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  * BRIAN PAUL 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    if (ctx->Stencil.Clear == (GLuint) s)
 113       return;
 114
 115    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 116    ctx->Stencil.Clear = (GLuint) s;
 117 }
 118
 119
 120 /**
 121  * Set the function and reference value for stencil testing.
 122  *
 123  * \param frontfunc front test function.
 124  * \param backfunc back test function.
 125  * \param ref front and back reference value.
 126  * \param mask front and back bitmask.
 127  *
 128  * \sa glStencilFunc().
 129  *
 130  * Verifies the parameters and updates the respective values in
 131  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 132  * driver via the dd_function_table::StencilFunc callback.
 133  */
 134 void GLAPIENTRY
 135 _mesa_StencilFuncSeparateATI( GLenum frontfunc, GLenum backfunc, GLint ref, GLuint mask )
 136 {
 137    GET_CURRENT_CONTEXT(ctx);
 138    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 139
 140    if (MESA_VERBOSE & VERBOSE_API)
 141       _mesa_debug(ctx, "glStencilFuncSeparateATI()\n");
 142
 143    if (!validate_stencil_func(ctx, frontfunc)) {
 144       _mesa_error(ctx, GL_INVALID_ENUM,
 145                   "glStencilFuncSeparateATI(frontfunc)");
 146       return;
 147    }
 148    if (!validate_stencil_func(ctx, backfunc)) {
 149       _mesa_error(ctx, GL_INVALID_ENUM,
 150                   "glStencilFuncSeparateATI(backfunc)");
 151       return;
 152    }
 153
 154    ref = CLAMP( ref, 0, stencilMax );
 155
 156    /* set both front and back state */
 157    if (ctx->Stencil.Function[0] == frontfunc &&
 158        ctx->Stencil.Function[1] == backfunc &&
 159        ctx->Stencil.ValueMask[0] == mask &&
 160        ctx->Stencil.ValueMask[1] == mask &&
 161        ctx->Stencil.Ref[0] == ref &&
 162        ctx->Stencil.Ref[1] == ref)
 163       return;
 164    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 165    ctx->Stencil.Function[0]  = frontfunc;
 166    ctx->Stencil.Function[1]  = backfunc;
 167    ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 168    ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 169    if (ctx->Driver.StencilFuncSeparate) {
 170       ctx->Driver.StencilFuncSeparate(ctx, GL_FRONT,
 171                                       frontfunc, ref, mask);
 172       ctx->Driver.StencilFuncSeparate(ctx, GL_BACK,
 173                                       backfunc, ref, mask);
 174    }
 175 }
 176
 177
 178 /**
 179  * Set the function and reference value for stencil testing.
 180  *
 181  * \param func test function.
 182  * \param ref reference value.
 183  * \param mask bitmask.
 184  *
 185  * \sa glStencilFunc().
 186  *
 187  * Verifies the parameters and updates the respective values in
 188  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 189  * driver via the dd_function_table::StencilFunc callback.
 190  */
 191 void GLAPIENTRY
 192 _mesa_StencilFunc( GLenum func, GLint ref, GLuint mask )
 193 {
 194    GET_CURRENT_CONTEXT(ctx);
 195    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 196    const GLint face = ctx->Stencil.ActiveFace;
 197
 198    if (MESA_VERBOSE & VERBOSE_API)
 199       _mesa_debug(ctx, "glStencilFunc()\n");
 200
 201    if (!validate_stencil_func(ctx, func)) {
 202       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFunc(func)");
 203       return;
 204    }
 205
 206    ref = CLAMP( ref, 0, stencilMax );
 207
 208    if (face != 0) {
 209       if (ctx->Stencil.Function[face] == func &&
 210           ctx->Stencil.ValueMask[face] == mask &&
 211           ctx->Stencil.Ref[face] == ref)
 212          return;
 213       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 214       ctx->Stencil.Function[face] = func;
 215       ctx->Stencil.Ref[face] = ref;
 216       ctx->Stencil.ValueMask[face] = mask;
 217
 218       /* Only propagate the change to the driver if EXT_stencil_two_side
 219        * is enabled.
 220        */
 221       if (ctx->Driver.StencilFuncSeparate && ctx->Stencil.TestTwoSide) {
 222          ctx->Driver.StencilFuncSeparate(ctx, GL_BACK, func, ref, mask);
 223       }
 224    }
 225    else {
 226       /* set both front and back state */
 227       if (ctx->Stencil.Function[0] == func &&
 228           ctx->Stencil.Function[1] == func &&
 229           ctx->Stencil.ValueMask[0] == mask &&
 230           ctx->Stencil.ValueMask[1] == mask &&
 231           ctx->Stencil.Ref[0] == ref &&
 232           ctx->Stencil.Ref[1] == ref)
 233          return;
 234       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 235       ctx->Stencil.Function[0]  = ctx->Stencil.Function[1]  = func;
 236       ctx->Stencil.Ref[0]       = ctx->Stencil.Ref[1]       = ref;
 237       ctx->Stencil.ValueMask[0] = ctx->Stencil.ValueMask[1] = mask;
 238       if (ctx->Driver.StencilFuncSeparate) {
 239          ctx->Driver.StencilFuncSeparate(ctx,
 240                                          ((ctx->Stencil.TestTwoSide)
 241                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 242                                          func, ref, mask);
 243       }
 244    }
 245 }
 246
 247
 248 /**
 249  * Set the stencil writing mask.
 250  *
 251  * \param mask bit-mask to enable/disable writing of individual bits in the
 252  * stencil planes.
 253  *
 254  * \sa glStencilMask().
 255  *
 256  * Updates gl_stencil_attrib::WriteMask. On change flushes the vertices and
 257  * notifies the driver via the dd_function_table::StencilMask callback.
 258  */
 259 void GLAPIENTRY
 260 _mesa_StencilMask( GLuint mask )
 261 {
 262    GET_CURRENT_CONTEXT(ctx);
 263    const GLint face = ctx->Stencil.ActiveFace;
 264
 265    if (MESA_VERBOSE & VERBOSE_API)
 266       _mesa_debug(ctx, "glStencilMask()\n");
 267
 268    if (face != 0) {
 269       /* Only modify the EXT_stencil_two_side back-face state.
 270        */
 271       if (ctx->Stencil.WriteMask[face] == mask)
 272          return;
 273       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 274       ctx->Stencil.WriteMask[face] = mask;
 275
 276       /* Only propagate the change to the driver if EXT_stencil_two_side
 277        * is enabled.
 278        */
 279       if (ctx->Driver.StencilMaskSeparate && ctx->Stencil.TestTwoSide) {
 280          ctx->Driver.StencilMaskSeparate(ctx, GL_BACK, mask);
 281       }
 282    }
 283    else {
 284       /* set both front and back state */
 285       if (ctx->Stencil.WriteMask[0] == mask &&
 286           ctx->Stencil.WriteMask[1] == mask)
 287          return;
 288       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 289       ctx->Stencil.WriteMask[0] = ctx->Stencil.WriteMask[1] = mask;
 290       if (ctx->Driver.StencilMaskSeparate) {
 291          ctx->Driver.StencilMaskSeparate(ctx,
 292                                          ((ctx->Stencil.TestTwoSide)
 293                                           ? GL_FRONT : GL_FRONT_AND_BACK),
 294                                           mask);
 295       }
 296    }
 297 }
 298
 299
 300 /**
 301  * Set the stencil test actions.
 302  *
 303  * \param fail action to take when stencil test fails.
 304  * \param zfail action to take when stencil test passes, but depth test fails.
 305  * \param zpass action to take when stencil test passes and the depth test
 306  * passes (or depth testing is not enabled).
 307  *
 308  * \sa glStencilOp().
 309  *
 310  * Verifies the parameters and updates the respective fields in
 311  * __struct gl_contextRec::Stencil. On change flushes the vertices and notifies the
 312  * driver via the dd_function_table::StencilOp callback.
 313  */
 314 void GLAPIENTRY
 315 _mesa_StencilOp(GLenum fail, GLenum zfail, GLenum zpass)
 316 {
 317    GET_CURRENT_CONTEXT(ctx);
 318    const GLint face = ctx->Stencil.ActiveFace;
 319
 320    if (MESA_VERBOSE & VERBOSE_API)
 321       _mesa_debug(ctx, "glStencilOp()\n");
 322
 323    if (!validate_stencil_op(ctx, fail)) {
 324       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(sfail)");
 325       return;
 326    }
 327    if (!validate_stencil_op(ctx, zfail)) {
 328       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zfail)");
 329       return;
 330    }
 331    if (!validate_stencil_op(ctx, zpass)) {
 332       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOp(zpass)");
 333       return;
 334    }
 335
 336    if (face != 0) {
 337       /* only set active face state */
 338       if (ctx->Stencil.ZFailFunc[face] == zfail &&
 339           ctx->Stencil.ZPassFunc[face] == zpass &&
 340           ctx->Stencil.FailFunc[face] == fail)
 341          return;
 342       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 343       ctx->Stencil.ZFailFunc[face] = zfail;
 344       ctx->Stencil.ZPassFunc[face] = zpass;
 345       ctx->Stencil.FailFunc[face] = fail;
 346
 347       /* Only propagate the change to the driver if EXT_stencil_two_side
 348        * is enabled.
 349        */
 350       if (ctx->Driver.StencilOpSeparate && ctx->Stencil.TestTwoSide) {
 351          ctx->Driver.StencilOpSeparate(ctx, GL_BACK, fail, zfail, zpass);
 352       }
 353    }
 354    else {
 355       /* set both front and back state */
 356       if (ctx->Stencil.ZFailFunc[0] == zfail &&
 357           ctx->Stencil.ZFailFunc[1] == zfail &&
 358           ctx->Stencil.ZPassFunc[0] == zpass &&
 359           ctx->Stencil.ZPassFunc[1] == zpass &&
 360           ctx->Stencil.FailFunc[0] == fail &&
 361           ctx->Stencil.FailFunc[1] == fail)
 362          return;
 363       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 364       ctx->Stencil.ZFailFunc[0] = ctx->Stencil.ZFailFunc[1] = zfail;
 365       ctx->Stencil.ZPassFunc[0] = ctx->Stencil.ZPassFunc[1] = zpass;
 366       ctx->Stencil.FailFunc[0]  = ctx->Stencil.FailFunc[1]  = fail;
 367       if (ctx->Driver.StencilOpSeparate) {
 368          ctx->Driver.StencilOpSeparate(ctx,
 369                                        ((ctx->Stencil.TestTwoSide)
 370                                         ? GL_FRONT : GL_FRONT_AND_BACK),
 371                                        fail, zfail, zpass);
 372       }
 373    }
 374 }
 375
 376
 377
 378 /* GL_EXT_stencil_two_side */
 379 void GLAPIENTRY
 380 _mesa_ActiveStencilFaceEXT(GLenum face)
 381 {
 382    GET_CURRENT_CONTEXT(ctx);
 383
 384    if (MESA_VERBOSE & VERBOSE_API)
 385       _mesa_debug(ctx, "glActiveStencilFaceEXT()\n");
 386
 387    if (!ctx->Extensions.EXT_stencil_two_side) {
 388       _mesa_error(ctx, GL_INVALID_OPERATION, "glActiveStencilFaceEXT");
 389       return;
 390    }
 391
 392    if (face == GL_FRONT || face == GL_BACK) {
 393       FLUSH_VERTICES(ctx, _NEW_STENCIL);
 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
 403 /**
 404  * OpenGL 2.0 function.
 405  * \todo Make StencilOp() call this function.  And eventually remove the
 406  * ctx->Driver.StencilOp function and use ctx->Driver.StencilOpSeparate
 407  * instead.
 408  */
 409 void GLAPIENTRY
 410 _mesa_StencilOpSeparate(GLenum face, GLenum sfail, GLenum zfail, GLenum zpass)
 411 {
 412    GLboolean set = GL_FALSE;
 413    GET_CURRENT_CONTEXT(ctx);
 414
 415    if (MESA_VERBOSE & VERBOSE_API)
 416       _mesa_debug(ctx, "glStencilOpSeparate()\n");
 417
 418    if (!validate_stencil_op(ctx, sfail)) {
 419       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(sfail)");
 420       return;
 421    }
 422    if (!validate_stencil_op(ctx, zfail)) {
 423       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zfail)");
 424       return;
 425    }
 426    if (!validate_stencil_op(ctx, zpass)) {
 427       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(zpass)");
 428       return;
 429    }
 430    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 431       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilOpSeparate(face)");
 432       return;
 433    }
 434
 435    if (face != GL_BACK) {
 436       /* set front */
 437       if (ctx->Stencil.ZFailFunc[0] != zfail ||
 438           ctx->Stencil.ZPassFunc[0] != zpass ||
 439           ctx->Stencil.FailFunc[0] != sfail){
 440          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 441          ctx->Stencil.ZFailFunc[0] = zfail;
 442          ctx->Stencil.ZPassFunc[0] = zpass;
 443          ctx->Stencil.FailFunc[0] = sfail;
 444          set = GL_TRUE;
 445       }
 446    }
 447    if (face != GL_FRONT) {
 448       /* set back */
 449       if (ctx->Stencil.ZFailFunc[1] != zfail ||
 450           ctx->Stencil.ZPassFunc[1] != zpass ||
 451           ctx->Stencil.FailFunc[1] != sfail) {
 452          FLUSH_VERTICES(ctx, _NEW_STENCIL);
 453          ctx->Stencil.ZFailFunc[1] = zfail;
 454          ctx->Stencil.ZPassFunc[1] = zpass;
 455          ctx->Stencil.FailFunc[1] = sfail;
 456          set = GL_TRUE;
 457       }
 458    }
 459    if (set && ctx->Driver.StencilOpSeparate) {
 460       ctx->Driver.StencilOpSeparate(ctx, face, sfail, zfail, zpass);
 461    }
 462 }
 463
 464
 465 /* OpenGL 2.0 */
 466 void GLAPIENTRY
 467 _mesa_StencilFuncSeparate(GLenum face, GLenum func, GLint ref, GLuint mask)
 468 {
 469    GET_CURRENT_CONTEXT(ctx);
 470    const GLint stencilMax = (1 << ctx->DrawBuffer->Visual.stencilBits) - 1;
 471
 472    if (MESA_VERBOSE & VERBOSE_API)
 473       _mesa_debug(ctx, "glStencilFuncSeparate()\n");
 474
 475    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 476       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(face)");
 477       return;
 478    }
 479    if (!validate_stencil_func(ctx, func)) {
 480       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilFuncSeparate(func)");
 481       return;
 482    }
 483
 484    ref = CLAMP(ref, 0, stencilMax);
 485
 486    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 487
 488    if (face != GL_BACK) {
 489       /* set front */
 490       ctx->Stencil.Function[0] = func;
 491       ctx->Stencil.Ref[0] = ref;
 492       ctx->Stencil.ValueMask[0] = mask;
 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    if (ctx->Driver.StencilFuncSeparate) {
 501       ctx->Driver.StencilFuncSeparate(ctx, face, func, ref, mask);
 502    }
 503 }
 504
 505
 506 /* OpenGL 2.0 */
 507 void GLAPIENTRY
 508 _mesa_StencilMaskSeparate(GLenum face, GLuint mask)
 509 {
 510    GET_CURRENT_CONTEXT(ctx);
 511
 512    if (MESA_VERBOSE & VERBOSE_API)
 513       _mesa_debug(ctx, "glStencilMaskSeparate()\n");
 514
 515    if (face != GL_FRONT && face != GL_BACK && face != GL_FRONT_AND_BACK) {
 516       _mesa_error(ctx, GL_INVALID_ENUM, "glStencilaMaskSeparate(face)");
 517       return;
 518    }
 519
 520    FLUSH_VERTICES(ctx, _NEW_STENCIL);
 521
 522    if (face != GL_BACK) {
 523       ctx->Stencil.WriteMask[0] = mask;
 524    }
 525    if (face != GL_FRONT) {
 526       ctx->Stencil.WriteMask[1] = mask;
 527    }
 528    if (ctx->Driver.StencilMaskSeparate) {
 529       ctx->Driver.StencilMaskSeparate(ctx, face, mask);
 530    }
 531 }
 532
 533
 534 /**
 535  * Update derived stencil state.
 536  */
 537 void
 538 _mesa_update_stencil(struct gl_context *ctx)
 539 {
 540    const GLint face = ctx->Stencil._BackFace;
 541
 542    ctx->Stencil._Enabled = (ctx->Stencil.Enabled &&
 543                             ctx->DrawBuffer->Visual.stencilBits > 0);
 544
 545     ctx->Stencil._TestTwoSide =
 546        ctx->Stencil._Enabled &&
 547        (ctx->Stencil.Function[0] != ctx->Stencil.Function[face] ||
 548         ctx->Stencil.FailFunc[0] != ctx->Stencil.FailFunc[face] ||
 549         ctx->Stencil.ZPassFunc[0] != ctx->Stencil.ZPassFunc[face] ||
 550         ctx->Stencil.ZFailFunc[0] != ctx->Stencil.ZFailFunc[face] ||
 551         ctx->Stencil.Ref[0] != ctx->Stencil.Ref[face] ||
 552         ctx->Stencil.ValueMask[0] != ctx->Stencil.ValueMask[face] ||
 553         ctx->Stencil.WriteMask[0] != ctx->Stencil.WriteMask[face]);
 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 }