src/mesa/swrast/s_blit.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5
   4  *
   5  * Copyright (C) 1999-2006  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 #include "main/glheader.h"
  27 #include "main/condrender.h"
  28 #include "main/image.h"
  29 #include "main/macros.h"
  30 #include "s_context.h"
  31
  32
  33 #define ABS(X)   ((X) < 0 ? -(X) : (X))
  34
  35
  36 /**
  37  * Generate a row resampler function for GL_NEAREST mode.
  38  */
  39 #define RESAMPLE(NAME, PIXELTYPE, SIZE)                 \
  40 static void                                             \
  41 NAME(GLint srcWidth, GLint dstWidth,                    \
  42      const GLvoid *srcBuffer, GLvoid *dstBuffer,        \
  43      GLboolean flip)                                    \
  44 {                                                       \
  45    const PIXELTYPE *src = (const PIXELTYPE *) srcBuffer;\
  46    PIXELTYPE *dst = (PIXELTYPE *) dstBuffer;            \
  47    GLint dstCol;                                        \
  48                                                         \
  49    if (flip) {                                          \
  50       for (dstCol = 0; dstCol < dstWidth; dstCol++) {   \
  51          GLint srcCol = (dstCol * srcWidth) / dstWidth; \
  52          ASSERT(srcCol >= 0);                           \
  53          ASSERT(srcCol < srcWidth);                     \
  54          srcCol = srcWidth - 1 - srcCol; /* flip */     \
  55          if (SIZE == 1) {                               \
  56             dst[dstCol] = src[srcCol];                  \
  57          }                                              \
  58          else if (SIZE == 2) {                          \
  59             dst[dstCol*2+0] = src[srcCol*2+0];          \
  60             dst[dstCol*2+1] = src[srcCol*2+1];          \
  61          }                                              \
  62          else if (SIZE == 4) {                          \
  63             dst[dstCol*4+0] = src[srcCol*4+0];          \
  64             dst[dstCol*4+1] = src[srcCol*4+1];          \
  65             dst[dstCol*4+2] = src[srcCol*4+2];          \
  66             dst[dstCol*4+3] = src[srcCol*4+3];          \
  67          }                                              \
  68       }                                                 \
  69    }                                                    \
  70    else {                                               \
  71       for (dstCol = 0; dstCol < dstWidth; dstCol++) {   \
  72          GLint srcCol = (dstCol * srcWidth) / dstWidth; \
  73          ASSERT(srcCol >= 0);                           \
  74          ASSERT(srcCol < srcWidth);                     \
  75          if (SIZE == 1) {                               \
  76             dst[dstCol] = src[srcCol];                  \
  77          }                                              \
  78          else if (SIZE == 2) {                          \
  79             dst[dstCol*2+0] = src[srcCol*2+0];          \
  80             dst[dstCol*2+1] = src[srcCol*2+1];          \
  81          }                                              \
  82          else if (SIZE == 4) {                          \
  83             dst[dstCol*4+0] = src[srcCol*4+0];          \
  84             dst[dstCol*4+1] = src[srcCol*4+1];          \
  85             dst[dstCol*4+2] = src[srcCol*4+2];          \
  86             dst[dstCol*4+3] = src[srcCol*4+3];          \
  87          }                                              \
  88       }                                                 \
  89    }                                                    \
  90 }
  91
  92 /**
  93  * Resamplers for 1, 2, 4, 8 and 16-byte pixels.
  94  */
  95 RESAMPLE(resample_row_1, GLubyte, 1)
  96 RESAMPLE(resample_row_2, GLushort, 1)
  97 RESAMPLE(resample_row_4, GLuint, 1)
  98 RESAMPLE(resample_row_8, GLuint, 2)
  99 RESAMPLE(resample_row_16, GLuint, 4)
 100
 101
 102 /**
 103  * Blit color, depth or stencil with GL_NEAREST filtering.
 104  */
 105 static void
 106 blit_nearest(GLcontext *ctx,
 107              GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
 108              GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
 109              GLbitfield buffer)
 110 {
 111    struct gl_renderbuffer *readRb, *drawRb;
 112
 113    const GLint srcWidth = ABS(srcX1 - srcX0);
 114    const GLint dstWidth = ABS(dstX1 - dstX0);
 115    const GLint srcHeight = ABS(srcY1 - srcY0);
 116    const GLint dstHeight = ABS(dstY1 - dstY0);
 117
 118    const GLint srcXpos = MIN2(srcX0, srcX1);
 119    const GLint srcYpos = MIN2(srcY0, srcY1);
 120    const GLint dstXpos = MIN2(dstX0, dstX1);
 121    const GLint dstYpos = MIN2(dstY0, dstY1);
 122
 123    const GLboolean invertX = (srcX1 < srcX0) ^ (dstX1 < dstX0);
 124    const GLboolean invertY = (srcY1 < srcY0) ^ (dstY1 < dstY0);
 125
 126    GLint dstRow;
 127
 128    GLint comps, pixelSize;
 129    GLvoid *srcBuffer, *dstBuffer;
 130    GLint prevY = -1;
 131
 132    typedef void (*resample_func)(GLint srcWidth, GLint dstWidth,
 133                                  const GLvoid *srcBuffer, GLvoid *dstBuffer,
 134                                  GLboolean flip);
 135    resample_func resampleRow;
 136
 137    switch (buffer) {
 138    case GL_COLOR_BUFFER_BIT:
 139       readRb = ctx->ReadBuffer->_ColorReadBuffer;
 140       drawRb = ctx->DrawBuffer->_ColorDrawBuffers[0];
 141       comps = 4;
 142       break;
 143    case GL_DEPTH_BUFFER_BIT:
 144       readRb = ctx->ReadBuffer->_DepthBuffer;
 145       drawRb = ctx->DrawBuffer->_DepthBuffer;
 146       comps = 1;
 147       break;
 148    case GL_STENCIL_BUFFER_BIT:
 149       readRb = ctx->ReadBuffer->_StencilBuffer;
 150       drawRb = ctx->DrawBuffer->_StencilBuffer;
 151       comps = 1;
 152       break;
 153    default:
 154       _mesa_problem(ctx, "unexpected buffer in blit_nearest()");
 155       return;
 156    }
 157
 158    switch (readRb->DataType) {
 159    case GL_UNSIGNED_BYTE:
 160       pixelSize = comps * sizeof(GLubyte);
 161       break;
 162    case GL_UNSIGNED_SHORT:
 163       pixelSize = comps * sizeof(GLushort);
 164       break;
 165    case GL_UNSIGNED_INT:
 166       pixelSize = comps * sizeof(GLuint);
 167       break;
 168    case GL_FLOAT:
 169       pixelSize = comps * sizeof(GLfloat);
 170       break;
 171    default:
 172       _mesa_problem(ctx, "unexpected buffer type (0x%x) in blit_nearest",
 173                     readRb->DataType);
 174       return;
 175    }
 176
 177    /* choose row resampler */
 178    switch (pixelSize) {
 179    case 1:
 180       resampleRow = resample_row_1;
 181       break;
 182    case 2:
 183       resampleRow = resample_row_2;
 184       break;
 185    case 4:
 186       resampleRow = resample_row_4;
 187       break;
 188    case 8:
 189       resampleRow = resample_row_8;
 190       break;
 191    case 16:
 192       resampleRow = resample_row_16;
 193       break;
 194    default:
 195       _mesa_problem(ctx, "unexpected pixel size (%d) in blit_nearest",
 196                     pixelSize);
 197       return;
 198    }
 199
 200    /* allocate the src/dst row buffers */
 201    srcBuffer = _mesa_malloc(pixelSize * srcWidth);
 202    if (!srcBuffer) {
 203       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 204       return;
 205    }
 206    dstBuffer = _mesa_malloc(pixelSize * dstWidth);
 207    if (!dstBuffer) {
 208       _mesa_free(srcBuffer);
 209       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 210       return;
 211    }
 212
 213    for (dstRow = 0; dstRow < dstHeight; dstRow++) {
 214       const GLint dstY = dstYpos + dstRow;
 215       GLint srcRow = (dstRow * srcHeight) / dstHeight;
 216       GLint srcY;
 217
 218       ASSERT(srcRow >= 0);
 219       ASSERT(srcRow < srcHeight);
 220
 221       if (invertY) {
 222          srcRow = srcHeight - 1 - srcRow;
 223       }
 224
 225       srcY = srcYpos + srcRow;
 226
 227       /* get pixel row from source and resample to match dest width */
 228       if (prevY != srcY) {
 229          readRb->GetRow(ctx, readRb, srcWidth, srcXpos, srcY, srcBuffer);
 230          (*resampleRow)(srcWidth, dstWidth, srcBuffer, dstBuffer, invertX);
 231          prevY = srcY;
 232       }
 233
 234       /* store pixel row in destination */
 235       drawRb->PutRow(ctx, drawRb, dstWidth, dstXpos, dstY, dstBuffer, NULL);
 236    }
 237
 238    _mesa_free(srcBuffer);
 239    _mesa_free(dstBuffer);
 240 }
 241
 242
 243
 244 #define LERP(T, A, B)  ( (A) + (T) * ((B) - (A)) )
 245
 246 static INLINE GLfloat
 247 lerp_2d(GLfloat a, GLfloat b,
 248         GLfloat v00, GLfloat v10, GLfloat v01, GLfloat v11)
 249 {
 250    const GLfloat temp0 = LERP(a, v00, v10);
 251    const GLfloat temp1 = LERP(a, v01, v11);
 252    return LERP(b, temp0, temp1);
 253 }
 254
 255
 256 /**
 257  * Bilinear interpolation of two source rows.
 258  * GLubyte pixels.
 259  */
 260 static void
 261 resample_linear_row_ub(GLint srcWidth, GLint dstWidth,
 262                        const GLvoid *srcBuffer0, const GLvoid *srcBuffer1,
 263                        GLvoid *dstBuffer, GLboolean flip, GLfloat rowWeight)
 264 {
 265    const GLubyte (*srcColor0)[4] = (const GLubyte (*)[4]) srcBuffer0;
 266    const GLubyte (*srcColor1)[4] = (const GLubyte (*)[4]) srcBuffer1;
 267    GLubyte (*dstColor)[4] = (GLubyte (*)[4]) dstBuffer;
 268    const GLfloat dstWidthF = (GLfloat) dstWidth;
 269    GLint dstCol;
 270
 271    for (dstCol = 0; dstCol < dstWidth; dstCol++) {
 272       const GLfloat srcCol = (dstCol * srcWidth) / dstWidthF;
 273       GLint srcCol0 = IFLOOR(srcCol);
 274       GLint srcCol1 = srcCol0 + 1;
 275       GLfloat colWeight = srcCol - srcCol0; /* fractional part of srcCol */
 276       GLfloat red, green, blue, alpha;
 277
 278       ASSERT(srcCol0 >= 0);
 279       ASSERT(srcCol0 < srcWidth);
 280       ASSERT(srcCol1 <= srcWidth);
 281
 282       if (srcCol1 == srcWidth) {
 283          /* last column fudge */
 284          srcCol1--;
 285          colWeight = 0.0;
 286       }
 287
 288       if (flip) {
 289          srcCol0 = srcWidth - 1 - srcCol0;
 290          srcCol1 = srcWidth - 1 - srcCol1;
 291       }
 292
 293       red = lerp_2d(colWeight, rowWeight,
 294                     srcColor0[srcCol0][RCOMP], srcColor0[srcCol1][RCOMP],
 295                     srcColor1[srcCol0][RCOMP], srcColor1[srcCol1][RCOMP]);
 296       green = lerp_2d(colWeight, rowWeight,
 297                     srcColor0[srcCol0][GCOMP], srcColor0[srcCol1][GCOMP],
 298                     srcColor1[srcCol0][GCOMP], srcColor1[srcCol1][GCOMP]);
 299       blue = lerp_2d(colWeight, rowWeight,
 300                     srcColor0[srcCol0][BCOMP], srcColor0[srcCol1][BCOMP],
 301                     srcColor1[srcCol0][BCOMP], srcColor1[srcCol1][BCOMP]);
 302       alpha = lerp_2d(colWeight, rowWeight,
 303                     srcColor0[srcCol0][ACOMP], srcColor0[srcCol1][ACOMP],
 304                     srcColor1[srcCol0][ACOMP], srcColor1[srcCol1][ACOMP]);
 305
 306       dstColor[dstCol][RCOMP] = IFLOOR(red);
 307       dstColor[dstCol][GCOMP] = IFLOOR(green);
 308       dstColor[dstCol][BCOMP] = IFLOOR(blue);
 309       dstColor[dstCol][ACOMP] = IFLOOR(alpha);
 310    }
 311 }
 312
 313
 314
 315 /**
 316  * Bilinear filtered blit (color only).
 317  */
 318 static void
 319 blit_linear(GLcontext *ctx,
 320             GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
 321             GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1)
 322 {
 323    struct gl_renderbuffer *readRb = ctx->ReadBuffer->_ColorReadBuffer;
 324    struct gl_renderbuffer *drawRb = ctx->DrawBuffer->_ColorDrawBuffers[0];
 325
 326    const GLint srcWidth = ABS(srcX1 - srcX0);
 327    const GLint dstWidth = ABS(dstX1 - dstX0);
 328    const GLint srcHeight = ABS(srcY1 - srcY0);
 329    const GLint dstHeight = ABS(dstY1 - dstY0);
 330    const GLfloat dstHeightF = (GLfloat) dstHeight;
 331
 332    const GLint srcXpos = MIN2(srcX0, srcX1);
 333    const GLint srcYpos = MIN2(srcY0, srcY1);
 334    const GLint dstXpos = MIN2(dstX0, dstX1);
 335    const GLint dstYpos = MIN2(dstY0, dstY1);
 336
 337    const GLboolean invertX = (srcX1 < srcX0) ^ (dstX1 < dstX0);
 338    const GLboolean invertY = (srcY1 < srcY0) ^ (dstY1 < dstY0);
 339
 340    GLint dstRow;
 341
 342    GLint pixelSize;
 343    GLvoid *srcBuffer0, *srcBuffer1;
 344    GLint srcBufferY0 = -1, srcBufferY1 = -1;
 345    GLvoid *dstBuffer;
 346
 347    switch (readRb->DataType) {
 348    case GL_UNSIGNED_BYTE:
 349       pixelSize = 4 * sizeof(GLubyte);
 350       break;
 351    case GL_UNSIGNED_SHORT:
 352       pixelSize = 4 * sizeof(GLushort);
 353       break;
 354    case GL_UNSIGNED_INT:
 355       pixelSize = 4 * sizeof(GLuint);
 356       break;
 357    case GL_FLOAT:
 358       pixelSize = 4 * sizeof(GLfloat);
 359       break;
 360    default:
 361       _mesa_problem(ctx, "unexpected buffer type (0x%x) in blit_nearest",
 362                     readRb->DataType);
 363       return;
 364    }
 365
 366    /* Allocate the src/dst row buffers.
 367     * Keep two adjacent src rows around for bilinear sampling.
 368     */
 369    srcBuffer0 = _mesa_malloc(pixelSize * srcWidth);
 370    if (!srcBuffer0) {
 371       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 372       return;
 373    }
 374    srcBuffer1 = _mesa_malloc(pixelSize * srcWidth);
 375    if (!srcBuffer1) {
 376       _mesa_free(srcBuffer0);
 377       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 378       return;
 379    }
 380    dstBuffer = _mesa_malloc(pixelSize * dstWidth);
 381    if (!dstBuffer) {
 382       _mesa_free(srcBuffer0);
 383       _mesa_free(srcBuffer1);
 384       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 385       return;
 386    }
 387
 388    for (dstRow = 0; dstRow < dstHeight; dstRow++) {
 389       const GLint dstY = dstYpos + dstRow;
 390       const GLfloat srcRow = (dstRow * srcHeight) / dstHeightF;
 391       GLint srcRow0 = IFLOOR(srcRow);
 392       GLint srcRow1 = srcRow0 + 1;
 393       GLfloat rowWeight = srcRow - srcRow0; /* fractional part of srcRow */
 394
 395       ASSERT(srcRow >= 0);
 396       ASSERT(srcRow < srcHeight);
 397
 398       if (srcRow1 == srcHeight) {
 399          /* last row fudge */
 400          srcRow1 = srcRow0;
 401          rowWeight = 0.0;
 402       }
 403
 404       if (invertY) {
 405          srcRow0 = srcHeight - 1 - srcRow0;
 406          srcRow1 = srcHeight - 1 - srcRow1;
 407       }
 408
 409       srcY0 = srcYpos + srcRow0;
 410       srcY1 = srcYpos + srcRow1;
 411
 412       /* get the two source rows */
 413       if (srcY0 == srcBufferY0 && srcY1 == srcBufferY1) {
 414          /* use same source row buffers again */
 415       }
 416       else if (srcY0 == srcBufferY1) {
 417          /* move buffer1 into buffer0 by swapping pointers */
 418          GLvoid *tmp = srcBuffer0;
 419          srcBuffer0 = srcBuffer1;
 420          srcBuffer1 = tmp;
 421          /* get y1 row */
 422          readRb->GetRow(ctx, readRb, srcWidth, srcXpos, srcY1, srcBuffer1);
 423          srcBufferY0 = srcY0;
 424          srcBufferY1 = srcY1;
 425       }
 426       else {
 427          /* get both new rows */
 428          readRb->GetRow(ctx, readRb, srcWidth, srcXpos, srcY0, srcBuffer0);
 429          readRb->GetRow(ctx, readRb, srcWidth, srcXpos, srcY1, srcBuffer1);
 430          srcBufferY0 = srcY0;
 431          srcBufferY1 = srcY1;
 432       }
 433
 434       if (readRb->DataType == GL_UNSIGNED_BYTE) {
 435          resample_linear_row_ub(srcWidth, dstWidth, srcBuffer0, srcBuffer1,
 436                                 dstBuffer, invertX, rowWeight);
 437       }
 438       else {
 439          _mesa_problem(ctx, "Unsupported color channel type in sw blit");
 440          break;
 441       }
 442
 443       /* store pixel row in destination */
 444       drawRb->PutRow(ctx, drawRb, dstWidth, dstXpos, dstY, dstBuffer, NULL);
 445    }
 446
 447    _mesa_free(srcBuffer0);
 448    _mesa_free(srcBuffer1);
 449    _mesa_free(dstBuffer);
 450 }
 451
 452
 453 /**
 454  * Simple case:  Blit color, depth or stencil with no scaling or flipping.
 455  * XXX we could easily support vertical flipping here.
 456  */
 457 static void
 458 simple_blit(GLcontext *ctx,
 459             GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
 460             GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
 461             GLbitfield buffer)
 462 {
 463    struct gl_renderbuffer *readRb, *drawRb;
 464    const GLint width = srcX1 - srcX0;
 465    const GLint height = srcY1 - srcY0;
 466    GLint row, srcY, dstY, yStep;
 467    GLint comps, bytesPerRow;
 468    void *rowBuffer;
 469
 470    /* only one buffer */
 471    ASSERT(_mesa_bitcount(buffer) == 1);
 472    /* no flipping checks */
 473    ASSERT(srcX0 < srcX1);
 474    ASSERT(srcY0 < srcY1);
 475    ASSERT(dstX0 < dstX1);
 476    ASSERT(dstY0 < dstY1);
 477    /* size checks */
 478    ASSERT(srcX1 - srcX0 == dstX1 - dstX0);
 479    ASSERT(srcY1 - srcY0 == dstY1 - dstY0);
 480
 481    /* determine if copy should be bottom-to-top or top-to-bottom */
 482    if (srcY0 > dstY0) {
 483       /* src above dst: copy bottom-to-top */
 484       yStep = 1;
 485       srcY = srcY0;
 486       dstY = dstY0;
 487    }
 488    else {
 489       /* src below dst: copy top-to-bottom */
 490       yStep = -1;
 491       srcY = srcY1 - 1;
 492       dstY = dstY1 - 1;
 493    }
 494
 495    switch (buffer) {
 496    case GL_COLOR_BUFFER_BIT:
 497       readRb = ctx->ReadBuffer->_ColorReadBuffer;
 498       drawRb = ctx->DrawBuffer->_ColorDrawBuffers[0];
 499       comps = 4;
 500       break;
 501    case GL_DEPTH_BUFFER_BIT:
 502       readRb = ctx->ReadBuffer->_DepthBuffer;
 503       drawRb = ctx->DrawBuffer->_DepthBuffer;
 504       comps = 1;
 505       break;
 506    case GL_STENCIL_BUFFER_BIT:
 507       readRb = ctx->ReadBuffer->_StencilBuffer;
 508       drawRb = ctx->DrawBuffer->_StencilBuffer;
 509       comps = 1;
 510       break;
 511    default:
 512       _mesa_problem(ctx, "unexpected buffer in simple_blit()");
 513       return;
 514    }
 515
 516    ASSERT(readRb->DataType == drawRb->DataType);
 517
 518    /* compute bytes per row */
 519    switch (readRb->DataType) {
 520    case GL_UNSIGNED_BYTE:
 521       bytesPerRow = comps * width * sizeof(GLubyte);
 522       break;
 523    case GL_UNSIGNED_SHORT:
 524       bytesPerRow = comps * width * sizeof(GLushort);
 525       break;
 526    case GL_UNSIGNED_INT:
 527       bytesPerRow = comps * width * sizeof(GLuint);
 528       break;
 529    case GL_FLOAT:
 530       bytesPerRow = comps * width * sizeof(GLfloat);
 531       break;
 532    default:
 533       _mesa_problem(ctx, "unexpected buffer type in simple_blit");
 534       return;
 535    }
 536
 537    /* allocate the row buffer */
 538    rowBuffer = _mesa_malloc(bytesPerRow);
 539    if (!rowBuffer) {
 540       _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBlitFrameBufferEXT");
 541       return;
 542    }
 543
 544    for (row = 0; row < height; row++) {
 545       readRb->GetRow(ctx, readRb, width, srcX0, srcY, rowBuffer);
 546       drawRb->PutRow(ctx, drawRb, width, dstX0, dstY, rowBuffer, NULL);
 547       srcY += yStep;
 548       dstY += yStep;
 549    }
 550
 551    _mesa_free(rowBuffer);
 552 }
 553
 554
 555 /**
 556  * Software fallback for glBlitFramebufferEXT().
 557  */
 558 void
 559 _swrast_BlitFramebuffer(GLcontext *ctx,
 560                         GLint srcX0, GLint srcY0, GLint srcX1, GLint srcY1,
 561                         GLint dstX0, GLint dstY0, GLint dstX1, GLint dstY1,
 562                         GLbitfield mask, GLenum filter)
 563 {
 564    static const GLbitfield buffers[3] = {
 565       GL_COLOR_BUFFER_BIT,
 566       GL_DEPTH_BUFFER_BIT,
 567       GL_STENCIL_BUFFER_BIT
 568    };
 569    GLint i;
 570
 571    if (!_mesa_check_conditional_render(ctx))
 572       return; /* don't clear */
 573
 574    if (!ctx->DrawBuffer->_NumColorDrawBuffers)
 575       return;
 576
 577    if (!_mesa_clip_blit(ctx, &srcX0, &srcY0, &srcX1, &srcY1,
 578                         &dstX0, &dstY0, &dstX1, &dstY1)) {
 579       return;
 580    }
 581
 582    swrast_render_start(ctx);
 583
 584    if (srcX1 - srcX0 == dstX1 - dstX0 &&
 585        srcY1 - srcY0 == dstY1 - dstY0 &&
 586        srcX0 < srcX1 &&
 587        srcY0 < srcY1 &&
 588        dstX0 < dstX1 &&
 589        dstY0 < dstY1) {
 590       /* no stretching or flipping.
 591        * filter doesn't matter.
 592        */
 593       for (i = 0; i < 3; i++) {
 594          if (mask & buffers[i]) {
 595             simple_blit(ctx, srcX0, srcY0, srcX1, srcY1,
 596                         dstX0, dstY0, dstX1, dstY1, buffers[i]);
 597          }
 598       }
 599    }
 600    else {
 601       if (filter == GL_NEAREST) {
 602          for (i = 0; i < 3; i++) {
 603             if (mask & buffers[i]) {
 604                blit_nearest(ctx,  srcX0, srcY0, srcX1, srcY1,
 605                             dstX0, dstY0, dstX1, dstY1, buffers[i]);
 606             }
 607          }
 608       }
 609       else {
 610          ASSERT(filter == GL_LINEAR);
 611          if (mask & GL_COLOR_BUFFER_BIT) {  /* depth/stencil not allowed */
 612             blit_linear(ctx,  srcX0, srcY0, srcX1, srcY1,
 613                         dstX0, dstY0, dstX1, dstY1);
 614          }
 615       }
 616    }
 617
 618    swrast_render_finish(ctx);
 619 }