src/mesa/main/stencil.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 stencil.c
  28  * Stencil operations.
  29  *
  30  * Note: There's some conflict between GL_EXT_stencil_two_side and
  31  * OpenGL 2.0's two-sided stencil feature.
  32  *
  33  * With GL_EXT_stencil_two_side, calling glStencilOp/Func/Mask() only the
  34  * front OR back face state (as set by glActiveStencilFaceEXT) is set.
  35  *
  36  * But with OpenGL 2.0, calling glStencilOp/Func/Mask() sets BOTH the
  37  * front AND back state.
  38  *
  39  * Also, note that GL_ATI_separate_stencil is different as well:
  40  * glStencilFuncSeparateATI(GLenum frontfunc, GLenum backfunc, ...)  vs.
  41  * glStencilFuncSeparate(GLenum face, GLenum func, ...).
  42  *
  43  * This problem is solved by keeping three sets of stencil state:
  44  *  state[0] = GL_FRONT state.
  45  *  state[1] = OpenGL 2.0 / GL_ATI_separate_stencil GL_BACK state.
  46  *  state[2] = GL_EXT_stencil_two_side GL_BACK state.
  47  */
  48
  49
  50 #include "glheader.h"
  51 #include "imports.h"
  52 #include "context.h"
  53 #include "macros.h"
  54 #include "stencil.h"
  55 #include "mtypes.h"
  56
  57
  58 static GLboolean
  59 validate_stencil_op(struct gl_context *ctx, GLenum op)
  60 {
  61    switch (op) {
  62    case GL_KEEP:
  63    case GL_ZERO:
  64    case GL_REPLACE:
  65    case GL_INCR:
  66    case GL_DECR:
  67    case GL_INVERT:
  68    case GL_INCR_WRAP:
  69    case GL_DECR_WRAP:
  70       return GL_TRUE;
  71    default:
  72       return GL_FALSE;
  73    }
  74 }
  75
  76
  77 static GLboolean
  78 validate_stencil_func(struct gl_context *ctx, GLenum func)
  79 {
  80    switch (func) {
  81    case GL_NEVER:
  82    case GL_LESS:
  83    case GL_LEQUAL:
  84    case GL_GREATER:
  85    case GL_GEQUAL:
  86    case GL_EQUAL:
  87    case GL_NOTEQUAL:
  88    case GL_ALWAYS:
  89       return GL_TRUE;
  90    default:
  91       return GL_FALSE;
  92    }
  93 }
  94
  95
  96 /**
  97  * Set the clear value for the stencil buffer.
  98  *
  99  * \param s clear value.
 100  *
 101  * \sa glClearStencil().
 102  *
 103  * Updates gl_stencil_attrib::Clear. On change
 104  * flushes the vertices and notifies the driver via
 105  * the dd_function_table::ClearStencil callback.
 106  */
 107 void GLAPIENTRY
 108 _mesa_ClearStencil( GLint s )
 109 {
 110    GET_CURRENT_CONTEXT(ctx);
 111
 112    if (MESA_VERBOSE & VERBOSE_API)
 113       _mesa_debug(ctx, "glClearStencil(%d)\n", s);
 114
 115    ctx->Stencil.Clear = (GLuint) s;
 116 }
 117
 118
 119 /**
 120  * Set the function and reference value for stencil testing.
 121  *
 122  * \param frontfunc front test function.
 123  * \param backfunc back test function.
 124  * \param ref front and back reference value.
 125  * \param mask front and back bitmask.
 126  *
 127  * \sa glStencilFunc().
 128  *
 129  * Verifies the parameters and updates the respective values in
 130  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies
 131  * the driver via the dd_function_table::StencilFunc callback.
 132  */
 133 void GLAPIENTRY
 134 _mesa_StencilFuncSeparateATI( GLenum frontfunc, GLenum backfunc, GLint ref, GLuint mask )
 135 {
 136    GET_CURRENT_CONTEXT(ctx);
 137
 138    if (MESA_VERBOSE & VERBOSE_API)
 139       _mesa_debug(ctx, "glStencilFuncSeparateATI()\n");
 140
 141    if (!validate_stencil_func(ctx, frontfunc)) {
 142       _mesa_error(ctx, GL_INVALID_ENUM,
 143                   "glStencilFuncSeparateATI(frontfunc)");
 144       return;
 145    }
 146    if (!validate_stencil_func(ctx, backfunc)) {
 147       _mesa_error(ctx, GL_INVALID_ENUM,
 148                   "glStencilFuncSeparateATI(backfunc)");
 149       return;
 150    }
 151
 152    /* set both front and back state */
 153    if (ctx->Stencil.Function[0] == frontfunc &&
 154        ctx->Stencil.Function[1] == backfunc &&
 155        ctx->Stencil.ValueMask[0] == mask &&
 156        ctx->Stencil.ValueMask[1] == mask &&
 157        ctx->Stencil.Ref[0] == ref &&
 158        ctx->Stencil.Ref[1] == ref)
 159       return;
 160    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 161    ctx->Stencil.Function[0]  = frontfunc;
 162    ctx->Stencil.Function[1]  = backfunc;
 163    ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 164    ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 165    if (ctx->Driver.StencilFuncSeparate) {
 166       ctx->Driver.StencilFuncSeparate(ctx, GL_FRONT,
 167                                       frontfunc, ref, mask);
 168       ctx->Driver.StencilFuncSeparate(ctx, GL_BACK,
 169                                       backfunc, ref, mask);
 170    }
 171 }
 172
 173
 174 /**
 175  * Set the function and reference value for stencil testing.
 176  *
 177  * \param func test function.
 178  * \param ref reference value.
 179  * \param mask bitmask.
 180  *
 181  * \sa glStencilFunc().
 182  *
 183  * Verifies the parameters and updates the respective values in
 184  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies
 185  * the driver via the dd_function_table::StencilFunc callback.
 186  */
 187 static void
 188 stencil_func(struct gl_context *ctx, GLenum func, GLint ref, GLuint mask)
 189 {
 190    const GLint face = ctx->Stencil.ActiveFace;
 191
 192    if (face != 0) {
 193       if (ctx->Stencil.Function[face] == func &&
 194           ctx->Stencil.ValueMask[face] == mask &&
 195           ctx->Stencil.Ref[face] == ref)
 196          return;
 197       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 198       ctx->Stencil.Function[face] = func;
 199       ctx->Stencil.Ref[face] = ref;
 200       ctx->Stencil.ValueMask[face] = mask;
 201
 202       /* Only propagate the change to the driver if EXT_stencil_two_side
 203        * is enabled.
 204        */
 205       if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
 206          ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
 207       }
 208    }
 209    else {
 210       /* set both front and back state */
 211       if (ctx->Stencil.Function[0] == func &&
 212           ctx->Stencil.Function[1] == func &&
 213           ctx->Stencil.ValueMask[0] == mask &&
 214           ctx->Stencil.ValueMask[1] == mask &&
 215           ctx->Stencil.Ref[0] == ref &&
 216           ctx->Stencil.Ref[1] == ref)
 217          return;
 218       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 219       ctx->Stencil.Function[0]  = ctx->Stencil.Function[1]  = func;
 220       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 221       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 222       if (ctx->Driver.StencilFuncSeparate) {
 223          ctx->Driver.StencilFuncSeparate(ctx,
 224                                          ((ctx->Stencil.TestTwoSide)
 225                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 226                                          func, ref, mask);
 227       }
 228    }
 229 }
 230
 231
 232 void GLAPIENTRY
 233 _mesa_StencilFunc(GLenum func, GLint ref, GLuint mask)
 234 {
 235    GET_CURRENT_CONTEXT(ctx);
 236
 237    if (MESA_VERBOSE & VERBOSE_API)
 238       _mesa_debug(ctx, "glStencilFunc()\n");
 239
 240    if (!validate_stencil_func(ctx, func)) {
 241       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 242       return;
 243    }
 244
 245    stencil_func(ctx, func, ref, mask);
 246 }
 247
 248
 249 /**
 250  * Set the stencil writing mask.
 251  *
 252  * \param mask bit-mask to enable/disable writing of individual bits in the
 253  * stencil planes.
 254  *
 255  * \sa glStencilMask().
 256  *
 257  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 258  * notifies the driver via the dd_function_table::StencilMask callback.
 259  */
 260 void GLAPIENTRY
 261 _mesa_StencilMask( GLuint mask )
 262 {
 263    GET_CURRENT_CONTEXT(ctx);
 264    const GLint face = ctx->Stencil.ActiveFace;
 265
 266    if (MESA_VERBOSE & VERBOSE_API)
 267       _mesa_debug(ctx, "glStencilMask()\n");
 268
 269    if (face != 0) {
 270       /* Only modify the EXT_stencil_two_side back-face state.
 271        */
 272       if (ctx->Stencil.WriteMask[face] == mask)
 273          return;
 274       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 275       ctx->Stencil.WriteMask[face] = mask;
 276
 277       /* Only propagate the change to the driver if EXT_stencil_two_side
 278        * is enabled.
 279        */
 280       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 281          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 282       }
 283    }
 284    else {
 285       /* set both front and back state */
 286       if (ctx->Stencil.WriteMask[0] == mask &&
 287           ctx->Stencil.WriteMask[1] == mask)
 288          return;
 289       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 290       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 291       if (ctx->Driver.StencilMaskSeparate) {
 292          ctx->Driver.StencilMaskSeparate(ctx,
 293                                          ((ctx->Stencil.TestTwoSide)
 294                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 295                                           mask);
 296       }
 297    }
 298 }
 299
 300
 301 /**
 302  * Set the stencil test actions.
 303  *
 304  * \param fail action to take when stencil test fails.
 305  * \param zfail action to take when stencil test passes, but depth test fails.
 306  * \param zpass action to take when stencil test passes and the depth test
 307  * passes (or depth testing is not enabled).
 308  *
 309  * \sa glStencilOp().
 310  *
 311  * Verifies the parameters and updates the respective fields in
 312  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies
 313  * the driver via the dd_function_table::StencilOp callback.
 314  */
 315 void GLAPIENTRY
 316 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 317 {
 318    GET_CURRENT_CONTEXT(ctx);
 319    const GLint face = ctx->Stencil.ActiveFace;
 320
 321    if (MESA_VERBOSE & VERBOSE_API)
 322       _mesa_debug(ctx, "glStencilOp()\n");
 323
 324    if (!validate_stencil_op(ctx, fail)) {
 325       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 326       return;
 327    }
 328    if (!validate_stencil_op(ctx, zfail)) {
 329       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 330       return;
 331    }
 332    if (!validate_stencil_op(ctx, zpass)) {
 333       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 334       return;
 335    }
 336
 337    if (face != 0) {
 338       /* only set active face state */
 339       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 340           ctx->Stencil.ZPassFunc[face] == zpass &&
 341           ctx->Stencil.FailFunc[face] == fail)
 342          return;
 343       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 344       ctx->Stencil.ZFailFunc[face] = zfail;
 345       ctx->Stencil.ZPassFunc[face] = zpass;
 346       ctx->Stencil.FailFunc[face] = fail;
 347
 348       /* Only propagate the change to the driver if EXT_stencil_two_side
 349        * is enabled.
 350        */
 351       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 352          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 353       }
 354    }
 355    else {
 356       /* set both front and back state */
 357       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 358           ctx->Stencil.ZFailFunc[1] == zfail &&
 359           ctx->Stencil.ZPassFunc[0] == zpass &&
 360           ctx->Stencil.ZPassFunc[1] == zpass &&
 361           ctx->Stencil.FailFunc[0] == fail &&
 362           ctx->Stencil.FailFunc[1] == fail)
 363          return;
 364       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 365       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 366       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 367       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 368       if (ctx->Driver.StencilOpSeparate) {
 369          ctx->Driver.StencilOpSeparate(ctx,
 370                                        ((ctx->Stencil.TestTwoSide)
 371                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 372                                        fail, zfail, zpass);
 373       }
 374    }
 375 }
 376
 377
 378
 379 /* GL_EXT_stencil_two_side */
 380 void GLAPIENTRY
 381 _mesa_ActiveStencilFaceEXT(GLenum face)
 382 {
 383    GET_CURRENT_CONTEXT(ctx);
 384
 385    if (MESA_VERBOSE & VERBOSE_API)
 386       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 387
 388    if (!ctx->Extensions.EXT_stencil_two_side) {
 389       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 390       return;
 391    }
 392
 393    if (face == GL_FRONT || face == GL_BACK) {
 394       ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
 395    }
 396    else {
 397       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
 398    }
 399 }
 400
 401
 402 static void
 403 stencil_op_separate(struct gl_context *ctx, GLenum face, GLenum sfail,
 404                     GLenum zfail, GLenum zpass)
 405 {
 406    GLboolean set = GL_FALSE;
 407
 408    if (face != GL_BACK) {
 409       /* set front */
 410       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 411           ctx->Stencil.ZPassFunc[0] != zpass ||
 412           ctx->Stencil.FailFunc[0] != sfail){
 413          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 414          ctx->Stencil.ZFailFunc[0] = zfail;
 415          ctx->Stencil.ZPassFunc[0] = zpass;
 416          ctx->Stencil.FailFunc[0] = sfail;
 417          set = GL_TRUE;
 418       }
 419    }
 420
 421    if (face != GL_FRONT) {
 422       /* set back */
 423       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 424           ctx->Stencil.ZPassFunc[1] != zpass ||
 425           ctx->Stencil.FailFunc[1] != sfail) {
 426          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 427          ctx->Stencil.ZFailFunc[1] = zfail;
 428          ctx->Stencil.ZPassFunc[1] = zpass;
 429          ctx->Stencil.FailFunc[1] = sfail;
 430          set = GL_TRUE;
 431       }
 432    }
 433
 434    if (set && ctx->Driver.StencilOpSeparate) {
 435       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 436    }
 437 }
 438
 439
 440 void GLAPIENTRY
 441 _mesa_StencilOpSeparate_no_error(GLenum face, GLenum sfail, GLenum zfail,
 442                                  GLenum zpass)
 443 {
 444    GET_CURRENT_CONTEXT(ctx);
 445    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 446 }
 447
 448
 449 void GLAPIENTRY
 450 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 451 {
 452    GET_CURRENT_CONTEXT(ctx);
 453
 454    if (MESA_VERBOSE & VERBOSE_API)
 455       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 456
 457    if (!validate_stencil_op(ctx, sfail)) {
 458       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 459       return;
 460    }
 461
 462    if (!validate_stencil_op(ctx, zfail)) {
 463       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 464       return;
 465    }
 466
 467    if (!validate_stencil_op(ctx, zpass)) {
 468       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 469       return;
 470    }
 471
 472    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 473       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 474       return;
 475    }
 476
 477    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 478 }
 479
 480
 481 static void
 482 stencil_func_separate(struct gl_context *ctx, GLenum face, GLenum func,
 483                       GLint ref, GLuint mask)
 484 {
 485    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 486
 487    if (face != GL_BACK) {
 488       /* set front */
 489       ctx->Stencil.Function[0] = func;
 490       ctx->Stencil.Ref[0] = ref;
 491       ctx->Stencil.ValueMask[0] = mask;
 492    }
 493
 494    if (face != GL_FRONT) {
 495       /* set back */
 496       ctx->Stencil.Function[1] = func;
 497       ctx->Stencil.Ref[1] = ref;
 498       ctx->Stencil.ValueMask[1] = mask;
 499    }
 500
 501    if (ctx->Driver.StencilFuncSeparate) {
 502       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 503    }
 504 }
 505
 506
 507 /* OpenGL 2.0 */
 508 void GLAPIENTRY
 509 _mesa_StencilFuncSeparate_no_error(GLenum face, GLenum func, GLint ref,
 510                                    GLuint mask)
 511 {
 512    GET_CURRENT_CONTEXT(ctx);
 513    stencil_func_separate(ctx, face, func, ref, mask);
 514 }
 515
 516
 517 void GLAPIENTRY
 518 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 519 {
 520    GET_CURRENT_CONTEXT(ctx);
 521
 522    if (MESA_VERBOSE & VERBOSE_API)
 523       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 524
 525    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 526       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 527       return;
 528    }
 529
 530    if (!validate_stencil_func(ctx, func)) {
 531       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 532       return;
 533    }
 534
 535    stencil_func_separate(ctx, face, func, ref, mask);
 536 }
 537
 538
 539 static void
 540 stencil_mask_separate(struct gl_context *ctx, GLenum face, GLuint mask)
 541 {
 542    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 543
 544    if (face != GL_BACK) {
 545       ctx->Stencil.WriteMask[0] = mask;
 546    }
 547
 548    if (face != GL_FRONT) {
 549       ctx->Stencil.WriteMask[1] = mask;
 550    }
 551
 552    if (ctx->Driver.StencilMaskSeparate) {
 553       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 554    }
 555 }
 556
 557
 558 /* OpenGL 2.0 */
 559 void GLAPIENTRY
 560 _mesa_StencilMaskSeparate_no_error(GLenum face, GLuint mask)
 561 {
 562    GET_CURRENT_CONTEXT(ctx);
 563    stencil_mask_separate(ctx, face, mask);
 564 }
 565
 566
 567 void GLAPIENTRY
 568 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 569 {
 570    GET_CURRENT_CONTEXT(ctx);
 571
 572    if (MESA_VERBOSE & VERBOSE_API)
 573       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 574
 575    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 576       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 577       return;
 578    }
 579
 580    stencil_mask_separate(ctx, face, mask);
 581 }
 582
 583
 584 /**
 585  * Update derived stencil state.
 586  */
 587 void
 588 _mesa_update_stencil(struct gl_context *ctx)
 589 {
 590    const GLint face = ctx->Stencil._BackFace;
 591
 592    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 593                             ctx->DrawBuffer->Visual.stencilBits > 0);
 594
 595     ctx->Stencil._TestTwoSide =
 596        ctx->Stencil._Enabled &&
 597        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 598         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 599         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 600         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 601         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 602         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 603         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 604
 605    ctx->Stencil._WriteEnabled =
 606       ctx->Stencil._Enabled &&
 607       (ctx->Stencil.WriteMask[0] != 0 ||
 608        (ctx->Stencil._TestTwoSide && ctx->Stencil.WriteMask[face] != 0));
 609 }
 610
 611
 612 /**
 613  * Initialize the context stipple state.
 614  *
 615  * \param ctx GL context.
 616  *
 617  * Initializes __struct gl_contextRec::Stencil attribute group.
 618  */
 619 void
 620 _mesa_init_stencil(struct gl_context *ctx)
 621 {
 622    ctx->Stencil.Enabled = GL_FALSE;
 623    ctx->Stencil.TestTwoSide = GL_FALSE;
 624    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 2 = GL_BACK */
 625    ctx->Stencil.Function[0] = GL_ALWAYS;
 626    ctx->Stencil.Function[1] = GL_ALWAYS;
 627    ctx->Stencil.Function[2] = GL_ALWAYS;
 628    ctx->Stencil.FailFunc[0] = GL_KEEP;
 629    ctx->Stencil.FailFunc[1] = GL_KEEP;
 630    ctx->Stencil.FailFunc[2] = GL_KEEP;
 631    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
 632    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
 633    ctx->Stencil.ZPassFunc[2] = GL_KEEP;
 634    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
 635    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
 636    ctx->Stencil.ZFailFunc[2] = GL_KEEP;
 637    ctx->Stencil.Ref[0] = 0;
 638    ctx->Stencil.Ref[1] = 0;
 639    ctx->Stencil.Ref[2] = 0;
 640
 641    /* 4.1.4 Stencil Test section of the GL-ES 3.0 specification says:
 642     *
 643     *     "In the initial state, [...] the front and back stencil mask are both
 644     *     set to the value 2^s − 1, where s is greater than or equal to the
 645     *     number of bits in the deepest stencil buffer* supported by the GL
 646     *     implementation."
 647     *
 648     * Since the maximum supported precision for stencil buffers is 8 bits,
 649     * mask values should be initialized to 2^8 - 1 = 0xFF.
 650     */
 651    ctx->Stencil.ValueMask[0] = 0xFF;
 652    ctx->Stencil.ValueMask[1] = 0xFF;
 653    ctx->Stencil.ValueMask[2] = 0xFF;
 654    ctx->Stencil.WriteMask[0] = 0xFF;
 655    ctx->Stencil.WriteMask[1] = 0xFF;
 656    ctx->Stencil.WriteMask[2] = 0xFF;
 657
 658    ctx->Stencil.Clear = 0;
 659    ctx->Stencil._BackFace = 1;
 660 }