src/mesa/main/buffers.c

   1 /* $Id: buffers.c,v 1.15 2000/10/28 18:34:48 brianp Exp $ */
   2
   3 /*
   4  * Mesa 3-D graphics library
   5  * Version:  3.5
   6  *
   7  * Copyright (C) 1999-2000  Brian Paul   All Rights Reserved.
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a
  10  * copy of this software and associated documentation files (the "Software"),
  11  * to deal in the Software without restriction, including without limitation
  12  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  13  * and/or sell copies of the Software, and to permit persons to whom the
  14  * Software is furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included
  17  * in all copies or substantial portions of the Software.
  18  *
  19  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  20  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  22  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  23  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  24  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  */
  26
  27
  28 #ifdef PC_HEADER
  29 #include "all.h"
  30 #else
  31 #include "glheader.h"
  32 #include "accum.h"
  33 #include "alphabuf.h"
  34 #include "buffers.h"
  35 #include "context.h"
  36 #include "depth.h"
  37 #include "enums.h"
  38 #include "macros.h"
  39 #include "masking.h"
  40 #include "mem.h"
  41 #include "stencil.h"
  42 #include "state.h"
  43 #include "types.h"
  44 #endif
  45
  46
  47
  48 void
  49 _mesa_ClearIndex( GLfloat c )
  50 {
  51    GET_CURRENT_CONTEXT(ctx);
  52    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glClearIndex");
  53    ctx->Color.ClearIndex = (GLuint) c;
  54    if (!ctx->Visual.RGBAflag) {
  55       /* it's OK to call glClearIndex in RGBA mode but it should be a NOP */
  56       (*ctx->Driver.ClearIndex)( ctx, ctx->Color.ClearIndex );
  57    }
  58 }
  59
  60
  61
  62 void
  63 _mesa_ClearColor( GLclampf red, GLclampf green,
  64                   GLclampf blue, GLclampf alpha )
  65 {
  66    GET_CURRENT_CONTEXT(ctx);
  67    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glClearColor");
  68
  69    ctx->Color.ClearColor[0] = CLAMP( red,   0.0F, 1.0F );
  70    ctx->Color.ClearColor[1] = CLAMP( green, 0.0F, 1.0F );
  71    ctx->Color.ClearColor[2] = CLAMP( blue,  0.0F, 1.0F );
  72    ctx->Color.ClearColor[3] = CLAMP( alpha, 0.0F, 1.0F );
  73
  74    if (ctx->Visual.RGBAflag) {
  75       GLchan r = (GLint) (ctx->Color.ClearColor[0] * CHAN_MAXF);
  76       GLchan g = (GLint) (ctx->Color.ClearColor[1] * CHAN_MAXF);
  77       GLchan b = (GLint) (ctx->Color.ClearColor[2] * CHAN_MAXF);
  78       GLchan a = (GLint) (ctx->Color.ClearColor[3] * CHAN_MAXF);
  79       (*ctx->Driver.ClearColor)( ctx, r, g, b, a );
  80    }
  81 }
  82
  83
  84
  85
  86 /*
  87  * Clear the color buffer when glColorMask or glIndexMask is in effect.
  88  */
  89 static void
  90 clear_color_buffer_with_masking( GLcontext *ctx )
  91 {
  92    const GLint x = ctx->DrawBuffer->Xmin;
  93    const GLint y = ctx->DrawBuffer->Ymin;
  94    const GLint height = ctx->DrawBuffer->Ymax - ctx->DrawBuffer->Ymin;
  95    const GLint width  = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin;
  96
  97    if (ctx->Visual.RGBAflag) {
  98       /* RGBA mode */
  99       const GLchan r = (GLint) (ctx->Color.ClearColor[0] * CHAN_MAXF);
 100       const GLchan g = (GLint) (ctx->Color.ClearColor[1] * CHAN_MAXF);
 101       const GLchan b = (GLint) (ctx->Color.ClearColor[2] * CHAN_MAXF);
 102       const GLchan a = (GLint) (ctx->Color.ClearColor[3] * CHAN_MAXF);
 103       GLint i;
 104       for (i = 0; i < height; i++) {
 105          GLchan rgba[MAX_WIDTH][4];
 106          GLint j;
 107          for (j=0; j<width; j++) {
 108             rgba[j][RCOMP] = r;
 109             rgba[j][GCOMP] = g;
 110             rgba[j][BCOMP] = b;
 111             rgba[j][ACOMP] = a;
 112          }
 113          _mesa_mask_rgba_span( ctx, width, x, y + i, rgba );
 114          (*ctx->Driver.WriteRGBASpan)( ctx, width, x, y + i,
 115                                        (CONST GLchan (*)[4]) rgba, NULL );
 116       }
 117    }
 118    else {
 119       /* Color index mode */
 120       GLuint span[MAX_WIDTH];
 121       GLubyte mask[MAX_WIDTH];
 122       GLint i, j;
 123       MEMSET( mask, 1, width );
 124       for (i=0;i<height;i++) {
 125          for (j=0;j<width;j++) {
 126             span[j] = ctx->Color.ClearIndex;
 127          }
 128          _mesa_mask_index_span( ctx, width, x, y + i, span );
 129          (*ctx->Driver.WriteCI32Span)( ctx, width, x, y + i, span, mask );
 130       }
 131    }
 132 }
 133
 134
 135
 136 /*
 137  * Clear a color buffer without index/channel masking.
 138  */
 139 static void
 140 clear_color_buffer(GLcontext *ctx)
 141 {
 142    const GLint x = ctx->DrawBuffer->Xmin;
 143    const GLint y = ctx->DrawBuffer->Ymin;
 144    const GLint height = ctx->DrawBuffer->Ymax - ctx->DrawBuffer->Ymin;
 145    const GLint width  = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin;
 146    const GLuint colorMask = *((GLuint *) &ctx->Color.ColorMask);
 147
 148    if (ctx->Visual.RGBAflag) {
 149       /* RGBA mode */
 150       const GLchan r = (GLint) (ctx->Color.ClearColor[0] * CHAN_MAXF);
 151       const GLchan g = (GLint) (ctx->Color.ClearColor[1] * CHAN_MAXF);
 152       const GLchan b = (GLint) (ctx->Color.ClearColor[2] * CHAN_MAXF);
 153       const GLchan a = (GLint) (ctx->Color.ClearColor[3] * CHAN_MAXF);
 154       GLchan span[MAX_WIDTH][4];
 155       GLint i;
 156
 157       ASSERT(colorMask == 0xffffffff);
 158
 159       for (i = 0; i < width; i++) {
 160          span[i][RCOMP] = r;
 161          span[i][GCOMP] = g;
 162          span[i][BCOMP] = b;
 163          span[i][ACOMP] = a;
 164       }
 165       for (i = 0; i < height; i++) {
 166          (*ctx->Driver.WriteRGBASpan)( ctx, width, x, y + i,
 167                                        (CONST GLchan (*)[4]) span, NULL );
 168       }
 169    }
 170    else {
 171       /* Color index mode */
 172       ASSERT(ctx->Color.IndexMask == ~0);
 173       if (ctx->Visual.IndexBits == 8) {
 174          /* 8-bit clear */
 175          GLchan span[MAX_WIDTH];
 176          GLint i;
 177          MEMSET(span, ctx->Color.ClearIndex, width);
 178          for (i = 0; i < height; i++) {
 179             (*ctx->Driver.WriteCI8Span)( ctx, width, x, y + i, span, NULL );
 180          }
 181       }
 182       else {
 183          /* non 8-bit clear */
 184          GLuint span[MAX_WIDTH];
 185          GLint i;
 186          for (i = 0; i < width; i++) {
 187             span[i] = ctx->Color.ClearIndex;
 188          }
 189          for (i = 0; i < height; i++) {
 190             (*ctx->Driver.WriteCI32Span)( ctx, width, x, y + i, span, NULL );
 191          }
 192       }
 193    }
 194 }
 195
 196
 197
 198 /*
 199  * Clear the front/back/left/right color buffers.
 200  * This function is usually only called if we need to clear the
 201  * buffers with masking.
 202  */
 203 static void
 204 clear_color_buffers(GLcontext *ctx)
 205 {
 206    const GLuint colorMask = *((GLuint *) &ctx->Color.ColorMask);
 207    GLuint bufferBit;
 208
 209    /* loop over four possible dest color buffers */
 210    for (bufferBit = 1; bufferBit <= 8; bufferBit = bufferBit << 1) {
 211       if (bufferBit & ctx->Color.DrawDestMask) {
 212          if (bufferBit == FRONT_LEFT_BIT) {
 213             (void) (*ctx->Driver.SetDrawBuffer)( ctx, GL_FRONT_LEFT);
 214             (void) (*ctx->Driver.SetReadBuffer)( ctx, ctx->DrawBuffer, GL_FRONT_LEFT);
 215          }
 216          else if (bufferBit == FRONT_RIGHT_BIT) {
 217             (void) (*ctx->Driver.SetDrawBuffer)( ctx, GL_FRONT_RIGHT);
 218             (void) (*ctx->Driver.SetReadBuffer)( ctx, ctx->DrawBuffer, GL_FRONT_RIGHT);
 219          }
 220          else if (bufferBit == BACK_LEFT_BIT) {
 221             (void) (*ctx->Driver.SetDrawBuffer)( ctx, GL_BACK_LEFT);
 222             (void) (*ctx->Driver.SetReadBuffer)( ctx, ctx->DrawBuffer, GL_BACK_LEFT);
 223          }
 224          else {
 225             (void) (*ctx->Driver.SetDrawBuffer)( ctx, GL_BACK_RIGHT);
 226             (void) (*ctx->Driver.SetReadBuffer)( ctx, ctx->DrawBuffer, GL_BACK_RIGHT);
 227          }
 228
 229          if (colorMask != 0xffffffff) {
 230             clear_color_buffer_with_masking(ctx);
 231          }
 232          else {
 233             clear_color_buffer(ctx);
 234          }
 235       }
 236    }
 237
 238    /* restore default read/draw buffers */
 239    (void) (*ctx->Driver.SetDrawBuffer)( ctx, ctx->Color.DriverDrawBuffer );
 240    (void) (*ctx->Driver.SetReadBuffer)( ctx, ctx->ReadBuffer, ctx->Pixel.DriverReadBuffer );
 241 }
 242
 243
 244
 245 void
 246 _mesa_Clear( GLbitfield mask )
 247 {
 248    GET_CURRENT_CONTEXT(ctx);
 249 #ifdef PROFILE
 250    GLdouble t0 = gl_time();
 251 #endif
 252    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glClear");
 253
 254    if (MESA_VERBOSE & VERBOSE_API)
 255       fprintf(stderr, "glClear 0x%x\n", mask);
 256
 257    if (ctx->NewState) {
 258       gl_update_state( ctx );
 259    }
 260
 261    if (ctx->RenderMode==GL_RENDER) {
 262       const GLint x = ctx->DrawBuffer->Xmin;
 263       const GLint y = ctx->DrawBuffer->Ymin;
 264       const GLint height = ctx->DrawBuffer->Ymax - ctx->DrawBuffer->Ymin;
 265       const GLint width  = ctx->DrawBuffer->Xmax - ctx->DrawBuffer->Xmin;
 266       GLbitfield ddMask;
 267       GLbitfield newMask;
 268
 269       /* don't clear depth buffer if depth writing disabled */
 270       if (!ctx->Depth.Mask)
 271          CLEAR_BITS(mask, GL_DEPTH_BUFFER_BIT);
 272
 273       /* Build bitmask to send to driver Clear function */
 274       ddMask = mask & (GL_DEPTH_BUFFER_BIT |
 275                        GL_STENCIL_BUFFER_BIT |
 276                        GL_ACCUM_BUFFER_BIT);
 277       if (mask & GL_COLOR_BUFFER_BIT) {
 278          ddMask |= ctx->Color.DrawDestMask;
 279       }
 280
 281       ASSERT(ctx->Driver.Clear);
 282       newMask = (*ctx->Driver.Clear)( ctx, ddMask, !ctx->Scissor.Enabled,
 283                                       x, y, width, height );
 284
 285 #ifdef DEBUG
 286       {
 287          GLbitfield legalBits = DD_FRONT_LEFT_BIT |
 288                                 DD_FRONT_RIGHT_BIT |
 289                                 DD_BACK_LEFT_BIT |
 290                                 DD_BACK_RIGHT_BIT |
 291                                 DD_DEPTH_BIT |
 292                                 DD_STENCIL_BIT |
 293                                 DD_ACCUM_BIT;
 294          assert((newMask & (~legalBits)) == 0);
 295       }
 296 #endif
 297
 298       RENDER_START(ctx);
 299
 300       /* do software clearing here */
 301       if (newMask) {
 302          if (newMask & ctx->Color.DrawDestMask)   clear_color_buffers(ctx);
 303          if (newMask & GL_DEPTH_BUFFER_BIT)    _mesa_clear_depth_buffer(ctx);
 304          if (newMask & GL_ACCUM_BUFFER_BIT)    _mesa_clear_accum_buffer(ctx);
 305          if (newMask & GL_STENCIL_BUFFER_BIT)  _mesa_clear_stencil_buffer(ctx);
 306       }
 307
 308       /* clear software-based alpha buffer(s) */
 309       if ( (mask & GL_COLOR_BUFFER_BIT)
 310            && ctx->DrawBuffer->UseSoftwareAlphaBuffers
 311            && ctx->Color.ColorMask[ACOMP]) {
 312          _mesa_clear_alpha_buffers( ctx );
 313       }
 314
 315       RENDER_FINISH(ctx);
 316
 317 #ifdef PROFILE
 318       ctx->ClearTime += gl_time() - t0;
 319       ctx->ClearCount++;
 320 #endif
 321    }
 322 }
 323
 324
 325 void
 326 _mesa_DrawBuffer( GLenum mode )
 327 {
 328    GET_CURRENT_CONTEXT(ctx);
 329    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glDrawBuffer");
 330
 331    if (MESA_VERBOSE & VERBOSE_API)
 332       fprintf(stderr, "glDrawBuffer %s\n", gl_lookup_enum_by_nr(mode));
 333
 334    switch (mode) {
 335       case GL_AUX0:
 336       case GL_AUX1:
 337       case GL_AUX2:
 338       case GL_AUX3:
 339          /* AUX buffers not implemented in Mesa at this time */
 340          gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 341          return;
 342       case GL_RIGHT:
 343          if (!ctx->Visual.StereoFlag) {
 344             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 345             return;}
 346          if (ctx->Visual.DBflag)
 347             ctx->Color.DrawDestMask = FRONT_RIGHT_BIT | BACK_RIGHT_BIT;
 348          else
 349             ctx->Color.DrawDestMask = FRONT_RIGHT_BIT;
 350          break;
 351       case GL_FRONT_RIGHT:
 352          if (!ctx->Visual.StereoFlag) {
 353             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 354             return;
 355          }
 356          ctx->Color.DrawDestMask = FRONT_RIGHT_BIT;
 357          break;
 358       case GL_BACK_RIGHT:
 359          if (!ctx->Visual.StereoFlag) {
 360             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 361             return;
 362          }
 363          if (!ctx->Visual.DBflag) {
 364             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 365             return;
 366          }
 367          ctx->Color.DrawDestMask = BACK_RIGHT_BIT;
 368          break;
 369       case GL_BACK_LEFT:
 370          if (!ctx->Visual.DBflag) {
 371             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 372             return;
 373          }
 374          ctx->Color.DrawDestMask = BACK_LEFT_BIT;
 375          break;
 376       case GL_FRONT_AND_BACK:
 377          if (!ctx->Visual.DBflag) {
 378             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 379             return;
 380          }
 381          if (ctx->Visual.StereoFlag)
 382             ctx->Color.DrawDestMask = FRONT_LEFT_BIT | BACK_LEFT_BIT
 383                                     | FRONT_RIGHT_BIT | BACK_RIGHT_BIT;
 384          else
 385             ctx->Color.DrawDestMask = FRONT_LEFT_BIT | BACK_LEFT_BIT;
 386          break;
 387       case GL_BACK:
 388          if (!ctx->Visual.DBflag) {
 389             gl_error( ctx, GL_INVALID_OPERATION, "glDrawBuffer" );
 390             return;
 391          }
 392          if (ctx->Visual.StereoFlag)
 393             ctx->Color.DrawDestMask = BACK_LEFT_BIT | BACK_RIGHT_BIT;
 394          else
 395             ctx->Color.DrawDestMask = BACK_LEFT_BIT;
 396          break;
 397       case GL_LEFT:
 398          /* never an error */
 399          if (ctx->Visual.DBflag)
 400             ctx->Color.DrawDestMask = FRONT_LEFT_BIT | BACK_LEFT_BIT;
 401          else
 402             ctx->Color.DrawDestMask = FRONT_LEFT_BIT;
 403          break;
 404       case GL_FRONT_LEFT:
 405          /* never an error */
 406          ctx->Color.DrawDestMask = FRONT_LEFT_BIT;
 407          break;
 408       case GL_FRONT:
 409          /* never an error */
 410          if (ctx->Visual.StereoFlag)
 411             ctx->Color.DrawDestMask = FRONT_LEFT_BIT | FRONT_RIGHT_BIT;
 412          else
 413             ctx->Color.DrawDestMask = FRONT_LEFT_BIT;
 414          break;
 415       case GL_NONE:
 416          /* never an error */
 417          ctx->Color.DrawDestMask = 0;
 418          break;
 419       default:
 420          gl_error( ctx, GL_INVALID_ENUM, "glDrawBuffer" );
 421          return;
 422    }
 423
 424    /*
 425     * Make the dest buffer mode more precise if possible
 426     */
 427    if (mode == GL_LEFT && !ctx->Visual.DBflag)
 428       ctx->Color.DriverDrawBuffer = GL_FRONT_LEFT;
 429    else if (mode == GL_RIGHT && !ctx->Visual.DBflag)
 430       ctx->Color.DriverDrawBuffer = GL_FRONT_RIGHT;
 431    else if (mode == GL_FRONT && !ctx->Visual.StereoFlag)
 432       ctx->Color.DriverDrawBuffer = GL_FRONT_LEFT;
 433    else if (mode == GL_BACK && !ctx->Visual.StereoFlag)
 434       ctx->Color.DriverDrawBuffer = GL_BACK_LEFT;
 435    else
 436       ctx->Color.DriverDrawBuffer = mode;
 437
 438    /*
 439     * Set current alpha buffer pointer
 440     */
 441    if (ctx->DrawBuffer->UseSoftwareAlphaBuffers) {
 442       if (ctx->Color.DriverDrawBuffer == GL_FRONT_LEFT)
 443          ctx->DrawBuffer->Alpha = ctx->DrawBuffer->FrontLeftAlpha;
 444       else if (ctx->Color.DriverDrawBuffer == GL_BACK_LEFT)
 445          ctx->DrawBuffer->Alpha = ctx->DrawBuffer->BackLeftAlpha;
 446       else if (ctx->Color.DriverDrawBuffer == GL_FRONT_RIGHT)
 447          ctx->DrawBuffer->Alpha = ctx->DrawBuffer->FrontRightAlpha;
 448       else if (ctx->Color.DriverDrawBuffer == GL_BACK_RIGHT)
 449          ctx->DrawBuffer->Alpha = ctx->DrawBuffer->BackRightAlpha;
 450    }
 451
 452    /*
 453     * If we get here there can't have been an error.
 454     * Now see if device driver can implement the drawing to the target
 455     * buffer(s).  The driver may not be able to do GL_FRONT_AND_BACK mode
 456     * for example.  We'll take care of that in the core code by looping
 457     * over the individual buffers.
 458     */
 459    ASSERT(ctx->Driver.SetDrawBuffer);
 460    if ( (*ctx->Driver.SetDrawBuffer)(ctx, ctx->Color.DriverDrawBuffer) ) {
 461       /* All OK, the driver will do all buffer writes */
 462       ctx->Color.MultiDrawBuffer = GL_FALSE;
 463    }
 464    else {
 465       /* We'll have to loop over the multiple draw buffer targets */
 466       ctx->Color.MultiDrawBuffer = GL_TRUE;
 467       /* Set drawing buffer to front for now */
 468       (void) (*ctx->Driver.SetDrawBuffer)(ctx, GL_FRONT_LEFT);
 469    }
 470
 471    ctx->Color.DrawBuffer = mode;
 472    ctx->NewState |= NEW_RASTER_OPS;
 473 }
 474
 475
 476
 477 void
 478 _mesa_ReadBuffer( GLenum mode )
 479 {
 480    GET_CURRENT_CONTEXT(ctx);
 481    ASSERT_OUTSIDE_BEGIN_END_AND_FLUSH(ctx, "glReadBuffer");
 482
 483    if (MESA_VERBOSE & VERBOSE_API)
 484       fprintf(stderr, "glReadBuffer %s\n", gl_lookup_enum_by_nr(mode));
 485
 486    switch (mode) {
 487       case GL_AUX0:
 488       case GL_AUX1:
 489       case GL_AUX2:
 490       case GL_AUX3:
 491          /* AUX buffers not implemented in Mesa at this time */
 492          gl_error( ctx, GL_INVALID_OPERATION, "glReadBuffer" );
 493          return;
 494       case GL_LEFT:
 495       case GL_FRONT:
 496       case GL_FRONT_LEFT:
 497          /* Front-Left buffer, always exists */
 498          ctx->Pixel.DriverReadBuffer = GL_FRONT_LEFT;
 499          break;
 500       case GL_BACK:
 501       case GL_BACK_LEFT:
 502          /* Back-Left buffer, requires double buffering */
 503          if (!ctx->Visual.DBflag) {
 504             gl_error( ctx, GL_INVALID_OPERATION, "glReadBuffer" );
 505             return;
 506          }
 507          ctx->Pixel.DriverReadBuffer = GL_BACK_LEFT;
 508          break;
 509       case GL_FRONT_RIGHT:
 510       case GL_RIGHT:
 511          if (!ctx->Visual.StereoFlag) {
 512             gl_error( ctx, GL_INVALID_OPERATION, "glReadBuffer" );
 513             return;
 514          }
 515          ctx->Pixel.DriverReadBuffer = GL_FRONT_RIGHT;
 516          break;
 517       case GL_BACK_RIGHT:
 518          if (!ctx->Visual.StereoFlag || !ctx->Visual.DBflag) {
 519             gl_error( ctx, GL_INVALID_OPERATION, "glReadBuffer" );
 520             return;
 521          }
 522          ctx->Pixel.DriverReadBuffer = GL_BACK_RIGHT;
 523          break;
 524       default:
 525          gl_error( ctx, GL_INVALID_ENUM, "glReadBuffer" );
 526          return;
 527    }
 528
 529    ctx->Pixel.ReadBuffer = mode;
 530    ctx->NewState |= NEW_RASTER_OPS;
 531 }
 532
 533
 534 /*
 535  * GL_MESA_resize_buffers extension
 536  */
 537 void
 538 _mesa_ResizeBuffersMESA( void )
 539 {
 540    GLcontext *ctx = _mesa_get_current_context();
 541
 542    GLuint buf_width, buf_height;
 543
 544    if (MESA_VERBOSE & VERBOSE_API)
 545       fprintf(stderr, "glResizeBuffersMESA\n");
 546
 547    /* ask device driver for size of output buffer */
 548    (*ctx->Driver.GetBufferSize)( ctx, &buf_width, &buf_height );
 549
 550    /* see if size of device driver's color buffer (window) has changed */
 551    if (ctx->DrawBuffer->Width == (GLint) buf_width &&
 552        ctx->DrawBuffer->Height == (GLint) buf_height)
 553       return;
 554
 555    ctx->NewState |= NEW_RASTER_OPS;  /* to update scissor / window bounds */
 556
 557    /* save buffer size */
 558    ctx->DrawBuffer->Width = buf_width;
 559    ctx->DrawBuffer->Height = buf_height;
 560
 561    /* Reallocate other buffers if needed. */
 562    if (ctx->DrawBuffer->UseSoftwareDepthBuffer) {
 563       _mesa_alloc_depth_buffer( ctx );
 564    }
 565    if (ctx->DrawBuffer->UseSoftwareStencilBuffer) {
 566       _mesa_alloc_stencil_buffer( ctx );
 567    }
 568    if (ctx->DrawBuffer->UseSoftwareAccumBuffer) {
 569       _mesa_alloc_accum_buffer( ctx );
 570    }
 571    if (ctx->DrawBuffer->UseSoftwareAlphaBuffers) {
 572       _mesa_alloc_alpha_buffers( ctx );
 573    }
 574 }