src/mesa/drivers/dri/mga/mga_texcombine.c

   1 /*
   2  * Copyright (c) 2003 Ville Syrjala
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  17  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  19  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  20  * DEALINGS IN THE SOFTWARE.
  21  *
  22  * Authors:
  23  *    Ville Syrjala <syrjala@sci.fi>
  24  */
  25
  26 #include "main/glheader.h"
  27
  28 #include "mgacontext.h"
  29 #include "mgatex.h"
  30 #include "mgaregs.h"
  31
  32 /*
  33  * GL_ARB_texture_env_combine
  34  * GL_EXT_texture_env_combine
  35  * GL_ARB_texture_env_crossbar
  36  * GL_ATI_texture_env_combine3
  37  */
  38
  39 #define ARG_DISABLE 0xffffffff
  40 #define MGA_ARG1  0
  41 #define MGA_ARG2  1
  42 #define MGA_ALPHA 2
  43
  44 GLboolean mgaUpdateTextureEnvCombine( GLcontext *ctx, int unit )
  45 {
  46    mgaContextPtr mmesa = MGA_CONTEXT(ctx);
  47    const int source = mmesa->tmu_source[unit];
  48    const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[source];
  49    GLuint *reg = ((GLuint *)&mmesa->setup.tdualstage0 + unit);
  50    GLuint numColorArgs = 0, numAlphaArgs = 0;
  51    GLuint arg1[3], arg2[3], alpha[3];
  52    int args[3];
  53    int i;
  54
  55    switch (texUnit->Combine.ModeRGB) {
  56    case GL_REPLACE:
  57       numColorArgs = 1;
  58       break;
  59    case GL_MODULATE:
  60    case GL_ADD:
  61    case GL_ADD_SIGNED:
  62    case GL_SUBTRACT:
  63       numColorArgs = 2;
  64       break;
  65    case GL_INTERPOLATE:
  66    case GL_MODULATE_ADD_ATI:
  67    case GL_MODULATE_SIGNED_ADD_ATI:
  68    case GL_MODULATE_SUBTRACT_ATI:
  69       numColorArgs = 3;
  70       break;
  71    default:
  72       return GL_FALSE;
  73    }
  74
  75    switch (texUnit->Combine.ModeA) {
  76    case GL_REPLACE:
  77       numAlphaArgs = 1;
  78       break;
  79    case GL_MODULATE:
  80    case GL_ADD:
  81    case GL_ADD_SIGNED:
  82    case GL_SUBTRACT:
  83       numAlphaArgs = 2;
  84       break;
  85    default:
  86       return GL_FALSE;
  87    }
  88
  89    /* Start fresh :) */
  90    *reg = 0;
  91
  92    /* COLOR */
  93    for (i = 0; i < 3; i++) {
  94       arg1[i] = 0;
  95       arg2[i] = 0;
  96       alpha[i] = 0;
  97    }
  98
  99    for (i = 0;i < numColorArgs; i++) {
 100       switch (texUnit->Combine.SourceRGB[i]) {
 101       case GL_TEXTURE:
 102          arg1[i] |= 0;
 103          arg2[i] |= ARG_DISABLE;
 104          alpha[i] |= TD0_color_alpha_currtex;
 105          break;
 106       case GL_TEXTURE0:
 107          if (source == 0) {
 108             arg1[i] |= 0;
 109             arg2[i] |= ARG_DISABLE;
 110             alpha[i] |= TD0_color_alpha_currtex;
 111          } else {
 112             if (ctx->Texture._EnabledUnits != 0x03) {
 113                /* disable texturing */
 114                mmesa->setup.dwgctl &= DC_opcod_MASK;
 115                mmesa->setup.dwgctl |= DC_opcod_trap;
 116                mmesa->hw.alpha_sel = AC_alphasel_diffused;
 117                /* return GL_TRUE since we don't need a fallback */
 118                return GL_TRUE;
 119             }
 120             arg1[i] |= ARG_DISABLE;
 121             arg2[i] |= ARG_DISABLE;
 122             alpha[i] |= TD0_color_alpha_prevtex;
 123          }
 124          break;
 125       case GL_TEXTURE1:
 126          if (source == 0) {
 127             if (ctx->Texture._EnabledUnits != 0x03) {
 128                /* disable texturing */
 129                mmesa->setup.dwgctl &= DC_opcod_MASK;
 130                mmesa->setup.dwgctl |= DC_opcod_trap;
 131                mmesa->hw.alpha_sel = AC_alphasel_diffused;
 132                /* return GL_TRUE since we don't need a fallback */
 133                return GL_TRUE;
 134             }
 135             arg1[i] |= ARG_DISABLE;
 136             /* G400 specs (TDUALSTAGE0) */
 137             arg2[i] |= TD0_color_arg2_prevstage;
 138             alpha[i] |= TD0_color_alpha_prevstage;
 139          } else {
 140             arg1[i] |= 0;
 141             arg2[i] |= ARG_DISABLE;
 142             alpha[i] |= TD0_color_alpha_currtex;
 143          }
 144          break;
 145       case GL_CONSTANT:
 146          if (mmesa->fcol_used &&
 147              mmesa->envcolor[source] != mmesa->envcolor[!source])
 148             return GL_FALSE;
 149
 150          arg1[i] |= ARG_DISABLE;
 151          arg2[i] |= TD0_color_arg2_fcol;
 152          alpha[i] |= TD0_color_alpha_fcol;
 153
 154          mmesa->setup.fcol = mmesa->envcolor[source];
 155          mmesa->fcol_used = GL_TRUE;
 156          break;
 157       case GL_PRIMARY_COLOR:
 158          arg1[i] |= ARG_DISABLE;
 159          /* G400 specs (TDUALSTAGE1) */
 160          if (unit == 0 || (mmesa->setup.tdualstage0 &
 161                            ((TD0_color_sel_mul & TD0_color_sel_add) |
 162                             (TD0_alpha_sel_mul & TD0_alpha_sel_add)))) {
 163             arg2[i] |= TD0_color_arg2_diffuse;
 164             alpha[i] |= TD0_color_alpha_diffuse;
 165          } else {
 166             arg2[i] |= ARG_DISABLE;
 167             alpha[i] |= ARG_DISABLE;
 168          }
 169          break;
 170       case GL_PREVIOUS:
 171          arg1[i] |= ARG_DISABLE;
 172          if (unit == 0) {
 173             arg2[i] |= TD0_color_arg2_diffuse;
 174             alpha[i] |= TD0_color_alpha_diffuse;
 175          } else {
 176             arg2[i] |= TD0_color_arg2_prevstage;
 177             alpha[i] |= TD0_color_alpha_prevstage;
 178          }
 179          break;
 180       default:
 181          return GL_FALSE;
 182       }
 183
 184       switch (texUnit->Combine.OperandRGB[i]) {
 185       case GL_SRC_COLOR:
 186          arg1[i] |= 0;
 187          arg2[i] |= 0;
 188          if (texUnit->Combine.SourceRGB[i] == GL_CONSTANT &&
 189              RGBA_EQUAL( mmesa->envcolor[source] )) {
 190             alpha[i] |= 0;
 191          } else {
 192             alpha[i] |= ARG_DISABLE;
 193          }
 194          break;
 195       case GL_ONE_MINUS_SRC_COLOR:
 196          arg1[i] |= TD0_color_arg1_inv_enable;
 197          arg2[i] |= TD0_color_arg2_inv_enable;
 198          if (texUnit->Combine.SourceRGB[i] == GL_CONSTANT &&
 199              RGBA_EQUAL( mmesa->envcolor[source] )) {
 200             alpha[i] |= (TD0_color_alpha1inv_enable |
 201                          TD0_color_alpha2inv_enable);
 202          } else {
 203             alpha[i] |= ARG_DISABLE;
 204          }
 205          break;
 206       case GL_SRC_ALPHA:
 207          arg1[i] |= TD0_color_arg1_replicatealpha_enable;
 208          arg2[i] |= TD0_color_arg2_replicatealpha_enable;
 209          alpha[i] |= 0;
 210          break;
 211       case GL_ONE_MINUS_SRC_ALPHA:
 212          arg1[i] |= (TD0_color_arg1_replicatealpha_enable |
 213                      TD0_color_arg1_inv_enable);
 214          arg2[i] |= (TD0_color_arg2_replicatealpha_enable |
 215                      TD0_color_arg2_inv_enable);
 216          alpha[i] |= (TD0_color_alpha1inv_enable |
 217                       TD0_color_alpha2inv_enable);
 218          break;
 219       }
 220    }
 221
 222    switch (texUnit->Combine.ModeRGB) {
 223    case GL_MODULATE_ADD_ATI:
 224    case GL_MODULATE_SIGNED_ADD_ATI:
 225       /* Special handling for ATI_texture_env_combine3.
 226        * If Arg1 == Arg0 or Arg1 == Arg2 we can use arg1 or arg2 as input for
 227        * both multiplier and adder.
 228        */
 229       /* Arg1 == arg1 */
 230       if (arg1[1] == arg1[0]) {
 231          if ((arg1[1] | arg2[2]) != ARG_DISABLE) {
 232             *reg |= arg1[1] | arg2[2];
 233             args[0] = MGA_ARG1; args[1] = MGA_ARG1; args[2] = MGA_ARG2;
 234             break;
 235          } else
 236          if ((arg1[1] | alpha[2]) != ARG_DISABLE) {
 237             *reg |= arg1[1] | alpha[2];
 238             args[0] = MGA_ARG1; args[1] = MGA_ARG1; args[2] = MGA_ALPHA;
 239             break;
 240          }
 241       }
 242       if (arg1[1] == arg1[2]) {
 243          if ((arg1[1] | arg2[0]) != ARG_DISABLE) {
 244             *reg |= arg1[1] | arg2[0];
 245             args[0] = MGA_ARG2; args[1] = MGA_ARG1; args[2] = MGA_ARG1;
 246             break;
 247          } else
 248          if ((arg1[1] | alpha[0]) != ARG_DISABLE) {
 249             *reg |= arg1[1] | alpha[0];
 250             args[0] = MGA_ALPHA; args[1] = MGA_ARG1; args[2] = MGA_ARG1;
 251             break;
 252          }
 253       }
 254       /* fallthrough */
 255    case GL_MODULATE_SUBTRACT_ATI:
 256       /* Arg1 == arg2 */
 257       if (arg2[1] == arg2[0]) {
 258          if ((arg2[1] | arg1[2]) != ARG_DISABLE) {
 259             *reg |= arg2[1] | arg1[2];
 260             args[0] = MGA_ARG2; args[1] = MGA_ARG2; args[2] = MGA_ARG1;
 261             break;
 262          } else
 263          if ((arg2[1] | alpha[2]) != ARG_DISABLE) {
 264             *reg |= arg2[1] | alpha[2];
 265             args[0] = MGA_ARG2; args[1] = MGA_ARG2; args[2] = MGA_ALPHA;
 266             break;
 267          }
 268       }
 269       if (arg2[1] == arg2[2]) {
 270          if ((arg2[1] | arg1[0]) != ARG_DISABLE) {
 271             *reg |= arg2[1] | arg1[0];
 272             args[0] = MGA_ARG1; args[1] = MGA_ARG2; args[2] = MGA_ARG2;
 273             break;
 274          } else
 275          if ((arg2[1] | alpha[0]) != ARG_DISABLE) {
 276             *reg |= arg2[1] | alpha[0];
 277             args[0] = MGA_ALPHA; args[1] = MGA_ARG2; args[2] = MGA_ARG2;
 278             break;
 279          }
 280       }
 281       /* fallthrough */
 282    default:
 283       /* Find working combo of arg1, arg2 and alpha.
 284        *
 285        * Keep the Arg0 != alpha cases first since there's
 286        * no way to get alpha out by itself (GL_REPLACE).
 287        *
 288        * Keep the Arg2 == alpha cases first because only alpha has the
 289        * capabilities to function as Arg2 (GL_INTERPOLATE). Also good for
 290        * GL_ADD, GL_ADD_SIGNED, GL_SUBTRACT since we can't get alpha to the
 291        * adder.
 292        *
 293        * Keep the Arg1 == alpha cases last for GL_MODULATE_ADD_ATI,
 294        * GL_MODULATE_SIGNED_ADD_ATI. Again because we can't get alpha to the
 295        * adder.
 296        *
 297        * GL_MODULATE_SUBTRACT_ATI needs special treatment since it requires
 298        * that Arg1 == arg2. This requirement clashes with those of other modes.
 299        */
 300       if ((arg1[0] | arg2[1] | alpha[2]) != ARG_DISABLE) {
 301          *reg |= arg1[0] | arg2[1] | alpha[2];
 302          args[0] = MGA_ARG1; args[1] = MGA_ARG2; args[2] = MGA_ALPHA;
 303       } else
 304       if ((arg1[1] | arg2[0] | alpha[2]) != ARG_DISABLE &&
 305           texUnit->Combine.ModeRGB != GL_MODULATE_SUBTRACT_ATI) {
 306          *reg |= arg1[1] | arg2[0] | alpha[2];
 307          args[0] = MGA_ARG2; args[1] = MGA_ARG1; args[2] = MGA_ALPHA;
 308       } else
 309       if ((arg1[1] | arg2[2] | alpha[0]) != ARG_DISABLE &&
 310           texUnit->Combine.ModeRGB != GL_MODULATE_SUBTRACT_ATI) {
 311          *reg |= arg1[1] | arg2[2] | alpha[0];
 312          args[0] = MGA_ALPHA; args[1] = MGA_ARG1; args[2] = MGA_ARG2;
 313       } else
 314       if ((arg1[2] | arg2[1] | alpha[0]) != ARG_DISABLE) {
 315          *reg |= arg1[2] | arg2[1] | alpha[0];
 316          args[0] = MGA_ALPHA; args[1] = MGA_ARG2; args[2] = MGA_ARG1;
 317       } else
 318       if ((arg1[0] | arg2[2] | alpha[1]) != ARG_DISABLE) {
 319          *reg |= arg1[0] | arg2[2] | alpha[1];
 320          args[0] = MGA_ARG1; args[1] = MGA_ALPHA; args[2] = MGA_ARG2;
 321       } else
 322       if ((arg1[2] | arg2[0] | alpha[1]) != ARG_DISABLE) {
 323          *reg |= arg1[2] | arg2[0] | alpha[1];
 324          args[0] = MGA_ARG2; args[1] = MGA_ALPHA; args[2] = MGA_ARG1;
 325       } else {
 326          /* nothing suitable */
 327          return GL_FALSE;
 328       }
 329    }
 330
 331    switch (texUnit->Combine.ModeRGB) {
 332    case GL_REPLACE:
 333       if (texUnit->Combine.ScaleShiftRGB) {
 334          return GL_FALSE;
 335       }
 336
 337       if (args[0] == MGA_ARG1) {
 338          *reg |= TD0_color_sel_arg1;
 339       } else if (args[0] == MGA_ARG2) {
 340          *reg |= TD0_color_sel_arg2;
 341       } else if (args[0] == MGA_ALPHA) {
 342          /* Can't get alpha out by itself */
 343          return GL_FALSE;
 344       }
 345       break;
 346    case GL_MODULATE:
 347       if (texUnit->Combine.ScaleShiftRGB == 1) {
 348          *reg |= TD0_color_modbright_2x;
 349       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 350          *reg |= TD0_color_modbright_4x;
 351       }
 352
 353       *reg |= TD0_color_sel_mul;
 354
 355       if (args[0] == MGA_ALPHA || args[1] == MGA_ALPHA) {
 356          if (args[0] == MGA_ARG1 || args[1] == MGA_ARG1) {
 357             *reg |= TD0_color_arg2mul_alpha2;
 358          } else if (args[0] == MGA_ARG2 || args[1] == MGA_ARG2) {
 359             *reg |= TD0_color_arg1mul_alpha1;
 360          }
 361       }
 362       break;
 363    case GL_ADD_SIGNED:
 364       *reg |= TD0_color_addbias_enable;
 365       /* fallthrough */
 366    case GL_ADD:
 367       if (args[0] == MGA_ALPHA || args[1] == MGA_ALPHA) {
 368          /* Can't get alpha to the adder */
 369          return GL_FALSE;
 370       }
 371       if (texUnit->Combine.ScaleShiftRGB == 1) {
 372          *reg |= TD0_color_add2x_enable;
 373       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 374          return GL_FALSE;
 375       }
 376
 377       *reg |= (TD0_color_add_add |
 378                TD0_color_sel_add);
 379       break;
 380    case GL_INTERPOLATE:
 381       if (args[2] != MGA_ALPHA) {
 382          /* Only alpha can function as Arg2 */
 383          return GL_FALSE;
 384       }
 385       if (texUnit->Combine.ScaleShiftRGB == 1) {
 386          *reg |= TD0_color_add2x_enable;
 387       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 388          return GL_FALSE;
 389       }
 390
 391       *reg |= (TD0_color_arg1mul_alpha1 |
 392                TD0_color_blend_enable |
 393                TD0_color_arg1add_mulout |
 394                TD0_color_arg2add_mulout |
 395                TD0_color_add_add |
 396                TD0_color_sel_add);
 397
 398       /* Have to do this with xor since GL_ONE_MINUS_SRC_ALPHA may have
 399        * already touched this bit.
 400        */
 401       *reg ^= TD0_color_alpha1inv_enable;
 402
 403       if (args[0] == MGA_ARG2) {
 404          /* Swap arguments */
 405          *reg ^= (TD0_color_arg1mul_alpha1 |
 406                   TD0_color_arg2mul_alpha2 |
 407                   TD0_color_alpha1inv_enable |
 408                   TD0_color_alpha2inv_enable);
 409       }
 410
 411       if (ctx->Texture._EnabledUnits != 0x03) {
 412          /* Linear blending mode needs dualtex enabled */
 413          *(reg+1) = (TD0_color_arg2_prevstage |
 414                      TD0_color_sel_arg2 |
 415                      TD0_alpha_arg2_prevstage |
 416                      TD0_alpha_sel_arg2);
 417          mmesa->force_dualtex = GL_TRUE;
 418       }
 419       break;
 420    case GL_SUBTRACT:
 421       if (args[0] == MGA_ALPHA || args[1] == MGA_ALPHA) {
 422          /* Can't get alpha to the adder */
 423          return GL_FALSE;
 424       }
 425       if (texUnit->Combine.ScaleShiftRGB == 1) {
 426          *reg |= TD0_color_add2x_enable;
 427       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 428          return GL_FALSE;
 429       }
 430
 431       *reg |= (TD0_color_add_sub |
 432                TD0_color_sel_add);
 433
 434       if (args[0] == MGA_ARG2) {
 435          /* Swap arguments */
 436          *reg ^= (TD0_color_arg1_inv_enable |
 437                   TD0_color_arg2_inv_enable);
 438       }
 439       break;
 440    case GL_MODULATE_SIGNED_ADD_ATI:
 441       *reg |= TD0_color_addbias_enable;
 442       /* fallthrough */
 443    case GL_MODULATE_ADD_ATI:
 444       if (args[1] == MGA_ALPHA) {
 445          /* Can't get alpha to the adder */
 446          return GL_FALSE;
 447       }
 448       if (texUnit->Combine.ScaleShiftRGB == 1) {
 449          *reg |= TD0_color_add2x_enable;
 450       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 451          return GL_FALSE;
 452       }
 453
 454       *reg |= (TD0_color_add_add |
 455                TD0_color_sel_add);
 456
 457       if (args[1] == args[0] || args[1] == args[2]) {
 458          *reg |= TD0_color_arg1add_mulout;
 459          if (args[0] == MGA_ALPHA || args[2] == MGA_ALPHA)
 460             *reg |= TD0_color_arg1mul_alpha1;
 461
 462          if (args[1] == MGA_ARG1) {
 463             /* Swap adder arguments */
 464             *reg ^= (TD0_color_arg1add_mulout |
 465                      TD0_color_arg2add_mulout);
 466             if (args[0] == MGA_ALPHA || args[2] == MGA_ALPHA) {
 467                /* Swap multiplier arguments */
 468                *reg ^= (TD0_color_arg1mul_alpha1 |
 469                         TD0_color_arg2mul_alpha2);
 470             }
 471          }
 472       } else {
 473          *reg |= (TD0_color_arg2mul_alpha2 |
 474                   TD0_color_arg1add_mulout);
 475
 476          if (args[1] == MGA_ARG1) {
 477             /* Swap arguments */
 478             *reg ^= (TD0_color_arg1mul_alpha1 |
 479                      TD0_color_arg2mul_alpha2 |
 480                      TD0_color_arg1add_mulout |
 481                      TD0_color_arg2add_mulout);
 482          }
 483       }
 484       break;
 485    case GL_MODULATE_SUBTRACT_ATI:
 486       if (args[1] != MGA_ARG2) {
 487          /* Can't swap arguments */
 488          return GL_FALSE;
 489       }
 490       if (texUnit->Combine.ScaleShiftRGB == 1) {
 491          *reg |= TD0_color_add2x_enable;
 492       } else if (texUnit->Combine.ScaleShiftRGB == 2) {
 493          return GL_FALSE;
 494       }
 495
 496       *reg |= (TD0_color_add_sub |
 497                TD0_color_sel_add);
 498
 499       if (args[1] == args[0] || args[1] == args[2]) {
 500          *reg |= TD0_color_arg1add_mulout;
 501          if (args[0] == MGA_ALPHA || args[2] == MGA_ALPHA)
 502             *reg |= TD0_color_arg1mul_alpha1;
 503       } else {
 504          *reg |= (TD0_color_arg2mul_alpha2 |
 505                   TD0_color_arg1add_mulout);
 506       }
 507       break;
 508    }
 509
 510
 511    /* ALPHA */
 512    for (i = 0; i < 2; i++) {
 513       arg1[i] = 0;
 514       arg2[i] = 0;
 515    }
 516
 517    for (i = 0; i < numAlphaArgs; i++) {
 518       switch (texUnit->Combine.SourceA[i]) {
 519       case GL_TEXTURE:
 520          arg1[i] |= 0;
 521          arg2[i] |= ARG_DISABLE;
 522          break;
 523       case GL_TEXTURE0:
 524          if (source == 0) {
 525             arg1[i] |= 0;
 526             arg2[i] |= ARG_DISABLE;
 527          } else {
 528             if (ctx->Texture._EnabledUnits != 0x03) {
 529                /* disable texturing */
 530                mmesa->setup.dwgctl &= DC_opcod_MASK;
 531                mmesa->setup.dwgctl |= DC_opcod_trap;
 532                mmesa->hw.alpha_sel = AC_alphasel_diffused;
 533                /* return GL_TRUE since we don't need a fallback */
 534                return GL_TRUE;
 535             }
 536             arg1[i] |= ARG_DISABLE;
 537             arg2[i] |= TD0_alpha_arg2_prevtex;
 538          }
 539          break;
 540       case GL_TEXTURE1:
 541          if (source == 0) {
 542             if (ctx->Texture._EnabledUnits != 0x03) {
 543                /* disable texturing */
 544                mmesa->setup.dwgctl &= DC_opcod_MASK;
 545                mmesa->setup.dwgctl |= DC_opcod_trap;
 546                mmesa->hw.alpha_sel = AC_alphasel_diffused;
 547                /* return GL_TRUE since we don't need a fallback */
 548                return GL_TRUE;
 549             }
 550             arg1[i] |= ARG_DISABLE;
 551             /* G400 specs (TDUALSTAGE0) */
 552             arg2[i] |= TD0_alpha_arg2_prevstage;
 553          } else {
 554             arg1[i] |= 0;
 555             arg2[i] |= ARG_DISABLE;
 556          }
 557          break;
 558       case GL_CONSTANT:
 559          if (mmesa->fcol_used &&
 560              mmesa->envcolor[source] != mmesa->envcolor[!source])
 561             return GL_FALSE;
 562
 563          arg1[i] |= ARG_DISABLE;
 564          arg2[i] |= TD0_alpha_arg2_fcol;
 565
 566          mmesa->setup.fcol = mmesa->envcolor[source];
 567          mmesa->fcol_used = GL_TRUE;
 568          break;
 569       case GL_PRIMARY_COLOR:
 570          arg1[i] |= ARG_DISABLE;
 571          /* G400 specs (TDUALSTAGE1) */
 572          if (unit == 0 || (mmesa->setup.tdualstage0 &
 573                            ((TD0_color_sel_mul & TD0_color_sel_add) |
 574                             (TD0_alpha_sel_mul & TD0_alpha_sel_add)))) {
 575             arg2[i] |= TD0_alpha_arg2_diffuse;
 576          } else {
 577             arg2[i] |= ARG_DISABLE;
 578          }
 579          break;
 580       case GL_PREVIOUS:
 581          arg1[i] |= ARG_DISABLE;
 582          if (unit == 0) {
 583             arg2[i] |= TD0_alpha_arg2_diffuse;
 584          } else {
 585             arg2[i] |= TD0_alpha_arg2_prevstage;
 586          }
 587          break;
 588       default:
 589          return GL_FALSE;
 590       }
 591
 592       switch (texUnit->Combine.OperandA[i]) {
 593       case GL_SRC_ALPHA:
 594          arg1[i] |= 0;
 595          arg2[i] |= 0;
 596          break;
 597       case GL_ONE_MINUS_SRC_ALPHA:
 598          arg1[i] |= TD0_alpha_arg1_inv_enable;
 599          arg2[i] |= TD0_alpha_arg2_inv_enable;
 600          break;
 601       }
 602    }
 603
 604    /* Find a working combo of arg1 and arg2 */
 605    if ((arg1[0] | arg2[1]) != ARG_DISABLE) {
 606       *reg |= arg1[0] | arg2[1];
 607       args[0] = MGA_ARG1; args[1] = MGA_ARG2;
 608    } else
 609    if ((arg1[1] | arg2[0]) != ARG_DISABLE) {
 610       *reg |= arg1[1] | arg2[0];
 611       args[0] = MGA_ARG2; args[1] = MGA_ARG1;
 612    } else {
 613       /* nothing suitable */
 614       return GL_FALSE;
 615    }
 616
 617    switch (texUnit->Combine.ModeA) {
 618    case GL_REPLACE:
 619       if (texUnit->Combine.ScaleShiftA) {
 620          return GL_FALSE;
 621       }
 622
 623       if (args[0] == MGA_ARG1) {
 624          *reg |= TD0_alpha_sel_arg1;
 625       } else if (args[0] == MGA_ARG2) {
 626          *reg |= TD0_alpha_sel_arg2;
 627       }
 628       break;
 629    case GL_MODULATE:
 630       if (texUnit->Combine.ScaleShiftA == 1) {
 631          *reg |= TD0_alpha_modbright_2x;
 632       } else if (texUnit->Combine.ScaleShiftA == 2) {
 633          *reg |= TD0_alpha_modbright_4x;
 634       }
 635
 636       *reg |= TD0_alpha_sel_mul;
 637       break;
 638    case GL_ADD_SIGNED:
 639       *reg |= TD0_alpha_addbias_enable;
 640       /* fallthrough */
 641    case GL_ADD:
 642       if (texUnit->Combine.ScaleShiftA == 1) {
 643          *reg |= TD0_alpha_add2x_enable;
 644       } else if (texUnit->Combine.ScaleShiftA == 2) {
 645          return GL_FALSE;
 646       }
 647
 648       *reg |= (TD0_alpha_add_enable |
 649                TD0_alpha_sel_add);
 650       break;
 651    case GL_SUBTRACT:
 652       if (texUnit->Combine.ScaleShiftA == 1) {
 653          *reg |= TD0_alpha_add2x_enable;
 654       } else if (texUnit->Combine.ScaleShiftA == 2) {
 655          return GL_FALSE;
 656       }
 657
 658       *reg |= (TD0_alpha_add_disable |
 659                TD0_alpha_sel_add);
 660
 661       if (args[0] == MGA_ARG2) {
 662          /* Swap arguments */
 663          *reg ^= (TD0_alpha_arg1_inv_enable |
 664                   TD0_alpha_arg2_inv_enable);
 665       }
 666       break;
 667    }
 668
 669    return GL_TRUE;
 670 }
 671
 672