src/mesa/state_tracker/st_cb_fbo.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
  22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
  23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27
  28
  29 /**
  30  * Framebuffer/renderbuffer functions.
  31  *
  32  * \author Brian Paul
  33  */
  34
  35
  36 #include "main/imports.h"
  37 #include "main/context.h"
  38 #include "main/fbobject.h"
  39 #include "main/framebuffer.h"
  40 #include "main/renderbuffer.h"
  41
  42 #include "pipe/p_context.h"
  43 #include "pipe/p_defines.h"
  44 #include "pipe/p_screen.h"
  45 #include "st_context.h"
  46 #include "st_cb_fbo.h"
  47 #include "st_cb_texture.h"
  48 #include "st_format.h"
  49 #include "st_public.h"
  50 #include "st_texture.h"
  51
  52 #include "util/u_format.h"
  53 #include "util/u_rect.h"
  54
  55
  56 /**
  57  * Compute the renderbuffer's Red/Green/EtcBit fields from the pipe format.
  58  */
  59 static int
  60 init_renderbuffer_bits(struct st_renderbuffer *strb,
  61                        enum pipe_format pipeFormat)
  62 {
  63    struct pipe_format_info info;
  64
  65    if (!st_get_format_info( pipeFormat, &info )) {
  66       assert( 0 );
  67    }
  68
  69    strb->Base.Format = info.mesa_format;
  70    strb->Base.DataType = st_format_datatype(pipeFormat);
  71
  72    return info.size;
  73 }
  74
  75 /**
  76  * gl_renderbuffer::AllocStorage()
  77  * This is called to allocate the original drawing surface, and
  78  * during window resize.
  79  */
  80 static GLboolean
  81 st_renderbuffer_alloc_storage(GLcontext * ctx, struct gl_renderbuffer *rb,
  82                               GLenum internalFormat,
  83                               GLuint width, GLuint height)
  84 {
  85    struct pipe_context *pipe = ctx->st->pipe;
  86    struct st_renderbuffer *strb = st_renderbuffer(rb);
  87    enum pipe_format format;
  88
  89    if (strb->format != PIPE_FORMAT_NONE)
  90       format = strb->format;
  91    else
  92       format = st_choose_renderbuffer_format(pipe->screen, internalFormat);
  93
  94    /* init renderbuffer fields */
  95    strb->Base.Width  = width;
  96    strb->Base.Height = height;
  97    init_renderbuffer_bits(strb, format);
  98
  99    strb->defined = GL_FALSE;  /* undefined contents now */
 100
 101    if(strb->software) {
 102       size_t size;
 103
 104       _mesa_free(strb->data);
 105
 106       assert(strb->format != PIPE_FORMAT_NONE);
 107
 108       strb->stride = util_format_get_stride(strb->format, width);
 109       size = util_format_get_2d_size(strb->format, strb->stride, height);
 110
 111       strb->data = _mesa_malloc(size);
 112
 113       return strb->data != NULL;
 114    }
 115    else {
 116       struct pipe_texture template;
 117       unsigned surface_usage;
 118
 119       /* Free the old surface and texture
 120        */
 121       pipe_surface_reference( &strb->surface, NULL );
 122       pipe_texture_reference( &strb->texture, NULL );
 123
 124       /* Setup new texture template.
 125        */
 126       memset(&template, 0, sizeof(template));
 127       template.target = PIPE_TEXTURE_2D;
 128       template.format = format;
 129       template.width0 = width;
 130       template.height0 = height;
 131       template.depth0 = 1;
 132       template.last_level = 0;
 133       template.nr_samples = rb->NumSamples;
 134       if (util_format_is_depth_or_stencil(format)) {
 135          template.tex_usage = PIPE_TEXTURE_USAGE_DEPTH_STENCIL;
 136       }
 137       else {
 138          template.tex_usage = (PIPE_TEXTURE_USAGE_DISPLAY_TARGET |
 139                                PIPE_TEXTURE_USAGE_RENDER_TARGET);
 140       }
 141
 142       /* Probably need dedicated flags for surface usage too:
 143        */
 144       surface_usage = (PIPE_BUFFER_USAGE_GPU_READ |
 145                        PIPE_BUFFER_USAGE_GPU_WRITE);
 146 #if 0
 147                        PIPE_BUFFER_USAGE_CPU_READ |
 148                        PIPE_BUFFER_USAGE_CPU_WRITE);
 149 #endif
 150
 151       strb->texture = pipe->screen->texture_create( pipe->screen,
 152                                                     &template );
 153
 154       if (!strb->texture)
 155          return FALSE;
 156
 157       strb->surface = pipe->screen->get_tex_surface( pipe->screen,
 158                                                      strb->texture,
 159                                                      0, 0, 0,
 160                                                      surface_usage );
 161       if (strb->surface) {
 162          assert(strb->surface->texture);
 163          assert(strb->surface->format);
 164          assert(strb->surface->width == width);
 165          assert(strb->surface->height == height);
 166       }
 167
 168       return strb->surface != NULL;
 169    }
 170 }
 171
 172
 173 /**
 174  * gl_renderbuffer::Delete()
 175  */
 176 static void
 177 st_renderbuffer_delete(struct gl_renderbuffer *rb)
 178 {
 179    struct st_renderbuffer *strb = st_renderbuffer(rb);
 180    ASSERT(strb);
 181    pipe_surface_reference(&strb->surface, NULL);
 182    pipe_texture_reference(&strb->texture, NULL);
 183    _mesa_free(strb->data);
 184    _mesa_free(strb);
 185 }
 186
 187
 188 /**
 189  * gl_renderbuffer::GetPointer()
 190  */
 191 static void *
 192 null_get_pointer(GLcontext * ctx, struct gl_renderbuffer *rb,
 193                  GLint x, GLint y)
 194 {
 195    /* By returning NULL we force all software rendering to go through
 196     * the span routines.
 197     */
 198 #if 0
 199    assert(0);  /* Should never get called with softpipe */
 200 #endif
 201    return NULL;
 202 }
 203
 204
 205 /**
 206  * Called via ctx->Driver.NewFramebuffer()
 207  */
 208 static struct gl_framebuffer *
 209 st_new_framebuffer(GLcontext *ctx, GLuint name)
 210 {
 211    /* XXX not sure we need to subclass gl_framebuffer for pipe */
 212    return _mesa_new_framebuffer(ctx, name);
 213 }
 214
 215
 216 /**
 217  * Called via ctx->Driver.NewRenderbuffer()
 218  */
 219 static struct gl_renderbuffer *
 220 st_new_renderbuffer(GLcontext *ctx, GLuint name)
 221 {
 222    struct st_renderbuffer *strb = ST_CALLOC_STRUCT(st_renderbuffer);
 223    if (strb) {
 224       _mesa_init_renderbuffer(&strb->Base, name);
 225       strb->Base.Delete = st_renderbuffer_delete;
 226       strb->Base.AllocStorage = st_renderbuffer_alloc_storage;
 227       strb->Base.GetPointer = null_get_pointer;
 228       strb->format = PIPE_FORMAT_NONE;
 229       return &strb->Base;
 230    }
 231    return NULL;
 232 }
 233
 234
 235 /**
 236  * Allocate a renderbuffer for a an on-screen window (not a user-created
 237  * renderbuffer).  The window system code determines the format.
 238  */
 239 struct gl_renderbuffer *
 240 st_new_renderbuffer_fb(enum pipe_format format, int samples, boolean sw)
 241 {
 242    struct st_renderbuffer *strb;
 243
 244    strb = ST_CALLOC_STRUCT(st_renderbuffer);
 245    if (!strb) {
 246       _mesa_error(NULL, GL_OUT_OF_MEMORY, "creating renderbuffer");
 247       return NULL;
 248    }
 249
 250    _mesa_init_renderbuffer(&strb->Base, 0);
 251    strb->Base.ClassID = 0x4242; /* just a unique value */
 252    strb->Base.NumSamples = samples;
 253    strb->format = format;
 254    init_renderbuffer_bits(strb, format);
 255    strb->software = sw;
 256
 257    switch (format) {
 258    case PIPE_FORMAT_A8R8G8B8_UNORM:
 259    case PIPE_FORMAT_B8G8R8A8_UNORM:
 260    case PIPE_FORMAT_X8R8G8B8_UNORM:
 261    case PIPE_FORMAT_B8G8R8X8_UNORM:
 262    case PIPE_FORMAT_A1R5G5B5_UNORM:
 263    case PIPE_FORMAT_A4R4G4B4_UNORM:
 264    case PIPE_FORMAT_R5G6B5_UNORM:
 265       strb->Base.InternalFormat = GL_RGBA;
 266       break;
 267    case PIPE_FORMAT_Z16_UNORM:
 268       strb->Base.InternalFormat = GL_DEPTH_COMPONENT16;
 269       break;
 270    case PIPE_FORMAT_Z32_UNORM:
 271       strb->Base.InternalFormat = GL_DEPTH_COMPONENT32;
 272       break;
 273    case PIPE_FORMAT_S8Z24_UNORM:
 274    case PIPE_FORMAT_Z24S8_UNORM:
 275    case PIPE_FORMAT_X8Z24_UNORM:
 276    case PIPE_FORMAT_Z24X8_UNORM:
 277       strb->Base.InternalFormat = GL_DEPTH24_STENCIL8_EXT;
 278       break;
 279    case PIPE_FORMAT_S8_UNORM:
 280       strb->Base.InternalFormat = GL_STENCIL_INDEX8_EXT;
 281       break;
 282    case PIPE_FORMAT_R16G16B16A16_SNORM:
 283       strb->Base.InternalFormat = GL_RGBA16;
 284       break;
 285    default:
 286       _mesa_problem(NULL,
 287                     "Unexpected format in st_new_renderbuffer_fb");
 288       _mesa_free(strb);
 289       return NULL;
 290    }
 291
 292    /* st-specific methods */
 293    strb->Base.Delete = st_renderbuffer_delete;
 294    strb->Base.AllocStorage = st_renderbuffer_alloc_storage;
 295    strb->Base.GetPointer = null_get_pointer;
 296
 297    /* surface is allocated in st_renderbuffer_alloc_storage() */
 298    strb->surface = NULL;
 299
 300    return &strb->Base;
 301 }
 302
 303
 304
 305
 306 /**
 307  * Called via ctx->Driver.BindFramebufferEXT().
 308  */
 309 static void
 310 st_bind_framebuffer(GLcontext *ctx, GLenum target,
 311                     struct gl_framebuffer *fb, struct gl_framebuffer *fbread)
 312 {
 313
 314 }
 315
 316 /**
 317  * Called by ctx->Driver.FramebufferRenderbuffer
 318  */
 319 static void
 320 st_framebuffer_renderbuffer(GLcontext *ctx,
 321                             struct gl_framebuffer *fb,
 322                             GLenum attachment,
 323                             struct gl_renderbuffer *rb)
 324 {
 325    /* XXX no need for derivation? */
 326    _mesa_framebuffer_renderbuffer(ctx, fb, attachment, rb);
 327 }
 328
 329
 330 /**
 331  * Called by ctx->Driver.RenderTexture
 332  */
 333 static void
 334 st_render_texture(GLcontext *ctx,
 335                   struct gl_framebuffer *fb,
 336                   struct gl_renderbuffer_attachment *att)
 337 {
 338    struct pipe_screen *screen = ctx->st->pipe->screen;
 339    struct st_renderbuffer *strb;
 340    struct gl_renderbuffer *rb;
 341    struct pipe_texture *pt = st_get_texobj_texture(att->Texture);
 342    struct st_texture_object *stObj;
 343    const struct gl_texture_image *texImage =
 344       att->Texture->Image[att->CubeMapFace][att->TextureLevel];
 345
 346    if (!pt)
 347       return;
 348
 349    /* create new renderbuffer which wraps the texture image */
 350    rb = st_new_renderbuffer(ctx, 0);
 351    if (!rb) {
 352       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glFramebufferTexture()");
 353       return;
 354    }
 355
 356    _mesa_reference_renderbuffer(&att->Renderbuffer, rb);
 357    assert(rb->RefCount == 1);
 358    rb->AllocStorage = NULL; /* should not get called */
 359    strb = st_renderbuffer(rb);
 360
 361    assert(strb->Base.RefCount > 0);
 362
 363    /* get the texture for the texture object */
 364    stObj = st_texture_object(att->Texture);
 365
 366    /* point renderbuffer at texobject */
 367    strb->rtt = stObj;
 368    strb->rtt_level = att->TextureLevel;
 369    strb->rtt_face = att->CubeMapFace;
 370    strb->rtt_slice = att->Zoffset;
 371
 372    rb->Width = texImage->Width2;
 373    rb->Height = texImage->Height2;
 374    rb->_BaseFormat = texImage->_BaseFormat;
 375    /*printf("***** render to texture level %d: %d x %d\n", att->TextureLevel, rb->Width, rb->Height);*/
 376
 377    /*printf("***** pipe texture %d x %d\n", pt->width0, pt->height0);*/
 378
 379    pipe_texture_reference( &strb->texture, pt );
 380
 381    pipe_surface_reference(&strb->surface, NULL);
 382
 383    /* new surface for rendering into the texture */
 384    strb->surface = screen->get_tex_surface(screen,
 385                                            strb->texture,
 386                                            strb->rtt_face,
 387                                            strb->rtt_level,
 388                                            strb->rtt_slice,
 389                                            PIPE_BUFFER_USAGE_GPU_READ |
 390                                            PIPE_BUFFER_USAGE_GPU_WRITE);
 391
 392    init_renderbuffer_bits(strb, pt->format);
 393
 394    /*
 395    printf("RENDER TO TEXTURE obj=%p pt=%p surf=%p  %d x %d\n",
 396           att->Texture, pt, strb->surface, rb->Width, rb->Height);
 397    */
 398
 399    /* Invalidate buffer state so that the pipe's framebuffer state
 400     * gets updated.
 401     * That's where the new renderbuffer (which we just created) gets
 402     * passed to the pipe as a (color/depth) render target.
 403     */
 404    st_invalidate_state(ctx, _NEW_BUFFERS);
 405 }
 406
 407
 408 /**
 409  * Called via ctx->Driver.FinishRenderTexture.
 410  */
 411 static void
 412 st_finish_render_texture(GLcontext *ctx,
 413                          struct gl_renderbuffer_attachment *att)
 414 {
 415    struct st_renderbuffer *strb = st_renderbuffer(att->Renderbuffer);
 416
 417    if (!strb)
 418       return;
 419
 420    st_flush( ctx->st, PIPE_FLUSH_RENDER_CACHE, NULL );
 421
 422    if (strb->surface)
 423       pipe_surface_reference( &strb->surface, NULL );
 424
 425    strb->rtt = NULL;
 426
 427    /*
 428    printf("FINISH RENDER TO TEXTURE surf=%p\n", strb->surface);
 429    */
 430
 431    _mesa_reference_renderbuffer(&att->Renderbuffer, NULL);
 432
 433    /* restore previous framebuffer state */
 434    st_invalidate_state(ctx, _NEW_BUFFERS);
 435 }
 436
 437
 438 /**
 439  * Validate a renderbuffer attachment for a particular usage.
 440  */
 441
 442 static GLboolean
 443 st_validate_attachment(struct pipe_screen *screen,
 444                        const struct gl_renderbuffer_attachment *att,
 445                        GLuint usage)
 446 {
 447    const struct st_texture_object *stObj =
 448       st_texture_object(att->Texture);
 449
 450    /**
 451     * Only validate texture attachments for now, since
 452     * st_renderbuffer_alloc_storage makes sure that
 453     * the format is supported.
 454     */
 455
 456    if (att->Type != GL_TEXTURE)
 457       return GL_TRUE;
 458
 459    if (!stObj)
 460       return GL_FALSE;
 461
 462    return screen->is_format_supported(screen, stObj->pt->format,
 463                                       PIPE_TEXTURE_2D,
 464                                       usage, 0);
 465 }
 466
 467 /**
 468  * Check that the framebuffer configuration is valid in terms of what
 469  * the driver can support.
 470  *
 471  * For Gallium we only supports combined Z+stencil, not separate buffers.
 472  */
 473 static void
 474 st_validate_framebuffer(GLcontext *ctx, struct gl_framebuffer *fb)
 475 {
 476    struct pipe_screen *screen = ctx->st->pipe->screen;
 477    const struct gl_renderbuffer *depthRb =
 478       fb->Attachment[BUFFER_DEPTH].Renderbuffer;
 479    const struct gl_renderbuffer *stencilRb =
 480       fb->Attachment[BUFFER_STENCIL].Renderbuffer;
 481    GLuint i;
 482
 483    if (stencilRb && depthRb && stencilRb != depthRb) {
 484       fb->_Status = GL_FRAMEBUFFER_UNSUPPORTED_EXT;
 485       return;
 486    }
 487
 488    if (!st_validate_attachment(screen,
 489                                &fb->Attachment[BUFFER_DEPTH],
 490                                PIPE_TEXTURE_USAGE_DEPTH_STENCIL)) {
 491       fb->_Status = GL_FRAMEBUFFER_UNSUPPORTED_EXT;
 492       return;
 493    }
 494    if (!st_validate_attachment(screen,
 495                                &fb->Attachment[BUFFER_STENCIL],
 496                                PIPE_TEXTURE_USAGE_DEPTH_STENCIL)) {
 497       fb->_Status = GL_FRAMEBUFFER_UNSUPPORTED_EXT;
 498       return;
 499    }
 500    for (i = 0; i < ctx->Const.MaxColorAttachments; i++) {
 501       if (!st_validate_attachment(screen,
 502                                   &fb->Attachment[BUFFER_COLOR0 + i],
 503                                   PIPE_TEXTURE_USAGE_RENDER_TARGET)) {
 504          fb->_Status = GL_FRAMEBUFFER_UNSUPPORTED_EXT;
 505          return;
 506       }
 507    }
 508 }
 509
 510
 511 /**
 512  * Copy back color buffer to front color buffer.
 513  */
 514 static void
 515 copy_back_to_front(struct st_context *st,
 516                    struct gl_framebuffer *fb,
 517                    gl_buffer_index frontIndex,
 518                    gl_buffer_index backIndex)
 519
 520 {
 521    struct st_framebuffer *stfb = (struct st_framebuffer *) fb;
 522    struct pipe_surface *surf_front, *surf_back;
 523
 524    (void) st_get_framebuffer_surface(stfb, frontIndex, &surf_front);
 525    (void) st_get_framebuffer_surface(stfb, backIndex, &surf_back);
 526
 527    if (surf_front && surf_back) {
 528       if (st->pipe->surface_copy) {
 529          st->pipe->surface_copy(st->pipe,
 530                                 surf_front, 0, 0,  /* dest */
 531                                 surf_back, 0, 0,   /* src */
 532                                 fb->Width, fb->Height);
 533       } else {
 534          util_surface_copy(st->pipe, FALSE,
 535                            surf_front, 0, 0,
 536                            surf_back, 0, 0,
 537                            fb->Width, fb->Height);
 538       }
 539    }
 540 }
 541
 542
 543 /**
 544  * Check if we're drawing into, or read from, a front color buffer.  If the
 545  * front buffer is missing, create it now.
 546  *
 547  * The back color buffer must exist since we'll use its format/samples info
 548  * for creating the front buffer.
 549  *
 550  * \param frontIndex  either BUFFER_FRONT_LEFT or BUFFER_FRONT_RIGHT
 551  * \param backIndex  either BUFFER_BACK_LEFT or BUFFER_BACK_RIGHT
 552  */
 553 static void
 554 check_create_front_buffer(GLcontext *ctx, struct gl_framebuffer *fb,
 555                           gl_buffer_index frontIndex,
 556                           gl_buffer_index backIndex)
 557 {
 558    if (fb->Attachment[frontIndex].Renderbuffer == NULL) {
 559       GLboolean create = GL_FALSE;
 560
 561       /* check if drawing to or reading from front buffer */
 562       if (fb->_ColorReadBufferIndex == frontIndex) {
 563          create = GL_TRUE;
 564       }
 565       else {
 566          GLuint b;
 567          for (b = 0; b < fb->_NumColorDrawBuffers; b++) {
 568             if (fb->_ColorDrawBufferIndexes[b] == frontIndex) {
 569                create = GL_TRUE;
 570                break;
 571             }
 572          }
 573       }
 574
 575       if (create) {
 576          struct st_renderbuffer *back;
 577          struct gl_renderbuffer *front;
 578          enum pipe_format colorFormat;
 579          uint samples;
 580
 581          if (0)
 582             _mesa_debug(ctx, "Allocate new front buffer\n");
 583
 584          /* get back renderbuffer info */
 585          back = st_renderbuffer(fb->Attachment[backIndex].Renderbuffer);
 586          colorFormat = back->format;
 587          samples = back->Base.NumSamples;
 588
 589          /* create front renderbuffer */
 590          front = st_new_renderbuffer_fb(colorFormat, samples, FALSE);
 591          _mesa_add_renderbuffer(fb, frontIndex, front);
 592
 593          /* alloc texture/surface for new front buffer */
 594          front->AllocStorage(ctx, front, front->InternalFormat,
 595                              fb->Width, fb->Height);
 596
 597          /* initialize the front color buffer contents by copying
 598           * the back buffer.
 599           */
 600          copy_back_to_front(ctx->st, fb, frontIndex, backIndex);
 601       }
 602    }
 603 }
 604
 605
 606 /**
 607  * If front left/right color buffers are missing, create them now.
 608  */
 609 static void
 610 check_create_front_buffers(GLcontext *ctx, struct gl_framebuffer *fb)
 611 {
 612    /* check if we need to create the front left buffer now */
 613    check_create_front_buffer(ctx, fb, BUFFER_FRONT_LEFT, BUFFER_BACK_LEFT);
 614
 615    if (fb->Visual.stereoMode) {
 616       check_create_front_buffer(ctx, fb, BUFFER_FRONT_RIGHT, BUFFER_BACK_RIGHT);
 617    }
 618
 619    st_invalidate_state(ctx, _NEW_BUFFERS);
 620 }
 621
 622
 623 /**
 624  * Called via glDrawBuffer.
 625  */
 626 static void
 627 st_DrawBuffers(GLcontext *ctx, GLsizei count, const GLenum *buffers)
 628 {
 629    (void) count;
 630    (void) buffers;
 631    check_create_front_buffers(ctx, ctx->DrawBuffer);
 632 }
 633
 634
 635 /**
 636  * Called via glReadBuffer.
 637  */
 638 static void
 639 st_ReadBuffer(GLcontext *ctx, GLenum buffer)
 640 {
 641    (void) buffer;
 642    check_create_front_buffers(ctx, ctx->ReadBuffer);
 643 }
 644
 645
 646 void st_init_fbo_functions(struct dd_function_table *functions)
 647 {
 648    functions->NewFramebuffer = st_new_framebuffer;
 649    functions->NewRenderbuffer = st_new_renderbuffer;
 650    functions->BindFramebuffer = st_bind_framebuffer;
 651    functions->FramebufferRenderbuffer = st_framebuffer_renderbuffer;
 652    functions->RenderTexture = st_render_texture;
 653    functions->FinishRenderTexture = st_finish_render_texture;
 654    functions->ValidateFramebuffer = st_validate_framebuffer;
 655    /* no longer needed by core Mesa, drivers handle resizes...
 656    functions->ResizeBuffers = st_resize_buffers;
 657    */
 658
 659    functions->DrawBuffers = st_DrawBuffers;
 660    functions->ReadBuffer = st_ReadBuffer;
 661 }