src/mesa/main/framebuffer.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.1
   4  *
   5  * Copyright (C) 1999-2006  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  * Functions for allocating/managing framebuffers and renderbuffers.
  28  * Also, routines for reading/writing renderbuffer data as ubytes,
  29  * ushorts, uints, etc.
  30  */
  31
  32
  33 #include "glheader.h"
  34 #include "imports.h"
  35 #include "buffers.h"
  36 #include "context.h"
  37 #include "depthstencil.h"
  38 #include "mtypes.h"
  39 #include "fbobject.h"
  40 #include "framebuffer.h"
  41 #include "renderbuffer.h"
  42 #include "texobj.h"
  43
  44
  45
  46 /**
  47  * Compute/set the _DepthMax field for the given framebuffer.
  48  * This value depends on the Z buffer resolution.
  49  */
  50 static void
  51 compute_depth_max(struct gl_framebuffer *fb)
  52 {
  53    if (fb->Visual.depthBits == 0) {
  54       /* Special case.  Even if we don't have a depth buffer we need
  55        * good values for DepthMax for Z vertex transformation purposes
  56        * and for per-fragment fog computation.
  57        */
  58       fb->_DepthMax = (1 << 16) - 1;
  59    }
  60    else if (fb->Visual.depthBits < 32) {
  61       fb->_DepthMax = (1 << fb->Visual.depthBits) - 1;
  62    }
  63    else {
  64       /* Special case since shift values greater than or equal to the
  65        * number of bits in the left hand expression's type are undefined.
  66        */
  67       fb->_DepthMax = 0xffffffff;
  68    }
  69    fb->_DepthMaxF = (GLfloat) fb->_DepthMax;
  70
  71    /* Minimum resolvable depth value, for polygon offset */
  72    fb->_MRD = 1.0 / fb->_DepthMaxF;
  73 }
  74
  75
  76 /**
  77  * Create and initialize a gl_framebuffer object.
  78  * This is intended for creating _window_system_ framebuffers, not generic
  79  * framebuffer objects ala GL_EXT_framebuffer_object.
  80  *
  81  * \sa _mesa_new_framebuffer
  82  */
  83 struct gl_framebuffer *
  84 _mesa_create_framebuffer(const GLvisual *visual)
  85 {
  86    struct gl_framebuffer *fb = CALLOC_STRUCT(gl_framebuffer);
  87    assert(visual);
  88    if (fb) {
  89       _mesa_initialize_framebuffer(fb, visual);
  90    }
  91    return fb;
  92 }
  93
  94
  95 /**
  96  * Allocate a new gl_framebuffer object.
  97  * This is the default function for ctx->Driver.NewFramebuffer().
  98  * This is for allocating user-created framebuffers, not window-system
  99  * framebuffers!
 100  * \sa _mesa_create_framebuffer
 101  */
 102 struct gl_framebuffer *
 103 _mesa_new_framebuffer(GLcontext *ctx, GLuint name)
 104 {
 105    struct gl_framebuffer *fb;
 106    (void) ctx;
 107    assert(name != 0);
 108    fb = CALLOC_STRUCT(gl_framebuffer);
 109    if (fb) {
 110       fb->Name = name;
 111       fb->RefCount = 1;
 112       fb->ColorDrawBuffer[0] = GL_COLOR_ATTACHMENT0_EXT;
 113       fb->_ColorDrawBufferMask[0] = BUFFER_BIT_COLOR0;
 114       fb->ColorReadBuffer = GL_COLOR_ATTACHMENT0_EXT;
 115       fb->_ColorReadBufferIndex = BUFFER_COLOR0;
 116       fb->Delete = _mesa_destroy_framebuffer;
 117    }
 118    return fb;
 119 }
 120
 121
 122 /**
 123  * Initialize a gl_framebuffer object.  Typically used to initialize
 124  * window system-created framebuffers, not user-created framebuffers.
 125  * \sa _mesa_create_framebuffer
 126  */
 127 void
 128 _mesa_initialize_framebuffer(struct gl_framebuffer *fb, const GLvisual *visual)
 129 {
 130    assert(fb);
 131    assert(visual);
 132
 133    _mesa_bzero(fb, sizeof(struct gl_framebuffer));
 134
 135    _glthread_INIT_MUTEX(fb->Mutex);
 136
 137    fb->RefCount = 1;
 138
 139    /* save the visual */
 140    fb->Visual = *visual;
 141
 142    /* Init read/draw renderbuffer state */
 143    if (visual->doubleBufferMode) {
 144       fb->ColorDrawBuffer[0] = GL_BACK;
 145       fb->_ColorDrawBufferMask[0] = BUFFER_BIT_BACK_LEFT;
 146       fb->ColorReadBuffer = GL_BACK;
 147       fb->_ColorReadBufferIndex = BUFFER_BACK_LEFT;
 148    }
 149    else {
 150       fb->ColorDrawBuffer[0] = GL_FRONT;
 151       fb->_ColorDrawBufferMask[0] = BUFFER_BIT_FRONT_LEFT;
 152       fb->ColorReadBuffer = GL_FRONT;
 153       fb->_ColorReadBufferIndex = BUFFER_FRONT_LEFT;
 154    }
 155
 156    fb->Delete = _mesa_destroy_framebuffer;
 157    fb->_Status = GL_FRAMEBUFFER_COMPLETE_EXT;
 158
 159    compute_depth_max(fb);
 160 }
 161
 162
 163 /**
 164  * Deallocate buffer and everything attached to it.
 165  * Typically called via the gl_framebuffer->Delete() method.
 166  */
 167 void
 168 _mesa_destroy_framebuffer(struct gl_framebuffer *fb)
 169 {
 170    if (fb) {
 171       _mesa_free_framebuffer_data(fb);
 172       _mesa_free(fb);
 173    }
 174 }
 175
 176
 177 /**
 178  * Free all the data hanging off the given gl_framebuffer, but don't free
 179  * the gl_framebuffer object itself.
 180  */
 181 void
 182 _mesa_free_framebuffer_data(struct gl_framebuffer *fb)
 183 {
 184    GLuint i;
 185
 186    assert(fb);
 187    assert(fb->RefCount == 0);
 188
 189    _glthread_DESTROY_MUTEX(fb->Mutex);
 190
 191    for (i = 0; i < BUFFER_COUNT; i++) {
 192       struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
 193       if (att->Renderbuffer) {
 194          _mesa_reference_renderbuffer(&att->Renderbuffer, NULL);
 195       }
 196       if (att->Texture) {
 197          _mesa_reference_texobj(&att->Texture, NULL);
 198       }
 199       ASSERT(!att->Renderbuffer);
 200       ASSERT(!att->Texture);
 201       att->Type = GL_NONE;
 202    }
 203
 204    /* unbind _Depth/_StencilBuffer to decr ref counts */
 205    _mesa_reference_renderbuffer(&fb->_DepthBuffer, NULL);
 206    _mesa_reference_renderbuffer(&fb->_StencilBuffer, NULL);
 207 }
 208
 209
 210 /**
 211  * Set *ptr to point to fb, with refcounting and locking.
 212  */
 213 void
 214 _mesa_reference_framebuffer(struct gl_framebuffer **ptr,
 215                             struct gl_framebuffer *fb)
 216 {
 217    assert(ptr);
 218    if (*ptr == fb) {
 219       /* no change */
 220       return;
 221    }
 222    if (*ptr) {
 223       _mesa_unreference_framebuffer(ptr);
 224    }
 225    assert(!*ptr);
 226    assert(fb);
 227    _glthread_LOCK_MUTEX(fb->Mutex);
 228    fb->RefCount++;
 229    _glthread_UNLOCK_MUTEX(fb->Mutex);
 230    *ptr = fb;
 231 }
 232
 233
 234 /**
 235  * Undo/remove a reference to a framebuffer object.
 236  * Decrement the framebuffer object's reference count and delete it when
 237  * the refcount hits zero.
 238  * Note: we pass the address of a pointer and set it to NULL.
 239  */
 240 void
 241 _mesa_unreference_framebuffer(struct gl_framebuffer **fb)
 242 {
 243    assert(fb);
 244    if (*fb) {
 245       GLboolean deleteFlag = GL_FALSE;
 246
 247       _glthread_LOCK_MUTEX((*fb)->Mutex);
 248       ASSERT((*fb)->RefCount > 0);
 249       (*fb)->RefCount--;
 250       deleteFlag = ((*fb)->RefCount == 0);
 251       _glthread_UNLOCK_MUTEX((*fb)->Mutex);
 252
 253       if (deleteFlag)
 254          (*fb)->Delete(*fb);
 255
 256       *fb = NULL;
 257    }
 258 }
 259
 260
 261
 262
 263 /**
 264  * Resize the given framebuffer's renderbuffers to the new width and height.
 265  * This should only be used for window-system framebuffers, not
 266  * user-created renderbuffers (i.e. made with GL_EXT_framebuffer_object).
 267  * This will typically be called via ctx->Driver.ResizeBuffers() or directly
 268  * from a device driver.
 269  *
 270  * \note it's possible for ctx to be null since a window can be resized
 271  * without a currently bound rendering context.
 272  */
 273 void
 274 _mesa_resize_framebuffer(GLcontext *ctx, struct gl_framebuffer *fb,
 275                          GLuint width, GLuint height)
 276 {
 277    GLuint i;
 278
 279    /* XXX I think we could check if the size is not changing
 280     * and return early.
 281     */
 282
 283    /* For window system framebuffers, Name is zero */
 284    assert(fb->Name == 0);
 285
 286    for (i = 0; i < BUFFER_COUNT; i++) {
 287       struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
 288       if (att->Type == GL_RENDERBUFFER_EXT && att->Renderbuffer) {
 289          struct gl_renderbuffer *rb = att->Renderbuffer;
 290          /* only resize if size is changing */
 291          if (rb->Width != width || rb->Height != height) {
 292             /* could just as well pass rb->_ActualFormat here */
 293             if (rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
 294                ASSERT(rb->Width == width);
 295                ASSERT(rb->Height == height);
 296             }
 297             else {
 298                _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
 299                /* no return */
 300             }
 301          }
 302       }
 303    }
 304
 305    if (fb->_DepthBuffer) {
 306       struct gl_renderbuffer *rb = fb->_DepthBuffer;
 307       if (rb->Width != width || rb->Height != height) {
 308          if (!rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
 309             _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
 310          }
 311       }
 312    }
 313
 314    if (fb->_StencilBuffer) {
 315       struct gl_renderbuffer *rb = fb->_StencilBuffer;
 316       if (rb->Width != width || rb->Height != height) {
 317          if (!rb->AllocStorage(ctx, rb, rb->InternalFormat, width, height)) {
 318             _mesa_error(ctx, GL_OUT_OF_MEMORY, "Resizing framebuffer");
 319          }
 320       }
 321    }
 322
 323    fb->Width = width;
 324    fb->Height = height;
 325
 326    if (ctx) {
 327       /* update scissor / window bounds */
 328       _mesa_update_draw_buffer_bounds(ctx);
 329       /* Signal new buffer state so that swrast will update its clipping
 330        * info (the CLIP_BIT flag).
 331        */
 332       ctx->NewState |= _NEW_BUFFERS;
 333    }
 334 }
 335
 336
 337 /**
 338  * Examine all the framebuffer's renderbuffers to update the Width/Height
 339  * fields of the framebuffer.  If we have renderbuffers with different
 340  * sizes, set the framebuffer's width and height to zero.
 341  * Note: this is only intended for user-created framebuffers, not
 342  * window-system framebuffes.
 343  */
 344 static void
 345 update_framebuffer_size(struct gl_framebuffer *fb)
 346 {
 347    GLboolean haveSize = GL_FALSE;
 348    GLuint i;
 349
 350    /* user-created framebuffers only */
 351    assert(fb->Name);
 352
 353    for (i = 0; i < BUFFER_COUNT; i++) {
 354       struct gl_renderbuffer_attachment *att = &fb->Attachment[i];
 355       const struct gl_renderbuffer *rb = att->Renderbuffer;
 356       if (rb) {
 357          if (haveSize) {
 358             if (rb->Width != fb->Width && rb->Height != fb->Height) {
 359                /* size mismatch! */
 360                fb->Width = 0;
 361                fb->Height = 0;
 362                return;
 363             }
 364          }
 365          else {
 366             fb->Width = rb->Width;
 367             fb->Height = rb->Height;
 368             haveSize = GL_TRUE;
 369          }
 370       }
 371    }
 372 }
 373
 374
 375 /**
 376  * Update the context's current drawing buffer's Xmin, Xmax, Ymin, Ymax fields.
 377  * These values are computed from the buffer's width and height and
 378  * the scissor box, if it's enabled.
 379  * \param ctx  the GL context.
 380  */
 381 void
 382 _mesa_update_draw_buffer_bounds(GLcontext *ctx)
 383 {
 384    struct gl_framebuffer *buffer = ctx->DrawBuffer;
 385
 386    if (!buffer)
 387       return;
 388
 389    if (buffer->Name) {
 390       /* user-created framebuffer size depends on the renderbuffers */
 391       update_framebuffer_size(buffer);
 392    }
 393
 394    buffer->_Xmin = 0;
 395    buffer->_Ymin = 0;
 396    buffer->_Xmax = buffer->Width;
 397    buffer->_Ymax = buffer->Height;
 398
 399    if (ctx->Scissor.Enabled) {
 400       if (ctx->Scissor.X > buffer->_Xmin) {
 401          buffer->_Xmin = ctx->Scissor.X;
 402       }
 403       if (ctx->Scissor.Y > buffer->_Ymin) {
 404          buffer->_Ymin = ctx->Scissor.Y;
 405       }
 406       if (ctx->Scissor.X + ctx->Scissor.Width < buffer->_Xmax) {
 407          buffer->_Xmax = ctx->Scissor.X + ctx->Scissor.Width;
 408       }
 409       if (ctx->Scissor.Y + ctx->Scissor.Height < buffer->_Ymax) {
 410          buffer->_Ymax = ctx->Scissor.Y + ctx->Scissor.Height;
 411       }
 412       /* finally, check for empty region */
 413       if (buffer->_Xmin > buffer->_Xmax) {
 414          buffer->_Xmin = buffer->_Xmax;
 415       }
 416       if (buffer->_Ymin > buffer->_Ymax) {
 417          buffer->_Ymin = buffer->_Ymax;
 418       }
 419    }
 420
 421    ASSERT(buffer->_Xmin <= buffer->_Xmax);
 422    ASSERT(buffer->_Ymin <= buffer->_Ymax);
 423 }
 424
 425
 426 /**
 427  * The glGet queries of the framebuffer red/green/blue size, stencil size,
 428  * etc. are satisfied by the fields of ctx->DrawBuffer->Visual.  These can
 429  * change depending on the renderbuffer bindings.  This function updates
 430  * the given framebuffer's Visual from the current renderbuffer bindings.
 431  *
 432  * This may apply to user-created framebuffers or window system framebuffers.
 433  *
 434  * Also note: ctx->DrawBuffer->Visual.depthBits might not equal
 435  * ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer.DepthBits.
 436  * The former one is used to convert floating point depth values into
 437  * integer Z values.
 438  */
 439 void
 440 _mesa_update_framebuffer_visual(struct gl_framebuffer *fb)
 441 {
 442    GLuint i;
 443
 444    _mesa_bzero(&fb->Visual, sizeof(fb->Visual));
 445    fb->Visual.rgbMode = GL_TRUE; /* assume this */
 446
 447 #if 0 /* this _might_ be needed */
 448    if (fb->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
 449       /* leave visual fields zero'd */
 450       return;
 451    }
 452 #endif
 453
 454    /* find first RGB or CI renderbuffer */
 455    for (i = 0; i < BUFFER_COUNT; i++) {
 456       if (fb->Attachment[i].Renderbuffer) {
 457          const struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
 458          if (rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB) {
 459             fb->Visual.redBits = rb->RedBits;
 460             fb->Visual.greenBits = rb->GreenBits;
 461             fb->Visual.blueBits = rb->BlueBits;
 462             fb->Visual.alphaBits = rb->AlphaBits;
 463             fb->Visual.rgbBits = fb->Visual.redBits
 464                + fb->Visual.greenBits + fb->Visual.blueBits;
 465             fb->Visual.floatMode = GL_FALSE;
 466             break;
 467          }
 468          else if (rb->_BaseFormat == GL_COLOR_INDEX) {
 469             fb->Visual.indexBits = rb->IndexBits;
 470             fb->Visual.rgbMode = GL_FALSE;
 471             break;
 472          }
 473       }
 474    }
 475
 476    if (fb->Attachment[BUFFER_DEPTH].Renderbuffer) {
 477       fb->Visual.haveDepthBuffer = GL_TRUE;
 478       fb->Visual.depthBits
 479          = fb->Attachment[BUFFER_DEPTH].Renderbuffer->DepthBits;
 480    }
 481
 482    if (fb->Attachment[BUFFER_STENCIL].Renderbuffer) {
 483       fb->Visual.haveStencilBuffer = GL_TRUE;
 484       fb->Visual.stencilBits
 485          = fb->Attachment[BUFFER_STENCIL].Renderbuffer->StencilBits;
 486    }
 487
 488    if (fb->Attachment[BUFFER_ACCUM].Renderbuffer) {
 489       fb->Visual.haveAccumBuffer = GL_TRUE;
 490       fb->Visual.accumRedBits
 491          = fb->Attachment[BUFFER_DEPTH].Renderbuffer->RedBits;
 492       fb->Visual.accumGreenBits
 493          = fb->Attachment[BUFFER_DEPTH].Renderbuffer->GreenBits;
 494       fb->Visual.accumBlueBits
 495          = fb->Attachment[BUFFER_DEPTH].Renderbuffer->BlueBits;
 496       fb->Visual.accumAlphaBits
 497          = fb->Attachment[BUFFER_DEPTH].Renderbuffer->AlphaBits;
 498    }
 499
 500    compute_depth_max(fb);
 501 }
 502
 503
 504 /**
 505  * Update the framebuffer's _DepthBuffer field using the renderbuffer
 506  * found at the given attachment index.
 507  *
 508  * If that attachment points to a combined GL_DEPTH_STENCIL renderbuffer,
 509  * create and install a depth wrapper/adaptor.
 510  *
 511  * \param fb  the framebuffer whose _DepthBuffer field to update
 512  * \param attIndex  indicates the renderbuffer to possibly wrap
 513  */
 514 void
 515 _mesa_update_depth_buffer(GLcontext *ctx,
 516                           struct gl_framebuffer *fb,
 517                           GLuint attIndex)
 518 {
 519    struct gl_renderbuffer *depthRb;
 520
 521    /* only one possiblity for now */
 522    ASSERT(attIndex == BUFFER_DEPTH);
 523
 524    depthRb = fb->Attachment[attIndex].Renderbuffer;
 525
 526    if (depthRb && depthRb->_ActualFormat == GL_DEPTH24_STENCIL8_EXT) {
 527       /* The attached depth buffer is a GL_DEPTH_STENCIL renderbuffer */
 528       if (!fb->_DepthBuffer
 529           || fb->_DepthBuffer->Wrapped != depthRb
 530           || fb->_DepthBuffer->_BaseFormat != GL_DEPTH_COMPONENT) {
 531          /* need to update wrapper */
 532          struct gl_renderbuffer *wrapper
 533             = _mesa_new_z24_renderbuffer_wrapper(ctx, depthRb);
 534          _mesa_reference_renderbuffer(&fb->_DepthBuffer, wrapper);
 535          ASSERT(fb->_DepthBuffer->Wrapped == depthRb);
 536       }
 537    }
 538    else {
 539       /* depthRb may be null */
 540       _mesa_reference_renderbuffer(&fb->_DepthBuffer, depthRb);
 541    }
 542 }
 543
 544
 545 /**
 546  * Update the framebuffer's _StencilBuffer field using the renderbuffer
 547  * found at the given attachment index.
 548  *
 549  * If that attachment points to a combined GL_DEPTH_STENCIL renderbuffer,
 550  * create and install a stencil wrapper/adaptor.
 551  *
 552  * \param fb  the framebuffer whose _StencilBuffer field to update
 553  * \param attIndex  indicates the renderbuffer to possibly wrap
 554  */
 555 void
 556 _mesa_update_stencil_buffer(GLcontext *ctx,
 557                             struct gl_framebuffer *fb,
 558                             GLuint attIndex)
 559 {
 560    struct gl_renderbuffer *stencilRb;
 561
 562    ASSERT(attIndex == BUFFER_DEPTH ||
 563           attIndex == BUFFER_STENCIL);
 564
 565    stencilRb = fb->Attachment[attIndex].Renderbuffer;
 566
 567    if (stencilRb && stencilRb->_ActualFormat == GL_DEPTH24_STENCIL8_EXT) {
 568       /* The attached stencil buffer is a GL_DEPTH_STENCIL renderbuffer */
 569       if (!fb->_StencilBuffer
 570           || fb->_StencilBuffer->Wrapped != stencilRb
 571           || fb->_StencilBuffer->_BaseFormat != GL_STENCIL_INDEX) {
 572          /* need to update wrapper */
 573          struct gl_renderbuffer *wrapper
 574             = _mesa_new_s8_renderbuffer_wrapper(ctx, stencilRb);
 575          _mesa_reference_renderbuffer(&fb->_StencilBuffer, wrapper);
 576          ASSERT(fb->_StencilBuffer->Wrapped == stencilRb);
 577       }
 578    }
 579    else {
 580       /* stencilRb may be null */
 581       _mesa_reference_renderbuffer(&fb->_StencilBuffer, stencilRb);
 582    }
 583 }
 584
 585
 586 /**
 587  * Update the (derived) list of color drawing renderbuffer pointers.
 588  * Later, when we're rendering we'll loop from 0 to _NumColorDrawBuffers
 589  * writing colors.
 590  */
 591 static void
 592 update_color_draw_buffers(GLcontext *ctx, struct gl_framebuffer *fb)
 593 {
 594    GLuint output;
 595
 596    /*
 597     * Fragment programs can write to multiple colorbuffers with
 598     * the GL_ARB_draw_buffers extension.
 599     */
 600    for (output = 0; output < ctx->Const.MaxDrawBuffers; output++) {
 601       GLbitfield bufferMask = fb->_ColorDrawBufferMask[output];
 602       GLuint count = 0;
 603       GLuint i;
 604       if (!fb->DeletePending) {
 605          /* We need the inner loop here because glDrawBuffer(GL_FRONT_AND_BACK)
 606           * can specify writing to two or four color buffers (for example).
 607           */
 608          for (i = 0; bufferMask && i < BUFFER_COUNT; i++) {
 609             const GLuint bufferBit = 1 << i;
 610             if (bufferBit & bufferMask) {
 611                struct gl_renderbuffer *rb = fb->Attachment[i].Renderbuffer;
 612                if (rb && rb->Width > 0 && rb->Height > 0) {
 613                   fb->_ColorDrawBuffers[output][count] = rb;
 614                   count++;
 615                }
 616                else {
 617                   /*
 618                   _mesa_warning(ctx, "DrawBuffer names a missing buffer!\n");
 619                   */
 620                }
 621                bufferMask &= ~bufferBit;
 622             }
 623          }
 624       }
 625       fb->_NumColorDrawBuffers[output] = count;
 626    }
 627 }
 628
 629
 630 /**
 631  * Update the (derived) color read renderbuffer pointer.
 632  * Unlike the DrawBuffer, we can only read from one (or zero) color buffers.
 633  */
 634 static void
 635 update_color_read_buffer(GLcontext *ctx, struct gl_framebuffer *fb)
 636 {
 637    (void) ctx;
 638    if (fb->_ColorReadBufferIndex == -1 ||
 639        fb->DeletePending ||
 640        fb->Width == 0 ||
 641        fb->Height == 0) {
 642       fb->_ColorReadBuffer = NULL; /* legal! */
 643    }
 644    else {
 645       ASSERT(fb->_ColorReadBufferIndex >= 0);
 646       ASSERT(fb->_ColorReadBufferIndex < BUFFER_COUNT);
 647       fb->_ColorReadBuffer
 648          = fb->Attachment[fb->_ColorReadBufferIndex].Renderbuffer;
 649    }
 650 }
 651
 652
 653 /**
 654  * Update a gl_framebuffer's derived state.
 655  *
 656  * Specifically, update these framebuffer fields:
 657  *    _ColorDrawBuffers
 658  *    _NumColorDrawBuffers
 659  *    _ColorReadBuffer
 660  *    _DepthBuffer
 661  *    _StencilBuffer
 662  *
 663  * If the framebuffer is user-created, make sure it's complete.
 664  *
 665  * The following functions (at least) can effect framebuffer state:
 666  * glReadBuffer, glDrawBuffer, glDrawBuffersARB, glFramebufferRenderbufferEXT,
 667  * glRenderbufferStorageEXT.
 668  */
 669 static void
 670 update_framebuffer(GLcontext *ctx, struct gl_framebuffer *fb)
 671 {
 672    if (fb->Name == 0) {
 673       /* This is a window-system framebuffer */
 674       /* Need to update the FB's GL_DRAW_BUFFER state to match the
 675        * context state (GL_READ_BUFFER too).
 676        */
 677       if (fb->ColorDrawBuffer[0] != ctx->Color.DrawBuffer[0]) {
 678          _mesa_drawbuffers(ctx, ctx->Const.MaxDrawBuffers,
 679                            ctx->Color.DrawBuffer, NULL);
 680       }
 681       if (fb->ColorReadBuffer != ctx->Pixel.ReadBuffer) {
 682
 683       }
 684    }
 685    else {
 686       /* This is a user-created framebuffer.
 687        * Completeness only matters for user-created framebuffers.
 688        */
 689       _mesa_test_framebuffer_completeness(ctx, fb);
 690       _mesa_update_framebuffer_visual(fb);
 691    }
 692
 693    /* Strictly speaking, we don't need to update the draw-state
 694     * if this FB is bound as ctx->ReadBuffer (and conversely, the
 695     * read-state if this FB is bound as ctx->DrawBuffer), but no
 696     * harm.
 697     */
 698    update_color_draw_buffers(ctx, fb);
 699    update_color_read_buffer(ctx, fb);
 700    _mesa_update_depth_buffer(ctx, fb, BUFFER_DEPTH);
 701    _mesa_update_stencil_buffer(ctx, fb, BUFFER_STENCIL);
 702
 703    compute_depth_max(fb);
 704 }
 705
 706
 707 /**
 708  * Update state related to the current draw/read framebuffers.
 709  */
 710 void
 711 _mesa_update_framebuffer(GLcontext *ctx)
 712 {
 713    struct gl_framebuffer *drawFb = ctx->DrawBuffer;
 714    struct gl_framebuffer *readFb = ctx->ReadBuffer;
 715
 716    update_framebuffer(ctx, drawFb);
 717    if (readFb != drawFb)
 718       update_framebuffer(ctx, readFb);
 719 }
 720
 721
 722 /**
 723  * Check if the renderbuffer for a read operation (glReadPixels, glCopyPixels,
 724  * glCopyTex[Sub]Image, etc. exists.
 725  * \param format  a basic image format such as GL_RGB, GL_RGBA, GL_ALPHA,
 726  *                GL_DEPTH_COMPONENT, etc. or GL_COLOR, GL_DEPTH, GL_STENCIL.
 727  * \return GL_TRUE if buffer exists, GL_FALSE otherwise
 728  */
 729 GLboolean
 730 _mesa_source_buffer_exists(GLcontext *ctx, GLenum format)
 731 {
 732    const struct gl_renderbuffer_attachment *att
 733       = ctx->ReadBuffer->Attachment;
 734
 735    if (ctx->ReadBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
 736       return GL_FALSE;
 737    }
 738
 739    switch (format) {
 740    case GL_COLOR:
 741    case GL_RED:
 742    case GL_GREEN:
 743    case GL_BLUE:
 744    case GL_ALPHA:
 745    case GL_LUMINANCE:
 746    case GL_LUMINANCE_ALPHA:
 747    case GL_INTENSITY:
 748    case GL_RGB:
 749    case GL_BGR:
 750    case GL_RGBA:
 751    case GL_BGRA:
 752    case GL_ABGR_EXT:
 753    case GL_COLOR_INDEX:
 754       if (ctx->ReadBuffer->_ColorReadBuffer == NULL) {
 755          return GL_FALSE;
 756       }
 757       /* XXX enable this post 6.5 release:
 758       ASSERT(ctx->ReadBuffer->_ColorReadBuffer->RedBits > 0 ||
 759              ctx->ReadBuffer->_ColorReadBuffer->IndexBits > 0);
 760       */
 761       break;
 762    case GL_DEPTH:
 763    case GL_DEPTH_COMPONENT:
 764       if (!att[BUFFER_DEPTH].Renderbuffer) {
 765          return GL_FALSE;
 766       }
 767       ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
 768       break;
 769    case GL_STENCIL:
 770    case GL_STENCIL_INDEX:
 771       if (!att[BUFFER_STENCIL].Renderbuffer) {
 772          return GL_FALSE;
 773       }
 774       ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
 775       break;
 776    case GL_DEPTH_STENCIL_EXT:
 777       if (!att[BUFFER_DEPTH].Renderbuffer ||
 778           !att[BUFFER_STENCIL].Renderbuffer) {
 779          return GL_FALSE;
 780       }
 781       ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
 782       ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
 783       break;
 784    default:
 785       _mesa_problem(ctx,
 786                     "Unexpected format 0x%x in _mesa_source_buffer_exists",
 787                     format);
 788       return GL_FALSE;
 789    }
 790
 791    /* OK */
 792    return GL_TRUE;
 793 }
 794
 795
 796 /**
 797  * As above, but for drawing operations.
 798  * XXX code do some code merging w/ above function.
 799  */
 800 GLboolean
 801 _mesa_dest_buffer_exists(GLcontext *ctx, GLenum format)
 802 {
 803    const struct gl_renderbuffer_attachment *att
 804       = ctx->ReadBuffer->Attachment;
 805
 806    if (ctx->DrawBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
 807       return GL_FALSE;
 808    }
 809
 810    switch (format) {
 811    case GL_COLOR:
 812    case GL_RED:
 813    case GL_GREEN:
 814    case GL_BLUE:
 815    case GL_ALPHA:
 816    case GL_LUMINANCE:
 817    case GL_LUMINANCE_ALPHA:
 818    case GL_INTENSITY:
 819    case GL_RGB:
 820    case GL_BGR:
 821    case GL_RGBA:
 822    case GL_BGRA:
 823    case GL_ABGR_EXT:
 824    case GL_COLOR_INDEX:
 825       /* nothing special */
 826       /* Could assert that colorbuffer has RedBits > 0 */
 827       break;
 828    case GL_DEPTH:
 829    case GL_DEPTH_COMPONENT:
 830       if (!att[BUFFER_DEPTH].Renderbuffer) {
 831          return GL_FALSE;
 832       }
 833       ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
 834       break;
 835    case GL_STENCIL:
 836    case GL_STENCIL_INDEX:
 837       if (!att[BUFFER_STENCIL].Renderbuffer) {
 838          return GL_FALSE;
 839       }
 840       ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
 841       break;
 842    case GL_DEPTH_STENCIL_EXT:
 843       if (!att[BUFFER_DEPTH].Renderbuffer ||
 844           !att[BUFFER_STENCIL].Renderbuffer) {
 845          return GL_FALSE;
 846       }
 847       ASSERT(att[BUFFER_DEPTH].Renderbuffer->DepthBits > 0);
 848       ASSERT(att[BUFFER_STENCIL].Renderbuffer->StencilBits > 0);
 849       break;
 850    default:
 851       _mesa_problem(ctx,
 852                     "Unexpected format 0x%x in _mesa_source_buffer_exists",
 853                     format);
 854       return GL_FALSE;
 855    }
 856
 857    /* OK */
 858    return GL_TRUE;
 859 }