1 /****************************************************************************
2 *
3 * afloader.c
4 *
5 * Auto-fitter glyph loading routines (body).
6 *
7 * Copyright (C) 2003-2020 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
25 #include FT_INTERNAL_CALC_H
26
27
28 /* Initialize glyph loader. */
29
30 FT_LOCAL_DEF( void )
31 af_loader_init( AF_Loader loader,
32 AF_GlyphHints hints )
33 {
34 FT_ZERO( loader );
35
36 loader->hints = hints;
37 }
38
39
40 /* Reset glyph loader and compute globals if necessary. */
41
42 FT_LOCAL_DEF( FT_Error )
43 af_loader_reset( AF_Loader loader,
44 AF_Module module,
45 FT_Face face )
46 {
47 FT_Error error = FT_Err_Ok;
48
49
50 loader->face = face;
51 loader->globals = (AF_FaceGlobals)face->autohint.data;
52
53 if ( !loader->globals )
54 {
55 error = af_face_globals_new( face, &loader->globals, module );
56 if ( !error )
57 {
58 face->autohint.data =
59 (FT_Pointer)loader->globals;
60 face->autohint.finalizer =
61 (FT_Generic_Finalizer)af_face_globals_free;
62 }
63 }
64
65 return error;
66 }
67
68
69 /* Finalize glyph loader. */
70
71 FT_LOCAL_DEF( void )
72 af_loader_done( AF_Loader loader )
73 {
74 loader->face = NULL;
75 loader->globals = NULL;
76 loader->hints = NULL;
77 }
78
79
80 #define af_intToFixed( i ) \
81 ( (FT_Fixed)( (FT_UInt32)(i) << 16 ) )
82 #define af_fixedToInt( x ) \
83 ( (FT_Short)( ( (FT_UInt32)(x) + 0x8000U ) >> 16 ) )
84 #define af_floatToFixed( f ) \
85 ( (FT_Fixed)( (f) * 65536.0 + 0.5 ) )
86
87
88 static FT_Error
89 af_loader_embolden_glyph_in_slot( AF_Loader loader,
90 FT_Face face,
91 AF_StyleMetrics style_metrics )
92 {
93 FT_Error error = FT_Err_Ok;
94
95 FT_GlyphSlot slot = face->glyph;
96 AF_FaceGlobals globals = loader->globals;
97 AF_WritingSystemClass writing_system_class;
98
99 FT_Size_Metrics* size_metrics = &face->size->internal->autohint_metrics;
100
101 FT_Pos stdVW = 0;
102 FT_Pos stdHW = 0;
103
104 FT_Bool size_changed = size_metrics->x_ppem !=
105 globals->stem_darkening_for_ppem;
106
107 FT_Fixed em_size = af_intToFixed( face->units_per_EM );
108 FT_Fixed em_ratio = FT_DivFix( af_intToFixed( 1000 ), em_size );
109
110 FT_Matrix scale_down_matrix = { 0x10000L, 0, 0, 0x10000L };
111
112
113 /* Skip stem darkening for broken fonts. */
114 if ( !face->units_per_EM )
115 {
116 error = FT_ERR( Corrupted_Font_Header );
117 goto Exit;
118 }
119
120 /*
121 * We depend on the writing system (script analyzers) to supply
122 * standard widths for the script of the glyph we are looking at. If
123 * it can't deliver, stem darkening is disabled.
124 */
125 writing_system_class =
126 af_writing_system_classes[style_metrics->style_class->writing_system];
127
128 if ( writing_system_class->style_metrics_getstdw )
129 writing_system_class->style_metrics_getstdw( style_metrics,
130 &stdHW,
131 &stdVW );
132 else
133 {
134 error = FT_ERR( Unimplemented_Feature );
135 goto Exit;
136 }
137
138 if ( size_changed ||
139 ( stdVW > 0 && stdVW != globals->standard_vertical_width ) )
140 {
141 FT_Fixed darken_by_font_units_x, darken_x;
142
143
144 darken_by_font_units_x =
145 af_intToFixed( af_loader_compute_darkening( loader,
146 face,
147 stdVW ) );
148 darken_x = FT_DivFix( FT_MulFix( darken_by_font_units_x,
149 size_metrics->x_scale ),
150 em_ratio );
151
152 globals->standard_vertical_width = stdVW;
153 globals->stem_darkening_for_ppem = size_metrics->x_ppem;
154 globals->darken_x = af_fixedToInt( darken_x );
155 }
156
157 if ( size_changed ||
158 ( stdHW > 0 && stdHW != globals->standard_horizontal_width ) )
159 {
160 FT_Fixed darken_by_font_units_y, darken_y;
161
162
163 darken_by_font_units_y =
164 af_intToFixed( af_loader_compute_darkening( loader,
165 face,
166 stdHW ) );
167 darken_y = FT_DivFix( FT_MulFix( darken_by_font_units_y,
168 size_metrics->y_scale ),
169 em_ratio );
170
171 globals->standard_horizontal_width = stdHW;
172 globals->stem_darkening_for_ppem = size_metrics->x_ppem;
173 globals->darken_y = af_fixedToInt( darken_y );
174
175 /*
176 * Scale outlines down on the Y-axis to keep them inside their blue
177 * zones. The stronger the emboldening, the stronger the downscaling
178 * (plus heuristical padding to prevent outlines still falling out
179 * their zones due to rounding).
180 *
181 * Reason: `FT_Outline_Embolden' works by shifting the rightmost
182 * points of stems farther to the right, and topmost points farther
183 * up. This positions points on the Y-axis outside their
184 * pre-computed blue zones and leads to distortion when applying the
185 * hints in the code further below. Code outside this emboldening
186 * block doesn't know we are presenting it with modified outlines the
187 * analyzer didn't see!
188 *
189 * An unfortunate side effect of downscaling is that the emboldening
190 * effect is slightly decreased. The loss becomes more pronounced
191 * versus the CFF driver at smaller sizes, e.g., at 9ppem and below.
192 */
193 globals->scale_down_factor =
194 FT_DivFix( em_size - ( darken_by_font_units_y + af_intToFixed( 8 ) ),
195 em_size );
196 }
197
198 FT_Outline_EmboldenXY( &slot->outline,
199 globals->darken_x,
200 globals->darken_y );
201
202 scale_down_matrix.yy = globals->scale_down_factor;
203 FT_Outline_Transform( &slot->outline, &scale_down_matrix );
204
205 Exit:
206 return error;
207 }
208
209
210 /* Load the glyph at index into the current slot of a face and hint it. */
211
212 FT_LOCAL_DEF( FT_Error )
213 af_loader_load_glyph( AF_Loader loader,
214 AF_Module module,
215 FT_Face face,
216 FT_UInt glyph_index,
217 FT_Int32 load_flags )
218 {
219 FT_Error error;
220
221 FT_Size size = face->size;
222 FT_Size_Internal size_internal = size->internal;
223 FT_GlyphSlot slot = face->glyph;
224 FT_Slot_Internal slot_internal = slot->internal;
225 FT_GlyphLoader gloader = slot_internal->loader;
226
227 AF_GlyphHints hints = loader->hints;
228 AF_ScalerRec scaler;
229 AF_StyleMetrics style_metrics;
230 FT_UInt style_options = AF_STYLE_NONE_DFLT;
231 AF_StyleClass style_class;
232 AF_WritingSystemClass writing_system_class;
233
234
235 if ( !size )
236 return FT_THROW( Invalid_Size_Handle );
237
238 FT_ZERO( &scaler );
239
240 if ( !size_internal->autohint_metrics.x_scale ||
241 size_internal->autohint_mode != FT_LOAD_TARGET_MODE( load_flags ) )
242 {
243 /* switching between hinting modes usually means different scaling */
244 /* values; this later on enforces recomputation of everything */
245 /* related to the current size */
246
247 size_internal->autohint_mode = FT_LOAD_TARGET_MODE( load_flags );
248 size_internal->autohint_metrics = size->metrics;
249
250 #ifdef AF_CONFIG_OPTION_TT_SIZE_METRICS
251 {
252 FT_Size_Metrics* size_metrics = &size_internal->autohint_metrics;
253
254
255 /* set metrics to integer values and adjust scaling accordingly; */
256 /* this is the same setup as with TrueType fonts, cf. function */
257 /* `tt_size_reset' in file `ttobjs.c' */
258 size_metrics->ascender = FT_PIX_ROUND(
259 FT_MulFix( face->ascender,
260 size_metrics->y_scale ) );
261 size_metrics->descender = FT_PIX_ROUND(
262 FT_MulFix( face->descender,
263 size_metrics->y_scale ) );
264 size_metrics->height = FT_PIX_ROUND(
265 FT_MulFix( face->height,
266 size_metrics->y_scale ) );
267
268 size_metrics->x_scale = FT_DivFix( size_metrics->x_ppem << 6,
269 face->units_per_EM );
270 size_metrics->y_scale = FT_DivFix( size_metrics->y_ppem << 6,
271 face->units_per_EM );
272 size_metrics->max_advance = FT_PIX_ROUND(
273 FT_MulFix( face->max_advance_width,
274 size_metrics->x_scale ) );
275 }
276 #endif /* AF_CONFIG_OPTION_TT_SIZE_METRICS */
277 }
278
279 /*
280 * TODO: This code currently doesn't support fractional advance widths,
281 * i.e., placing hinted glyphs at anything other than integer
282 * x-positions. This is only relevant for the warper code, which
283 * scales and shifts glyphs to optimize blackness of stems (hinting on
284 * the x-axis by nature places things on pixel integers, hinting on the
285 * y-axis only, i.e., LIGHT mode, doesn't touch the x-axis). The delta
286 * values of the scaler would need to be adjusted.
287 */
288 scaler.face = face;
289 scaler.x_scale = size_internal->autohint_metrics.x_scale;
290 scaler.x_delta = 0;
291 scaler.y_scale = size_internal->autohint_metrics.y_scale;
292 scaler.y_delta = 0;
293
294 scaler.render_mode = FT_LOAD_TARGET_MODE( load_flags );
295 scaler.flags = 0;
296
297 /* note that the fallback style can't be changed anymore */
298 /* after the first call of `af_loader_load_glyph' */
299 error = af_loader_reset( loader, module, face );
300 if ( error )
301 goto Exit;
302
303 #ifdef FT_OPTION_AUTOFIT2
304 /* XXX: undocumented hook to activate the latin2 writing system. */
305 if ( load_flags & ( 1UL << 20 ) )
306 style_options = AF_STYLE_LTN2_DFLT;
307 #endif
308
309 /*
310 * Glyphs (really code points) are assigned to scripts. Script
311 * analysis is done lazily: For each glyph that passes through here,
312 * the corresponding script analyzer is called, but returns immediately
313 * if it has been run already.
314 */
315 error = af_face_globals_get_metrics( loader->globals, glyph_index,
316 style_options, &style_metrics );
317 if ( error )
318 goto Exit;
319
320 style_class = style_metrics->style_class;
321 writing_system_class =
322 af_writing_system_classes[style_class->writing_system];
323
324 loader->metrics = style_metrics;
325
326 if ( writing_system_class->style_metrics_scale )
327 writing_system_class->style_metrics_scale( style_metrics, &scaler );
328 else
329 style_metrics->scaler = scaler;
330
331 if ( writing_system_class->style_hints_init )
332 {
333 error = writing_system_class->style_hints_init( hints,
334 style_metrics );
335 if ( error )
336 goto Exit;
337 }
338
339 /*
340 * Do the main work of `af_loader_load_glyph'. Note that we never have
341 * to deal with composite glyphs as those get loaded into
342 * FT_GLYPH_FORMAT_OUTLINE by the recursed `FT_Load_Glyph' function.
343 * In the rare cases where FT_LOAD_NO_RECURSE is set, it implies
344 * FT_LOAD_NO_SCALE and as such the auto-hinter is never called.
345 */
346 load_flags |= FT_LOAD_NO_SCALE |
347 FT_LOAD_IGNORE_TRANSFORM |
348 FT_LOAD_LINEAR_DESIGN;
349 load_flags &= ~FT_LOAD_RENDER;
350
351 error = FT_Load_Glyph( face, glyph_index, load_flags );
352 if ( error )
353 goto Exit;
354
355 /*
356 * Apply stem darkening (emboldening) here before hints are applied to
357 * the outline. Glyphs are scaled down proportionally to the
358 * emboldening so that curve points don't fall outside their
359 * precomputed blue zones.
360 *
361 * Any emboldening done by the font driver (e.g., the CFF driver)
362 * doesn't reach here because the autohinter loads the unprocessed
363 * glyphs in font units for analysis (functions `af_*_metrics_init_*')
364 * and then above to prepare it for the rasterizers by itself,
365 * independently of the font driver. So emboldening must be done here,
366 * within the autohinter.
367 *
368 * All glyphs to be autohinted pass through here one by one. The
369 * standard widths can therefore change from one glyph to the next,
370 * depending on what script a glyph is assigned to (each script has its
371 * own set of standard widths and other metrics). The darkening amount
372 * must therefore be recomputed for each size and
373 * `standard_{vertical,horizontal}_width' change.
374 *
375 * Ignore errors and carry on without emboldening.
376 *
377 */
378
379 /* stem darkening only works well in `light' mode */
380 if ( scaler.render_mode == FT_RENDER_MODE_LIGHT &&
381 ( !face->internal->no_stem_darkening ||
382 ( face->internal->no_stem_darkening < 0 &&
383 !module->no_stem_darkening ) ) )
384 af_loader_embolden_glyph_in_slot( loader, face, style_metrics );
385
386 loader->transformed = slot_internal->glyph_transformed;
387 if ( loader->transformed )
388 {
389 FT_Matrix inverse;
390
391
392 loader->trans_matrix = slot_internal->glyph_matrix;
393 loader->trans_delta = slot_internal->glyph_delta;
394
395 inverse = loader->trans_matrix;
396 if ( !FT_Matrix_Invert( &inverse ) )
397 FT_Vector_Transform( &loader->trans_delta, &inverse );
398 }
399
400 switch ( slot->format )
401 {
402 case FT_GLYPH_FORMAT_OUTLINE:
403 /* translate the loaded glyph when an internal transform is needed */
404 if ( loader->transformed )
405 FT_Outline_Translate( &slot->outline,
406 loader->trans_delta.x,
407 loader->trans_delta.y );
408
409 /* compute original horizontal phantom points */
410 /* (and ignore vertical ones) */
411 loader->pp1.x = hints->x_delta;
412 loader->pp1.y = hints->y_delta;
413 loader->pp2.x = FT_MulFix( slot->metrics.horiAdvance,
414 hints->x_scale ) + hints->x_delta;
415 loader->pp2.y = hints->y_delta;
416
417 /* be sure to check for spacing glyphs */
418 if ( slot->outline.n_points == 0 )
419 goto Hint_Metrics;
420
421 /* now load the slot image into the auto-outline */
422 /* and run the automatic hinting process */
423 if ( writing_system_class->style_hints_apply )
424 {
425 error = writing_system_class->style_hints_apply(
426 glyph_index,
427 hints,
428 &gloader->base.outline,
429 style_metrics );
430 if ( error )
431 goto Exit;
432 }
433
434 /* we now need to adjust the metrics according to the change in */
435 /* width/positioning that occurred during the hinting process */
436 if ( scaler.render_mode != FT_RENDER_MODE_LIGHT )
437 {
438 AF_AxisHints axis = &hints->axis[AF_DIMENSION_HORZ];
439
440
441 if ( axis->num_edges > 1 && AF_HINTS_DO_ADVANCE( hints ) )
442 {
443 AF_Edge edge1 = axis->edges; /* leftmost edge */
444 AF_Edge edge2 = edge1 +
445 axis->num_edges - 1; /* rightmost edge */
446
447 FT_Pos old_rsb = loader->pp2.x - edge2->opos;
448 /* loader->pp1.x is always zero at this point of time */
449 FT_Pos old_lsb = edge1->opos; /* - loader->pp1.x */
450 FT_Pos new_lsb = edge1->pos;
451
452 /* remember unhinted values to later account */
453 /* for rounding errors */
454 FT_Pos pp1x_uh = new_lsb - old_lsb;
455 FT_Pos pp2x_uh = edge2->pos + old_rsb;
456
457
458 /* prefer too much space over too little space */
459 /* for very small sizes */
460
461 if ( old_lsb < 24 )
462 pp1x_uh -= 8;
463
464 if ( old_rsb < 24 )
465 pp2x_uh += 8;
466
467 loader->pp1.x = FT_PIX_ROUND( pp1x_uh );
468 loader->pp2.x = FT_PIX_ROUND( pp2x_uh );
469
470 if ( loader->pp1.x >= new_lsb && old_lsb > 0 )
471 loader->pp1.x -= 64;
472
473 if ( loader->pp2.x <= edge2->pos && old_rsb > 0 )
474 loader->pp2.x += 64;
475
476 slot->lsb_delta = loader->pp1.x - pp1x_uh;
477 slot->rsb_delta = loader->pp2.x - pp2x_uh;
478 }
479 else
480 {
481 FT_Pos pp1x = loader->pp1.x;
482 FT_Pos pp2x = loader->pp2.x;
483
484
485 loader->pp1.x = FT_PIX_ROUND( pp1x + hints->xmin_delta );
486 loader->pp2.x = FT_PIX_ROUND( pp2x + hints->xmax_delta );
487
488 slot->lsb_delta = loader->pp1.x - pp1x;
489 slot->rsb_delta = loader->pp2.x - pp2x;
490 }
491 }
492 /* `light' mode uses integer advance widths */
493 /* but sets `lsb_delta' and `rsb_delta' */
494 else
495 {
496 FT_Pos pp1x = loader->pp1.x;
497 FT_Pos pp2x = loader->pp2.x;
498
499
500 loader->pp1.x = FT_PIX_ROUND( pp1x );
501 loader->pp2.x = FT_PIX_ROUND( pp2x );
502
503 slot->lsb_delta = loader->pp1.x - pp1x;
504 slot->rsb_delta = loader->pp2.x - pp2x;
505 }
506
507 break;
508
509 default:
510 /* we don't support other formats (yet?) */
511 error = FT_THROW( Unimplemented_Feature );
512 }
513
514 Hint_Metrics:
515 {
516 FT_BBox bbox;
517 FT_Vector vvector;
518
519
520 vvector.x = slot->metrics.vertBearingX - slot->metrics.horiBearingX;
521 vvector.y = slot->metrics.vertBearingY - slot->metrics.horiBearingY;
522 vvector.x = FT_MulFix( vvector.x, style_metrics->scaler.x_scale );
523 vvector.y = FT_MulFix( vvector.y, style_metrics->scaler.y_scale );
524
525 /* transform the hinted outline if needed */
526 if ( loader->transformed )
527 {
528 FT_Outline_Transform( &gloader->base.outline, &loader->trans_matrix );
529 FT_Vector_Transform( &vvector, &loader->trans_matrix );
530 }
531
532 /* we must translate our final outline by -pp1.x and compute */
533 /* the new metrics */
534 if ( loader->pp1.x )
535 FT_Outline_Translate( &gloader->base.outline, -loader->pp1.x, 0 );
536
537 FT_Outline_Get_CBox( &gloader->base.outline, &bbox );
538
539 bbox.xMin = FT_PIX_FLOOR( bbox.xMin );
540 bbox.yMin = FT_PIX_FLOOR( bbox.yMin );
541 bbox.xMax = FT_PIX_CEIL( bbox.xMax );
542 bbox.yMax = FT_PIX_CEIL( bbox.yMax );
543
544 slot->metrics.width = bbox.xMax - bbox.xMin;
545 slot->metrics.height = bbox.yMax - bbox.yMin;
546 slot->metrics.horiBearingX = bbox.xMin;
547 slot->metrics.horiBearingY = bbox.yMax;
548
549 slot->metrics.vertBearingX = FT_PIX_FLOOR( bbox.xMin + vvector.x );
550 slot->metrics.vertBearingY = FT_PIX_FLOOR( bbox.yMax + vvector.y );
551
552 /* for mono-width fonts (like Andale, Courier, etc.) we need */
553 /* to keep the original rounded advance width; ditto for */
554 /* digits if all have the same advance width */
555 if ( scaler.render_mode != FT_RENDER_MODE_LIGHT &&
556 ( FT_IS_FIXED_WIDTH( slot->face ) ||
557 ( af_face_globals_is_digit( loader->globals, glyph_index ) &&
558 style_metrics->digits_have_same_width ) ) )
559 {
560 slot->metrics.horiAdvance =
561 FT_MulFix( slot->metrics.horiAdvance,
562 style_metrics->scaler.x_scale );
563
564 /* Set delta values to 0. Otherwise code that uses them is */
565 /* going to ruin the fixed advance width. */
566 slot->lsb_delta = 0;
567 slot->rsb_delta = 0;
568 }
569 else
570 {
571 /* non-spacing glyphs must stay as-is */
572 if ( slot->metrics.horiAdvance )
573 slot->metrics.horiAdvance = loader->pp2.x - loader->pp1.x;
574 }
575
576 slot->metrics.vertAdvance = FT_MulFix( slot->metrics.vertAdvance,
577 style_metrics->scaler.y_scale );
578
579 slot->metrics.horiAdvance = FT_PIX_ROUND( slot->metrics.horiAdvance );
580 slot->metrics.vertAdvance = FT_PIX_ROUND( slot->metrics.vertAdvance );
581
582 slot->format = FT_GLYPH_FORMAT_OUTLINE;
583 }
584
585 Exit:
586 return error;
587 }
588
589
590 /*
591 * Compute amount of font units the face should be emboldened by, in
592 * analogy to the CFF driver's `cf2_computeDarkening' function. See there
593 * for details of the algorithm.
594 *
595 * XXX: Currently a crude adaption of the original algorithm. Do better?
596 */
597 FT_LOCAL_DEF( FT_Int32 )
598 af_loader_compute_darkening( AF_Loader loader,
599 FT_Face face,
600 FT_Pos standard_width )
601 {
602 AF_Module module = loader->globals->module;
603
604 FT_UShort units_per_EM;
605 FT_Fixed ppem, em_ratio;
606 FT_Fixed stem_width, stem_width_per_1000, scaled_stem, darken_amount;
607 FT_Int log_base_2;
608 FT_Int x1, y1, x2, y2, x3, y3, x4, y4;
609
610
611 ppem = FT_MAX( af_intToFixed( 4 ),
612 af_intToFixed( face->size->metrics.x_ppem ) );
613 units_per_EM = face->units_per_EM;
614
615 em_ratio = FT_DivFix( af_intToFixed( 1000 ),
616 af_intToFixed ( units_per_EM ) );
617 if ( em_ratio < af_floatToFixed( .01 ) )
618 {
619 /* If something goes wrong, don't embolden. */
620 return 0;
621 }
622
623 x1 = module->darken_params[0];
624 y1 = module->darken_params[1];
625 x2 = module->darken_params[2];
626 y2 = module->darken_params[3];
627 x3 = module->darken_params[4];
628 y3 = module->darken_params[5];
629 x4 = module->darken_params[6];
630 y4 = module->darken_params[7];
631
632 if ( standard_width <= 0 )
633 {
634 stem_width = af_intToFixed( 75 ); /* taken from cf2font.c */
635 stem_width_per_1000 = stem_width;
636 }
637 else
638 {
639 stem_width = af_intToFixed( standard_width );
640 stem_width_per_1000 = FT_MulFix( stem_width, em_ratio );
641 }
642
643 log_base_2 = FT_MSB( (FT_UInt32)stem_width_per_1000 ) +
644 FT_MSB( (FT_UInt32)ppem );
645
646 if ( log_base_2 >= 46 )
647 {
648 /* possible overflow */
649 scaled_stem = af_intToFixed( x4 );
650 }
651 else
652 scaled_stem = FT_MulFix( stem_width_per_1000, ppem );
653
654 /* now apply the darkening parameters */
655 if ( scaled_stem < af_intToFixed( x1 ) )
656 darken_amount = FT_DivFix( af_intToFixed( y1 ), ppem );
657
658 else if ( scaled_stem < af_intToFixed( x2 ) )
659 {
660 FT_Int xdelta = x2 - x1;
661 FT_Int ydelta = y2 - y1;
662 FT_Int x = stem_width_per_1000 -
663 FT_DivFix( af_intToFixed( x1 ), ppem );
664
665
666 if ( !xdelta )
667 goto Try_x3;
668
669 darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
670 FT_DivFix( af_intToFixed( y1 ), ppem );
671 }
672
673 else if ( scaled_stem < af_intToFixed( x3 ) )
674 {
675 Try_x3:
676 {
677 FT_Int xdelta = x3 - x2;
678 FT_Int ydelta = y3 - y2;
679 FT_Int x = stem_width_per_1000 -
680 FT_DivFix( af_intToFixed( x2 ), ppem );
681
682
683 if ( !xdelta )
684 goto Try_x4;
685
686 darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
687 FT_DivFix( af_intToFixed( y2 ), ppem );
688 }
689 }
690
691 else if ( scaled_stem < af_intToFixed( x4 ) )
692 {
693 Try_x4:
694 {
695 FT_Int xdelta = x4 - x3;
696 FT_Int ydelta = y4 - y3;
697 FT_Int x = stem_width_per_1000 -
698 FT_DivFix( af_intToFixed( x3 ), ppem );
699
700
701 if ( !xdelta )
702 goto Use_y4;
703
704 darken_amount = FT_MulDiv( x, ydelta, xdelta ) +
705 FT_DivFix( af_intToFixed( y3 ), ppem );
706 }
707 }
708
709 else
710 {
711 Use_y4:
712 darken_amount = FT_DivFix( af_intToFixed( y4 ), ppem );
713 }
714
715 /* Convert darken_amount from per 1000 em to true character space. */
716 return af_fixedToInt( FT_DivFix( darken_amount, em_ratio ) );
717 }
718
719
720 /* END */