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 void GLAPIENTRY
 188 _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
 189 {
 190    GET_CURRENT_CONTEXT(ctx);
 191    const GLint face = ctx->Stencil.ActiveFace;
 192
 193    if (MESA_VERBOSE & VERBOSE_API)
 194       _mesa_debug(ctx, "glStencilFunc()\n");
 195
 196    if (!validate_stencil_func(ctx, func)) {
 197       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 198       return;
 199    }
 200
 201    if (face != 0) {
 202       if (ctx->Stencil.Function[face] == func &&
 203           ctx->Stencil.ValueMask[face] == mask &&
 204           ctx->Stencil.Ref[face] == ref)
 205          return;
 206       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 207       ctx->Stencil.Function[face] = func;
 208       ctx->Stencil.Ref[face] = ref;
 209       ctx->Stencil.ValueMask[face] = mask;
 210
 211       /* Only propagate the change to the driver if EXT_stencil_two_side
 212        * is enabled.
 213        */
 214       if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
 215          ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
 216       }
 217    }
 218    else {
 219       /* set both front and back state */
 220       if (ctx->Stencil.Function[0] == func &&
 221           ctx->Stencil.Function[1] == func &&
 222           ctx->Stencil.ValueMask[0] == mask &&
 223           ctx->Stencil.ValueMask[1] == mask &&
 224           ctx->Stencil.Ref[0] == ref &&
 225           ctx->Stencil.Ref[1] == ref)
 226          return;
 227       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 228       ctx->Stencil.Function[0]  = ctx->Stencil.Function[1]  = func;
 229       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 230       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 231       if (ctx->Driver.StencilFuncSeparate) {
 232          ctx->Driver.StencilFuncSeparate(ctx,
 233                                          ((ctx->Stencil.TestTwoSide)
 234                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 235                                          func, ref, mask);
 236       }
 237    }
 238 }
 239
 240
 241 /**
 242  * Set the stencil writing mask.
 243  *
 244  * \param mask bit-mask to enable/disable writing of individual bits in the
 245  * stencil planes.
 246  *
 247  * \sa glStencilMask().
 248  *
 249  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 250  * notifies the driver via the dd_function_table::StencilMask callback.
 251  */
 252 void GLAPIENTRY
 253 _mesa_StencilMask( GLuint mask )
 254 {
 255    GET_CURRENT_CONTEXT(ctx);
 256    const GLint face = ctx->Stencil.ActiveFace;
 257
 258    if (MESA_VERBOSE & VERBOSE_API)
 259       _mesa_debug(ctx, "glStencilMask()\n");
 260
 261    if (face != 0) {
 262       /* Only modify the EXT_stencil_two_side back-face state.
 263        */
 264       if (ctx->Stencil.WriteMask[face] == mask)
 265          return;
 266       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 267       ctx->Stencil.WriteMask[face] = mask;
 268
 269       /* Only propagate the change to the driver if EXT_stencil_two_side
 270        * is enabled.
 271        */
 272       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 273          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 274       }
 275    }
 276    else {
 277       /* set both front and back state */
 278       if (ctx->Stencil.WriteMask[0] == mask &&
 279           ctx->Stencil.WriteMask[1] == mask)
 280          return;
 281       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 282       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 283       if (ctx->Driver.StencilMaskSeparate) {
 284          ctx->Driver.StencilMaskSeparate(ctx,
 285                                          ((ctx->Stencil.TestTwoSide)
 286                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 287                                           mask);
 288       }
 289    }
 290 }
 291
 292
 293 /**
 294  * Set the stencil test actions.
 295  *
 296  * \param fail action to take when stencil test fails.
 297  * \param zfail action to take when stencil test passes, but depth test fails.
 298  * \param zpass action to take when stencil test passes and the depth test
 299  * passes (or depth testing is not enabled).
 300  *
 301  * \sa glStencilOp().
 302  *
 303  * Verifies the parameters and updates the respective fields in
 304  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies
 305  * the driver via the dd_function_table::StencilOp callback.
 306  */
 307 void GLAPIENTRY
 308 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 309 {
 310    GET_CURRENT_CONTEXT(ctx);
 311    const GLint face = ctx->Stencil.ActiveFace;
 312
 313    if (MESA_VERBOSE & VERBOSE_API)
 314       _mesa_debug(ctx, "glStencilOp()\n");
 315
 316    if (!validate_stencil_op(ctx, fail)) {
 317       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 318       return;
 319    }
 320    if (!validate_stencil_op(ctx, zfail)) {
 321       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 322       return;
 323    }
 324    if (!validate_stencil_op(ctx, zpass)) {
 325       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 326       return;
 327    }
 328
 329    if (face != 0) {
 330       /* only set active face state */
 331       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 332           ctx->Stencil.ZPassFunc[face] == zpass &&
 333           ctx->Stencil.FailFunc[face] == fail)
 334          return;
 335       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 336       ctx->Stencil.ZFailFunc[face] = zfail;
 337       ctx->Stencil.ZPassFunc[face] = zpass;
 338       ctx->Stencil.FailFunc[face] = fail;
 339
 340       /* Only propagate the change to the driver if EXT_stencil_two_side
 341        * is enabled.
 342        */
 343       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 344          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 345       }
 346    }
 347    else {
 348       /* set both front and back state */
 349       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 350           ctx->Stencil.ZFailFunc[1] == zfail &&
 351           ctx->Stencil.ZPassFunc[0] == zpass &&
 352           ctx->Stencil.ZPassFunc[1] == zpass &&
 353           ctx->Stencil.FailFunc[0] == fail &&
 354           ctx->Stencil.FailFunc[1] == fail)
 355          return;
 356       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 357       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 358       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 359       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 360       if (ctx->Driver.StencilOpSeparate) {
 361          ctx->Driver.StencilOpSeparate(ctx,
 362                                        ((ctx->Stencil.TestTwoSide)
 363                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 364                                        fail, zfail, zpass);
 365       }
 366    }
 367 }
 368
 369
 370
 371 /* GL_EXT_stencil_two_side */
 372 void GLAPIENTRY
 373 _mesa_ActiveStencilFaceEXT(GLenum face)
 374 {
 375    GET_CURRENT_CONTEXT(ctx);
 376
 377    if (MESA_VERBOSE & VERBOSE_API)
 378       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 379
 380    if (!ctx->Extensions.EXT_stencil_two_side) {
 381       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 382       return;
 383    }
 384
 385    if (face == GL_FRONT || face == GL_BACK) {
 386       ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
 387    }
 388    else {
 389       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
 390    }
 391 }
 392
 393
 394 static void
 395 stencil_op_separate(struct gl_context *ctx, GLenum face, GLenum sfail,
 396                     GLenum zfail, GLenum zpass)
 397 {
 398    GLboolean set = GL_FALSE;
 399
 400    if (face != GL_BACK) {
 401       /* set front */
 402       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 403           ctx->Stencil.ZPassFunc[0] != zpass ||
 404           ctx->Stencil.FailFunc[0] != sfail){
 405          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 406          ctx->Stencil.ZFailFunc[0] = zfail;
 407          ctx->Stencil.ZPassFunc[0] = zpass;
 408          ctx->Stencil.FailFunc[0] = sfail;
 409          set = GL_TRUE;
 410       }
 411    }
 412
 413    if (face != GL_FRONT) {
 414       /* set back */
 415       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 416           ctx->Stencil.ZPassFunc[1] != zpass ||
 417           ctx->Stencil.FailFunc[1] != sfail) {
 418          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 419          ctx->Stencil.ZFailFunc[1] = zfail;
 420          ctx->Stencil.ZPassFunc[1] = zpass;
 421          ctx->Stencil.FailFunc[1] = sfail;
 422          set = GL_TRUE;
 423       }
 424    }
 425
 426    if (set && ctx->Driver.StencilOpSeparate) {
 427       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 428    }
 429 }
 430
 431
 432 void GLAPIENTRY
 433 _mesa_StencilOpSeparate_no_error(GLenum face, GLenum sfail, GLenum zfail,
 434                                  GLenum zpass)
 435 {
 436    GET_CURRENT_CONTEXT(ctx);
 437    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 438 }
 439
 440
 441 void GLAPIENTRY
 442 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 443 {
 444    GET_CURRENT_CONTEXT(ctx);
 445
 446    if (MESA_VERBOSE & VERBOSE_API)
 447       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 448
 449    if (!validate_stencil_op(ctx, sfail)) {
 450       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 451       return;
 452    }
 453
 454    if (!validate_stencil_op(ctx, zfail)) {
 455       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 456       return;
 457    }
 458
 459    if (!validate_stencil_op(ctx, zpass)) {
 460       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 461       return;
 462    }
 463
 464    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 465       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 466       return;
 467    }
 468
 469    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 470 }
 471
 472
 473 static void
 474 stencil_func_separate(struct gl_context *ctx, GLenum face, GLenum func,
 475                       GLint ref, GLuint mask)
 476 {
 477    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 478
 479    if (face != GL_BACK) {
 480       /* set front */
 481       ctx->Stencil.Function[0] = func;
 482       ctx->Stencil.Ref[0] = ref;
 483       ctx->Stencil.ValueMask[0] = mask;
 484    }
 485
 486    if (face != GL_FRONT) {
 487       /* set back */
 488       ctx->Stencil.Function[1] = func;
 489       ctx->Stencil.Ref[1] = ref;
 490       ctx->Stencil.ValueMask[1] = mask;
 491    }
 492
 493    if (ctx->Driver.StencilFuncSeparate) {
 494       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 495    }
 496 }
 497
 498
 499 /* OpenGL 2.0 */
 500 void GLAPIENTRY
 501 _mesa_StencilFuncSeparate_no_error(GLenum face, GLenum func, GLint ref,
 502                                    GLuint mask)
 503 {
 504    GET_CURRENT_CONTEXT(ctx);
 505    stencil_func_separate(ctx, face, func, ref, mask);
 506 }
 507
 508
 509 void GLAPIENTRY
 510 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 511 {
 512    GET_CURRENT_CONTEXT(ctx);
 513
 514    if (MESA_VERBOSE & VERBOSE_API)
 515       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 516
 517    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 518       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 519       return;
 520    }
 521
 522    if (!validate_stencil_func(ctx, func)) {
 523       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 524       return;
 525    }
 526
 527    stencil_func_separate(ctx, face, func, ref, mask);
 528 }
 529
 530
 531 static void
 532 stencil_mask_separate(struct gl_context *ctx, GLenum face, GLuint mask)
 533 {
 534    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 535
 536    if (face != GL_BACK) {
 537       ctx->Stencil.WriteMask[0] = mask;
 538    }
 539
 540    if (face != GL_FRONT) {
 541       ctx->Stencil.WriteMask[1] = mask;
 542    }
 543
 544    if (ctx->Driver.StencilMaskSeparate) {
 545       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 546    }
 547 }
 548
 549
 550 /* OpenGL 2.0 */
 551 void GLAPIENTRY
 552 _mesa_StencilMaskSeparate_no_error(GLenum face, GLuint mask)
 553 {
 554    GET_CURRENT_CONTEXT(ctx);
 555    stencil_mask_separate(ctx, face, mask);
 556 }
 557
 558
 559 void GLAPIENTRY
 560 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 561 {
 562    GET_CURRENT_CONTEXT(ctx);
 563
 564    if (MESA_VERBOSE & VERBOSE_API)
 565       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 566
 567    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 568       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 569       return;
 570    }
 571
 572    stencil_mask_separate(ctx, face, mask);
 573 }
 574
 575
 576 /**
 577  * Update derived stencil state.
 578  */
 579 void
 580 _mesa_update_stencil(struct gl_context *ctx)
 581 {
 582    const GLint face = ctx->Stencil._BackFace;
 583
 584    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 585                             ctx->DrawBuffer->Visual.stencilBits > 0);
 586
 587     ctx->Stencil._TestTwoSide =
 588        ctx->Stencil._Enabled &&
 589        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 590         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 591         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 592         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 593         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 594         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 595         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 596
 597    ctx->Stencil._WriteEnabled =
 598       ctx->Stencil._Enabled &&
 599       (ctx->Stencil.WriteMask[0] != 0 ||
 600        (ctx->Stencil._TestTwoSide && ctx->Stencil.WriteMask[face] != 0));
 601 }
 602
 603
 604 /**
 605  * Initialize the context stipple state.
 606  *
 607  * \param ctx GL context.
 608  *
 609  * Initializes __struct gl_contextRec::Stencil attribute group.
 610  */
 611 void
 612 _mesa_init_stencil(struct gl_context *ctx)
 613 {
 614    ctx->Stencil.Enabled = GL_FALSE;
 615    ctx->Stencil.TestTwoSide = GL_FALSE;
 616    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 2 = GL_BACK */
 617    ctx->Stencil.Function[0] = GL_ALWAYS;
 618    ctx->Stencil.Function[1] = GL_ALWAYS;
 619    ctx->Stencil.Function[2] = GL_ALWAYS;
 620    ctx->Stencil.FailFunc[0] = GL_KEEP;
 621    ctx->Stencil.FailFunc[1] = GL_KEEP;
 622    ctx->Stencil.FailFunc[2] = GL_KEEP;
 623    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
 624    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
 625    ctx->Stencil.ZPassFunc[2] = GL_KEEP;
 626    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
 627    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
 628    ctx->Stencil.ZFailFunc[2] = GL_KEEP;
 629    ctx->Stencil.Ref[0] = 0;
 630    ctx->Stencil.Ref[1] = 0;
 631    ctx->Stencil.Ref[2] = 0;
 632
 633    /* 4.1.4 Stencil Test section of the GL-ES 3.0 specification says:
 634     *
 635     *     "In the initial state, [...] the front and back stencil mask are both
 636     *     set to the value 2^s − 1, where s is greater than or equal to the
 637     *     number of bits in the deepest stencil buffer* supported by the GL
 638     *     implementation."
 639     *
 640     * Since the maximum supported precision for stencil buffers is 8 bits,
 641     * mask values should be initialized to 2^8 - 1 = 0xFF.
 642     */
 643    ctx->Stencil.ValueMask[0] = 0xFF;
 644    ctx->Stencil.ValueMask[1] = 0xFF;
 645    ctx->Stencil.ValueMask[2] = 0xFF;
 646    ctx->Stencil.WriteMask[0] = 0xFF;
 647    ctx->Stencil.WriteMask[1] = 0xFF;
 648    ctx->Stencil.WriteMask[2] = 0xFF;
 649
 650    ctx->Stencil.Clear = 0;
 651    ctx->Stencil._BackFace = 1;
 652 }