src/mesa/main/clear.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 clear.c
  28  * glClearColor, glClearIndex, glClear() functions.
  29  */
  30
  31
  32
  33 #include "glheader.h"
  34 #include "clear.h"
  35 #include "context.h"
  36 #include "colormac.h"
  37 #include "enums.h"
  38 #include "macros.h"
  39 #include "mtypes.h"
  40 #include "state.h"
  41
  42
  43
  44 #if _HAVE_FULL_GL
  45 void GLAPIENTRY
  46 _mesa_ClearIndex( GLfloat c )
  47 {
  48    GET_CURRENT_CONTEXT(ctx);
  49    ASSERT_OUTSIDE_BEGIN_END(ctx);
  50
  51    if (ctx->Color.ClearIndex == (GLuint) c)
  52       return;
  53
  54    FLUSH_VERTICES(ctx, _NEW_COLOR);
  55    ctx->Color.ClearIndex = (GLuint) c;
  56 }
  57 #endif
  58
  59
  60 /**
  61  * Specify the clear values for the color buffers.
  62  *
  63  * \param red red color component.
  64  * \param green green color component.
  65  * \param blue blue color component.
  66  * \param alpha alpha component.
  67  *
  68  * \sa glClearColor().
  69  *
  70  * Clamps the parameters and updates gl_colorbuffer_attrib::ClearColor.  On a
  71  * change, flushes the vertices and notifies the driver via the
  72  * dd_function_table::ClearColor callback.
  73  */
  74 void GLAPIENTRY
  75 _mesa_ClearColor( GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha )
  76 {
  77    GLfloat tmp[4];
  78    GET_CURRENT_CONTEXT(ctx);
  79    ASSERT_OUTSIDE_BEGIN_END(ctx);
  80
  81    tmp[0] = red;
  82    tmp[1] = green;
  83    tmp[2] = blue;
  84    tmp[3] = alpha;
  85
  86    if (TEST_EQ_4V(tmp, ctx->Color.ClearColor.f))
  87       return; /* no change */
  88
  89    FLUSH_VERTICES(ctx, _NEW_COLOR);
  90    COPY_4V(ctx->Color.ClearColor.f, tmp);
  91 }
  92
  93
  94 /**
  95  * GL_EXT_texture_integer
  96  */
  97 void GLAPIENTRY
  98 _mesa_ClearColorIiEXT(GLint r, GLint g, GLint b, GLint a)
  99 {
 100    GLint tmp[4];
 101    GET_CURRENT_CONTEXT(ctx);
 102    ASSERT_OUTSIDE_BEGIN_END(ctx);
 103
 104    tmp[0] = r;
 105    tmp[1] = g;
 106    tmp[2] = b;
 107    tmp[3] = a;
 108
 109    if (TEST_EQ_4V(tmp, ctx->Color.ClearColor.i))
 110       return; /* no change */
 111
 112    FLUSH_VERTICES(ctx, _NEW_COLOR);
 113    COPY_4V(ctx->Color.ClearColor.i, tmp);
 114 }
 115
 116
 117 /**
 118  * GL_EXT_texture_integer
 119  */
 120 void GLAPIENTRY
 121 _mesa_ClearColorIuiEXT(GLuint r, GLuint g, GLuint b, GLuint a)
 122 {
 123    GLuint tmp[4];
 124    GET_CURRENT_CONTEXT(ctx);
 125    ASSERT_OUTSIDE_BEGIN_END(ctx);
 126
 127    tmp[0] = r;
 128    tmp[1] = g;
 129    tmp[2] = b;
 130    tmp[3] = a;
 131
 132    if (TEST_EQ_4V(tmp, ctx->Color.ClearColor.ui))
 133       return; /* no change */
 134
 135    FLUSH_VERTICES(ctx, _NEW_COLOR);
 136    COPY_4V(ctx->Color.ClearColor.ui, tmp);
 137 }
 138
 139
 140 /**
 141  * Clear buffers.
 142  *
 143  * \param mask bit-mask indicating the buffers to be cleared.
 144  *
 145  * Flushes the vertices and verifies the parameter. If __struct gl_contextRec::NewState
 146  * is set then calls _mesa_update_state() to update gl_frame_buffer::_Xmin,
 147  * etc. If the rasterization mode is set to GL_RENDER then requests the driver
 148  * to clear the buffers, via the dd_function_table::Clear callback.
 149  */
 150 void GLAPIENTRY
 151 _mesa_Clear( GLbitfield mask )
 152 {
 153    GET_CURRENT_CONTEXT(ctx);
 154    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 155
 156    FLUSH_CURRENT(ctx, 0);
 157
 158    if (MESA_VERBOSE & VERBOSE_API)
 159       _mesa_debug(ctx, "glClear 0x%x\n", mask);
 160
 161    if (mask & ~(GL_COLOR_BUFFER_BIT |
 162                 GL_DEPTH_BUFFER_BIT |
 163                 GL_STENCIL_BUFFER_BIT |
 164                 GL_ACCUM_BUFFER_BIT)) {
 165       /* invalid bit set */
 166       _mesa_error( ctx, GL_INVALID_VALUE, "glClear(0x%x)", mask);
 167       return;
 168    }
 169
 170    /* Accumulation buffers were removed in core contexts, and they never
 171     * existed in OpenGL ES.
 172     */
 173    if ((mask & GL_ACCUM_BUFFER_BIT) != 0
 174        && (ctx->API == API_OPENGL_CORE || _mesa_is_gles(ctx))) {
 175       _mesa_error( ctx, GL_INVALID_VALUE, "glClear(GL_ACCUM_BUFFER_BIT)");
 176       return;
 177    }
 178
 179    if (ctx->NewState) {
 180       _mesa_update_state( ctx );        /* update _Xmin, etc */
 181    }
 182
 183    if (ctx->DrawBuffer->_Status != GL_FRAMEBUFFER_COMPLETE_EXT) {
 184       _mesa_error(ctx, GL_INVALID_FRAMEBUFFER_OPERATION_EXT,
 185                   "glClear(incomplete framebuffer)");
 186       return;
 187    }
 188
 189    if (ctx->DrawBuffer->Width == 0 || ctx->DrawBuffer->Height == 0 ||
 190        ctx->DrawBuffer->_Xmin >= ctx->DrawBuffer->_Xmax ||
 191        ctx->DrawBuffer->_Ymin >= ctx->DrawBuffer->_Ymax)
 192       return;
 193
 194    if (ctx->RasterDiscard)
 195       return;
 196
 197    if (ctx->RenderMode == GL_RENDER) {
 198       GLbitfield bufferMask;
 199
 200       /* don't clear depth buffer if depth writing disabled */
 201       if (!ctx->Depth.Mask)
 202          mask &= ~GL_DEPTH_BUFFER_BIT;
 203
 204       /* Build the bitmask to send to device driver's Clear function.
 205        * Note that the GL_COLOR_BUFFER_BIT flag will expand to 0, 1, 2 or 4
 206        * of the BUFFER_BIT_FRONT/BACK_LEFT/RIGHT flags, or one of the
 207        * BUFFER_BIT_COLORn flags.
 208        */
 209       bufferMask = 0;
 210       if (mask & GL_COLOR_BUFFER_BIT) {
 211          GLuint i;
 212          for (i = 0; i < ctx->DrawBuffer->_NumColorDrawBuffers; i++) {
 213             bufferMask |= (1 << ctx->DrawBuffer->_ColorDrawBufferIndexes[i]);
 214          }
 215       }
 216
 217       if ((mask & GL_DEPTH_BUFFER_BIT)
 218           && ctx->DrawBuffer->Visual.haveDepthBuffer) {
 219          bufferMask |= BUFFER_BIT_DEPTH;
 220       }
 221
 222       if ((mask & GL_STENCIL_BUFFER_BIT)
 223           && ctx->DrawBuffer->Visual.haveStencilBuffer) {
 224          bufferMask |= BUFFER_BIT_STENCIL;
 225       }
 226
 227       if ((mask & GL_ACCUM_BUFFER_BIT)
 228           && ctx->DrawBuffer->Visual.haveAccumBuffer) {
 229          bufferMask |= BUFFER_BIT_ACCUM;
 230       }
 231
 232       ASSERT(ctx->Driver.Clear);
 233       ctx->Driver.Clear(ctx, bufferMask);
 234    }
 235 }
 236
 237
 238 /** Returned by make_color_buffer_mask() for errors */
 239 #define INVALID_MASK ~0x0
 240
 241
 242 /**
 243  * Convert the glClearBuffer 'drawbuffer' parameter into a bitmask of
 244  * BUFFER_BIT_x values.
 245  * Return INVALID_MASK if the drawbuffer value is invalid.
 246  */
 247 static GLbitfield
 248 make_color_buffer_mask(struct gl_context *ctx, GLint drawbuffer)
 249 {
 250    const struct gl_renderbuffer_attachment *att = ctx->DrawBuffer->Attachment;
 251    GLbitfield mask = 0x0;
 252
 253    switch (drawbuffer) {
 254    case GL_FRONT:
 255       if (att[BUFFER_FRONT_LEFT].Renderbuffer)
 256          mask |= BUFFER_BIT_FRONT_LEFT;
 257       if (att[BUFFER_FRONT_RIGHT].Renderbuffer)
 258          mask |= BUFFER_BIT_FRONT_RIGHT;
 259       break;
 260    case GL_BACK:
 261       if (att[BUFFER_BACK_LEFT].Renderbuffer)
 262          mask |= BUFFER_BIT_BACK_LEFT;
 263       if (att[BUFFER_BACK_RIGHT].Renderbuffer)
 264          mask |= BUFFER_BIT_BACK_RIGHT;
 265       break;
 266    case GL_LEFT:
 267       if (att[BUFFER_FRONT_LEFT].Renderbuffer)
 268          mask |= BUFFER_BIT_FRONT_LEFT;
 269       if (att[BUFFER_BACK_LEFT].Renderbuffer)
 270          mask |= BUFFER_BIT_BACK_LEFT;
 271       break;
 272    case GL_RIGHT:
 273       if (att[BUFFER_FRONT_RIGHT].Renderbuffer)
 274          mask |= BUFFER_BIT_FRONT_RIGHT;
 275       if (att[BUFFER_BACK_RIGHT].Renderbuffer)
 276          mask |= BUFFER_BIT_BACK_RIGHT;
 277       break;
 278    case GL_FRONT_AND_BACK:
 279       if (att[BUFFER_FRONT_LEFT].Renderbuffer)
 280          mask |= BUFFER_BIT_FRONT_LEFT;
 281       if (att[BUFFER_BACK_LEFT].Renderbuffer)
 282          mask |= BUFFER_BIT_BACK_LEFT;
 283       if (att[BUFFER_FRONT_RIGHT].Renderbuffer)
 284          mask |= BUFFER_BIT_FRONT_RIGHT;
 285       if (att[BUFFER_BACK_RIGHT].Renderbuffer)
 286          mask |= BUFFER_BIT_BACK_RIGHT;
 287       break;
 288    default:
 289       if (drawbuffer < 0 || drawbuffer >= (GLint)ctx->Const.MaxDrawBuffers) {
 290          mask = INVALID_MASK;
 291       }
 292       else if (att[BUFFER_COLOR0 + drawbuffer].Renderbuffer) {
 293          mask |= (BUFFER_BIT_COLOR0 << drawbuffer);
 294       }
 295    }
 296
 297    return mask;
 298 }
 299
 300
 301
 302 /**
 303  * New in GL 3.0
 304  * Clear signed integer color buffer or stencil buffer (not depth).
 305  */
 306 void GLAPIENTRY
 307 _mesa_ClearBufferiv(GLenum buffer, GLint drawbuffer, const GLint *value)
 308 {
 309    GET_CURRENT_CONTEXT(ctx);
 310    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 311
 312    FLUSH_CURRENT(ctx, 0);
 313
 314    if (ctx->NewState) {
 315       _mesa_update_state( ctx );
 316    }
 317
 318    switch (buffer) {
 319    case GL_STENCIL:
 320       /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 321        *
 322        *     "ClearBuffer generates an INVALID VALUE error if buffer is
 323        *     COLOR and drawbuffer is less than zero, or greater than the
 324        *     value of MAX DRAW BUFFERS minus one; or if buffer is DEPTH,
 325        *     STENCIL, or DEPTH STENCIL and drawbuffer is not zero."
 326        */
 327       if (drawbuffer != 0) {
 328          _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferiv(drawbuffer=%d)",
 329                      drawbuffer);
 330          return;
 331       }
 332       else if (ctx->DrawBuffer->Attachment[BUFFER_STENCIL].Renderbuffer && !ctx->RasterDiscard) {
 333          /* Save current stencil clear value, set to 'value', do the
 334           * stencil clear and restore the clear value.
 335           * XXX in the future we may have a new ctx->Driver.ClearBuffer()
 336           * hook instead.
 337           */
 338          const GLuint clearSave = ctx->Stencil.Clear;
 339          ctx->Stencil.Clear = *value;
 340          ctx->Driver.Clear(ctx, BUFFER_BIT_STENCIL);
 341          ctx->Stencil.Clear = clearSave;
 342       }
 343       break;
 344    case GL_COLOR:
 345       {
 346          const GLbitfield mask = make_color_buffer_mask(ctx, drawbuffer);
 347          if (mask == INVALID_MASK) {
 348             _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferiv(drawbuffer=%d)",
 349                         drawbuffer);
 350             return;
 351          }
 352          else if (mask && !ctx->RasterDiscard) {
 353             union gl_color_union clearSave;
 354
 355             /* save color */
 356             clearSave = ctx->Color.ClearColor;
 357             /* set color */
 358             COPY_4V(ctx->Color.ClearColor.i, value);
 359             /* clear buffer(s) */
 360             ctx->Driver.Clear(ctx, mask);
 361             /* restore color */
 362             ctx->Color.ClearColor = clearSave;
 363          }
 364       }
 365       break;
 366    case GL_DEPTH:
 367       /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 368        *
 369        *     "The result of ClearBuffer is undefined if no conversion between
 370        *     the type of the specified value and the type of the buffer being
 371        *     cleared is defined (for example, if ClearBufferiv is called for a
 372        *     fixed- or floating-point buffer, or if ClearBufferfv is called
 373        *     for a signed or unsigned integer buffer). This is not an error."
 374        *
 375        * In this case we take "undefined" and "not an error" to mean "ignore."
 376        * Note that we still need to generate an error for the invalid
 377        * drawbuffer case (see the GL_STENCIL case above).
 378        */
 379       if (drawbuffer != 0) {
 380          _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferiv(drawbuffer=%d)",
 381                      drawbuffer);
 382          return;
 383       }
 384       return;
 385    default:
 386       _mesa_error(ctx, GL_INVALID_ENUM, "glClearBufferiv(buffer=%s)",
 387                   _mesa_lookup_enum_by_nr(buffer));
 388       return;
 389    }
 390 }
 391
 392
 393 /**
 394  * New in GL 3.0
 395  * Clear unsigned integer color buffer (not depth, not stencil).
 396  */
 397 void GLAPIENTRY
 398 _mesa_ClearBufferuiv(GLenum buffer, GLint drawbuffer, const GLuint *value)
 399 {
 400    GET_CURRENT_CONTEXT(ctx);
 401    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 402
 403    FLUSH_CURRENT(ctx, 0);
 404
 405    if (ctx->NewState) {
 406       _mesa_update_state( ctx );
 407    }
 408
 409    switch (buffer) {
 410    case GL_COLOR:
 411       {
 412          const GLbitfield mask = make_color_buffer_mask(ctx, drawbuffer);
 413          if (mask == INVALID_MASK) {
 414             _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferuiv(drawbuffer=%d)",
 415                         drawbuffer);
 416             return;
 417          }
 418          else if (mask && !ctx->RasterDiscard) {
 419             union gl_color_union clearSave;
 420
 421             /* save color */
 422             clearSave = ctx->Color.ClearColor;
 423             /* set color */
 424             COPY_4V(ctx->Color.ClearColor.ui, value);
 425             /* clear buffer(s) */
 426             ctx->Driver.Clear(ctx, mask);
 427             /* restore color */
 428             ctx->Color.ClearColor = clearSave;
 429          }
 430       }
 431       break;
 432    case GL_DEPTH:
 433    case GL_STENCIL:
 434       /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 435        *
 436        *     "The result of ClearBuffer is undefined if no conversion between
 437        *     the type of the specified value and the type of the buffer being
 438        *     cleared is defined (for example, if ClearBufferiv is called for a
 439        *     fixed- or floating-point buffer, or if ClearBufferfv is called
 440        *     for a signed or unsigned integer buffer). This is not an error."
 441        *
 442        * In this case we take "undefined" and "not an error" to mean "ignore."
 443        * Even though we could do something sensible for GL_STENCIL, page 263
 444        * (page 279 of the PDF) says:
 445        *
 446        *     "Only ClearBufferiv should be used to clear stencil buffers."
 447        *
 448        * Note that we still need to generate an error for the invalid
 449        * drawbuffer case (see the GL_STENCIL case in _mesa_ClearBufferiv).
 450        */
 451       if (drawbuffer != 0) {
 452          _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferuiv(drawbuffer=%d)",
 453                      drawbuffer);
 454          return;
 455       }
 456       return;
 457    default:
 458       _mesa_error(ctx, GL_INVALID_ENUM, "glClearBufferuiv(buffer=%s)",
 459                   _mesa_lookup_enum_by_nr(buffer));
 460       return;
 461    }
 462 }
 463
 464
 465 /**
 466  * New in GL 3.0
 467  * Clear fixed-pt or float color buffer or depth buffer (not stencil).
 468  */
 469 void GLAPIENTRY
 470 _mesa_ClearBufferfv(GLenum buffer, GLint drawbuffer, const GLfloat *value)
 471 {
 472    GET_CURRENT_CONTEXT(ctx);
 473    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 474
 475    FLUSH_CURRENT(ctx, 0);
 476
 477    if (ctx->NewState) {
 478       _mesa_update_state( ctx );
 479    }
 480
 481    switch (buffer) {
 482    case GL_DEPTH:
 483       /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 484        *
 485        *     "ClearBuffer generates an INVALID VALUE error if buffer is
 486        *     COLOR and drawbuffer is less than zero, or greater than the
 487        *     value of MAX DRAW BUFFERS minus one; or if buffer is DEPTH,
 488        *     STENCIL, or DEPTH STENCIL and drawbuffer is not zero."
 489        */
 490       if (drawbuffer != 0) {
 491          _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferfv(drawbuffer=%d)",
 492                      drawbuffer);
 493          return;
 494       }
 495       else if (ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer && !ctx->RasterDiscard) {
 496          /* Save current depth clear value, set to 'value', do the
 497           * depth clear and restore the clear value.
 498           * XXX in the future we may have a new ctx->Driver.ClearBuffer()
 499           * hook instead.
 500           */
 501          const GLclampd clearSave = ctx->Depth.Clear;
 502          ctx->Depth.Clear = *value;
 503          ctx->Driver.Clear(ctx, BUFFER_BIT_DEPTH);
 504          ctx->Depth.Clear = clearSave;
 505       }
 506       /* clear depth buffer to value */
 507       break;
 508    case GL_COLOR:
 509       {
 510          const GLbitfield mask = make_color_buffer_mask(ctx, drawbuffer);
 511          if (mask == INVALID_MASK) {
 512             _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferfv(drawbuffer=%d)",
 513                         drawbuffer);
 514             return;
 515          }
 516          else if (mask && !ctx->RasterDiscard) {
 517             union gl_color_union clearSave;
 518
 519             /* save color */
 520             clearSave = ctx->Color.ClearColor;
 521             /* set color */
 522             COPY_4V(ctx->Color.ClearColor.f, value);
 523             /* clear buffer(s) */
 524             ctx->Driver.Clear(ctx, mask);
 525             /* restore color */
 526             ctx->Color.ClearColor = clearSave;
 527          }
 528       }
 529       break;
 530    case GL_STENCIL:
 531       /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 532        *
 533        *     "The result of ClearBuffer is undefined if no conversion between
 534        *     the type of the specified value and the type of the buffer being
 535        *     cleared is defined (for example, if ClearBufferiv is called for a
 536        *     fixed- or floating-point buffer, or if ClearBufferfv is called
 537        *     for a signed or unsigned integer buffer). This is not an error."
 538        *
 539        * In this case we take "undefined" and "not an error" to mean "ignore."
 540        * Note that we still need to generate an error for the invalid
 541        * drawbuffer case (see the GL_DEPTH case above).
 542        */
 543       if (drawbuffer != 0) {
 544          _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferfv(drawbuffer=%d)",
 545                      drawbuffer);
 546          return;
 547       }
 548       return;
 549    default:
 550       _mesa_error(ctx, GL_INVALID_ENUM, "glClearBufferfv(buffer=%s)",
 551                   _mesa_lookup_enum_by_nr(buffer));
 552       return;
 553    }
 554 }
 555
 556
 557 /**
 558  * New in GL 3.0
 559  * Clear depth/stencil buffer only.
 560  */
 561 void GLAPIENTRY
 562 _mesa_ClearBufferfi(GLenum buffer, GLint drawbuffer,
 563                     GLfloat depth, GLint stencil)
 564 {
 565    GET_CURRENT_CONTEXT(ctx);
 566    GLbitfield mask = 0;
 567
 568    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx);
 569
 570    FLUSH_CURRENT(ctx, 0);
 571
 572    if (buffer != GL_DEPTH_STENCIL) {
 573       _mesa_error(ctx, GL_INVALID_ENUM, "glClearBufferfi(buffer=%s)",
 574                   _mesa_lookup_enum_by_nr(buffer));
 575       return;
 576    }
 577
 578    /* Page 264 (page 280 of the PDF) of the OpenGL 3.0 spec says:
 579     *
 580     *     "ClearBuffer generates an INVALID VALUE error if buffer is
 581     *     COLOR and drawbuffer is less than zero, or greater than the
 582     *     value of MAX DRAW BUFFERS minus one; or if buffer is DEPTH,
 583     *     STENCIL, or DEPTH STENCIL and drawbuffer is not zero."
 584     */
 585    if (drawbuffer != 0) {
 586       _mesa_error(ctx, GL_INVALID_VALUE, "glClearBufferfi(drawbuffer=%d)",
 587                   drawbuffer);
 588       return;
 589    }
 590
 591    if (ctx->RasterDiscard)
 592       return;
 593
 594    if (ctx->NewState) {
 595       _mesa_update_state( ctx );
 596    }
 597
 598    if (ctx->DrawBuffer->Attachment[BUFFER_DEPTH].Renderbuffer)
 599       mask |= BUFFER_BIT_DEPTH;
 600    if (ctx->DrawBuffer->Attachment[BUFFER_STENCIL].Renderbuffer)
 601       mask |= BUFFER_BIT_STENCIL;
 602
 603    if (mask) {
 604       /* save current clear values */
 605       const GLclampd clearDepthSave = ctx->Depth.Clear;
 606       const GLuint clearStencilSave = ctx->Stencil.Clear;
 607
 608       /* set new clear values */
 609       ctx->Depth.Clear = depth;
 610       ctx->Stencil.Clear = stencil;
 611
 612       /* clear buffers */
 613       ctx->Driver.Clear(ctx, mask);
 614
 615       /* restore */
 616       ctx->Depth.Clear = clearDepthSave;
 617       ctx->Stencil.Clear = clearStencilSave;
 618    }
 619 }