src/egl/main/eglcontext.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2008 VMware, Inc.
   4  * Copyright 2009-2010 Chia-I Wu <olvaffe@gmail.com>
   5  * Copyright 2010-2011 LunarG, Inc.
   6  * 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
  10  * "Software"), to deal in the Software without restriction, including
  11  * without limitation the rights to use, copy, modify, merge, publish,
  12  * distribute, sub license, and/or sell copies of the Software, and to
  13  * permit persons to whom the Software is furnished to do so, subject to
  14  * the following conditions:
  15  *
  16  * The above copyright notice and this permission notice (including the
  17  * next paragraph) shall be included in all copies or substantial portions
  18  * of the Software.
  19  *
  20  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  23  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  25  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  26  * DEALINGS IN THE SOFTWARE.
  27  *
  28  **************************************************************************/
  29
  30
  31 #include <assert.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include "eglconfig.h"
  35 #include "eglcontext.h"
  36 #include "egldisplay.h"
  37 #include "eglcurrent.h"
  38 #include "eglsurface.h"
  39 #include "egllog.h"
  40
  41
  42 /**
  43  * Return the API bit (one of EGL_xxx_BIT) of the context.
  44  */
  45 static EGLint
  46 _eglGetContextAPIBit(_EGLContext *ctx)
  47 {
  48    EGLint bit = 0;
  49
  50    switch (ctx->ClientAPI) {
  51    case EGL_OPENGL_ES_API:
  52       switch (ctx->ClientMajorVersion) {
  53       case 1:
  54          bit = EGL_OPENGL_ES_BIT;
  55          break;
  56       case 2:
  57          bit = EGL_OPENGL_ES2_BIT;
  58          break;
  59       case 3:
  60          bit = EGL_OPENGL_ES3_BIT_KHR;
  61          break;
  62       default:
  63          break;
  64       }
  65       break;
  66    case EGL_OPENVG_API:
  67       bit = EGL_OPENVG_BIT;
  68       break;
  69    case EGL_OPENGL_API:
  70       bit = EGL_OPENGL_BIT;
  71       break;
  72    default:
  73       break;
  74    }
  75
  76    return bit;
  77 }
  78
  79
  80 /**
  81  * Parse the list of context attributes and return the proper error code.
  82  */
  83 static EGLint
  84 _eglParseContextAttribList(_EGLContext *ctx, _EGLDisplay *dpy,
  85                            const EGLint *attrib_list)
  86 {
  87    EGLenum api = ctx->ClientAPI;
  88    EGLint i, err = EGL_SUCCESS;
  89
  90    if (!attrib_list)
  91       return EGL_SUCCESS;
  92
  93    if (api == EGL_OPENVG_API && attrib_list[0] != EGL_NONE) {
  94       _eglLog(_EGL_DEBUG, "bad context attribute 0x%04x", attrib_list[0]);
  95       return EGL_BAD_ATTRIBUTE;
  96    }
  97
  98    for (i = 0; attrib_list[i] != EGL_NONE; i++) {
  99       EGLint attr = attrib_list[i++];
 100       EGLint val = attrib_list[i];
 101
 102       switch (attr) {
 103       case EGL_CONTEXT_CLIENT_VERSION:
 104          /* The EGL 1.4 spec says:
 105           *
 106           *     "attribute EGL_CONTEXT_CLIENT_VERSION is only valid when the
 107           *      current rendering API is EGL_OPENGL_ES_API"
 108           *
 109           * The EGL_KHR_create_context spec says:
 110           *
 111           *     "EGL_CONTEXT_MAJOR_VERSION_KHR           0x3098
 112           *      (this token is an alias for EGL_CONTEXT_CLIENT_VERSION)"
 113           *
 114           *     "The values for attributes EGL_CONTEXT_MAJOR_VERSION_KHR and
 115           *      EGL_CONTEXT_MINOR_VERSION_KHR specify the requested client API
 116           *      version. They are only meaningful for OpenGL and OpenGL ES
 117           *      contexts, and specifying them for other types of contexts will
 118           *      generate an error."
 119           */
 120          if ((api != EGL_OPENGL_ES_API &&
 121              (!dpy->Extensions.KHR_create_context || api != EGL_OPENGL_API))) {
 122                err = EGL_BAD_ATTRIBUTE;
 123                break;
 124          }
 125
 126          ctx->ClientMajorVersion = val;
 127          break;
 128
 129       case EGL_CONTEXT_MINOR_VERSION_KHR:
 130          /* The EGL_KHR_create_context spec says:
 131           *
 132           *     "The values for attributes EGL_CONTEXT_MAJOR_VERSION_KHR and
 133           *      EGL_CONTEXT_MINOR_VERSION_KHR specify the requested client API
 134           *      version. They are only meaningful for OpenGL and OpenGL ES
 135           *      contexts, and specifying them for other types of contexts will
 136           *      generate an error."
 137           */
 138          if (!dpy->Extensions.KHR_create_context ||
 139              (api != EGL_OPENGL_ES_API && api != EGL_OPENGL_API)) {
 140             err = EGL_BAD_ATTRIBUTE;
 141             break;
 142          }
 143
 144          ctx->ClientMinorVersion = val;
 145          break;
 146
 147       case EGL_CONTEXT_FLAGS_KHR:
 148          if (!dpy->Extensions.KHR_create_context) {
 149             err = EGL_BAD_ATTRIBUTE;
 150             break;
 151          }
 152
 153          /* The EGL_KHR_create_context spec says:
 154           *
 155           *     "If the EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR flag bit is set in
 156           *     EGL_CONTEXT_FLAGS_KHR, then a <debug context> will be created.
 157           *     [...]
 158           *     In some cases a debug context may be identical to a non-debug
 159           *     context. This bit is supported for OpenGL and OpenGL ES
 160           *     contexts."
 161           */
 162          if ((val & EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR) &&
 163              (api != EGL_OPENGL_API && api != EGL_OPENGL_ES_API)) {
 164             err = EGL_BAD_ATTRIBUTE;
 165             break;
 166          }
 167
 168          /* The EGL_KHR_create_context spec says:
 169           *
 170           *     "If the EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR flag bit
 171           *     is set in EGL_CONTEXT_FLAGS_KHR, then a <forward-compatible>
 172           *     context will be created. Forward-compatible contexts are
 173           *     defined only for OpenGL versions 3.0 and later. They must not
 174           *     support functionality marked as <deprecated> by that version of
 175           *     the API, while a non-forward-compatible context must support
 176           *     all functionality in that version, deprecated or not. This bit
 177           *     is supported for OpenGL contexts, and requesting a
 178           *     forward-compatible context for OpenGL versions less than 3.0
 179           *     will generate an error."
 180           */
 181          if ((val & EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR) &&
 182              (api != EGL_OPENGL_API || ctx->ClientMajorVersion < 3)) {
 183             err = EGL_BAD_ATTRIBUTE;
 184             break;
 185          }
 186
 187          if ((val & EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR) &&
 188              api != EGL_OPENGL_API) {
 189             /* The EGL_KHR_create_context spec says:
 190              *
 191              *   10) Which error should be generated if robust buffer access
 192              *       or reset notifications are requested under OpenGL ES?
 193              *
 194              *       As per Issue 6, this extension does not support creating
 195              *       robust contexts for OpenGL ES. This is only supported via
 196              *       the EGL_EXT_create_context_robustness extension.
 197              *
 198              *       Attempting to use this extension to create robust OpenGL
 199              *       ES context will generate an EGL_BAD_ATTRIBUTE error. This
 200              *       specific error is generated because this extension does
 201              *       not define the EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR
 202              *       and EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_KHR
 203              *       bits for OpenGL ES contexts. Thus, use of these bits fall
 204              *       under condition described by: "If an attribute is
 205              *       specified that is not meaningful for the client API
 206              *       type.." in the above specification.
 207              *
 208              * The spec requires that we emit the error even if the display
 209              * supports EGL_EXT_create_context_robustness. To create a robust
 210              * GLES context, the *attribute*
 211              * EGL_CONTEXT_OPENGL_ROBUST_ACCESS_EXT must be used, not the
 212              * *flag* EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR.
 213              */
 214             err = EGL_BAD_ATTRIBUTE;
 215             break;
 216          }
 217
 218          ctx->Flags |= val;
 219          break;
 220
 221       case EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR:
 222          if (!dpy->Extensions.KHR_create_context) {
 223             err = EGL_BAD_ATTRIBUTE;
 224             break;
 225          }
 226
 227          /* The EGL_KHR_create_context spec says:
 228           *
 229           *     "[EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR] is only meaningful for
 230           *     OpenGL contexts, and specifying it for other types of
 231           *     contexts, including OpenGL ES contexts, will generate an
 232           *     error."
 233           */
 234          if (api != EGL_OPENGL_API) {
 235             err = EGL_BAD_ATTRIBUTE;
 236             break;
 237          }
 238
 239          ctx->Profile = val;
 240          break;
 241
 242       case EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_KHR:
 243          /* The EGL_KHR_create_context spec says:
 244           *
 245           *     "[EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_KHR] is only
 246           *     meaningful for OpenGL contexts, and specifying it for other
 247           *     types of contexts, including OpenGL ES contexts, will generate
 248           *     an error."
 249           */
 250            if (!dpy->Extensions.KHR_create_context
 251                || api != EGL_OPENGL_API) {
 252             err = EGL_BAD_ATTRIBUTE;
 253             break;
 254          }
 255
 256          ctx->ResetNotificationStrategy = val;
 257          break;
 258
 259       case EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_EXT:
 260          /* The EGL_EXT_create_context_robustness spec says:
 261           *
 262           *     "[EGL_CONTEXT_OPENGL_RESET_NOTIFICATION_STRATEGY_EXT] is only
 263           *     meaningful for OpenGL ES contexts, and specifying it for other
 264           *     types of contexts will generate an EGL_BAD_ATTRIBUTE error."
 265           */
 266          if (!dpy->Extensions.EXT_create_context_robustness
 267              || api != EGL_OPENGL_ES_API) {
 268             err = EGL_BAD_ATTRIBUTE;
 269             break;
 270          }
 271
 272          ctx->ResetNotificationStrategy = val;
 273          break;
 274
 275       case EGL_CONTEXT_OPENGL_ROBUST_ACCESS_EXT:
 276          if (!dpy->Extensions.EXT_create_context_robustness) {
 277             err = EGL_BAD_ATTRIBUTE;
 278             break;
 279          }
 280
 281          if (val == EGL_TRUE)
 282             ctx->Flags |= EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR;
 283          break;
 284
 285       case EGL_CONTEXT_OPENGL_ROBUST_ACCESS:
 286          if (dpy->Version < 15) {
 287             err = EGL_BAD_ATTRIBUTE;
 288             break;
 289          }
 290
 291          if (val == EGL_TRUE)
 292             ctx->Flags |= EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR;
 293          break;
 294
 295       case EGL_CONTEXT_OPENGL_DEBUG:
 296          if (dpy->Version < 15) {
 297             err = EGL_BAD_ATTRIBUTE;
 298             break;
 299          }
 300
 301          if (val == EGL_TRUE)
 302             ctx->Flags |= EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR;
 303          break;
 304
 305       case EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE:
 306          if (dpy->Version < 15) {
 307             err = EGL_BAD_ATTRIBUTE;
 308             break;
 309          }
 310
 311          if (val == EGL_TRUE)
 312             ctx->Flags |= EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR;
 313          break;
 314
 315       case EGL_CONTEXT_OPENGL_NO_ERROR_KHR:
 316          if (dpy->Version < 14 ||
 317              !dpy->Extensions.KHR_create_context_no_error) {
 318             err = EGL_BAD_ATTRIBUTE;
 319             break;
 320          }
 321
 322          /* The KHR_no_error spec only applies against OpenGL 2.0+ and
 323           * OpenGL ES 2.0+
 324           */
 325          if ((api != EGL_OPENGL_API && api != EGL_OPENGL_ES_API) ||
 326              ctx->ClientMajorVersion < 2) {
 327             err = EGL_BAD_ATTRIBUTE;
 328             break;
 329          }
 330
 331          /* Canonicalize value to EGL_TRUE/EGL_FALSE definitions */
 332          ctx->NoError = !!val;
 333          break;
 334
 335       default:
 336          err = EGL_BAD_ATTRIBUTE;
 337          break;
 338       }
 339
 340       if (err != EGL_SUCCESS) {
 341          _eglLog(_EGL_DEBUG, "bad context attribute 0x%04x", attr);
 342          break;
 343       }
 344    }
 345
 346    if (api == EGL_OPENGL_API) {
 347       /* The EGL_KHR_create_context spec says:
 348        *
 349        *     "If the requested OpenGL version is less than 3.2,
 350        *     EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR is ignored and the
 351        *     functionality of the context is determined solely by the
 352        *     requested version."
 353        *
 354        * Since the value is ignored, only validate the setting if the version
 355        * is >= 3.2.
 356        */
 357       if (ctx->ClientMajorVersion >= 4
 358           || (ctx->ClientMajorVersion == 3 && ctx->ClientMinorVersion >= 2)) {
 359          switch (ctx->Profile) {
 360          case EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR:
 361          case EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT_KHR:
 362             break;
 363
 364          default:
 365             /* The EGL_KHR_create_context spec says:
 366              *
 367              *     "* If an OpenGL context is requested, the requested version
 368              *        is greater than 3.2, and the value for attribute
 369              *        EGL_CONTEXT_OPENGL_PROFILE_MASK_KHR has no bits set; has
 370              *        any bits set other than EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR
 371              *        and EGL_CONTEXT_OPENGL_COMPATIBILITY_PROFILE_BIT_KHR; has
 372              *        more than one of these bits set; or if the implementation does
 373              *        not support the requested profile, then an EGL_BAD_MATCH error
 374              *        is generated."
 375              */
 376             err = EGL_BAD_MATCH;
 377             break;
 378          }
 379       }
 380
 381       /* The EGL_KHR_create_context spec says:
 382        *
 383        *     "* If an OpenGL context is requested and the values for
 384        *        attributes EGL_CONTEXT_MAJOR_VERSION_KHR and
 385        *        EGL_CONTEXT_MINOR_VERSION_KHR, when considered together with
 386        *        the value for attribute
 387        *        EGL_CONTEXT_FORWARD_COMPATIBLE_BIT_KHR, specify an OpenGL
 388        *        version and feature set that are not defined, than an
 389        *        EGL_BAD_MATCH error is generated.
 390        *
 391        *        ... Thus, examples of invalid combinations of attributes
 392        *        include:
 393        *
 394        *          - Major version < 1 or > 4
 395        *          - Major version == 1 and minor version < 0 or > 5
 396        *          - Major version == 2 and minor version < 0 or > 1
 397        *          - Major version == 3 and minor version < 0 or > 2
 398        *          - Major version == 4 and minor version < 0 or > 2
 399        *          - Forward-compatible flag set and major version < 3"
 400        */
 401       if (ctx->ClientMajorVersion < 1 || ctx->ClientMinorVersion < 0)
 402          err = EGL_BAD_MATCH;
 403
 404       switch (ctx->ClientMajorVersion) {
 405       case 1:
 406          if (ctx->ClientMinorVersion > 5
 407              || (ctx->Flags & EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR) != 0)
 408             err = EGL_BAD_MATCH;
 409          break;
 410
 411       case 2:
 412          if (ctx->ClientMinorVersion > 1
 413              || (ctx->Flags & EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR) != 0)
 414             err = EGL_BAD_MATCH;
 415          break;
 416
 417       case 3:
 418          /* Note: The text above is incorrect.  There *is* an OpenGL 3.3!
 419           */
 420          if (ctx->ClientMinorVersion > 3)
 421             err = EGL_BAD_MATCH;
 422          break;
 423
 424       case 4:
 425       default:
 426          /* Don't put additional version checks here.  We don't know that
 427           * there won't be versions > 4.2.
 428           */
 429          break;
 430       }
 431    } else if (api == EGL_OPENGL_ES_API) {
 432       /* The EGL_KHR_create_context spec says:
 433        *
 434        *     "* If an OpenGL ES context is requested and the values for
 435        *        attributes EGL_CONTEXT_MAJOR_VERSION_KHR and
 436        *        EGL_CONTEXT_MINOR_VERSION_KHR specify an OpenGL ES version that
 437        *        is not defined, than an EGL_BAD_MATCH error is generated.
 438        *
 439        *        ... Examples of invalid combinations of attributes include:
 440        *
 441        *          - Major version < 1 or > 2
 442        *          - Major version == 1 and minor version < 0 or > 1
 443        *          - Major version == 2 and minor version != 0
 444        */
 445       if (ctx->ClientMajorVersion < 1 || ctx->ClientMinorVersion < 0)
 446          err = EGL_BAD_MATCH;
 447
 448       switch (ctx->ClientMajorVersion) {
 449       case 1:
 450          if (ctx->ClientMinorVersion > 1)
 451             err = EGL_BAD_MATCH;
 452          break;
 453
 454       case 2:
 455          if (ctx->ClientMinorVersion > 0)
 456             err = EGL_BAD_MATCH;
 457          break;
 458
 459       case 3:
 460          /* Don't put additional version checks here.  We don't know that
 461           * there won't be versions > 3.0.
 462           */
 463          break;
 464
 465       default:
 466          err = EGL_BAD_MATCH;
 467          break;
 468       }
 469    }
 470
 471    switch (ctx->ResetNotificationStrategy) {
 472    case EGL_NO_RESET_NOTIFICATION_KHR:
 473    case EGL_LOSE_CONTEXT_ON_RESET_KHR:
 474       break;
 475
 476    default:
 477       err = EGL_BAD_ATTRIBUTE;
 478       break;
 479    }
 480
 481    /* The EGL_KHR_create_context_no_error spec says:
 482     *
 483     *    "BAD_MATCH is generated if the EGL_CONTEXT_OPENGL_NO_ERROR_KHR is TRUE at
 484     *    the same time as a debug or robustness context is specified."
 485     */
 486    if (ctx->NoError && (ctx->Flags & EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR ||
 487                         ctx->Flags & EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR)) {
 488       err = EGL_BAD_MATCH;
 489    }
 490
 491    if ((ctx->Flags & ~(EGL_CONTEXT_OPENGL_DEBUG_BIT_KHR
 492                       | EGL_CONTEXT_OPENGL_FORWARD_COMPATIBLE_BIT_KHR
 493                       | EGL_CONTEXT_OPENGL_ROBUST_ACCESS_BIT_KHR)) != 0) {
 494       err = EGL_BAD_ATTRIBUTE;
 495    }
 496
 497    return err;
 498 }
 499
 500
 501 /**
 502  * Initialize the given _EGLContext object to defaults and/or the values
 503  * in the attrib_list.
 504  *
 505  * According to EGL 1.5 Section 3.7:
 506  *
 507  *      "EGL_OPENGL_API and EGL_OPENGL_ES_API are interchangeable for all
 508  *      purposes except eglCreateContext."
 509  *
 510  * And since we only support GL and GLES, this is the only place where the
 511  * bound API matters at all. We look up the current API from the current
 512  * thread, and stash that in the context we're initializing. Our caller is
 513  * responsible for determining whether that's an API it supports.
 514  */
 515 EGLBoolean
 516 _eglInitContext(_EGLContext *ctx, _EGLDisplay *dpy, _EGLConfig *conf,
 517                 const EGLint *attrib_list)
 518 {
 519    const EGLenum api = eglQueryAPI();
 520    EGLint err;
 521
 522    if (api == EGL_NONE)
 523       return _eglError(EGL_BAD_MATCH, "eglCreateContext(no client API)");
 524
 525    _eglInitResource(&ctx->Resource, sizeof(*ctx), dpy);
 526    ctx->ClientAPI = api;
 527    ctx->Config = conf;
 528    ctx->WindowRenderBuffer = EGL_NONE;
 529    ctx->Profile = EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR;
 530
 531    ctx->ClientMajorVersion = 1; /* the default, per EGL spec */
 532    ctx->ClientMinorVersion = 0;
 533    ctx->Flags = 0;
 534    ctx->Profile = EGL_CONTEXT_OPENGL_CORE_PROFILE_BIT_KHR;
 535    ctx->ResetNotificationStrategy = EGL_NO_RESET_NOTIFICATION_KHR;
 536
 537    err = _eglParseContextAttribList(ctx, dpy, attrib_list);
 538    if (err == EGL_SUCCESS && ctx->Config) {
 539       EGLint api_bit;
 540
 541       api_bit = _eglGetContextAPIBit(ctx);
 542       if (!(ctx->Config->RenderableType & api_bit)) {
 543          _eglLog(_EGL_DEBUG, "context api is 0x%x while config supports 0x%x",
 544                api_bit, ctx->Config->RenderableType);
 545          err = EGL_BAD_CONFIG;
 546       }
 547    }
 548    if (err != EGL_SUCCESS)
 549       return _eglError(err, "eglCreateContext");
 550
 551    return EGL_TRUE;
 552 }
 553
 554
 555 static EGLint
 556 _eglQueryContextRenderBuffer(_EGLContext *ctx)
 557 {
 558    _EGLSurface *surf = ctx->DrawSurface;
 559    EGLint rb;
 560
 561    if (!surf)
 562       return EGL_NONE;
 563    if (surf->Type == EGL_WINDOW_BIT && ctx->WindowRenderBuffer != EGL_NONE)
 564       rb = ctx->WindowRenderBuffer;
 565    else
 566       rb = surf->RenderBuffer;
 567    return rb;
 568 }
 569
 570
 571 EGLBoolean
 572 _eglQueryContext(_EGLDriver *drv, _EGLDisplay *dpy, _EGLContext *c,
 573                  EGLint attribute, EGLint *value)
 574 {
 575    (void) drv;
 576    (void) dpy;
 577
 578    if (!value)
 579       return _eglError(EGL_BAD_PARAMETER, "eglQueryContext");
 580
 581    switch (attribute) {
 582    case EGL_CONFIG_ID:
 583       /*
 584        * From EGL_KHR_no_config_context:
 585        *
 586        *    "Querying EGL_CONFIG_ID returns the ID of the EGLConfig with
 587        *     respect to which the context was created, or zero if created
 588        *     without respect to an EGLConfig."
 589        */
 590       *value = c->Config ? c->Config->ConfigID : 0;
 591       break;
 592    case EGL_CONTEXT_CLIENT_VERSION:
 593       *value = c->ClientMajorVersion;
 594       break;
 595    case EGL_CONTEXT_CLIENT_TYPE:
 596       *value = c->ClientAPI;
 597       break;
 598    case EGL_RENDER_BUFFER:
 599       *value = _eglQueryContextRenderBuffer(c);
 600       break;
 601    default:
 602       return _eglError(EGL_BAD_ATTRIBUTE, "eglQueryContext");
 603    }
 604
 605    return EGL_TRUE;
 606 }
 607
 608
 609 /**
 610  * Bind the context to the thread and return the previous context.
 611  *
 612  * Note that the context may be NULL.
 613  */
 614 _EGLContext *
 615 _eglBindContextToThread(_EGLContext *ctx, _EGLThreadInfo *t)
 616 {
 617    _EGLContext *oldCtx;
 618
 619    oldCtx = t->CurrentContext;
 620    if (ctx != oldCtx) {
 621       if (oldCtx)
 622          oldCtx->Binding = NULL;
 623       if (ctx)
 624          ctx->Binding = t;
 625
 626       t->CurrentContext = ctx;
 627    }
 628
 629    return oldCtx;
 630 }
 631
 632
 633 /**
 634  * Return true if the given context and surfaces can be made current.
 635  */
 636 static EGLBoolean
 637 _eglCheckMakeCurrent(_EGLContext *ctx, _EGLSurface *draw, _EGLSurface *read)
 638 {
 639    _EGLThreadInfo *t = _eglGetCurrentThread();
 640    _EGLDisplay *dpy;
 641
 642    if (_eglIsCurrentThreadDummy())
 643       return _eglError(EGL_BAD_ALLOC, "eglMakeCurrent");
 644
 645    /* this is easy */
 646    if (!ctx) {
 647       if (draw || read)
 648          return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
 649       return EGL_TRUE;
 650    }
 651
 652    dpy = ctx->Resource.Display;
 653    if (!dpy->Extensions.KHR_surfaceless_context
 654        && (draw == NULL || read == NULL))
 655       return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
 656
 657    /*
 658     * The spec says
 659     *
 660     * "If ctx is current to some other thread, or if either draw or read are
 661     * bound to contexts in another thread, an EGL_BAD_ACCESS error is
 662     * generated."
 663     *
 664     * and
 665     *
 666     * "at most one context may be bound to a particular surface at a given
 667     * time"
 668     */
 669    if (ctx->Binding && ctx->Binding != t)
 670       return _eglError(EGL_BAD_ACCESS, "eglMakeCurrent");
 671    if (draw && draw->CurrentContext && draw->CurrentContext != ctx) {
 672       if (draw->CurrentContext->Binding != t)
 673          return _eglError(EGL_BAD_ACCESS, "eglMakeCurrent");
 674    }
 675    if (read && read->CurrentContext && read->CurrentContext != ctx) {
 676       if (read->CurrentContext->Binding != t)
 677          return _eglError(EGL_BAD_ACCESS, "eglMakeCurrent");
 678    }
 679
 680    /* If the context has a config then it must match that of the two
 681     * surfaces */
 682    if (ctx->Config) {
 683       if ((draw && draw->Config != ctx->Config) ||
 684           (read && read->Config != ctx->Config))
 685          return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
 686    } else {
 687       /* Otherwise we must be using the EGL_KHR_no_config_context
 688        * extension */
 689       assert(dpy->Extensions.KHR_no_config_context);
 690
 691       /* The extension doesn't permit binding draw and read buffers with
 692        * differing contexts */
 693       if (draw && read && draw->Config != read->Config)
 694          return _eglError(EGL_BAD_MATCH, "eglMakeCurrent");
 695    }
 696
 697    return EGL_TRUE;
 698 }
 699
 700
 701 /**
 702  * Bind the context to the current thread and given surfaces.  Return the
 703  * previous bound context and surfaces.  The caller should unreference the
 704  * returned context and surfaces.
 705  *
 706  * Making a second call with the resources returned by the first call
 707  * unsurprisingly undoes the first call, except for the resouce reference
 708  * counts.
 709  */
 710 EGLBoolean
 711 _eglBindContext(_EGLContext *ctx, _EGLSurface *draw, _EGLSurface *read,
 712                 _EGLContext **old_ctx,
 713                 _EGLSurface **old_draw, _EGLSurface **old_read)
 714 {
 715    _EGLThreadInfo *t = _eglGetCurrentThread();
 716    _EGLContext *prev_ctx;
 717    _EGLSurface *prev_draw, *prev_read;
 718
 719    if (!_eglCheckMakeCurrent(ctx, draw, read))
 720       return EGL_FALSE;
 721
 722    /* increment refcounts before binding */
 723    _eglGetContext(ctx);
 724    _eglGetSurface(draw);
 725    _eglGetSurface(read);
 726
 727    /* bind the new context */
 728    prev_ctx = _eglBindContextToThread(ctx, t);
 729
 730    /* break previous bindings */
 731    if (prev_ctx) {
 732       prev_draw = prev_ctx->DrawSurface;
 733       prev_read = prev_ctx->ReadSurface;
 734
 735       if (prev_draw)
 736          prev_draw->CurrentContext = NULL;
 737       if (prev_read)
 738          prev_read->CurrentContext = NULL;
 739
 740       prev_ctx->DrawSurface = NULL;
 741       prev_ctx->ReadSurface = NULL;
 742    }
 743    else {
 744       prev_draw = prev_read = NULL;
 745    }
 746
 747    /* establish new bindings */
 748    if (ctx) {
 749       if (draw)
 750          draw->CurrentContext = ctx;
 751       if (read)
 752          read->CurrentContext = ctx;
 753
 754       ctx->DrawSurface = draw;
 755       ctx->ReadSurface = read;
 756    }
 757
 758    assert(old_ctx && old_draw && old_read);
 759    *old_ctx = prev_ctx;
 760    *old_draw = prev_draw;
 761    *old_read = prev_read;
 762
 763    return EGL_TRUE;
 764 }