src/mesa/main/arrayobj.c

   1 /*
   2  * Mesa 3-D graphics library
   3  *
   4  * Copyright (C) 1999-2008  Brian Paul   All Rights Reserved.
   5  * (C) Copyright IBM Corporation 2006
   6  * Copyright (C) 2009  VMware, Inc.  All Rights Reserved.
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a
   9  * copy of this software and associated documentation files (the "Software"),
  10  * to deal in the Software without restriction, including without limitation
  11  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  12  * and/or sell copies of the Software, and to permit persons to whom the
  13  * Software is furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included
  16  * in all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  21  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  22  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  23  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  24  * OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 /**
  29  * \file arrayobj.c
  30  *
  31  * Implementation of Vertex Array Objects (VAOs), from OpenGL 3.1+ /
  32  * the GL_ARB_vertex_array_object extension.
  33  *
  34  * \todo
  35  * The code in this file borrows a lot from bufferobj.c.  There's a certain
  36  * amount of cruft left over from that origin that may be unnecessary.
  37  *
  38  * \author Ian Romanick <idr@us.ibm.com>
  39  * \author Brian Paul
  40  */
  41
  42
  43 #include "glheader.h"
  44 #include "hash.h"
  45 #include "image.h"
  46 #include "imports.h"
  47 #include "context.h"
  48 #include "bufferobj.h"
  49 #include "arrayobj.h"
  50 #include "macros.h"
  51 #include "mtypes.h"
  52 #include "varray.h"
  53 #include "main/dispatch.h"
  54 #include "util/bitscan.h"
  55
  56
  57 /**
  58  * Look up the array object for the given ID.
  59  *
  60  * \returns
  61  * Either a pointer to the array object with the specified ID or \c NULL for
  62  * a non-existent ID.  The spec defines ID 0 as being technically
  63  * non-existent.
  64  */
  65
  66 struct gl_vertex_array_object *
  67 _mesa_lookup_vao(struct gl_context *ctx, GLuint id)
  68 {
  69    if (id == 0)
  70       return NULL;
  71    else
  72       return (struct gl_vertex_array_object *)
  73          _mesa_HashLookupLocked(ctx->Array.Objects, id);
  74 }
  75
  76
  77 /**
  78  * Looks up the array object for the given ID.
  79  *
  80  * Unlike _mesa_lookup_vao, this function generates a GL_INVALID_OPERATION
  81  * error if the array object does not exist. It also returns the default
  82  * array object when ctx is a compatibility profile context and id is zero.
  83  */
  84 struct gl_vertex_array_object *
  85 _mesa_lookup_vao_err(struct gl_context *ctx, GLuint id, const char *caller)
  86 {
  87    /* The ARB_direct_state_access specification says:
  88     *
  89     *    "<vaobj> is [compatibility profile:
  90     *     zero, indicating the default vertex array object, or]
  91     *     the name of the vertex array object."
  92     */
  93    if (id == 0) {
  94       if (ctx->API == API_OPENGL_CORE) {
  95          _mesa_error(ctx, GL_INVALID_OPERATION,
  96                      "%s(zero is not valid vaobj name in a core profile "
  97                      "context)", caller);
  98          return NULL;
  99       }
 100
 101       return ctx->Array.DefaultVAO;
 102    } else {
 103       struct gl_vertex_array_object *vao;
 104
 105       if (ctx->Array.LastLookedUpVAO &&
 106           ctx->Array.LastLookedUpVAO->Name == id) {
 107          vao = ctx->Array.LastLookedUpVAO;
 108       } else {
 109          vao = (struct gl_vertex_array_object *)
 110             _mesa_HashLookupLocked(ctx->Array.Objects, id);
 111
 112          /* The ARB_direct_state_access specification says:
 113           *
 114           *    "An INVALID_OPERATION error is generated if <vaobj> is not
 115           *     [compatibility profile: zero or] the name of an existing
 116           *     vertex array object."
 117           */
 118          if (!vao || !vao->EverBound) {
 119             _mesa_error(ctx, GL_INVALID_OPERATION,
 120                         "%s(non-existent vaobj=%u)", caller, id);
 121             return NULL;
 122          }
 123
 124          _mesa_reference_vao(ctx, &ctx->Array.LastLookedUpVAO, vao);
 125       }
 126
 127       return vao;
 128    }
 129 }
 130
 131
 132 /**
 133  * For all the vertex binding points in the array object, unbind any pointers
 134  * to any buffer objects (VBOs).
 135  * This is done just prior to array object destruction.
 136  */
 137 static void
 138 unbind_array_object_vbos(struct gl_context *ctx, struct gl_vertex_array_object *obj)
 139 {
 140    GLuint i;
 141
 142    for (i = 0; i < ARRAY_SIZE(obj->BufferBinding); i++)
 143       _mesa_reference_buffer_object(ctx, &obj->BufferBinding[i].BufferObj, NULL);
 144
 145    for (i = 0; i < ARRAY_SIZE(obj->_VertexAttrib); i++)
 146       _mesa_reference_buffer_object(ctx, &obj->_VertexAttrib[i].BufferObj, NULL);
 147 }
 148
 149
 150 /**
 151  * Allocate and initialize a new vertex array object.
 152  */
 153 struct gl_vertex_array_object *
 154 _mesa_new_vao(struct gl_context *ctx, GLuint name)
 155 {
 156    struct gl_vertex_array_object *obj = CALLOC_STRUCT(gl_vertex_array_object);
 157    if (obj)
 158       _mesa_initialize_vao(ctx, obj, name);
 159    return obj;
 160 }
 161
 162
 163 /**
 164  * Delete an array object.
 165  */
 166 void
 167 _mesa_delete_vao(struct gl_context *ctx, struct gl_vertex_array_object *obj)
 168 {
 169    unbind_array_object_vbos(ctx, obj);
 170    _mesa_reference_buffer_object(ctx, &obj->IndexBufferObj, NULL);
 171    free(obj->Label);
 172    free(obj);
 173 }
 174
 175
 176 /**
 177  * Set ptr to vao w/ reference counting.
 178  * Note: this should only be called from the _mesa_reference_vao()
 179  * inline function.
 180  */
 181 void
 182 _mesa_reference_vao_(struct gl_context *ctx,
 183                      struct gl_vertex_array_object **ptr,
 184                      struct gl_vertex_array_object *vao)
 185 {
 186    assert(*ptr != vao);
 187
 188    if (*ptr) {
 189       /* Unreference the old array object */
 190       struct gl_vertex_array_object *oldObj = *ptr;
 191
 192       assert(oldObj->RefCount > 0);
 193       oldObj->RefCount--;
 194
 195       if (oldObj->RefCount == 0)
 196          _mesa_delete_vao(ctx, oldObj);
 197
 198       *ptr = NULL;
 199    }
 200    assert(!*ptr);
 201
 202    if (vao) {
 203       /* reference new array object */
 204       assert(vao->RefCount > 0);
 205
 206       vao->RefCount++;
 207       *ptr = vao;
 208    }
 209 }
 210
 211
 212 /**
 213  * Initialize attribtes of a vertex array within a vertex array object.
 214  * \param vao  the container vertex array object
 215  * \param index  which array in the VAO to initialize
 216  * \param size  number of components (1, 2, 3 or 4) per attribute
 217  * \param type  datatype of the attribute (GL_FLOAT, GL_INT, etc).
 218  */
 219 static void
 220 init_array(struct gl_context *ctx,
 221            struct gl_vertex_array_object *vao,
 222            GLuint index, GLint size, GLint type)
 223 {
 224    struct gl_array_attributes *array = &vao->VertexAttrib[index];
 225    struct gl_vertex_buffer_binding *binding = &vao->BufferBinding[index];
 226
 227    array->Size = size;
 228    array->Type = type;
 229    array->Format = GL_RGBA; /* only significant for GL_EXT_vertex_array_bgra */
 230    array->Stride = 0;
 231    array->Ptr = NULL;
 232    array->RelativeOffset = 0;
 233    array->Enabled = GL_FALSE;
 234    array->Normalized = GL_FALSE;
 235    array->Integer = GL_FALSE;
 236    array->Doubles = GL_FALSE;
 237    array->_ElementSize = size * _mesa_sizeof_type(type);
 238    array->BufferBindingIndex = index;
 239
 240    binding->Offset = 0;
 241    binding->Stride = array->_ElementSize;
 242    binding->BufferObj = NULL;
 243    binding->_BoundArrays = BITFIELD64_BIT(index);
 244
 245    /* Vertex array buffers */
 246    _mesa_reference_buffer_object(ctx, &binding->BufferObj,
 247                                  ctx->Shared->NullBufferObj);
 248 }
 249
 250
 251 /**
 252  * Initialize a gl_vertex_array_object's arrays.
 253  */
 254 void
 255 _mesa_initialize_vao(struct gl_context *ctx,
 256                      struct gl_vertex_array_object *vao,
 257                      GLuint name)
 258 {
 259    GLuint i;
 260
 261    vao->Name = name;
 262
 263    vao->RefCount = 1;
 264
 265    /* Init the individual arrays */
 266    for (i = 0; i < ARRAY_SIZE(vao->VertexAttrib); i++) {
 267       switch (i) {
 268       case VERT_ATTRIB_WEIGHT:
 269          init_array(ctx, vao, VERT_ATTRIB_WEIGHT, 1, GL_FLOAT);
 270          break;
 271       case VERT_ATTRIB_NORMAL:
 272          init_array(ctx, vao, VERT_ATTRIB_NORMAL, 3, GL_FLOAT);
 273          break;
 274       case VERT_ATTRIB_COLOR1:
 275          init_array(ctx, vao, VERT_ATTRIB_COLOR1, 3, GL_FLOAT);
 276          break;
 277       case VERT_ATTRIB_FOG:
 278          init_array(ctx, vao, VERT_ATTRIB_FOG, 1, GL_FLOAT);
 279          break;
 280       case VERT_ATTRIB_COLOR_INDEX:
 281          init_array(ctx, vao, VERT_ATTRIB_COLOR_INDEX, 1, GL_FLOAT);
 282          break;
 283       case VERT_ATTRIB_EDGEFLAG:
 284          init_array(ctx, vao, VERT_ATTRIB_EDGEFLAG, 1, GL_BOOL);
 285          break;
 286       case VERT_ATTRIB_POINT_SIZE:
 287          init_array(ctx, vao, VERT_ATTRIB_POINT_SIZE, 1, GL_FLOAT);
 288          break;
 289       default:
 290          init_array(ctx, vao, i, 4, GL_FLOAT);
 291          break;
 292       }
 293    }
 294
 295    _mesa_reference_buffer_object(ctx, &vao->IndexBufferObj,
 296                                  ctx->Shared->NullBufferObj);
 297 }
 298
 299
 300 /**
 301  * Updates the derived gl_vertex_arrays when a gl_vertex_attrib_array
 302  * or a gl_vertex_buffer_binding has changed.
 303  */
 304 void
 305 _mesa_update_vao_client_arrays(struct gl_context *ctx,
 306                                struct gl_vertex_array_object *vao)
 307 {
 308    GLbitfield64 arrays = vao->NewArrays;
 309
 310    while (arrays) {
 311       const int attrib = u_bit_scan64(&arrays);
 312       struct gl_vertex_array *client_array = &vao->_VertexAttrib[attrib];
 313       const struct gl_array_attributes *attrib_array =
 314          &vao->VertexAttrib[attrib];
 315       const struct gl_vertex_buffer_binding *buffer_binding =
 316          &vao->BufferBinding[attrib_array->BufferBindingIndex];
 317
 318       _mesa_update_client_array(ctx, client_array, attrib_array,
 319                                 buffer_binding);
 320    }
 321 }
 322
 323
 324 bool
 325 _mesa_all_varyings_in_vbos(const struct gl_vertex_array_object *vao)
 326 {
 327    /* Walk those enabled arrays that have the default vbo attached */
 328    GLbitfield64 mask = vao->_Enabled & ~vao->VertexAttribBufferMask;
 329
 330    while (mask) {
 331       /* Do not use u_bit_scan64 as we can walk multiple
 332        * attrib arrays at once
 333        */
 334       const int i = ffsll(mask) - 1;
 335       const struct gl_array_attributes *attrib_array =
 336          &vao->VertexAttrib[i];
 337       const struct gl_vertex_buffer_binding *buffer_binding =
 338          &vao->BufferBinding[attrib_array->BufferBindingIndex];
 339
 340       /* Only enabled arrays shall appear in the _Enabled bitmask */
 341       assert(attrib_array->Enabled);
 342       /* We have already masked out vao->VertexAttribBufferMask  */
 343       assert(!_mesa_is_bufferobj(buffer_binding->BufferObj));
 344
 345       /* Bail out once we find the first non vbo with a non zero stride */
 346       if (buffer_binding->Stride != 0)
 347          return false;
 348
 349       /* Note that we cannot use the xor variant since the _BoundArray mask
 350        * may contain array attributes that are bound but not enabled.
 351        */
 352       mask &= ~buffer_binding->_BoundArrays;
 353    }
 354
 355    return true;
 356 }
 357
 358 bool
 359 _mesa_all_buffers_are_unmapped(const struct gl_vertex_array_object *vao)
 360 {
 361    /* Walk the enabled arrays that have a vbo attached */
 362    GLbitfield64 mask = vao->_Enabled & vao->VertexAttribBufferMask;
 363
 364    while (mask) {
 365       const int i = ffsll(mask) - 1;
 366       const struct gl_array_attributes *attrib_array =
 367          &vao->VertexAttrib[i];
 368       const struct gl_vertex_buffer_binding *buffer_binding =
 369          &vao->BufferBinding[attrib_array->BufferBindingIndex];
 370
 371       /* Only enabled arrays shall appear in the _Enabled bitmask */
 372       assert(attrib_array->Enabled);
 373       /* We have already masked with vao->VertexAttribBufferMask  */
 374       assert(_mesa_is_bufferobj(buffer_binding->BufferObj));
 375
 376       /* Bail out once we find the first disallowed mapping */
 377       if (_mesa_check_disallowed_mapping(buffer_binding->BufferObj))
 378          return false;
 379
 380       /* We have handled everything that is bound to this buffer_binding. */
 381       mask &= ~buffer_binding->_BoundArrays;
 382    }
 383
 384    return true;
 385 }
 386
 387 /**********************************************************************/
 388 /* API Functions                                                      */
 389 /**********************************************************************/
 390
 391
 392 /**
 393  * ARB version of glBindVertexArray()
 394  */
 395 void GLAPIENTRY
 396 _mesa_BindVertexArray( GLuint id )
 397 {
 398    GET_CURRENT_CONTEXT(ctx);
 399
 400    struct gl_vertex_array_object * const oldObj = ctx->Array.VAO;
 401    struct gl_vertex_array_object *newObj = NULL;
 402
 403    assert(oldObj != NULL);
 404
 405    if (oldObj->Name == id)
 406       return;   /* rebinding the same array object- no change */
 407
 408    /*
 409     * Get pointer to new array object (newObj)
 410     */
 411    if (id == 0) {
 412       /* The spec says there is no array object named 0, but we use
 413        * one internally because it simplifies things.
 414        */
 415       newObj = ctx->Array.DefaultVAO;
 416    }
 417    else {
 418       /* non-default array object */
 419       newObj = _mesa_lookup_vao(ctx, id);
 420       if (!newObj) {
 421          _mesa_error(ctx, GL_INVALID_OPERATION,
 422                      "glBindVertexArray(non-gen name)");
 423          return;
 424       }
 425
 426       newObj->EverBound = GL_TRUE;
 427    }
 428
 429    if (ctx->Array.DrawMethod == DRAW_ARRAYS) {
 430       /* The _DrawArrays pointer is pointing at the VAO being unbound and
 431        * that VAO may be in the process of being deleted. If it's not going
 432        * to be deleted, this will have no effect, because the pointer needs
 433        * to be updated by the VBO module anyway.
 434        *
 435        * Before the VBO module can update the pointer, we have to set it
 436        * to NULL for drivers not to set up arrays which are not bound,
 437        * or to prevent a crash if the VAO being unbound is going to be
 438        * deleted.
 439        */
 440       ctx->Array._DrawArrays = NULL;
 441       ctx->Array.DrawMethod = DRAW_NONE;
 442    }
 443
 444    ctx->NewState |= _NEW_ARRAY;
 445    _mesa_reference_vao(ctx, &ctx->Array.VAO, newObj);
 446 }
 447
 448
 449 /**
 450  * Delete a set of array objects.
 451  *
 452  * \param n      Number of array objects to delete.
 453  * \param ids    Array of \c n array object IDs.
 454  */
 455 void GLAPIENTRY
 456 _mesa_DeleteVertexArrays(GLsizei n, const GLuint *ids)
 457 {
 458    GET_CURRENT_CONTEXT(ctx);
 459    GLsizei i;
 460
 461    if (n < 0) {
 462       _mesa_error(ctx, GL_INVALID_VALUE, "glDeleteVertexArray(n)");
 463       return;
 464    }
 465
 466    for (i = 0; i < n; i++) {
 467       struct gl_vertex_array_object *obj = _mesa_lookup_vao(ctx, ids[i]);
 468
 469       if (obj) {
 470          assert(obj->Name == ids[i]);
 471
 472          /* If the array object is currently bound, the spec says "the binding
 473           * for that object reverts to zero and the default vertex array
 474           * becomes current."
 475           */
 476          if (obj == ctx->Array.VAO)
 477             _mesa_BindVertexArray(0);
 478
 479          /* The ID is immediately freed for re-use */
 480          _mesa_HashRemoveLocked(ctx->Array.Objects, obj->Name);
 481
 482          if (ctx->Array.LastLookedUpVAO == obj)
 483             _mesa_reference_vao(ctx, &ctx->Array.LastLookedUpVAO, NULL);
 484
 485          /* Unreference the array object.
 486           * If refcount hits zero, the object will be deleted.
 487           */
 488          _mesa_reference_vao(ctx, &obj, NULL);
 489       }
 490    }
 491 }
 492
 493
 494 /**
 495  * Generate a set of unique array object IDs and store them in \c arrays.
 496  * Helper for _mesa_GenVertexArrays() and _mesa_CreateVertexArrays()
 497  * below.
 498  *
 499  * \param n       Number of IDs to generate.
 500  * \param arrays  Array of \c n locations to store the IDs.
 501  * \param create  Indicates that the objects should also be created.
 502  * \param func    The name of the GL entry point.
 503  */
 504 static void
 505 gen_vertex_arrays(struct gl_context *ctx, GLsizei n, GLuint *arrays,
 506                   bool create, const char *func)
 507 {
 508    GLuint first;
 509    GLint i;
 510
 511    if (!arrays)
 512       return;
 513
 514    first = _mesa_HashFindFreeKeyBlock(ctx->Array.Objects, n);
 515
 516    /* For the sake of simplicity we create the array objects in both
 517     * the Gen* and Create* cases.  The only difference is the value of
 518     * EverBound, which is set to true in the Create* case.
 519     */
 520    for (i = 0; i < n; i++) {
 521       struct gl_vertex_array_object *obj;
 522       GLuint name = first + i;
 523
 524       obj = _mesa_new_vao(ctx, name);
 525       if (!obj) {
 526          _mesa_error(ctx, GL_OUT_OF_MEMORY, "%s", func);
 527          return;
 528       }
 529       obj->EverBound = create;
 530       _mesa_HashInsertLocked(ctx->Array.Objects, obj->Name, obj);
 531       arrays[i] = first + i;
 532    }
 533 }
 534
 535
 536 static void
 537 gen_vertex_arrays_err(struct gl_context *ctx, GLsizei n, GLuint *arrays,
 538                       bool create, const char *func)
 539 {
 540    if (n < 0) {
 541       _mesa_error(ctx, GL_INVALID_VALUE, "%s(n < 0)", func);
 542       return;
 543    }
 544
 545    gen_vertex_arrays(ctx, n, arrays, create, func);
 546 }
 547
 548
 549 /**
 550  * ARB version of glGenVertexArrays()
 551  * All arrays will be required to live in VBOs.
 552  */
 553 void GLAPIENTRY
 554 _mesa_GenVertexArrays(GLsizei n, GLuint *arrays)
 555 {
 556    GET_CURRENT_CONTEXT(ctx);
 557    gen_vertex_arrays_err(ctx, n, arrays, false, "glGenVertexArrays");
 558 }
 559
 560
 561 /**
 562  * ARB_direct_state_access
 563  * Generates ID's and creates the array objects.
 564  */
 565 void GLAPIENTRY
 566 _mesa_CreateVertexArrays(GLsizei n, GLuint *arrays)
 567 {
 568    GET_CURRENT_CONTEXT(ctx);
 569    gen_vertex_arrays_err(ctx, n, arrays, true, "glCreateVertexArrays");
 570 }
 571
 572
 573 /**
 574  * Determine if ID is the name of an array object.
 575  *
 576  * \param id  ID of the potential array object.
 577  * \return  \c GL_TRUE if \c id is the name of a array object,
 578  *          \c GL_FALSE otherwise.
 579  */
 580 GLboolean GLAPIENTRY
 581 _mesa_IsVertexArray( GLuint id )
 582 {
 583    struct gl_vertex_array_object * obj;
 584    GET_CURRENT_CONTEXT(ctx);
 585    ASSERT_OUTSIDE_BEGIN_END_WITH_RETVAL(ctx, GL_FALSE);
 586
 587    obj = _mesa_lookup_vao(ctx, id);
 588
 589    return obj != NULL && obj->EverBound;
 590 }
 591
 592
 593 /**
 594  * Sets the element array buffer binding of a vertex array object.
 595  *
 596  * This is the ARB_direct_state_access equivalent of
 597  * glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffer).
 598  */
 599 void GLAPIENTRY
 600 _mesa_VertexArrayElementBuffer(GLuint vaobj, GLuint buffer)
 601 {
 602    GET_CURRENT_CONTEXT(ctx);
 603    struct gl_vertex_array_object *vao;
 604    struct gl_buffer_object *bufObj;
 605
 606    ASSERT_OUTSIDE_BEGIN_END(ctx);
 607
 608    /* The GL_ARB_direct_state_access specification says:
 609     *
 610     *    "An INVALID_OPERATION error is generated by VertexArrayElementBuffer
 611     *     if <vaobj> is not [compatibility profile: zero or] the name of an
 612     *     existing vertex array object."
 613     */
 614    vao =_mesa_lookup_vao_err(ctx, vaobj, "glVertexArrayElementBuffer");
 615    if (!vao)
 616       return;
 617
 618    /* The GL_ARB_direct_state_access specification says:
 619     *
 620     *    "An INVALID_OPERATION error is generated if <buffer> is not zero or
 621     *     the name of an existing buffer object."
 622     */
 623    if (buffer != 0)
 624       bufObj = _mesa_lookup_bufferobj_err(ctx, buffer,
 625                                           "glVertexArrayElementBuffer");
 626    else
 627       bufObj = ctx->Shared->NullBufferObj;
 628
 629    if (bufObj)
 630       _mesa_reference_buffer_object(ctx, &vao->IndexBufferObj, bufObj);
 631 }
 632
 633
 634 void GLAPIENTRY
 635 _mesa_GetVertexArrayiv(GLuint vaobj, GLenum pname, GLint *param)
 636 {
 637    GET_CURRENT_CONTEXT(ctx);
 638    struct gl_vertex_array_object *vao;
 639
 640    ASSERT_OUTSIDE_BEGIN_END(ctx);
 641
 642    /* The GL_ARB_direct_state_access specification says:
 643     *
 644     *   "An INVALID_OPERATION error is generated if <vaobj> is not
 645     *    [compatibility profile: zero or] the name of an existing
 646     *    vertex array object."
 647     */
 648    vao =_mesa_lookup_vao_err(ctx, vaobj, "glGetVertexArrayiv");
 649    if (!vao)
 650       return;
 651
 652    /* The GL_ARB_direct_state_access specification says:
 653     *
 654     *   "An INVALID_ENUM error is generated if <pname> is not
 655     *    ELEMENT_ARRAY_BUFFER_BINDING."
 656     */
 657    if (pname != GL_ELEMENT_ARRAY_BUFFER_BINDING) {
 658       _mesa_error(ctx, GL_INVALID_ENUM,
 659                   "glGetVertexArrayiv(pname != "
 660                   "GL_ELEMENT_ARRAY_BUFFER_BINDING)");
 661       return;
 662    }
 663
 664    param[0] = vao->IndexBufferObj->Name;
 665 }