lib/tacontrol.h

   1 /* tacontrol.h */
   2
   3 /*
   4  * Copyright (C) 2014 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_Type;
  66
  67
  68 /*
  69  * A structure to hold control instructions for a glyph.  A linked list of it
  70  * gets allocated by a successful call to `TA_control_parse_buffer'.  Use
  71  * `TA_control_free' to deallocate the list.
  72  *
  73  * `x_shift' and `y_shift' are always in the range [-8;8].
  74  *
  75  * The `Control' typedef is in `ta.h'.
  76  */
  77
  78 struct Control_
  79 {
  80   Control_Type type;
  81
  82   long font_idx;
  83   long glyph_idx;
  84   number_range* points;
  85   char x_shift;
  86   char y_shift;
  87   number_range* ppems;
  88
  89   struct Control_* next;
  90 };
  91
  92
  93 /*
  94  * A structure to hold a single control instruction.
  95  */
  96
  97 typedef struct Ctrl_
  98 {
  99   Control_Type type;
 100
 101   long font_idx;
 102   long glyph_idx;
 103   int ppem;
 104   int point_idx;
 105
 106   char x_shift;
 107   char y_shift;
 108 } Ctrl;
 109
 110
 111 /*
 112  * This structure is used for communication with `TA_control_parse'.
 113  */
 114
 115 typedef struct Control_Context_
 116 {
 117   /* The error code returned by the parser or lexer. */
 118   TA_Error error;
 119
 120   /* If no error, this holds the parsing result. */
 121   Control* result;
 122
 123   /*
 124    * The parser's or lexer's error message in case of error; might be the
 125    * empty string.
 126    */
 127   char errmsg[256];
 128
 129   /*
 130    * In case of error, `errline_num' gives the line number of the offending
 131    * line in `font->control_buf', starting with value 1; `errline_pos_left'
 132    * and `errline_pos_right' hold the left and right position of the
 133    * offending token in this line, also starting with value 1.  For
 134    * allocation errors or internal parser or lexer errors those values are
 135    * meaningless, though.
 136    */
 137   int errline_num;
 138   int errline_pos_left;
 139   int errline_pos_right;
 140
 141   /*
 142    * The current font index, useful for `TA_Err_Control_Invalid_Font_Index'.
 143    */
 144   long font_idx;
 145
 146   /*
 147    * The current glyph index, useful for
 148    * `TA_Err_Control_Invalid_Glyph_Index'.
 149    */
 150   long glyph_idx;
 151
 152   /*
 153    * If the returned error is `TA_Err_Control_Invalid_Range', these two
 154    * values set up the allowed range.
 155    */
 156   long number_set_min;
 157   long number_set_max;
 158
 159   /* private flex data */
 160   void* scanner;
 161   int eof;
 162   jmp_buf jump_buffer;
 163
 164   /* private bison data */
 165   FONT* font;
 166 } Control_Context;
 167
 168
 169 /*
 170  * Create and initialize a `Control' object.  In case of an allocation error,
 171  * the return value is NULL.  `point_set' and `ppem_set' are expected to be
 172  * in reverse list order; `TA_control_new' then reverts them to normal order.
 173  */
 174
 175 Control*
 176 TA_control_new(Control_Type type,
 177                long font_idx,
 178                long glyph_idx,
 179                number_range* point_set,
 180                double x_shift,
 181                double y_shift,
 182                number_range* ppem_set);
 183
 184
 185 /*
 186  * Prepend `element' to `list' of `Control' objects.  If `element' is NULL,
 187  * return `list.
 188  */
 189
 190 Control*
 191 TA_control_prepend(Control* list,
 192                    Control* element);
 193
 194
 195 /*
 196  * Reverse a list of `Control' objects.
 197  */
 198
 199 Control*
 200 TA_control_reverse(Control* list);
 201
 202
 203 /*
 204  * Initialize the scanner data within a `Control_Context' object.
 205  * `font->control_buf' is the control instructions buffer to be parsed,
 206  * `font->control_len' its length.
 207  *
 208  * This function is defined in `tacontrol.flex'.
 209  */
 210
 211 void
 212 TA_control_scanner_init(Control_Context* context,
 213                         FONT* font);
 214
 215
 216 /*
 217  * Free the scanner data within a `Control_Context' object.
 218  *
 219  * This function is defined in `tacontrol.flex'.
 220  */
 221
 222 void
 223 TA_control_scanner_done(Control_Context* context);
 224
 225
 226 /*
 227  * Parse buffer with ttfautohint control instructions, stored in
 228  * `font->control_buf' with length `font->control_len'.
 229  *
 230  * The format of entries in such a control instructions buffer is given in
 231  * `ttfautohint.h' (option `control-file'); the following describes more
 232  * technical details, using the constants defined above.
 233  *
 234  * x shift and y shift values represent floating point numbers that get
 235  * rounded to multiples of 1/(2^CONTROL_DELTA_SHIFT) pixels.
 236  *
 237  * Values for x and y shifts must be in the range
 238  * [CONTROL_DELTA_SHIFT_MIN;CONTROL_DELTA_SHIFT_MAX].  Values for ppems must
 239  * be in the range [CONTROL_DELTA_PPEM_MIN;CONTROL_DELTA_PPEM_MAX].
 240  *
 241  * The returned error codes are 0 (TA_Err_Ok) or in the range 0x200-0x2FF;
 242  * see `ttfautohint-errors.h' for all possible values.
 243  *
 244  * `TA_control_parse_buffer' stores the parsed result in `font->control', to
 245  * be freed with `TA_control_free' after use.  If there is no control
 246  * instructions data (for example, an empty string or whitespace only)
 247  * nothing gets allocated, and `font->control' is set to NULL.
 248  *
 249  * In case of error, `error_string_p' holds an error message, `errlinenum_p'
 250  * gives the line number in the control instructions buffer where the error
 251  * occurred, `errline_p' the corresponding line, and `errpos_p' the position
 252  * in this line.  After use, `error_string_p' and `errline_p' must be
 253  * deallocated by the user.  Note that `errline_p' and `errpos_p' can be
 254  * NULL even in case of an error.  If there is no error, those four values
 255  * are undefined.
 256  */
 257
 258 TA_Error
 259 TA_control_parse_buffer(FONT* font,
 260                         char** error_string_p,
 261                         unsigned int* errlinenum_p,
 262                         char** errline_p,
 263                         char** errpos_p);
 264
 265
 266 /*
 267  * Free the allocated data in `control'.
 268  */
 269
 270 void
 271 TA_control_free(Control* control);
 272
 273
 274 /*
 275  * Return a string representation of `font->control'.  After use, the string
 276  * should be deallocated with a call to `free'.  In case of an allocation
 277  * error, the return value is NULL.
 278  */
 279
 280 char*
 281 TA_control_show(FONT* font);
 282
 283
 284 /*
 285  * Build a tree providing sequential access to the control instructions data
 286  * in `font->control'.  This also sets `font->control_data_cur' to the first
 287  * element (or NULL if there isn't one).
 288  */
 289
 290 TA_Error
 291 TA_control_build_tree(FONT* font);
 292
 293
 294 /*
 295  * Free the control instructions data tree.
 296  */
 297
 298 void
 299 TA_control_free_tree(FONT* font);
 300
 301
 302 /*
 303  * Get next control instruction and store it in `font->control_data_cur'.
 304  */
 305
 306 void
 307 TA_control_get_next(FONT* font);
 308
 309
 310 /*
 311  * Access control instruction.  Return NULL if there is no more data.
 312  */
 313
 314 const Ctrl*
 315 TA_control_get_ctrl(FONT* font);
 316
 317
 318 /*
 319  * Collect forced point directions and store them in
 320  * `font->control_point_dirs'.
 321  */
 322
 323 TA_Error
 324 TA_control_point_dir_collect(FONT* font,
 325                              long font_idx,
 326                              long glyph_idx);
 327
 328 /*
 329  * Access next forced point direction.  Returns 1 on success or 0 if no more
 330  * data.  In the latter case, it resets the internal iterator so that
 331  * calling this function another time starts at the beginning again.
 332  */
 333
 334 int
 335 TA_control_point_dir_get_next(FONT* font,
 336                               int* point_idx,
 337                               TA_Direction* dir);
 338
 339
 340 #ifdef __cplusplus
 341 } /* extern "C" */
 342 #endif
 343
 344 #endif /* __TACONTROL_H__ */
 345
 346 /* end of control.h */