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_no_error(GLenum func, GLint ref, GLuint mask)
 234 {
 235    GET_CURRENT_CONTEXT(ctx);
 236    stencil_func(ctx, func, ref, mask);
 237 }
 238
 239
 240 void GLAPIENTRY
 241 _mesa_StencilFunc(GLenum func, GLint ref, GLuint mask)
 242 {
 243    GET_CURRENT_CONTEXT(ctx);
 244
 245    if (MESA_VERBOSE & VERBOSE_API)
 246       _mesa_debug(ctx, "glStencilFunc()\n");
 247
 248    if (!validate_stencil_func(ctx, func)) {
 249       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 250       return;
 251    }
 252
 253    stencil_func(ctx, func, ref, mask);
 254 }
 255
 256
 257 /**
 258  * Set the stencil writing mask.
 259  *
 260  * \param mask bit-mask to enable/disable writing of individual bits in the
 261  * stencil planes.
 262  *
 263  * \sa glStencilMask().
 264  *
 265  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 266  * notifies the driver via the dd_function_table::StencilMask callback.
 267  */
 268 void GLAPIENTRY
 269 _mesa_StencilMask( GLuint mask )
 270 {
 271    GET_CURRENT_CONTEXT(ctx);
 272    const GLint face = ctx->Stencil.ActiveFace;
 273
 274    if (MESA_VERBOSE & VERBOSE_API)
 275       _mesa_debug(ctx, "glStencilMask()\n");
 276
 277    if (face != 0) {
 278       /* Only modify the EXT_stencil_two_side back-face state.
 279        */
 280       if (ctx->Stencil.WriteMask[face] == mask)
 281          return;
 282       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 283       ctx->Stencil.WriteMask[face] = mask;
 284
 285       /* Only propagate the change to the driver if EXT_stencil_two_side
 286        * is enabled.
 287        */
 288       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 289          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 290       }
 291    }
 292    else {
 293       /* set both front and back state */
 294       if (ctx->Stencil.WriteMask[0] == mask &&
 295           ctx->Stencil.WriteMask[1] == mask)
 296          return;
 297       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 298       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 299       if (ctx->Driver.StencilMaskSeparate) {
 300          ctx->Driver.StencilMaskSeparate(ctx,
 301                                          ((ctx->Stencil.TestTwoSide)
 302                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 303                                           mask);
 304       }
 305    }
 306 }
 307
 308
 309 /**
 310  * Set the stencil test actions.
 311  *
 312  * \param fail action to take when stencil test fails.
 313  * \param zfail action to take when stencil test passes, but depth test fails.
 314  * \param zpass action to take when stencil test passes and the depth test
 315  * passes (or depth testing is not enabled).
 316  *
 317  * \sa glStencilOp().
 318  *
 319  * Verifies the parameters and updates the respective fields in
 320  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies
 321  * the driver via the dd_function_table::StencilOp callback.
 322  */
 323 void GLAPIENTRY
 324 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 325 {
 326    GET_CURRENT_CONTEXT(ctx);
 327    const GLint face = ctx->Stencil.ActiveFace;
 328
 329    if (MESA_VERBOSE & VERBOSE_API)
 330       _mesa_debug(ctx, "glStencilOp()\n");
 331
 332    if (!validate_stencil_op(ctx, fail)) {
 333       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 334       return;
 335    }
 336    if (!validate_stencil_op(ctx, zfail)) {
 337       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 338       return;
 339    }
 340    if (!validate_stencil_op(ctx, zpass)) {
 341       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 342       return;
 343    }
 344
 345    if (face != 0) {
 346       /* only set active face state */
 347       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 348           ctx->Stencil.ZPassFunc[face] == zpass &&
 349           ctx->Stencil.FailFunc[face] == fail)
 350          return;
 351       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 352       ctx->Stencil.ZFailFunc[face] = zfail;
 353       ctx->Stencil.ZPassFunc[face] = zpass;
 354       ctx->Stencil.FailFunc[face] = fail;
 355
 356       /* Only propagate the change to the driver if EXT_stencil_two_side
 357        * is enabled.
 358        */
 359       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 360          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 361       }
 362    }
 363    else {
 364       /* set both front and back state */
 365       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 366           ctx->Stencil.ZFailFunc[1] == zfail &&
 367           ctx->Stencil.ZPassFunc[0] == zpass &&
 368           ctx->Stencil.ZPassFunc[1] == zpass &&
 369           ctx->Stencil.FailFunc[0] == fail &&
 370           ctx->Stencil.FailFunc[1] == fail)
 371          return;
 372       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 373       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 374       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 375       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 376       if (ctx->Driver.StencilOpSeparate) {
 377          ctx->Driver.StencilOpSeparate(ctx,
 378                                        ((ctx->Stencil.TestTwoSide)
 379                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 380                                        fail, zfail, zpass);
 381       }
 382    }
 383 }
 384
 385
 386
 387 /* GL_EXT_stencil_two_side */
 388 void GLAPIENTRY
 389 _mesa_ActiveStencilFaceEXT(GLenum face)
 390 {
 391    GET_CURRENT_CONTEXT(ctx);
 392
 393    if (MESA_VERBOSE & VERBOSE_API)
 394       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 395
 396    if (!ctx->Extensions.EXT_stencil_two_side) {
 397       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 398       return;
 399    }
 400
 401    if (face == GL_FRONT || face == GL_BACK) {
 402       ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
 403    }
 404    else {
 405       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
 406    }
 407 }
 408
 409
 410 static void
 411 stencil_op_separate(struct gl_context *ctx, GLenum face, GLenum sfail,
 412                     GLenum zfail, GLenum zpass)
 413 {
 414    GLboolean set = GL_FALSE;
 415
 416    if (face != GL_BACK) {
 417       /* set front */
 418       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 419           ctx->Stencil.ZPassFunc[0] != zpass ||
 420           ctx->Stencil.FailFunc[0] != sfail){
 421          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 422          ctx->Stencil.ZFailFunc[0] = zfail;
 423          ctx->Stencil.ZPassFunc[0] = zpass;
 424          ctx->Stencil.FailFunc[0] = sfail;
 425          set = GL_TRUE;
 426       }
 427    }
 428
 429    if (face != GL_FRONT) {
 430       /* set back */
 431       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 432           ctx->Stencil.ZPassFunc[1] != zpass ||
 433           ctx->Stencil.FailFunc[1] != sfail) {
 434          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 435          ctx->Stencil.ZFailFunc[1] = zfail;
 436          ctx->Stencil.ZPassFunc[1] = zpass;
 437          ctx->Stencil.FailFunc[1] = sfail;
 438          set = GL_TRUE;
 439       }
 440    }
 441
 442    if (set && ctx->Driver.StencilOpSeparate) {
 443       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 444    }
 445 }
 446
 447
 448 void GLAPIENTRY
 449 _mesa_StencilOpSeparate_no_error(GLenum face, GLenum sfail, GLenum zfail,
 450                                  GLenum zpass)
 451 {
 452    GET_CURRENT_CONTEXT(ctx);
 453    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 454 }
 455
 456
 457 void GLAPIENTRY
 458 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 459 {
 460    GET_CURRENT_CONTEXT(ctx);
 461
 462    if (MESA_VERBOSE & VERBOSE_API)
 463       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 464
 465    if (!validate_stencil_op(ctx, sfail)) {
 466       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 467       return;
 468    }
 469
 470    if (!validate_stencil_op(ctx, zfail)) {
 471       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 472       return;
 473    }
 474
 475    if (!validate_stencil_op(ctx, zpass)) {
 476       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 477       return;
 478    }
 479
 480    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 481       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 482       return;
 483    }
 484
 485    stencil_op_separate(ctx, face, sfail, zfail, zpass);
 486 }
 487
 488
 489 static void
 490 stencil_func_separate(struct gl_context *ctx, GLenum face, GLenum func,
 491                       GLint ref, GLuint mask)
 492 {
 493    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 494
 495    if (face != GL_BACK) {
 496       /* set front */
 497       ctx->Stencil.Function[0] = func;
 498       ctx->Stencil.Ref[0] = ref;
 499       ctx->Stencil.ValueMask[0] = mask;
 500    }
 501
 502    if (face != GL_FRONT) {
 503       /* set back */
 504       ctx->Stencil.Function[1] = func;
 505       ctx->Stencil.Ref[1] = ref;
 506       ctx->Stencil.ValueMask[1] = mask;
 507    }
 508
 509    if (ctx->Driver.StencilFuncSeparate) {
 510       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 511    }
 512 }
 513
 514
 515 /* OpenGL 2.0 */
 516 void GLAPIENTRY
 517 _mesa_StencilFuncSeparate_no_error(GLenum face, GLenum func, GLint ref,
 518                                    GLuint mask)
 519 {
 520    GET_CURRENT_CONTEXT(ctx);
 521    stencil_func_separate(ctx, face, func, ref, mask);
 522 }
 523
 524
 525 void GLAPIENTRY
 526 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 527 {
 528    GET_CURRENT_CONTEXT(ctx);
 529
 530    if (MESA_VERBOSE & VERBOSE_API)
 531       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 532
 533    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 534       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 535       return;
 536    }
 537
 538    if (!validate_stencil_func(ctx, func)) {
 539       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 540       return;
 541    }
 542
 543    stencil_func_separate(ctx, face, func, ref, mask);
 544 }
 545
 546
 547 static void
 548 stencil_mask_separate(struct gl_context *ctx, GLenum face, GLuint mask)
 549 {
 550    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 551
 552    if (face != GL_BACK) {
 553       ctx->Stencil.WriteMask[0] = mask;
 554    }
 555
 556    if (face != GL_FRONT) {
 557       ctx->Stencil.WriteMask[1] = mask;
 558    }
 559
 560    if (ctx->Driver.StencilMaskSeparate) {
 561       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 562    }
 563 }
 564
 565
 566 /* OpenGL 2.0 */
 567 void GLAPIENTRY
 568 _mesa_StencilMaskSeparate_no_error(GLenum face, GLuint mask)
 569 {
 570    GET_CURRENT_CONTEXT(ctx);
 571    stencil_mask_separate(ctx, face, mask);
 572 }
 573
 574
 575 void GLAPIENTRY
 576 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 577 {
 578    GET_CURRENT_CONTEXT(ctx);
 579
 580    if (MESA_VERBOSE & VERBOSE_API)
 581       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 582
 583    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 584       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 585       return;
 586    }
 587
 588    stencil_mask_separate(ctx, face, mask);
 589 }
 590
 591
 592 /**
 593  * Update derived stencil state.
 594  */
 595 void
 596 _mesa_update_stencil(struct gl_context *ctx)
 597 {
 598    const GLint face = ctx->Stencil._BackFace;
 599
 600    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 601                             ctx->DrawBuffer->Visual.stencilBits > 0);
 602
 603     ctx->Stencil._TestTwoSide =
 604        ctx->Stencil._Enabled &&
 605        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 606         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 607         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 608         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 609         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 610         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 611         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 612
 613    ctx->Stencil._WriteEnabled =
 614       ctx->Stencil._Enabled &&
 615       (ctx->Stencil.WriteMask[0] != 0 ||
 616        (ctx->Stencil._TestTwoSide && ctx->Stencil.WriteMask[face] != 0));
 617 }
 618
 619
 620 /**
 621  * Initialize the context stipple state.
 622  *
 623  * \param ctx GL context.
 624  *
 625  * Initializes __struct gl_contextRec::Stencil attribute group.
 626  */
 627 void
 628 _mesa_init_stencil(struct gl_context *ctx)
 629 {
 630    ctx->Stencil.Enabled = GL_FALSE;
 631    ctx->Stencil.TestTwoSide = GL_FALSE;
 632    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 2 = GL_BACK */
 633    ctx->Stencil.Function[0] = GL_ALWAYS;
 634    ctx->Stencil.Function[1] = GL_ALWAYS;
 635    ctx->Stencil.Function[2] = GL_ALWAYS;
 636    ctx->Stencil.FailFunc[0] = GL_KEEP;
 637    ctx->Stencil.FailFunc[1] = GL_KEEP;
 638    ctx->Stencil.FailFunc[2] = GL_KEEP;
 639    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
 640    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
 641    ctx->Stencil.ZPassFunc[2] = GL_KEEP;
 642    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
 643    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
 644    ctx->Stencil.ZFailFunc[2] = GL_KEEP;
 645    ctx->Stencil.Ref[0] = 0;
 646    ctx->Stencil.Ref[1] = 0;
 647    ctx->Stencil.Ref[2] = 0;
 648
 649    /* 4.1.4 Stencil Test section of the GL-ES 3.0 specification says:
 650     *
 651     *     "In the initial state, [...] the front and back stencil mask are both
 652     *     set to the value 2^s − 1, where s is greater than or equal to the
 653     *     number of bits in the deepest stencil buffer* supported by the GL
 654     *     implementation."
 655     *
 656     * Since the maximum supported precision for stencil buffers is 8 bits,
 657     * mask values should be initialized to 2^8 - 1 = 0xFF.
 658     */
 659    ctx->Stencil.ValueMask[0] = 0xFF;
 660    ctx->Stencil.ValueMask[1] = 0xFF;
 661    ctx->Stencil.ValueMask[2] = 0xFF;
 662    ctx->Stencil.WriteMask[0] = 0xFF;
 663    ctx->Stencil.WriteMask[1] = 0xFF;
 664    ctx->Stencil.WriteMask[2] = 0xFF;
 665
 666    ctx->Stencil.Clear = 0;
 667    ctx->Stencil._BackFace = 1;
 668 }