lib/tacontrol.h

   1 /* tacontrol.h */
   2
   3 /*
   4  * Copyright (C) 2014-2017 by Werner Lemberg.
   5  *
   6  * This file is part of the ttfautohint library, and may only be used,
   7  * modified, and distributed under the terms given in `COPYING'.  By
   8  * continuing to use, modify, or distribute this file you indicate that you
   9  * have read `COPYING' and understand and accept it fully.
  10  *
  11  * The file `COPYING' mentioned in the previous paragraph is distributed
  12  * with the ttfautohint library.
  13  */
  14
  15
  16 #ifndef TACONTROL_H_
  17 #define TACONTROL_H_
  18
  19 #ifdef __cplusplus
  20 extern "C" {
  21 #endif
  22
  23 #include <setjmp.h>  /* for flex error handling */
  24
  25
  26 /* see the section `Managing exceptions' in chapter 6 */
  27 /* (`The TrueType Instruction Set') of the OpenType reference */
  28 /* how `delta_shift' works */
  29
  30 #define CONTROL_DELTA_SHIFT 3 /* 1/8px */
  31 #define CONTROL_DELTA_FACTOR (1 << CONTROL_DELTA_SHIFT)
  32
  33 #define CONTROL_DELTA_SHIFT_MAX ((1.0 / CONTROL_DELTA_FACTOR) * 8)
  34 #define CONTROL_DELTA_SHIFT_MIN -CONTROL_DELTA_SHIFT_MAX
  35
  36
  37 /*
  38  * For the generated TrueType bytecode, we use
  39  *
  40  *   delta_base = 6   ,
  41  *
  42  * which gives us the following ppem ranges for the three delta
  43  * instructions:
  44  *
  45  *   DELTAP1    6-21ppem
  46  *   DELTAP2   22-37ppem
  47  *   DELTAP3   38-53ppem   .
  48  */
  49
  50 #define CONTROL_DELTA_PPEM_MIN 6
  51 #define CONTROL_DELTA_PPEM_MAX 53
  52
  53
  54 /*
  55  * The control type.
  56  */
  57
  58 typedef enum Control_Type_
  59 {
  60   Control_Delta_before_IUP,
  61   Control_Delta_after_IUP,
  62   Control_Segment_Left,
  63   Control_Segment_Right,
  64   Control_Segment_None,
  65   Control_Script_Feature
  66 } Control_Type;
  67
  68
  69 /*
  70  * A structure to hold control instructions.  A linked list of it gets
  71  * allocated by a successful call to `TA_control_parse_buffer'.  Use
  72  * `TA_control_free' to deallocate the list.
  73  *
  74  * `x_shift' and `y_shift' are in the range [-8;8] for delta exceptions
  75  * and in the range [SHRT_MIN;SHRT_MAX] for one-point segment offsets.
  76  *
  77  * The `Control' typedef is in `ta.h'.
  78  */
  79
  80 struct Control_
  81 {
  82   Control_Type type;
  83
  84   long font_idx;
  85   long glyph_idx;
  86   number_range* points;
  87   int x_shift;
  88   int y_shift;
  89   number_range* ppems;
  90
  91   struct Control_* next;
  92 };
  93
  94
  95 /*
  96  * A structure to hold a single control instruction.
  97  */
  98
  99 typedef struct Ctrl_
 100 {
 101   Control_Type type;
 102
 103   long font_idx;
 104   long glyph_idx;
 105   int ppem;
 106   int point_idx;
 107
 108   int x_shift;
 109   int y_shift;
 110 } Ctrl;
 111
 112
 113 /*
 114  * This structure is used for communication with `TA_control_parse'.
 115  */
 116
 117 typedef struct Control_Context_
 118 {
 119   /* The error code returned by the parser or lexer. */
 120   TA_Error error;
 121
 122   /* If no error, this holds the parsing result. */
 123   Control* result;
 124
 125   /*
 126    * The parser's or lexer's error message in case of error; might be the
 127    * empty string.
 128    */
 129   char errmsg[256];
 130
 131   /*
 132    * In case of error, `errline_num' gives the line number of the offending
 133    * line in `font->control_buf', starting with value 1; `errline_pos_left'
 134    * and `errline_pos_right' hold the left and right position of the
 135    * offending token in this line, also starting with value 1.  For
 136    * allocation errors or internal parser or lexer errors those values are
 137    * meaningless, though.
 138    */
 139   int errline_num;
 140   int errline_pos_left;
 141   int errline_pos_right;
 142
 143   /*
 144    * The current font index, useful for `TA_Err_Control_Invalid_Font_Index'.
 145    */
 146   long font_idx;
 147
 148   /*
 149    * The current glyph index, useful for
 150    * `TA_Err_Control_Invalid_Glyph_Index'.
 151    */
 152   long glyph_idx;
 153
 154   /*
 155    * If the returned error is `TA_Err_Control_Invalid_Range', these two
 156    * values set up the allowed range.
 157    */
 158   int number_set_min;
 159   int number_set_max;
 160
 161   /* private flex data */
 162   void* scanner;
 163   int eof;
 164   jmp_buf jump_buffer;
 165
 166   /* private bison data */
 167   FONT* font;
 168 } Control_Context;
 169
 170
 171 /*
 172  * Create and initialize a `Control' object.  In case of an allocation error,
 173  * the return value is NULL.  `point_set' and `ppem_set' are expected to be
 174  * in reverse list order; `TA_control_new' then reverts them to normal order.
 175  */
 176
 177 Control*
 178 TA_control_new(Control_Type type,
 179                long font_idx,
 180                long glyph_idx,
 181                number_range* point_set,
 182                double x_shift,
 183                double y_shift,
 184                number_range* ppem_set);
 185
 186
 187 /*
 188  * Prepend `element' to `list' of `Control' objects.  If `element' is NULL,
 189  * return `list.
 190  */
 191
 192 Control*
 193 TA_control_prepend(Control* list,
 194                    Control* element);
 195
 196
 197 /*
 198  * Reverse a list of `Control' objects.
 199  */
 200
 201 Control*
 202 TA_control_reverse(Control* list);
 203
 204
 205 /*
 206  * Initialize the scanner data within a `Control_Context' object.
 207  * `font->control_buf' is the control instructions buffer to be parsed,
 208  * `font->control_len' its length.
 209  *
 210  * This function is defined in `tacontrol.flex'.
 211  */
 212
 213 void
 214 TA_control_scanner_init(Control_Context* context,
 215                         FONT* font);
 216
 217
 218 /*
 219  * Free the scanner data within a `Control_Context' object.
 220  *
 221  * This function is defined in `tacontrol.flex'.
 222  */
 223
 224 void
 225 TA_control_scanner_done(Control_Context* context);
 226
 227
 228 /*
 229  * Parse buffer with ttfautohint control instructions, stored in
 230  * `font->control_buf' with length `font->control_len'.
 231  *
 232  * The format of entries in such a control instructions buffer is given in
 233  * `ttfautohint.h' (option `control-file'); the following describes more
 234  * technical details, using the constants defined above.
 235  *
 236  * x shift and y shift values represent floating point numbers that get
 237  * rounded to multiples of 1/(2^CONTROL_DELTA_SHIFT) pixels.
 238  *
 239  * Values for x and y shifts must be in the range
 240  * [CONTROL_DELTA_SHIFT_MIN;CONTROL_DELTA_SHIFT_MAX].  Values for ppems must
 241  * be in the range [CONTROL_DELTA_PPEM_MIN;CONTROL_DELTA_PPEM_MAX].
 242  *
 243  * The returned error codes are 0 (TA_Err_Ok) or in the range 0x200-0x2FF;
 244  * see `ttfautohint-errors.h' for all possible values.
 245  *
 246  * `TA_control_parse_buffer' stores the parsed result in `font->control', to
 247  * be freed with `TA_control_free' after use.  If there is no control
 248  * instructions data (for example, an empty string or whitespace only)
 249  * nothing gets allocated, and `font->control' is set to NULL.
 250  *
 251  * In case of error, `error_string_p' holds an error message, `errlinenum_p'
 252  * gives the line number in the control instructions buffer where the error
 253  * occurred, `errline_p' the corresponding line, and `errpos_p' the position
 254  * in this line.  After use, `error_string_p' and `errline_p' must be
 255  * deallocated by the user.  Note that `errline_p' and `errpos_p' can be
 256  * NULL even in case of an error.  If there is no error, those four values
 257  * are undefined.
 258  */
 259
 260 TA_Error
 261 TA_control_parse_buffer(FONT* font,
 262                         char** error_string_p,
 263                         unsigned int* errlinenum_p,
 264                         char** errline_p,
 265                         char** errpos_p);
 266
 267
 268 /*
 269  * Apply coverage data from the control instructions file.
 270  */
 271
 272 void
 273 TA_control_apply_coverage(SFNT* sfnt,
 274                           FONT* font);
 275 /*
 276  * Free the allocated data in `control'.
 277  */
 278
 279 void
 280 TA_control_free(Control* control);
 281
 282
 283 /*
 284  * Return a string representation of `font->control'.  After use, the string
 285  * should be deallocated with a call to `free'.  In case of an allocation
 286  * error, the return value is NULL.
 287  */
 288
 289 char*
 290 TA_control_show(FONT* font);
 291
 292
 293 /*
 294  * Build a tree providing sequential access to the control instructions data
 295  * in `font->control'.  This also sets `font->control_data_cur' to the first
 296  * element (or NULL if there isn't one).
 297  */
 298
 299 TA_Error
 300 TA_control_build_tree(FONT* font);
 301
 302
 303 /*
 304  * Free the control instructions data tree.
 305  */
 306
 307 void
 308 TA_control_free_tree(FONT* font);
 309
 310
 311 /*
 312  * Get next control instruction and store it in `font->control_data_cur'.
 313  */
 314
 315 void
 316 TA_control_get_next(FONT* font);
 317
 318
 319 /*
 320  * Access control instruction.  Return NULL if there is no more data.
 321  */
 322
 323 const Ctrl*
 324 TA_control_get_ctrl(FONT* font);
 325
 326
 327 /*
 328  * Collect one-point segment data for a given glyph index and store them in
 329  * `font->control_segment_dirs'.
 330  */
 331
 332 TA_Error
 333 TA_control_segment_dir_collect(FONT* font,
 334                                long font_idx,
 335                                long glyph_idx);
 336
 337 /*
 338  * Access next one-point segment data.  Returns 1 on success or 0 if no more
 339  * data.  In the latter case, it resets the internal iterator so that
 340  * calling this function another time starts at the beginning again.
 341  */
 342
 343 int
 344 TA_control_segment_dir_get_next(FONT* font,
 345                                 int* point_idx,
 346                                 TA_Direction* dir,
 347                                 int* left_offset,
 348                                 int* right_offset);
 349
 350
 351 #ifdef __cplusplus
 352 } /* extern "C" */
 353 #endif
 354
 355 #endif /* TACONTROL_H_ */
 356
 357 /* end of control.h */