1 /*
   2  * Copyright © 2011,2012  Google, Inc.
   3  *
   4  *  This is part of HarfBuzz, a text shaping library.
   5  *
   6  * Permission is hereby granted, without written agreement and without
   7  * license or royalty fees, to use, copy, modify, and distribute this
   8  * software and its documentation for any purpose, provided that the
   9  * above copyright notice and the following two paragraphs appear in
  10  * all copies of this software.
  11  *
  12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  16  * DAMAGE.
  17  *
  18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  *
  24  * Google Author(s): Behdad Esfahbod, Roderick Sheeter
  25  */
  26 
  27 #ifndef HB_OT_HMTX_TABLE_HH
  28 #define HB_OT_HMTX_TABLE_HH
  29 
  30 #include "hb-open-type.hh"
  31 #include "hb-ot-hhea-table.hh"
  32 #include "hb-ot-os2-table.hh"
  33 #include "hb-ot-var-hvar-table.hh"
  34 
  35 /*
  36  * hmtx -- Horizontal Metrics
  37  * https://docs.microsoft.com/en-us/typography/opentype/spec/hmtx
  38  * vmtx -- Vertical Metrics
  39  * https://docs.microsoft.com/en-us/typography/opentype/spec/vmtx
  40  */
  41 #define HB_OT_TAG_hmtx HB_TAG('h','m','t','x')
  42 #define HB_OT_TAG_vmtx HB_TAG('v','m','t','x')
  43 
  44 
  45 namespace OT {
  46 
  47 
  48 struct LongMetric
  49 {
  50   UFWORD        advance; /* Advance width/height. */
  51   FWORD         sb; /* Leading (left/top) side bearing. */
  52   public:
  53   DEFINE_SIZE_STATIC (4);
  54 };
  55 
  56 template <typename T, typename H>
  57 struct hmtxvmtx
  58 {
  59   bool sanitize (hb_sanitize_context_t *c HB_UNUSED) const
  60   {
  61     TRACE_SANITIZE (this);
  62     /* We don't check for anything specific here.  The users of the
  63      * struct do all the hard work... */
  64     return_trace (true);
  65   }
  66 
  67 
  68   bool subset_update_header (hb_subset_plan_t *plan,
  69                                     unsigned int num_hmetrics) const
  70   {
  71     hb_blob_t *src_blob = hb_sanitize_context_t ().reference_table<H> (plan->source, H::tableTag);
  72     hb_blob_t *dest_blob = hb_blob_copy_writable_or_fail (src_blob);
  73     hb_blob_destroy (src_blob);
  74 
  75     if (unlikely (!dest_blob)) {
  76       return false;
  77     }
  78 
  79     unsigned int length;
  80     H *table = (H *) hb_blob_get_data (dest_blob, &length);
  81     table->numberOfLongMetrics.set (num_hmetrics);
  82 
  83     bool result = plan->add_table (H::tableTag, dest_blob);
  84     hb_blob_destroy (dest_blob);
  85 
  86     return result;
  87   }
  88 
  89   bool subset (hb_subset_plan_t *plan) const
  90   {
  91     typename T::accelerator_t _mtx;
  92     _mtx.init (plan->source);
  93 
  94     /* All the trailing glyphs with the same advance can use one LongMetric
  95      * and just keep LSB */
  96     hb_vector_t<hb_codepoint_t> &gids = plan->glyphs;
  97     unsigned int num_advances = gids.length;
  98     unsigned int last_advance = _mtx.get_advance (gids[num_advances - 1]);
  99     while (num_advances > 1 &&
 100            last_advance == _mtx.get_advance (gids[num_advances - 2]))
 101     {
 102       num_advances--;
 103     }
 104 
 105     /* alloc the new table */
 106     size_t dest_sz = num_advances * 4
 107                   + (gids.length - num_advances) * 2;
 108     void *dest = (void *) malloc (dest_sz);
 109     if (unlikely (!dest))
 110     {
 111       return false;
 112     }
 113     DEBUG_MSG(SUBSET, nullptr, "%c%c%c%c in src has %d advances, %d lsbs", HB_UNTAG(T::tableTag), _mtx.num_advances, _mtx.num_metrics - _mtx.num_advances);
 114     DEBUG_MSG(SUBSET, nullptr, "%c%c%c%c in dest has %d advances, %d lsbs, %u bytes", HB_UNTAG(T::tableTag), num_advances, gids.length - num_advances, (unsigned int) dest_sz);
 115 
 116     const char *source_table = hb_blob_get_data (_mtx.table.get_blob (), nullptr);
 117     // Copy everything over
 118     LongMetric * old_metrics = (LongMetric *) source_table;
 119     FWORD *lsbs = (FWORD *) (old_metrics + _mtx.num_advances);
 120     char * dest_pos = (char *) dest;
 121 
 122     bool failed = false;
 123     for (unsigned int i = 0; i < gids.length; i++)
 124     {
 125       /* the last metric or the one for gids[i] */
 126       LongMetric *src_metric = old_metrics + MIN ((hb_codepoint_t) _mtx.num_advances - 1, gids[i]);
 127       if (gids[i] < _mtx.num_advances)
 128       {
 129         /* src is a LongMetric */
 130         if (i < num_advances)
 131         {
 132           /* dest is a LongMetric, copy it */
 133           *((LongMetric *) dest_pos) = *src_metric;
 134         }
 135         else
 136         {
 137           /* dest just sb */
 138           *((FWORD *) dest_pos) = src_metric->sb;
 139         }
 140       }
 141       else
 142       {
 143         if (gids[i] >= _mtx.num_metrics)
 144         {
 145           DEBUG_MSG(SUBSET, nullptr, "gid %d is >= number of source metrics %d",
 146                     gids[i], _mtx.num_metrics);
 147           failed = true;
 148           break;
 149         }
 150         FWORD src_sb = *(lsbs + gids[i] - _mtx.num_advances);
 151         if (i < num_advances)
 152         {
 153           /* dest needs a full LongMetric */
 154           LongMetric *metric = (LongMetric *)dest_pos;
 155           metric->advance = src_metric->advance;
 156           metric->sb = src_sb;
 157         }
 158         else
 159         {
 160           /* dest just needs an sb */
 161           *((FWORD *) dest_pos) = src_sb;
 162         }
 163       }
 164       dest_pos += (i < num_advances ? 4 : 2);
 165     }
 166     _mtx.fini ();
 167 
 168     // Amend header num hmetrics
 169     if (failed || unlikely (!subset_update_header (plan, num_advances)))
 170     {
 171       free (dest);
 172       return false;
 173     }
 174 
 175     hb_blob_t *result = hb_blob_create ((const char *)dest,
 176                                         dest_sz,
 177                                         HB_MEMORY_MODE_READONLY,
 178                                         dest,
 179                                         free);
 180     bool success = plan->add_table (T::tableTag, result);
 181     hb_blob_destroy (result);
 182     return success;
 183   }
 184 
 185   struct accelerator_t
 186   {
 187     friend struct hmtxvmtx;
 188 
 189     void init (hb_face_t *face,
 190                       unsigned int default_advance_ = 0)
 191     {
 192       default_advance = default_advance_ ? default_advance_ : hb_face_get_upem (face);
 193 
 194       bool got_font_extents = false;
 195       if (T::os2Tag != HB_TAG_NONE && face->table.OS2->is_typo_metrics ())
 196       {
 197         ascender = abs (face->table.OS2->sTypoAscender);
 198         descender = -abs (face->table.OS2->sTypoDescender);
 199         line_gap = face->table.OS2->sTypoLineGap;
 200         got_font_extents = (ascender | descender) != 0;
 201       }
 202 
 203       hb_blob_t *_hea_blob = hb_sanitize_context_t().reference_table<H> (face);
 204       const H *_hea_table = _hea_blob->as<H> ();
 205       num_advances = _hea_table->numberOfLongMetrics;
 206       if (!got_font_extents)
 207       {
 208         ascender = abs (_hea_table->ascender);
 209         descender = -abs (_hea_table->descender);
 210         line_gap = _hea_table->lineGap;
 211         got_font_extents = (ascender | descender) != 0;
 212       }
 213       hb_blob_destroy (_hea_blob);
 214 
 215       has_font_extents = got_font_extents;
 216 
 217       table = hb_sanitize_context_t().reference_table<hmtxvmtx> (face, T::tableTag);
 218 
 219       /* Cap num_metrics() and num_advances() based on table length. */
 220       unsigned int len = table.get_length ();
 221       if (unlikely (num_advances * 4 > len))
 222         num_advances = len / 4;
 223       num_metrics = num_advances + (len - 4 * num_advances) / 2;
 224 
 225       /* We MUST set num_metrics to zero if num_advances is zero.
 226        * Our get_advance() depends on that. */
 227       if (unlikely (!num_advances))
 228       {
 229         num_metrics = num_advances = 0;
 230         table.destroy ();
 231         table = hb_blob_get_empty ();
 232       }
 233 
 234       var_table = hb_sanitize_context_t().reference_table<HVARVVAR> (face, T::variationsTag);
 235     }
 236 
 237     void fini ()
 238     {
 239       table.destroy ();
 240       var_table.destroy ();
 241     }
 242 
 243     /* TODO Add variations version. */
 244     unsigned int get_side_bearing (hb_codepoint_t glyph) const
 245     {
 246       if (glyph < num_advances)
 247         return table->longMetricZ[glyph].sb;
 248 
 249       if (unlikely (glyph >= num_metrics))
 250         return 0;
 251 
 252       const FWORD *bearings = (const FWORD *) &table->longMetricZ[num_advances];
 253       return bearings[glyph - num_advances];
 254     }
 255 
 256     unsigned int get_advance (hb_codepoint_t glyph) const
 257     {
 258       if (unlikely (glyph >= num_metrics))
 259       {
 260         /* If num_metrics is zero, it means we don't have the metrics table
 261          * for this direction: return default advance.  Otherwise, it means that the
 262          * glyph index is out of bound: return zero. */
 263         if (num_metrics)
 264           return 0;
 265         else
 266           return default_advance;
 267       }
 268 
 269       return table->longMetricZ[MIN (glyph, (uint32_t) num_advances - 1)].advance;
 270     }
 271 
 272     unsigned int get_advance (hb_codepoint_t  glyph,
 273                               hb_font_t      *font) const
 274     {
 275       unsigned int advance = get_advance (glyph);
 276       if (likely (glyph < num_metrics))
 277       {
 278         advance += (font->num_coords ? var_table->get_advance_var (glyph, font->coords, font->num_coords) : 0); // TODO Optimize?!
 279       }
 280       return advance;
 281     }
 282 
 283     public:
 284     bool has_font_extents;
 285     int ascender;
 286     int descender;
 287     int line_gap;
 288 
 289     protected:
 290     unsigned int num_metrics;
 291     unsigned int num_advances;
 292     unsigned int default_advance;
 293 
 294     private:
 295     hb_blob_ptr_t<hmtxvmtx> table;
 296     hb_blob_ptr_t<HVARVVAR> var_table;
 297   };
 298 
 299   protected:
 300   UnsizedArrayOf<LongMetric>longMetricZ;/* Paired advance width and leading
 301                                          * bearing values for each glyph. The
 302                                          * value numOfHMetrics comes from
 303                                          * the 'hhea' table. If the font is
 304                                          * monospaced, only one entry need
 305                                          * be in the array, but that entry is
 306                                          * required. The last entry applies to
 307                                          * all subsequent glyphs. */
 308 /*UnsizedArrayOf<FWORD> leadingBearingX;*//* Here the advance is assumed
 309                                          * to be the same as the advance
 310                                          * for the last entry above. The
 311                                          * number of entries in this array is
 312                                          * derived from numGlyphs (from 'maxp'
 313                                          * table) minus numberOfLongMetrics.
 314                                          * This generally is used with a run
 315                                          * of monospaced glyphs (e.g., Kanji
 316                                          * fonts or Courier fonts). Only one
 317                                          * run is allowed and it must be at
 318                                          * the end. This allows a monospaced
 319                                          * font to vary the side bearing
 320                                          * values for each glyph. */
 321   public:
 322   DEFINE_SIZE_ARRAY (0, longMetricZ);
 323 };
 324 
 325 struct hmtx : hmtxvmtx<hmtx, hhea> {
 326   static constexpr hb_tag_t tableTag = HB_OT_TAG_hmtx;
 327   static constexpr hb_tag_t variationsTag = HB_OT_TAG_HVAR;
 328   static constexpr hb_tag_t os2Tag = HB_OT_TAG_OS2;
 329 };
 330 struct vmtx : hmtxvmtx<vmtx, vhea> {
 331   static constexpr hb_tag_t tableTag = HB_OT_TAG_vmtx;
 332   static constexpr hb_tag_t variationsTag = HB_OT_TAG_VVAR;
 333   static constexpr hb_tag_t os2Tag = HB_TAG_NONE;
 334 };
 335 
 336 struct hmtx_accelerator_t : hmtx::accelerator_t {};
 337 struct vmtx_accelerator_t : vmtx::accelerator_t {};
 338 
 339 } /* namespace OT */
 340 
 341 
 342 #endif /* HB_OT_HMTX_TABLE_HH */