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      1 /***************************************************************************/
      2 /*                                                                         */
      3 /*  afloader.c                                                             */
      4 /*                                                                         */
      5 /*    Auto-fitter glyph loading routines (body).                           */
      6 /*                                                                         */
      7 /*  Copyright 2003-2017 by                                                 */
      8 /*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
      9 /*                                                                         */
     10 /*  This file is part of the FreeType project, and may only be used,       */
     11 /*  modified, and distributed under the terms of the FreeType project      */
     12 /*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
     13 /*  this file you indicate that you have read the license and              */
     14 /*  understand and accept it fully.                                        */
     15 /*                                                                         */
     16 /***************************************************************************/
     17 
     18 
     19 #include "afglobal.h"
     20 #include "afloader.h"
     21 #include "afhints.h"
     22 #include "aferrors.h"
     23 #include "afmodule.h"
     24 #include "afpic.h"
     25 
     26 #include FT_INTERNAL_CALC_H
     27 
     28 
     29   /* Initialize glyph loader. */
     30 
     31   FT_LOCAL_DEF( void )
     32   af_loader_init( AF_Loader      loader,
     33                   AF_GlyphHints  hints )
     34   {
     35     FT_ZERO( loader );
     36 
     37     loader->hints = hints;
     38   }
     39 
     40 
     41   /* Reset glyph loader and compute globals if necessary. */
     42 
     43   FT_LOCAL_DEF( FT_Error )
     44   af_loader_reset( AF_Loader  loader,
     45                    AF_Module  module,
     46                    FT_Face    face )
     47   {
     48     FT_Error  error = FT_Err_Ok;
     49 
     50 
     51     loader->face    = face;
     52     loader->globals = (AF_FaceGlobals)face->autohint.data;
     53 
     54     if ( !loader->globals )
     55     {
     56       error = af_face_globals_new( face, &loader->globals, module );
     57       if ( !error )
     58       {
     59         face->autohint.data =
     60           (FT_Pointer)loader->globals;
     61         face->autohint.finalizer =
     62           (FT_Generic_Finalizer)af_face_globals_free;
     63       }
     64     }
     65 
     66     return error;
     67   }
     68 
     69 
     70   /* Finalize glyph loader. */
     71 
     72   FT_LOCAL_DEF( void )
     73   af_loader_done( AF_Loader  loader )
     74   {
     75     loader->face    = NULL;
     76     loader->globals = NULL;
     77     loader->hints   = NULL;
     78   }
     79 
     80 
     81 #define af_intToFixed( i ) \
     82           ( (FT_Fixed)( (FT_UInt32)(i) << 16 ) )
     83 #define af_fixedToInt( x ) \
     84           ( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
     85 #define af_floatToFixed( f ) \
     86           ( (FT_Fixed)( (f) * 65536.0 + 0.5 ) )
     87 
     88 
     89   static FT_Error
     90   af_loader_embolden_glyph_in_slot( AF_Loader        loader,
     91                                     FT_Face          face,
     92                                     AF_StyleMetrics  style_metrics )
     93   {
     94     FT_Error  error = FT_Err_Ok;
     95 
     96     FT_GlyphSlot           slot    = face->glyph;
     97     AF_FaceGlobals         globals = loader->globals;
     98     AF_WritingSystemClass  writing_system_class;
     99 
    100     FT_Pos  stdVW = 0;
    101     FT_Pos  stdHW = 0;
    102 
    103     FT_Bool  size_changed = face->size->metrics.x_ppem
    104                               != globals->stem_darkening_for_ppem;
    105 
    106     FT_Fixed  em_size  = af_intToFixed( face->units_per_EM );
    107     FT_Fixed  em_ratio = FT_DivFix( af_intToFixed( 1000 ), em_size );
    108 
    109     FT_Matrix  scale_down_matrix = { 0x10000L, 0, 0, 0x10000L };
    110 
    111 
    112     /* Skip stem darkening for broken fonts. */
    113     if ( !face->units_per_EM )
    114     {
    115       error = FT_ERR( Corrupted_Font_Header );
    116       goto Exit;
    117     }
    118 
    119     /*
    120      *  We depend on the writing system (script analyzers) to supply
    121      *  standard widths for the script of the glyph we are looking at.  If
    122      *  it can't deliver, stem darkening is disabled.
    123      */
    124     writing_system_class =
    125       AF_WRITING_SYSTEM_CLASSES_GET[style_metrics->style_class->writing_system];
    126 
    127     if ( writing_system_class->style_metrics_getstdw )
    128       writing_system_class->style_metrics_getstdw( style_metrics,
    129                                                    &stdHW,
    130                                                    &stdVW );
    131     else
    132     {
    133       error = FT_ERR( Unimplemented_Feature );
    134       goto Exit;
    135     }
    136 
    137     if ( size_changed                                               ||
    138          ( stdVW > 0 && stdVW != globals->standard_vertical_width ) )
    139     {
    140       FT_Fixed  darken_by_font_units_x, darken_x;
    141 
    142 
    143       darken_by_font_units_x =
    144         af_intToFixed( af_loader_compute_darkening( loader,
    145                                                     face,
    146                                                     stdVW ) );
    147       darken_x = FT_DivFix( FT_MulFix( darken_by_font_units_x,
    148                                        face->size->metrics.x_scale ),
    149                             em_ratio );
    150 
    151       globals->standard_vertical_width = stdVW;
    152       globals->stem_darkening_for_ppem = face->size->metrics.x_ppem;
    153       globals->darken_x                = af_fixedToInt( darken_x );
    154     }
    155 
    156     if ( size_changed                                                 ||
    157          ( stdHW > 0 && stdHW != globals->standard_horizontal_width ) )
    158     {
    159       FT_Fixed  darken_by_font_units_y, darken_y;
    160 
    161 
    162       darken_by_font_units_y =
    163         af_intToFixed( af_loader_compute_darkening( loader,
    164                                                     face,
    165                                                     stdHW ) );
    166       darken_y = FT_DivFix( FT_MulFix( darken_by_font_units_y,
    167                                        face->size->metrics.y_scale ),
    168                             em_ratio );
    169 
    170       globals->standard_horizontal_width = stdHW;
    171       globals->stem_darkening_for_ppem   = face->size->metrics.x_ppem;
    172       globals->darken_y                  = af_fixedToInt( darken_y );
    173 
    174       /*
    175        *  Scale outlines down on the Y-axis to keep them inside their blue
    176        *  zones.  The stronger the emboldening, the stronger the downscaling
    177        *  (plus heuristical padding to prevent outlines still falling out
    178        *  their zones due to rounding).
    179        *
    180        *  Reason: `FT_Outline_Embolden' works by shifting the rightmost
    181        *  points of stems farther to the right, and topmost points farther
    182        *  up.  This positions points on the Y-axis outside their
    183        *  pre-computed blue zones and leads to distortion when applying the
    184        *  hints in the code further below.  Code outside this emboldening
    185        *  block doesn't know we are presenting it with modified outlines the
    186        *  analyzer didn't see!
    187        *
    188        *  An unfortunate side effect of downscaling is that the emboldening
    189        *  effect is slightly decreased.  The loss becomes more pronounced
    190        *  versus the CFF driver at smaller sizes, e.g., at 9ppem and below.
    191        */
    192       globals->scale_down_factor =
    193         FT_DivFix( em_size - ( darken_by_font_units_y + af_intToFixed( 8 ) ),
    194                    em_size );
    195     }
    196 
    197     FT_Outline_EmboldenXY( &slot->outline,
    198                            globals->darken_x,
    199                            globals->darken_y );
    200 
    201     scale_down_matrix.yy = globals->scale_down_factor;
    202     FT_Outline_Transform( &slot->outline, &scale_down_matrix );
    203 
    204   Exit:
    205     return error;
    206   }
    207 
    208 
    209   /* Load the glyph at index into the current slot of a face and hint it. */
    210 
    211   FT_LOCAL_DEF( FT_Error )
    212   af_loader_load_glyph( AF_Loader  loader,
    213                         AF_Module  module,
    214                         FT_Face    face,
    215                         FT_UInt    glyph_index,
    216                         FT_Int32   load_flags )
    217   {
    218     FT_Error  error;
    219 
    220     FT_Size           size     = face->size;
    221     FT_GlyphSlot      slot     = face->glyph;
    222     FT_Slot_Internal  internal = slot->internal;
    223     FT_GlyphLoader    gloader  = internal->loader;
    224 
    225     AF_GlyphHints          hints         = loader->hints;
    226     AF_ScalerRec           scaler;
    227     AF_StyleMetrics        style_metrics;
    228     FT_UInt                style_options = AF_STYLE_NONE_DFLT;
    229     AF_StyleClass          style_class;
    230     AF_WritingSystemClass  writing_system_class;
    231 
    232 #ifdef FT_CONFIG_OPTION_PIC
    233     AF_FaceGlobals  globals = loader->globals;
    234 #endif
    235 
    236 
    237     if ( !size )
    238       return FT_THROW( Invalid_Size_Handle );
    239 
    240     FT_ZERO( &scaler );
    241 
    242     /*
    243      *  TODO: This code currently doesn't support fractional advance widths,
    244      *  i.e., placing hinted glyphs at anything other than integer
    245      *  x-positions.  This is only relevant for the warper code, which
    246      *  scales and shifts glyphs to optimize blackness of stems (hinting on
    247      *  the x-axis by nature places things on pixel integers, hinting on the
    248      *  y-axis only, i.e., LIGHT mode, doesn't touch the x-axis).  The delta
    249      *  values of the scaler would need to be adjusted.
    250      */
    251     scaler.face    = face;
    252     scaler.x_scale = size->metrics.x_scale;
    253     scaler.x_delta = 0;
    254     scaler.y_scale = size->metrics.y_scale;
    255     scaler.y_delta = 0;
    256 
    257     scaler.render_mode = FT_LOAD_TARGET_MODE( load_flags );
    258     scaler.flags       = 0;
    259 
    260     /* note that the fallback style can't be changed anymore */
    261     /* after the first call of `ta_loader_load_glyph'        */
    262     error = af_loader_reset( loader, module, face );
    263     if ( error )
    264       goto Exit;
    265 
    266 #ifdef FT_OPTION_AUTOFIT2
    267     /* XXX: undocumented hook to activate the latin2 writing system. */
    268     if ( load_flags & ( 1UL << 20 ) )
    269       style_options = AF_STYLE_LTN2_DFLT;
    270 #endif
    271 
    272     /*
    273      *  Glyphs (really code points) are assigned to scripts.  Script
    274      *  analysis is done lazily: For each glyph that passes through here,
    275      *  the corresponding script analyzer is called, but returns immediately
    276      *  if it has been run already.
    277      */
    278     error = af_face_globals_get_metrics( loader->globals, glyph_index,
    279                                          style_options, &style_metrics );
    280     if ( error )
    281       goto Exit;
    282 
    283     style_class          = style_metrics->style_class;
    284     writing_system_class =
    285       AF_WRITING_SYSTEM_CLASSES_GET[style_class->writing_system];
    286 
    287     loader->metrics = style_metrics;
    288 
    289     if ( writing_system_class->style_metrics_scale )
    290       writing_system_class->style_metrics_scale( style_metrics, &scaler );
    291     else
    292       style_metrics->scaler = scaler;
    293 
    294     if ( writing_system_class->style_hints_init )
    295     {
    296       error = writing_system_class->style_hints_init( hints,
    297                                                       style_metrics );
    298       if ( error )
    299         goto Exit;
    300     }
    301 
    302     /*
    303      *  Do the main work of `af_loader_load_glyph'.  Note that we never have
    304      *  to deal with composite glyphs as those get loaded into
    305      *  FT_GLYPH_FORMAT_OUTLINE by the recursed `FT_Load_Glyph' function.
    306      *  In the rare cases where FT_LOAD_NO_RECURSE is set, it implies
    307      *  FT_LOAD_NO_SCALE and as such the auto-hinter is never called.
    308      */
    309     load_flags |=  FT_LOAD_NO_SCALE         |
    310                    FT_LOAD_IGNORE_TRANSFORM |
    311                    FT_LOAD_LINEAR_DESIGN;
    312     load_flags &= ~FT_LOAD_RENDER;
    313 
    314     error = FT_Load_Glyph( face, glyph_index, load_flags );
    315     if ( error )
    316       goto Exit;
    317 
    318     /*
    319      *  Apply stem darkening (emboldening) here before hints are applied to
    320      *  the outline.  Glyphs are scaled down proportionally to the
    321      *  emboldening so that curve points don't fall outside their
    322      *  precomputed blue zones.
    323      *
    324      *  Any emboldening done by the font driver (e.g., the CFF driver)
    325      *  doesn't reach here because the autohinter loads the unprocessed
    326      *  glyphs in font units for analysis (functions `af_*_metrics_init_*')
    327      *  and then above to prepare it for the rasterizers by itself,
    328      *  independently of the font driver.  So emboldening must be done here,
    329      *  within the autohinter.
    330      *
    331      *  All glyphs to be autohinted pass through here one by one.  The
    332      *  standard widths can therefore change from one glyph to the next,
    333      *  depending on what script a glyph is assigned to (each script has its
    334      *  own set of standard widths and other metrics).  The darkening amount
    335      *  must therefore be recomputed for each size and
    336      *  `standard_{vertical,horizontal}_width' change.
    337      *
    338      *  Ignore errors and carry on without emboldening.
    339      */
    340     if ( !module->no_stem_darkening )
    341       af_loader_embolden_glyph_in_slot( loader, face, style_metrics );
    342 
    343     loader->transformed = internal->glyph_transformed;
    344     if ( loader->transformed )
    345     {
    346       FT_Matrix  inverse;
    347 
    348 
    349       loader->trans_matrix = internal->glyph_matrix;
    350       loader->trans_delta  = internal->glyph_delta;
    351 
    352       inverse = loader->trans_matrix;
    353       if ( !FT_Matrix_Invert( &inverse ) )
    354         FT_Vector_Transform( &loader->trans_delta, &inverse );
    355     }
    356 
    357     switch ( slot->format )
    358     {
    359     case FT_GLYPH_FORMAT_OUTLINE:
    360       /* translate the loaded glyph when an internal transform is needed */
    361       if ( loader->transformed )
    362         FT_Outline_Translate( &slot->outline,
    363                               loader->trans_delta.x,
    364                               loader->trans_delta.y );
    365 
    366       /* compute original horizontal phantom points */
    367       /* (and ignore vertical ones)                 */
    368       loader->pp1.x = hints->x_delta;
    369       loader->pp1.y = hints->y_delta;
    370       loader->pp2.x = FT_MulFix( slot->metrics.horiAdvance,
    371                                  hints->x_scale ) + hints->x_delta;
    372       loader->pp2.y = hints->y_delta;
    373 
    374       /* be sure to check for spacing glyphs */
    375       if ( slot->outline.n_points == 0 )
    376         goto Hint_Metrics;
    377 
    378       /* now load the slot image into the auto-outline */
    379       /* and run the automatic hinting process         */
    380       if ( writing_system_class->style_hints_apply )
    381         writing_system_class->style_hints_apply( glyph_index,
    382                                                  hints,
    383                                                  &gloader->base.outline,
    384                                                  style_metrics );
    385 
    386       /* we now need to adjust the metrics according to the change in */
    387       /* width/positioning that occurred during the hinting process   */
    388       if ( scaler.render_mode != FT_RENDER_MODE_LIGHT )
    389       {
    390         FT_Pos  old_rsb, old_lsb, new_lsb;
    391         FT_Pos  pp1x_uh, pp2x_uh;
    392 
    393         AF_AxisHints  axis  = &hints->axis[AF_DIMENSION_HORZ];
    394         AF_Edge       edge1 = axis->edges;         /* leftmost edge  */
    395         AF_Edge       edge2 = edge1 +
    396                               axis->num_edges - 1; /* rightmost edge */
    397 
    398 
    399         if ( axis->num_edges > 1 && AF_HINTS_DO_ADVANCE( hints ) )
    400         {
    401           old_rsb = loader->pp2.x - edge2->opos;
    402           /* loader->pp1.x is always zero at this point of time */
    403           old_lsb = edge1->opos /* - loader->pp1.x */;
    404           new_lsb = edge1->pos;
    405 
    406           /* remember unhinted values to later account */
    407           /* for rounding errors                       */
    408           pp1x_uh = new_lsb    - old_lsb;
    409           pp2x_uh = edge2->pos + old_rsb;
    410 
    411           /* prefer too much space over too little space */
    412           /* for very small sizes                        */
    413 
    414           if ( old_lsb < 24 )
    415             pp1x_uh -= 8;
    416 
    417           if ( old_rsb < 24 )
    418             pp2x_uh += 8;
    419 
    420           loader->pp1.x = FT_PIX_ROUND( pp1x_uh );
    421           loader->pp2.x = FT_PIX_ROUND( pp2x_uh );
    422 
    423           if ( loader->pp1.x >= new_lsb && old_lsb > 0 )
    424             loader->pp1.x -= 64;
    425 
    426           if ( loader->pp2.x <= edge2->pos && old_rsb > 0 )
    427             loader->pp2.x += 64;
    428 
    429           slot->lsb_delta = loader->pp1.x - pp1x_uh;
    430           slot->rsb_delta = loader->pp2.x - pp2x_uh;
    431         }
    432         else
    433         {
    434           FT_Pos  pp1x = loader->pp1.x;
    435           FT_Pos  pp2x = loader->pp2.x;
    436 
    437 
    438           loader->pp1.x = FT_PIX_ROUND( pp1x );
    439           loader->pp2.x = FT_PIX_ROUND( pp2x );
    440 
    441           slot->lsb_delta = loader->pp1.x - pp1x;
    442           slot->rsb_delta = loader->pp2.x - pp2x;
    443         }
    444       }
    445       else
    446       {
    447         FT_Pos  pp1x = loader->pp1.x;
    448         FT_Pos  pp2x = loader->pp2.x;
    449 
    450 
    451         loader->pp1.x = FT_PIX_ROUND( pp1x + hints->xmin_delta );
    452         loader->pp2.x = FT_PIX_ROUND( pp2x + hints->xmax_delta );
    453 
    454         slot->lsb_delta = loader->pp1.x - pp1x;
    455         slot->rsb_delta = loader->pp2.x - pp2x;
    456       }
    457 
    458       break;
    459 
    460     default:
    461       /* we don't support other formats (yet?) */
    462       error = FT_THROW( Unimplemented_Feature );
    463     }
    464 
    465   Hint_Metrics:
    466     {
    467       FT_BBox    bbox;
    468       FT_Vector  vvector;
    469 
    470 
    471       vvector.x = slot->metrics.vertBearingX - slot->metrics.horiBearingX;
    472       vvector.y = slot->metrics.vertBearingY - slot->metrics.horiBearingY;
    473       vvector.x = FT_MulFix( vvector.x, style_metrics->scaler.x_scale );
    474       vvector.y = FT_MulFix( vvector.y, style_metrics->scaler.y_scale );
    475 
    476       /* transform the hinted outline if needed */
    477       if ( loader->transformed )
    478       {
    479         FT_Outline_Transform( &gloader->base.outline, &loader->trans_matrix );
    480         FT_Vector_Transform( &vvector, &loader->trans_matrix );
    481       }
    482 
    483       /* we must translate our final outline by -pp1.x and compute */
    484       /* the new metrics                                           */
    485       if ( loader->pp1.x )
    486         FT_Outline_Translate( &gloader->base.outline, -loader->pp1.x, 0 );
    487 
    488       FT_Outline_Get_CBox( &gloader->base.outline, &bbox );
    489 
    490       bbox.xMin = FT_PIX_FLOOR( bbox.xMin );
    491       bbox.yMin = FT_PIX_FLOOR( bbox.yMin );
    492       bbox.xMax = FT_PIX_CEIL(  bbox.xMax );
    493       bbox.yMax = FT_PIX_CEIL(  bbox.yMax );
    494 
    495       slot->metrics.width        = bbox.xMax - bbox.xMin;
    496       slot->metrics.height       = bbox.yMax - bbox.yMin;
    497       slot->metrics.horiBearingX = bbox.xMin;
    498       slot->metrics.horiBearingY = bbox.yMax;
    499 
    500       slot->metrics.vertBearingX = FT_PIX_FLOOR( bbox.xMin + vvector.x );
    501       slot->metrics.vertBearingY = FT_PIX_FLOOR( bbox.yMax + vvector.y );
    502 
    503       /* for mono-width fonts (like Andale, Courier, etc.) we need */
    504       /* to keep the original rounded advance width; ditto for     */
    505       /* digits if all have the same advance width                 */
    506       if ( scaler.render_mode != FT_RENDER_MODE_LIGHT                       &&
    507            ( FT_IS_FIXED_WIDTH( slot->face )                              ||
    508              ( af_face_globals_is_digit( loader->globals, glyph_index ) &&
    509                style_metrics->digits_have_same_width                    ) ) )
    510       {
    511         slot->metrics.horiAdvance =
    512           FT_MulFix( slot->metrics.horiAdvance,
    513                      style_metrics->scaler.x_scale );
    514 
    515         /* Set delta values to 0.  Otherwise code that uses them is */
    516         /* going to ruin the fixed advance width.                   */
    517         slot->lsb_delta = 0;
    518         slot->rsb_delta = 0;
    519       }
    520       else
    521       {
    522         /* non-spacing glyphs must stay as-is */
    523         if ( slot->metrics.horiAdvance )
    524           slot->metrics.horiAdvance = loader->pp2.x - loader->pp1.x;
    525       }
    526 
    527       slot->metrics.vertAdvance = FT_MulFix( slot->metrics.vertAdvance,
    528                                              style_metrics->scaler.y_scale );
    529 
    530       slot->metrics.horiAdvance = FT_PIX_ROUND( slot->metrics.horiAdvance );
    531       slot->metrics.vertAdvance = FT_PIX_ROUND( slot->metrics.vertAdvance );
    532 
    533       slot->format  = FT_GLYPH_FORMAT_OUTLINE;
    534     }
    535 
    536   Exit:
    537     return error;
    538   }
    539 
    540 
    541   /*
    542    * Compute amount of font units the face should be emboldened by, in
    543    * analogy to the CFF driver's `cf2_computeDarkening' function.  See there
    544    * for details of the algorithm.
    545    *
    546    * XXX: Currently a crude adaption of the original algorithm.  Do better?
    547    */
    548   FT_LOCAL_DEF( FT_Int32 )
    549   af_loader_compute_darkening( AF_Loader  loader,
    550                                FT_Face    face,
    551                                FT_Pos     standard_width )
    552   {
    553     AF_Module  module = loader->globals->module;
    554 
    555     FT_UShort  units_per_EM;
    556     FT_Fixed   ppem, em_ratio;
    557     FT_Fixed   stem_width, stem_width_per_1000, scaled_stem, darken_amount;
    558     FT_Int     log_base_2;
    559     FT_Int     x1, y1, x2, y2, x3, y3, x4, y4;
    560 
    561 
    562     ppem         = FT_MAX( af_intToFixed( 4 ),
    563                            af_intToFixed( face->size->metrics.x_ppem ) );
    564     units_per_EM = face->units_per_EM;
    565 
    566     em_ratio = FT_DivFix( af_intToFixed( 1000 ),
    567                           af_intToFixed ( units_per_EM ) );
    568     if ( em_ratio < af_floatToFixed( .01 ) )
    569     {
    570       /* If something goes wrong, don't embolden. */
    571       return 0;
    572     }
    573 
    574     x1 = module->darken_params[0];
    575     y1 = module->darken_params[1];
    576     x2 = module->darken_params[2];
    577     y2 = module->darken_params[3];
    578     x3 = module->darken_params[4];
    579     y3 = module->darken_params[5];
    580     x4 = module->darken_params[6];
    581     y4 = module->darken_params[7];
    582 
    583     if ( standard_width <= 0 )
    584     {
    585       stem_width          = af_intToFixed( 75 ); /* taken from cf2font.c */
    586       stem_width_per_1000 = stem_width;
    587     }
    588     else
    589     {
    590       stem_width          = af_intToFixed( standard_width );
    591       stem_width_per_1000 = FT_MulFix( stem_width, em_ratio );
    592     }
    593 
    594     log_base_2 = FT_MSB( (FT_UInt32)stem_width_per_1000 ) +
    595                  FT_MSB( (FT_UInt32)ppem );
    596 
    597     if ( log_base_2 >= 46 )
    598     {
    599       /* possible overflow */
    600       scaled_stem = af_intToFixed( x4 );
    601     }
    602     else
    603       scaled_stem = FT_MulFix( stem_width_per_1000, ppem );
    604 
    605     /* now apply the darkening parameters */
    606     if ( scaled_stem < af_intToFixed( x1 ) )
    607       darken_amount = FT_DivFix( af_intToFixed( y1 ), ppem );
    608 
    609     else if ( scaled_stem < af_intToFixed( x2 ) )
    610     {
    611       FT_Int  xdelta = x2 - x1;
    612       FT_Int  ydelta = y2 - y1;
    613       FT_Int  x      = stem_width_per_1000 -
    614                        FT_DivFix( af_intToFixed( x1 ), ppem );
    615 
    616 
    617       if ( !xdelta )
    618         goto Try_x3;
    619 
    620       darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
    621                       FT_DivFix( af_intToFixed( y1 ), ppem );
    622     }
    623 
    624     else if ( scaled_stem < af_intToFixed( x3 ) )
    625     {
    626     Try_x3:
    627       {
    628         FT_Int  xdelta = x3 - x2;
    629         FT_Int  ydelta = y3 - y2;
    630         FT_Int  x      = stem_width_per_1000 -
    631                          FT_DivFix( af_intToFixed( x2 ), ppem );
    632 
    633 
    634         if ( !xdelta )
    635           goto Try_x4;
    636 
    637         darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
    638                         FT_DivFix( af_intToFixed( y2 ), ppem );
    639       }
    640     }
    641 
    642     else if ( scaled_stem < af_intToFixed( x4 ) )
    643     {
    644     Try_x4:
    645       {
    646         FT_Int  xdelta = x4 - x3;
    647         FT_Int  ydelta = y4 - y3;
    648         FT_Int  x      = stem_width_per_1000 -
    649                          FT_DivFix( af_intToFixed( x3 ), ppem );
    650 
    651 
    652         if ( !xdelta )
    653           goto Use_y4;
    654 
    655         darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
    656                         FT_DivFix( af_intToFixed( y3 ), ppem );
    657       }
    658     }
    659 
    660     else
    661     {
    662     Use_y4:
    663       darken_amount = FT_DivFix( af_intToFixed( y4 ), ppem );
    664     }
    665 
    666     /* Convert darken_amount from per 1000 em to true character space. */
    667     return af_fixedToInt( FT_DivFix( darken_amount, em_ratio ) );
    668   }
    669 
    670 
    671 /* END */
    672