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 BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR 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    ctx->Stencil.Clear = (GLuint) s;
 113 }
 114
 115
 116 /**
 117  * Set the function and reference value for stencil testing.
 118  *
 119  * \param frontfunc front test function.
 120  * \param backfunc back test function.
 121  * \param ref front and back reference value.
 122  * \param mask front and back bitmask.
 123  *
 124  * \sa glStencilFunc().
 125  *
 126  * Verifies the parameters and updates the respective values in
 127  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 128  * driver via the dd_function_table::StencilFunc callback.
 129  */
 130 void GLAPIENTRY
 131 _mesa_StencilFuncSeparateATI( GLenum frontfunc, GLenum backfunc, GLint ref, GLuint mask )
 132 {
 133    GET_CURRENT_CONTEXT(ctx);
 134    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 135
 136    if (MESA_VERBOSE & VERBOSE_API)
 137       _mesa_debug(ctx, "glStencilFuncSeparateATI()\n");
 138
 139    if (!validate_stencil_func(ctx, frontfunc)) {
 140       _mesa_error(ctx, GL_INVALID_ENUM,
 141                   "glStencilFuncSeparateATI(frontfunc)");
 142       return;
 143    }
 144    if (!validate_stencil_func(ctx, backfunc)) {
 145       _mesa_error(ctx, GL_INVALID_ENUM,
 146                   "glStencilFuncSeparateATI(backfunc)");
 147       return;
 148    }
 149
 150    ref = CLAMP( ref, 0, stencilMax );
 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 the
 185  * 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 stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 192    const GLint face = ctx->Stencil.ActiveFace;
 193
 194    if (MESA_VERBOSE & VERBOSE_API)
 195       _mesa_debug(ctx, "glStencilFunc()\n");
 196
 197    if (!validate_stencil_func(ctx, func)) {
 198       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 199       return;
 200    }
 201
 202    ref = CLAMP( ref, 0, stencilMax );
 203
 204    if (face != 0) {
 205       if (ctx->Stencil.Function[face] == func &&
 206           ctx->Stencil.ValueMask[face] == mask &&
 207           ctx->Stencil.Ref[face] == ref)
 208          return;
 209       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 210       ctx->Stencil.Function[face] = func;
 211       ctx->Stencil.Ref[face] = ref;
 212       ctx->Stencil.ValueMask[face] = mask;
 213
 214       /* Only propagate the change to the driver if EXT_stencil_two_side
 215        * is enabled.
 216        */
 217       if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
 218          ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
 219       }
 220    }
 221    else {
 222       /* set both front and back state */
 223       if (ctx->Stencil.Function[0] == func &&
 224           ctx->Stencil.Function[1] == func &&
 225           ctx->Stencil.ValueMask[0] == mask &&
 226           ctx->Stencil.ValueMask[1] == mask &&
 227           ctx->Stencil.Ref[0] == ref &&
 228           ctx->Stencil.Ref[1] == ref)
 229          return;
 230       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 231       ctx->Stencil.Function[0]  = ctx->Stencil.Function[1]  = func;
 232       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 233       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 234       if (ctx->Driver.StencilFuncSeparate) {
 235          ctx->Driver.StencilFuncSeparate(ctx,
 236                                          ((ctx->Stencil.TestTwoSide)
 237                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 238                                          func, ref, mask);
 239       }
 240    }
 241 }
 242
 243
 244 /**
 245  * Set the stencil writing mask.
 246  *
 247  * \param mask bit-mask to enable/disable writing of individual bits in the
 248  * stencil planes.
 249  *
 250  * \sa glStencilMask().
 251  *
 252  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 253  * notifies the driver via the dd_function_table::StencilMask callback.
 254  */
 255 void GLAPIENTRY
 256 _mesa_StencilMask( GLuint mask )
 257 {
 258    GET_CURRENT_CONTEXT(ctx);
 259    const GLint face = ctx->Stencil.ActiveFace;
 260
 261    if (MESA_VERBOSE & VERBOSE_API)
 262       _mesa_debug(ctx, "glStencilMask()\n");
 263
 264    if (face != 0) {
 265       /* Only modify the EXT_stencil_two_side back-face state.
 266        */
 267       if (ctx->Stencil.WriteMask[face] == mask)
 268          return;
 269       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 270       ctx->Stencil.WriteMask[face] = mask;
 271
 272       /* Only propagate the change to the driver if EXT_stencil_two_side
 273        * is enabled.
 274        */
 275       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 276          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 277       }
 278    }
 279    else {
 280       /* set both front and back state */
 281       if (ctx->Stencil.WriteMask[0] == mask &&
 282           ctx->Stencil.WriteMask[1] == mask)
 283          return;
 284       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 285       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 286       if (ctx->Driver.StencilMaskSeparate) {
 287          ctx->Driver.StencilMaskSeparate(ctx,
 288                                          ((ctx->Stencil.TestTwoSide)
 289                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 290                                           mask);
 291       }
 292    }
 293 }
 294
 295
 296 /**
 297  * Set the stencil test actions.
 298  *
 299  * \param fail action to take when stencil test fails.
 300  * \param zfail action to take when stencil test passes, but depth test fails.
 301  * \param zpass action to take when stencil test passes and the depth test
 302  * passes (or depth testing is not enabled).
 303  *
 304  * \sa glStencilOp().
 305  *
 306  * Verifies the parameters and updates the respective fields in
 307  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 308  * driver via the dd_function_table::StencilOp callback.
 309  */
 310 void GLAPIENTRY
 311 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 312 {
 313    GET_CURRENT_CONTEXT(ctx);
 314    const GLint face = ctx->Stencil.ActiveFace;
 315
 316    if (MESA_VERBOSE & VERBOSE_API)
 317       _mesa_debug(ctx, "glStencilOp()\n");
 318
 319    if (!validate_stencil_op(ctx, fail)) {
 320       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 321       return;
 322    }
 323    if (!validate_stencil_op(ctx, zfail)) {
 324       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 325       return;
 326    }
 327    if (!validate_stencil_op(ctx, zpass)) {
 328       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 329       return;
 330    }
 331
 332    if (face != 0) {
 333       /* only set active face state */
 334       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 335           ctx->Stencil.ZPassFunc[face] == zpass &&
 336           ctx->Stencil.FailFunc[face] == fail)
 337          return;
 338       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 339       ctx->Stencil.ZFailFunc[face] = zfail;
 340       ctx->Stencil.ZPassFunc[face] = zpass;
 341       ctx->Stencil.FailFunc[face] = fail;
 342
 343       /* Only propagate the change to the driver if EXT_stencil_two_side
 344        * is enabled.
 345        */
 346       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 347          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 348       }
 349    }
 350    else {
 351       /* set both front and back state */
 352       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 353           ctx->Stencil.ZFailFunc[1] == zfail &&
 354           ctx->Stencil.ZPassFunc[0] == zpass &&
 355           ctx->Stencil.ZPassFunc[1] == zpass &&
 356           ctx->Stencil.FailFunc[0] == fail &&
 357           ctx->Stencil.FailFunc[1] == fail)
 358          return;
 359       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 360       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 361       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 362       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 363       if (ctx->Driver.StencilOpSeparate) {
 364          ctx->Driver.StencilOpSeparate(ctx,
 365                                        ((ctx->Stencil.TestTwoSide)
 366                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 367                                        fail, zfail, zpass);
 368       }
 369    }
 370 }
 371
 372
 373
 374 /* GL_EXT_stencil_two_side */
 375 void GLAPIENTRY
 376 _mesa_ActiveStencilFaceEXT(GLenum face)
 377 {
 378    GET_CURRENT_CONTEXT(ctx);
 379
 380    if (MESA_VERBOSE & VERBOSE_API)
 381       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 382
 383    if (!ctx->Extensions.EXT_stencil_two_side) {
 384       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 385       return;
 386    }
 387
 388    if (face == GL_FRONT || face == GL_BACK) {
 389       ctx->Stencil.ActiveFace = (face == GL_FRONT) ? 0 : 2;
 390    }
 391    else {
 392       _mesa_error(ctx, GL_INVALID_ENUM, "glActiveStencilFaceEXT(face)");
 393    }
 394 }
 395
 396
 397
 398 /**
 399  * OpenGL 2.0 function.
 400  * \todo Make StencilOp() call this function.  And eventually remove the
 401  * ctx->Driver.StencilOp function and use ctx->Driver.StencilOpSeparate
 402  * instead.
 403  */
 404 void GLAPIENTRY
 405 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 406 {
 407    GLboolean set = GL_FALSE;
 408    GET_CURRENT_CONTEXT(ctx);
 409
 410    if (MESA_VERBOSE & VERBOSE_API)
 411       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 412
 413    if (!validate_stencil_op(ctx, sfail)) {
 414       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 415       return;
 416    }
 417    if (!validate_stencil_op(ctx, zfail)) {
 418       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 419       return;
 420    }
 421    if (!validate_stencil_op(ctx, zpass)) {
 422       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 423       return;
 424    }
 425    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 426       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 427       return;
 428    }
 429
 430    if (face != GL_BACK) {
 431       /* set front */
 432       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 433           ctx->Stencil.ZPassFunc[0] != zpass ||
 434           ctx->Stencil.FailFunc[0] != sfail){
 435          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 436          ctx->Stencil.ZFailFunc[0] = zfail;
 437          ctx->Stencil.ZPassFunc[0] = zpass;
 438          ctx->Stencil.FailFunc[0] = sfail;
 439          set = GL_TRUE;
 440       }
 441    }
 442    if (face != GL_FRONT) {
 443       /* set back */
 444       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 445           ctx->Stencil.ZPassFunc[1] != zpass ||
 446           ctx->Stencil.FailFunc[1] != sfail) {
 447          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 448          ctx->Stencil.ZFailFunc[1] = zfail;
 449          ctx->Stencil.ZPassFunc[1] = zpass;
 450          ctx->Stencil.FailFunc[1] = sfail;
 451          set = GL_TRUE;
 452       }
 453    }
 454    if (set && ctx->Driver.StencilOpSeparate) {
 455       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 456    }
 457 }
 458
 459
 460 /* OpenGL 2.0 */
 461 void GLAPIENTRY
 462 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 463 {
 464    GET_CURRENT_CONTEXT(ctx);
 465    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 466
 467    if (MESA_VERBOSE & VERBOSE_API)
 468       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 469
 470    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 471       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 472       return;
 473    }
 474    if (!validate_stencil_func(ctx, func)) {
 475       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 476       return;
 477    }
 478
 479    ref = CLAMP(ref, 0, stencilMax);
 480
 481    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 482
 483    if (face != GL_BACK) {
 484       /* set front */
 485       ctx->Stencil.Function[0] = func;
 486       ctx->Stencil.Ref[0] = ref;
 487       ctx->Stencil.ValueMask[0] = mask;
 488    }
 489    if (face != GL_FRONT) {
 490       /* set back */
 491       ctx->Stencil.Function[1] = func;
 492       ctx->Stencil.Ref[1] = ref;
 493       ctx->Stencil.ValueMask[1] = mask;
 494    }
 495    if (ctx->Driver.StencilFuncSeparate) {
 496       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 497    }
 498 }
 499
 500
 501 /* OpenGL 2.0 */
 502 void GLAPIENTRY
 503 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 504 {
 505    GET_CURRENT_CONTEXT(ctx);
 506
 507    if (MESA_VERBOSE & VERBOSE_API)
 508       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 509
 510    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 511       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 512       return;
 513    }
 514
 515    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 516
 517    if (face != GL_BACK) {
 518       ctx->Stencil.WriteMask[0] = mask;
 519    }
 520    if (face != GL_FRONT) {
 521       ctx->Stencil.WriteMask[1] = mask;
 522    }
 523    if (ctx->Driver.StencilMaskSeparate) {
 524       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 525    }
 526 }
 527
 528
 529 /**
 530  * Update derived stencil state.
 531  */
 532 void
 533 _mesa_update_stencil(struct gl_context *ctx)
 534 {
 535    const GLint face = ctx->Stencil._BackFace;
 536
 537    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 538                             ctx->DrawBuffer->Visual.stencilBits > 0);
 539
 540     ctx->Stencil._TestTwoSide =
 541        ctx->Stencil._Enabled &&
 542        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 543         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 544         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 545         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 546         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 547         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 548         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 549
 550    ctx->Stencil._WriteEnabled =
 551       ctx->Stencil._Enabled &&
 552       (ctx->Stencil.WriteMask[0] != 0 ||
 553        (ctx->Stencil._TestTwoSide && ctx->Stencil.WriteMask[face] != 0));
 554 }
 555
 556
 557 /**
 558  * Initialize the context stipple state.
 559  *
 560  * \param ctx GL context.
 561  *
 562  * Initializes __struct gl_contextRec::Stencil attribute group.
 563  */
 564 void
 565 _mesa_init_stencil(struct gl_context *ctx)
 566 {
 567    ctx->Stencil.Enabled = GL_FALSE;
 568    ctx->Stencil.TestTwoSide = GL_FALSE;
 569    ctx->Stencil.ActiveFace = 0;  /* 0 = GL_FRONT, 2 = GL_BACK */
 570    ctx->Stencil.Function[0] = GL_ALWAYS;
 571    ctx->Stencil.Function[1] = GL_ALWAYS;
 572    ctx->Stencil.Function[2] = GL_ALWAYS;
 573    ctx->Stencil.FailFunc[0] = GL_KEEP;
 574    ctx->Stencil.FailFunc[1] = GL_KEEP;
 575    ctx->Stencil.FailFunc[2] = GL_KEEP;
 576    ctx->Stencil.ZPassFunc[0] = GL_KEEP;
 577    ctx->Stencil.ZPassFunc[1] = GL_KEEP;
 578    ctx->Stencil.ZPassFunc[2] = GL_KEEP;
 579    ctx->Stencil.ZFailFunc[0] = GL_KEEP;
 580    ctx->Stencil.ZFailFunc[1] = GL_KEEP;
 581    ctx->Stencil.ZFailFunc[2] = GL_KEEP;
 582    ctx->Stencil.Ref[0] = 0;
 583    ctx->Stencil.Ref[1] = 0;
 584    ctx->Stencil.Ref[2] = 0;
 585    ctx->Stencil.ValueMask[0] = ~0U;
 586    ctx->Stencil.ValueMask[1] = ~0U;
 587    ctx->Stencil.ValueMask[2] = ~0U;
 588    ctx->Stencil.WriteMask[0] = ~0U;
 589    ctx->Stencil.WriteMask[1] = ~0U;
 590    ctx->Stencil.WriteMask[2] = ~0U;
 591    ctx->Stencil.Clear = 0;
 592    ctx->Stencil._BackFace = 1;
 593 }