, an INVALID_ENUM error is generated.
 358           */
 359          if (destMask[output] == BAD_MASK) {
 360             _mesa_error(ctx, GL_INVALID_ENUM, "glDrawBuffersARB(buffer)");
 361             return;
 362          }
 363
 364          /* From the OpenGL 3.0 specification, page 259:
 365           * "For both the default framebuffer and framebuffer objects, the
 366           *  constants FRONT, BACK, LEFT, RIGHT, and FRONT_AND_BACK are not
 367           *  valid in the bufs array passed to DrawBuffers, and will result in
 368           *  the error INVALID_OPERATION.  This restriction is because these
 369           *  constants may themselves refer to multiple buffers, as shown in
 370           *  table 4.4."
 371           */
 372          if (_mesa_bitcount(destMask[output]) > 1) {
 373             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffersARB(buffer)");
 374             return;
 375          }
 376
 377          /* From the OpenGL 3.0 specification, page 259:
 378           * "If the GL is bound to the default framebuffer and DrawBuffers is
 379           *  supplied with a constant (other than NONE) that does not indicate
 380           *  any of the color buffers allocated to the GL context by the window
 381           *  system, the error INVALID_OPERATION will be generated.
 382           *
 383           *  If the GL is bound to a framebuffer object and DrawBuffers is
 384           *  supplied with a constant from table 4.6 [...] then the error
 385           *  INVALID_OPERATION results."
 386           */
 387          destMask[output] &= supportedMask;
 388          if (destMask[output] == 0) {
 389             _mesa_error(ctx, GL_INVALID_OPERATION,
 390                         "glDrawBuffersARB(unsupported buffer)");
 391             return;
 392          }
 393
 394          /* ES 3.0 is even more restrictive.  From the ES 3.0 spec, page 180:
 395           * "If the GL is bound to a framebuffer object, the ith buffer listed
 396           *  in bufs must be COLOR_ATTACHMENTi or NONE. [...] INVALID_OPERATION."
 397           */
 398          if (_mesa_is_gles3(ctx) && _mesa_is_user_fbo(ctx->DrawBuffer) &&
 399              buffers[output] != GL_NONE &&
 400              buffers[output] != GL_COLOR_ATTACHMENT0 + output) {
 401             _mesa_error(ctx, GL_INVALID_OPERATION, "glDrawBuffers(buffer)");
 402             return;
 403          }
 404
 405          /* From the OpenGL 3.0 specification, page 258:
 406           * "Except for NONE, a buffer may not appear more than once in the
 407           *  array pointed to by bufs.  Specifying a buffer more then once will
 408           *  result in the error INVALID_OPERATION."
 409           */
 410          if (destMask[output] & usedBufferMask) {
 411             _mesa_error(ctx, GL_INVALID_OPERATION,
 412                         "glDrawBuffersARB(duplicated buffer)");
 413             return;
 414          }
 415
 416          /* update bitmask */
 417          usedBufferMask |= destMask[output];
 418       }
 419    }
 420
 421    /* OK, if we get here, there were no errors so set the new state */
 422    _mesa_drawbuffers(ctx, n, buffers, destMask);
 423
 424    /*
 425     * Call device driver function.  Note that n can be equal to 0,
 426     * in which case we don't want to reference buffers[0], which
 427     * may not be valid.
 428     */
 429    if (ctx->Driver.DrawBuffers)
 430       ctx->Driver.DrawBuffers(ctx, n, buffers);
 431    else if (ctx->Driver.DrawBuffer)
 432       ctx->Driver.DrawBuffer(ctx, n > 0 ? buffers[0] : GL_NONE);
 433 }
 434
 435
 436 /**
 437  * Performs necessary state updates when _mesa_drawbuffers makes an
 438  * actual change.
 439  */
 440 static void
 441 updated_drawbuffers(struct gl_context *ctx)
 442 {
 443    FLUSH_VERTICES(ctx, _NEW_BUFFERS);
 444
 445    if (ctx->API == API_OPENGL_COMPAT && !ctx->Extensions.ARB_ES2_compatibility) {
 446       struct gl_framebuffer *fb = ctx->DrawBuffer;
 447
 448       /* Flag the FBO as requiring validation. */
 449       if (_mesa_is_user_fbo(fb)) {
 450          fb->_Status = 0;
 451       }
 452    }
 453 }
 454
 455
 456 /**
 457  * Helper function to set the GL_DRAW_BUFFER state in the context and
 458  * current FBO.  Called via glDrawBuffer(), glDrawBuffersARB()
 459  *
 460  * All error checking will have been done prior to calling this function
 461  * so nothing should go wrong at this point.
 462  *
 463  * \param ctx  current context
 464  * \param n    number of color outputs to set
 465  * \param buffers  array[n] of colorbuffer names, like GL_LEFT.
 466  * \param destMask  array[n] of BUFFER_BIT_* bitmasks which correspond to the
 467  *                  colorbuffer names.  (i.e. GL_FRONT_AND_BACK =>
 468  *                  BUFFER_BIT_FRONT_LEFT | BUFFER_BIT_BACK_LEFT).
 469  */
 470 void
 471 _mesa_drawbuffers(struct gl_context *ctx, GLuint n, const GLenum *buffers,
 472                   const GLbitfield *destMask)
 473 {
 474    struct gl_framebuffer *fb = ctx->DrawBuffer;
 475    GLbitfield mask[MAX_DRAW_BUFFERS];
 476    GLuint buf;
 477
 478    if (!destMask) {
 479       /* compute destMask values now */
 480       const GLbitfield supportedMask = supported_buffer_bitmask(ctx, fb);
 481       GLuint output;
 482       for (output = 0; output < n; output++) {
 483          mask[output] = draw_buffer_enum_to_bitmask(ctx, buffers[output]);
 484          ASSERT(mask[output] != BAD_MASK);
 485          mask[output] &= supportedMask;
 486       }
 487       destMask = mask;
 488    }
 489
 490    /*
 491     * If n==1, destMask[0] may have up to four bits set.
 492     * Otherwise, destMask[x] can only have one bit set.
 493     */
 494    if (n == 1) {
 495       GLuint count = 0, destMask0 = destMask[0];
 496       while (destMask0) {
 497          GLint bufIndex = ffs(destMask0) - 1;
 498          if (fb->_ColorDrawBufferIndexes[count] != bufIndex) {
 499             updated_drawbuffers(ctx);
 500             fb->_ColorDrawBufferIndexes[count] = bufIndex;
 501          }
 502          count++;
 503          destMask0 &= ~(1 << bufIndex);
 504       }
 505       fb->ColorDrawBuffer[0] = buffers[0];
 506       fb->_NumColorDrawBuffers = count;
 507    }
 508    else {
 509       GLuint count = 0;
 510       for (buf = 0; buf < n; buf++ ) {
 511          if (destMask[buf]) {
 512             GLint bufIndex = ffs(destMask[buf]) - 1;
 513             /* only one bit should be set in the destMask[buf] field */
 514             ASSERT(_mesa_bitcount(destMask[buf]) == 1);
 515             if (fb->_ColorDrawBufferIndexes[buf] != bufIndex) {
 516                updated_drawbuffers(ctx);
 517                fb->_ColorDrawBufferIndexes[buf] = bufIndex;
 518             }
 519             count = buf + 1;
 520          }
 521          else {
 522             if (fb->_ColorDrawBufferIndexes[buf] != -1) {
 523                updated_drawbuffers(ctx);
 524                fb->_ColorDrawBufferIndexes[buf] = -1;
 525             }
 526          }
 527          fb->ColorDrawBuffer[buf] = buffers[buf];
 528       }
 529       fb->_NumColorDrawBuffers = count;
 530    }
 531
 532    /* set remaining outputs to -1 (GL_NONE) */
 533    for (buf = fb->_NumColorDrawBuffers; buf < ctx->Const.MaxDrawBuffers; buf++) {
 534       if (fb->_ColorDrawBufferIndexes[buf] != -1) {
 535          updated_drawbuffers(ctx);
 536          fb->_ColorDrawBufferIndexes[buf] = -1;
 537       }
 538    }
 539    for (buf = n; buf < ctx->Const.MaxDrawBuffers; buf++) {
 540       fb->ColorDrawBuffer[buf] = GL_NONE;
 541    }
 542
 543    if (_mesa_is_winsys_fbo(fb)) {
 544       /* also set context drawbuffer state */
 545       for (buf = 0; buf < ctx->Const.MaxDrawBuffers; buf++) {
 546          if (ctx->Color.DrawBuffer[buf] != fb->ColorDrawBuffer[buf]) {
 547             updated_drawbuffers(ctx);
 548             ctx->Color.DrawBuffer[buf] = fb->ColorDrawBuffer[buf];
 549          }
 550       }
 551    }
 552 }
 553
 554
 555 /**
 556  * Update the current drawbuffer's _ColorDrawBufferIndex[] list, etc.
 557  * from the context's Color.DrawBuffer[] state.
 558  * Use when changing contexts.
 559  */
 560 void
 561 _mesa_update_draw_buffers(struct gl_context *ctx)
 562 {
 563    GLenum buffers[MAX_DRAW_BUFFERS];
 564    GLuint i;
 565
 566    /* should be a window system FBO */
 567    assert(_mesa_is_winsys_fbo(ctx->DrawBuffer));
 568
 569    for (i = 0; i < ctx->Const.MaxDrawBuffers; i++)
 570       buffers[i] = ctx->Color.DrawBuffer[i];
 571
 572    _mesa_drawbuffers(ctx, ctx->Const.MaxDrawBuffers, buffers, NULL);
 573 }
 574
 575
 576 /**
 577  * Like \sa _mesa_drawbuffers(), this is a helper function for setting
 578  * GL_READ_BUFFER state in the context and current FBO.
 579  * \param ctx  the rendering context
 580  * \param buffer  GL_FRONT, GL_BACK, GL_COLOR_ATTACHMENT0, etc.
 581  * \param bufferIndex  the numerical index corresponding to 'buffer'
 582  */
 583 void
 584 _mesa_readbuffer(struct gl_context *ctx, GLenum buffer, GLint bufferIndex)
 585 {
 586    struct gl_framebuffer *fb = ctx->ReadBuffer;
 587
 588    if (_mesa_is_winsys_fbo(fb)) {
 589       /* Only update the per-context READ_BUFFER state if we're bound to
 590        * a window-system framebuffer.
 591        */
 592       ctx->Pixel.ReadBuffer = buffer;
 593    }
 594
 595    fb->ColorReadBuffer = buffer;
 596    fb->_ColorReadBufferIndex = bufferIndex;
 597
 598    ctx->NewState |= _NEW_BUFFERS;
 599 }
 600
 601
 602
 603 /**
 604  * Called by glReadBuffer to set the source renderbuffer for reading pixels.
 605  * \param mode color buffer such as GL_FRONT, GL_BACK, etc.
 606  */
 607 void GLAPIENTRY
 608 _mesa_ReadBuffer(GLenum buffer)
 609 {
 610    struct gl_framebuffer *fb;
 611    GLbitfield supportedMask;
 612    GLint srcBuffer;
 613    GET_CURRENT_CONTEXT(ctx);
 614
 615    FLUSH_VERTICES(ctx, 0);
 616
 617    if (MESA_VERBOSE & VERBOSE_API)
 618       _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 619
 620    fb = ctx->ReadBuffer;
 621
 622    if (MESA_VERBOSE & VERBOSE_API)
 623       _mesa_debug(ctx, "glReadBuffer %s\n", _mesa_lookup_enum_by_nr(buffer));
 624
 625    if (buffer == GL_NONE) {
 626       /* This is legal--it means that no buffer should be bound for reading. */
 627       srcBuffer = -1;
 628    }
 629    else {
 630       /* general case / window-system framebuffer */
 631       srcBuffer = read_buffer_enum_to_index(buffer);
 632       if (srcBuffer == -1) {
 633          _mesa_error(ctx, GL_INVALID_ENUM,
 634                      "glReadBuffer(buffer=0x%x)", buffer);
 635          return;
 636       }
 637       supportedMask = supported_buffer_bitmask(ctx, fb);
 638       if (((1 << srcBuffer) & supportedMask) == 0) {
 639          _mesa_error(ctx, GL_INVALID_OPERATION,
 640                      "glReadBuffer(buffer=0x%x)", buffer);
 641          return;
 642       }
 643    }
 644
 645    /* OK, all error checking has been completed now */
 646
 647    _mesa_readbuffer(ctx, buffer, srcBuffer);
 648
 649    /*
 650     * Call device driver function.
 651     */
 652    if (ctx->Driver.ReadBuffer)
 653       (*ctx->Driver.ReadBuffer)(ctx, buffer);
 654 }