src/mesa/main/stencil.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.1
   4  *
   5  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  21  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  22  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  23  * OTHER DEALINGS IN THE SOFTWARE.
  24  */
  25
  26
  27 /**
  28  * \file stencil.c
  29  * Stencil operations.
  30  *
  31  * Note: There's some conflict between GL_EXT_stencil_two_side and
  32  * OpenGL 2.0's two-sided stencil feature.
  33  *
  34  * With GL_EXT_stencil_two_side, calling glStencilOp/Func/Mask() only the
  35  * front OR back face state (as set by glActiveStencilFaceEXT) is set.
  36  *
  37  * But with OpenGL 2.0, calling glStencilOp/Func/Mask() sets BOTH the
  38  * front AND back state.
  39  *
  40  * Also, note that GL_ATI_separate_stencil is different as well:
  41  * glStencilFuncSeparateATI(GLenum frontfunc, GLenum backfunc, ...)  vs.
  42  * glStencilFuncSeparate(GLenum face, GLenum func, ...).
  43  *
  44  * This problem is solved by keeping three sets of stencil state:
  45  *  state[0] = GL_FRONT state.
  46  *  state[1] = OpenGL 2.0 / GL_ATI_separate_stencil GL_BACK state.
  47  *  state[2] = GL_EXT_stencil_two_side GL_BACK state.
  48  */
  49
  50
  51 #include "glheader.h"
  52 #include "imports.h"
  53 #include "context.h"
  54 #include "macros.h"
  55 #include "stencil.h"
  56 #include "mtypes.h"
  57
  58
  59 static GLboolean
  60 validate_stencil_op(struct gl_context *ctx, GLenum op)
  61 {
  62    switch (op) {
  63    case GL_KEEP:
  64    case GL_ZERO:
  65    case GL_REPLACE:
  66    case GL_INCR:
  67    case GL_DECR:
  68    case GL_INVERT:
  69    case GL_INCR_WRAP:
  70    case GL_DECR_WRAP:
  71       return GL_TRUE;
  72    default:
  73       return GL_FALSE;
  74    }
  75 }
  76
  77
  78 static GLboolean
  79 validate_stencil_func(struct gl_context *ctx, GLenum func)
  80 {
  81    switch (func) {
  82    case GL_NEVER:
  83    case GL_LESS:
  84    case GL_LEQUAL:
  85    case GL_GREATER:
  86    case GL_GEQUAL:
  87    case GL_EQUAL:
  88    case GL_NOTEQUAL:
  89    case GL_ALWAYS:
  90       return GL_TRUE;
  91    default:
  92       return GL_FALSE;
  93    }
  94 }
  95
  96
  97 /**
  98  * Set the clear value for the stencil buffer.
  99  *
 100  * \param s clear value.
 101  *
 102  * \sa glClearStencil().
 103  *
 104  * Updates gl_stencil_attrib::Clear. On change
 105  * flushes the vertices and notifies the driver via
 106  * the dd_function_table::ClearStencil callback.
 107  */
 108 void GLAPIENTRY
 109 _mesa_ClearStencil( GLint s )
 110 {
 111    GET_CURRENT_CONTEXT(ctx);
 112
 113    ctx->Stencil.Clear = (GLuint) s;
 114 }
 115
 116
 117 /**
 118  * Set the function and reference value for stencil testing.
 119  *
 120  * \param frontfunc front test function.
 121  * \param backfunc back test function.
 122  * \param ref front and back reference value.
 123  * \param mask front and back bitmask.
 124  *
 125  * \sa glStencilFunc().
 126  *
 127  * Verifies the parameters and updates the respective values in
 128  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 129  * driver via the dd_function_table::StencilFunc callback.
 130  */
 131 void GLAPIENTRY
 132 _mesa_StencilFuncSeparateATI( GLenum frontfunc, GLenum backfunc, GLint ref, GLuint mask )
 133 {
 134    GET_CURRENT_CONTEXT(ctx);
 135    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 136
 137    if (MESA_VERBOSE & VERBOSE_API)
 138       _mesa_debug(ctx, "glStencilFuncSeparateATI()\n");
 139
 140    if (!validate_stencil_func(ctx, frontfunc)) {
 141       _mesa_error(ctx, GL_INVALID_ENUM,
 142                   "glStencilFuncSeparateATI(frontfunc)");
 143       return;
 144    }
 145    if (!validate_stencil_func(ctx, backfunc)) {
 146       _mesa_error(ctx, GL_INVALID_ENUM,
 147                   "glStencilFuncSeparateATI(backfunc)");
 148       return;
 149    }
 150
 151    ref = CLAMP( ref, 0, stencilMax );
 152
 153    /* set both front and back state */
 154    if (ctx->Stencil.Function[0] == frontfunc &&
 155        ctx->Stencil.Function[1] == backfunc &&
 156        ctx->Stencil.ValueMask[0] == mask &&
 157        ctx->Stencil.ValueMask[1] == mask &&
 158        ctx->Stencil.Ref[0] == ref &&
 159        ctx->Stencil.Ref[1] == ref)
 160       return;
 161    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 162    ctx->Stencil.Function[0]  = frontfunc;
 163    ctx->Stencil.Function[1]  = backfunc;
 164    ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 165    ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 166    if (ctx->Driver.StencilFuncSeparate) {
 167       ctx->Driver.StencilFuncSeparate(ctx, GL_FRONT,
 168                                       frontfunc, ref, mask);
 169       ctx->Driver.StencilFuncSeparate(ctx, GL_BACK,
 170                                       backfunc, ref, mask);
 171    }
 172 }
 173
 174
 175 /**
 176  * Set the function and reference value for stencil testing.
 177  *
 178  * \param func test function.
 179  * \param ref reference value.
 180  * \param mask bitmask.
 181  *
 182  * \sa glStencilFunc().
 183  *
 184  * Verifies the parameters and updates the respective values in
 185  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 186  * driver via the dd_function_table::StencilFunc callback.
 187  */
 188 void GLAPIENTRY
 189 _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
 190 {
 191    GET_CURRENT_CONTEXT(ctx);
 192    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 193    const GLint face = ctx->Stencil.ActiveFace;
 194
 195    if (MESA_VERBOSE & VERBOSE_API)
 196       _mesa_debug(ctx, "glStencilFunc()\n");
 197
 198    if (!validate_stencil_func(ctx, func)) {
 199       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 200       return;
 201    }
 202
 203    ref = CLAMP( ref, 0, stencilMax );
 204
 205    if (face != 0) {
 206       if (ctx->Stencil.Function[face] == func &&
 207           ctx->Stencil.ValueMask[face] == mask &&
 208           ctx->Stencil.Ref[face] == ref)
 209          return;
 210       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 211       ctx->Stencil.Function[face] = func;
 212       ctx->Stencil.Ref[face] = ref;
 213       ctx->Stencil.ValueMask[face] = mask;
 214
 215       /* Only propagate the change to the driver if EXT_stencil_two_side
 216        * is enabled.
 217        */
 218       if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
 219          ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
 220       }
 221    }
 222    else {
 223       /* set both front and back state */
 224       if (ctx->Stencil.Function[0] == func &&
 225           ctx->Stencil.Function[1] == func &&
 226           ctx->Stencil.ValueMask[0] == mask &&
 227           ctx->Stencil.ValueMask[1] == mask &&
 228           ctx->Stencil.Ref[0] == ref &&
 229           ctx->Stencil.Ref[1] == ref)
 230          return;
 231       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 232       ctx->Stencil.Function[0]  = ctx->Stencil.Function[1]  = func;
 233       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 234       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 235       if (ctx->Driver.StencilFuncSeparate) {
 236          ctx->Driver.StencilFuncSeparate(ctx,
 237                                          ((ctx->Stencil.TestTwoSide)
 238                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 239                                          func, ref, mask);
 240       }
 241    }
 242 }
 243
 244
 245 /**
 246  * Set the stencil writing mask.
 247  *
 248  * \param mask bit-mask to enable/disable writing of individual bits in the
 249  * stencil planes.
 250  *
 251  * \sa glStencilMask().
 252  *
 253  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 254  * notifies the driver via the dd_function_table::StencilMask callback.
 255  */
 256 void GLAPIENTRY
 257 _mesa_StencilMask( GLuint mask )
 258 {
 259    GET_CURRENT_CONTEXT(ctx);
 260    const GLint face = ctx->Stencil.ActiveFace;
 261
 262    if (MESA_VERBOSE & VERBOSE_API)
 263       _mesa_debug(ctx, "glStencilMask()\n");
 264
 265    if (face != 0) {
 266       /* Only modify the EXT_stencil_two_side back-face state.
 267        */
 268       if (ctx->Stencil.WriteMask[face] == mask)
 269          return;
 270       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 271       ctx->Stencil.WriteMask[face] = mask;
 272
 273       /* Only propagate the change to the driver if EXT_stencil_two_side
 274        * is enabled.
 275        */
 276       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 277          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 278       }
 279    }
 280    else {
 281       /* set both front and back state */
 282       if (ctx->Stencil.WriteMask[0] == mask &&
 283           ctx->Stencil.WriteMask[1] == mask)
 284          return;
 285       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 286       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 287       if (ctx->Driver.StencilMaskSeparate) {
 288          ctx->Driver.StencilMaskSeparate(ctx,
 289                                          ((ctx->Stencil.TestTwoSide)
 290                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 291                                           mask);
 292       }
 293    }
 294 }
 295
 296
 297 /**
 298  * Set the stencil test actions.
 299  *
 300  * \param fail action to take when stencil test fails.
 301  * \param zfail action to take when stencil test passes, but depth test fails.
 302  * \param zpass action to take when stencil test passes and the depth test
 303  * passes (or depth testing is not enabled).
 304  *
 305  * \sa glStencilOp().
 306  *
 307  * Verifies the parameters and updates the respective fields in
 308  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 309  * driver via the dd_function_table::StencilOp callback.
 310  */
 311 void GLAPIENTRY
 312 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 313 {
 314    GET_CURRENT_CONTEXT(ctx);
 315    const GLint face = ctx->Stencil.ActiveFace;
 316
 317    if (MESA_VERBOSE & VERBOSE_API)
 318       _mesa_debug(ctx, "glStencilOp()\n");
 319
 320    if (!validate_stencil_op(ctx, fail)) {
 321       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 322       return;
 323    }
 324    if (!validate_stencil_op(ctx, zfail)) {
 325       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 326       return;
 327    }
 328    if (!validate_stencil_op(ctx, zpass)) {
 329       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 330       return;
 331    }
 332
 333    if (face != 0) {
 334       /* only set active face state */
 335       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 336           ctx->Stencil.ZPassFunc[face] == zpass &&
 337           ctx->Stencil.FailFunc[face] == fail)
 338          return;
 339       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 340       ctx->Stencil.ZFailFunc[face] = zfail;
 341       ctx->Stencil.ZPassFunc[face] = zpass;
 342       ctx->Stencil.FailFunc[face] = fail;
 343
 344       /* Only propagate the change to the driver if EXT_stencil_two_side
 345        * is enabled.
 346        */
 347       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 348          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 349       }
 350    }
 351    else {
 352       /* set both front and back state */
 353       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 354           ctx->Stencil.ZFailFunc[1] == zfail &&
 355           ctx->Stencil.ZPassFunc[0] == zpass &&
 356           ctx->Stencil.ZPassFunc[1] == zpass &&
 357           ctx->Stencil.FailFunc[0] == fail &&
 358           ctx->Stencil.FailFunc[1] == fail)
 359          return;
 360       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 361       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 362       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 363       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 364       if (ctx->Driver.StencilOpSeparate) {
 365          ctx->Driver.StencilOpSeparate(ctx,
 366                                        ((ctx->Stencil.TestTwoSide)
 367                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 368                                        fail, zfail, zpass);
 369       }
 370    }
 371 }
 372
 373
 374
 375 /* GL_EXT_stencil_two_side */
 376 void GLAPIENTRY
 377 _mesa_ActiveStencilFaceEXT(GLenum face)
 378 {
 379    GET_CURRENT_CONTEXT(ctx);
 380
 381    if (MESA_VERBOSE & VERBOSE_API)
 382       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 383
 384    if (!ctx->Extensions.EXT_stencil_two_side) {
 385       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 386       return;
 387    }
 388
 389    if (face == GL_FRONT || face == GL_BACK) {
 390       ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
 391    }
 392    else {
 393       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
 394    }
 395 }
 396
 397
 398
 399 /**
 400  * OpenGL 2.0 function.
 401  * \todo Make StencilOp() call this function.  And eventually remove the
 402  * ctx->Driver.StencilOp function and use ctx->Driver.StencilOpSeparate
 403  * instead.
 404  */
 405 void GLAPIENTRY
 406 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 407 {
 408    GLboolean set = GL_FALSE;
 409    GET_CURRENT_CONTEXT(ctx);
 410
 411    if (MESA_VERBOSE & VERBOSE_API)
 412       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 413
 414    if (!validate_stencil_op(ctx, sfail)) {
 415       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 416       return;
 417    }
 418    if (!validate_stencil_op(ctx, zfail)) {
 419       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 420       return;
 421    }
 422    if (!validate_stencil_op(ctx, zpass)) {
 423       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 424       return;
 425    }
 426    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 427       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 428       return;
 429    }
 430
 431    if (face != GL_BACK) {
 432       /* set front */
 433       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 434           ctx->Stencil.ZPassFunc[0] != zpass ||
 435           ctx->Stencil.FailFunc[0] != sfail){
 436          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 437          ctx->Stencil.ZFailFunc[0] = zfail;
 438          ctx->Stencil.ZPassFunc[0] = zpass;
 439          ctx->Stencil.FailFunc[0] = sfail;
 440          set = GL_TRUE;
 441       }
 442    }
 443    if (face != GL_FRONT) {
 444       /* set back */
 445       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 446           ctx->Stencil.ZPassFunc[1] != zpass ||
 447           ctx->Stencil.FailFunc[1] != sfail) {
 448          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 449          ctx->Stencil.ZFailFunc[1] = zfail;
 450          ctx->Stencil.ZPassFunc[1] = zpass;
 451          ctx->Stencil.FailFunc[1] = sfail;
 452          set = GL_TRUE;
 453       }
 454    }
 455    if (set && ctx->Driver.StencilOpSeparate) {
 456       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 457    }
 458 }
 459
 460
 461 /* OpenGL 2.0 */
 462 void GLAPIENTRY
 463 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 464 {
 465    GET_CURRENT_CONTEXT(ctx);
 466    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 467
 468    if (MESA_VERBOSE & VERBOSE_API)
 469       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 470
 471    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 472       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 473       return;
 474    }
 475    if (!validate_stencil_func(ctx, func)) {
 476       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 477       return;
 478    }
 479
 480    ref = CLAMP(ref, 0, stencilMax);
 481
 482    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 483
 484    if (face != GL_BACK) {
 485       /* set front */
 486       ctx->Stencil.Function[0] = func;
 487       ctx->Stencil.Ref[0] = ref;
 488       ctx->Stencil.ValueMask[0] = mask;
 489    }
 490    if (face != GL_FRONT) {
 491       /* set back */
 492       ctx->Stencil.Function[1] = func;
 493       ctx->Stencil.Ref[1] = ref;
 494       ctx->Stencil.ValueMask[1] = mask;
 495    }
 496    if (ctx->Driver.StencilFuncSeparate) {
 497       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 498    }
 499 }
 500
 501
 502 /* OpenGL 2.0 */
 503 void GLAPIENTRY
 504 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 505 {
 506    GET_CURRENT_CONTEXT(ctx);
 507
 508    if (MESA_VERBOSE & VERBOSE_API)
 509       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 510
 511    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 512       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 513       return;
 514    }
 515
 516    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 517
 518    if (face != GL_BACK) {
 519       ctx->Stencil.WriteMask[0] = mask;
 520    }
 521    if (face != GL_FRONT) {
 522       ctx->Stencil.WriteMask[1] = mask;
 523    }
 524    if (ctx->Driver.StencilMaskSeparate) {
 525       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 526    }
 527 }
 528
 529
 530 /**
 531  * Update derived stencil state.
 532  */
 533 void
 534 _mesa_update_stencil(struct gl_context *ctx)
 535 {
 536    const GLint face = ctx->Stencil._BackFace;
 537
 538    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 539                             ctx->DrawBuffer->Visual.stencilBits > 0);
 540
 541     ctx->Stencil._TestTwoSide =
 542        ctx->Stencil._Enabled &&
 543        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 544         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 545         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 546         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 547         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 548         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 549         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 550
 551    ctx->Stencil._WriteEnabled =
 552       ctx->Stencil._Enabled &&
 553       (ctx->Stencil.WriteMask[0] != 0 ||
 554        (ctx->Stencil._TestTwoSide && ctx->Stencil.WriteMask[face] != 0));
 555 }
 556
 557
 558 /**
 559  * Initialize the context stipple state.
 560  *
 561  * \param ctx GL context.
 562  *
 563  * Initializes __struct gl_contextRec::Stencil attribute group.
 564  */
 565 void
 566 _mesa_init_stencil(struct gl_context *ctx)
 567 {
 568    ctx->Stencil.Enabled = GL_FALSE;
 569    ctx->Stencil.TestTwoSide = GL_FALSE;
 570    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 2 = GL_BACK */
 571    ctx->Stencil.Function[0] = GL_ALWAYS;
 572    ctx->Stencil.Function[1] = GL_ALWAYS;
 573    ctx->Stencil.Function[2] = GL_ALWAYS;
 574    ctx->Stencil.FailFunc[0] = GL_KEEP;
 575    ctx->Stencil.FailFunc[1] = GL_KEEP;
 576    ctx->Stencil.FailFunc[2] = GL_KEEP;
 577    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
 578    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
 579    ctx->Stencil.ZPassFunc[2] = GL_KEEP;
 580    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
 581    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
 582    ctx->Stencil.ZFailFunc[2] = GL_KEEP;
 583    ctx->Stencil.Ref[0] = 0;
 584    ctx->Stencil.Ref[1] = 0;
 585    ctx->Stencil.Ref[2] = 0;
 586    ctx->Stencil.ValueMask[0] = ~0U;
 587    ctx->Stencil.ValueMask[1] = ~0U;
 588    ctx->Stencil.ValueMask[2] = ~0U;
 589    ctx->Stencil.WriteMask[0] = ~0U;
 590    ctx->Stencil.WriteMask[1] = ~0U;
 591    ctx->Stencil.WriteMask[2] = ~0U;
 592    ctx->Stencil.Clear = 0;
 593    ctx->Stencil._BackFace = 1;
 594 }