lib/tacontrol.h

   1 /* tacontrol.h */
   2
   3 /*
   4  * Copyright (C) 2014-2015 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 in the range [-8;8] for delta exceptions
  74  * and in the range [SHRT_MIN;SHRT_MAX] for one-point segment offsets.
  75  *
  76  * The `Control' typedef is in `ta.h'.
  77  */
  78
  79 struct Control_
  80 {
  81   Control_Type type;
  82
  83   long font_idx;
  84   long glyph_idx;
  85   number_range* points;
  86   int x_shift;
  87   int y_shift;
  88   number_range* ppems;
  89
  90   struct Control_* next;
  91 };
  92
  93
  94 /*
  95  * A structure to hold a single control instruction.
  96  */
  97
  98 typedef struct Ctrl_
  99 {
 100   Control_Type type;
 101
 102   long font_idx;
 103   long glyph_idx;
 104   int ppem;
 105   int point_idx;
 106
 107   int x_shift;
 108   int y_shift;
 109 } Ctrl;
 110
 111
 112 /*
 113  * This structure is used for communication with `TA_control_parse'.
 114  */
 115
 116 typedef struct Control_Context_
 117 {
 118   /* The error code returned by the parser or lexer. */
 119   TA_Error error;
 120
 121   /* If no error, this holds the parsing result. */
 122   Control* result;
 123
 124   /*
 125    * The parser's or lexer's error message in case of error; might be the
 126    * empty string.
 127    */
 128   char errmsg[256];
 129
 130   /*
 131    * In case of error, `errline_num' gives the line number of the offending
 132    * line in `font->control_buf', starting with value 1; `errline_pos_left'
 133    * and `errline_pos_right' hold the left and right position of the
 134    * offending token in this line, also starting with value 1.  For
 135    * allocation errors or internal parser or lexer errors those values are
 136    * meaningless, though.
 137    */
 138   int errline_num;
 139   int errline_pos_left;
 140   int errline_pos_right;
 141
 142   /*
 143    * The current font index, useful for `TA_Err_Control_Invalid_Font_Index'.
 144    */
 145   long font_idx;
 146
 147   /*
 148    * The current glyph index, useful for
 149    * `TA_Err_Control_Invalid_Glyph_Index'.
 150    */
 151   long glyph_idx;
 152
 153   /*
 154    * If the returned error is `TA_Err_Control_Invalid_Range', these two
 155    * values set up the allowed range.
 156    */
 157   long number_set_min;
 158   long number_set_max;
 159
 160   /* private flex data */
 161   void* scanner;
 162   int eof;
 163   jmp_buf jump_buffer;
 164
 165   /* private bison data */
 166   FONT* font;
 167 } Control_Context;
 168
 169
 170 /*
 171  * Create and initialize a `Control' object.  In case of an allocation error,
 172  * the return value is NULL.  `point_set' and `ppem_set' are expected to be
 173  * in reverse list order; `TA_control_new' then reverts them to normal order.
 174  */
 175
 176 Control*
 177 TA_control_new(Control_Type type,
 178                long font_idx,
 179                long glyph_idx,
 180                number_range* point_set,
 181                double x_shift,
 182                double y_shift,
 183                number_range* ppem_set);
 184
 185
 186 /*
 187  * Prepend `element' to `list' of `Control' objects.  If `element' is NULL,
 188  * return `list.
 189  */
 190
 191 Control*
 192 TA_control_prepend(Control* list,
 193                    Control* element);
 194
 195
 196 /*
 197  * Reverse a list of `Control' objects.
 198  */
 199
 200 Control*
 201 TA_control_reverse(Control* list);
 202
 203
 204 /*
 205  * Initialize the scanner data within a `Control_Context' object.
 206  * `font->control_buf' is the control instructions buffer to be parsed,
 207  * `font->control_len' its length.
 208  *
 209  * This function is defined in `tacontrol.flex'.
 210  */
 211
 212 void
 213 TA_control_scanner_init(Control_Context* context,
 214                         FONT* font);
 215
 216
 217 /*
 218  * Free the scanner data within a `Control_Context' object.
 219  *
 220  * This function is defined in `tacontrol.flex'.
 221  */
 222
 223 void
 224 TA_control_scanner_done(Control_Context* context);
 225
 226
 227 /*
 228  * Parse buffer with ttfautohint control instructions, stored in
 229  * `font->control_buf' with length `font->control_len'.
 230  *
 231  * The format of entries in such a control instructions buffer is given in
 232  * `ttfautohint.h' (option `control-file'); the following describes more
 233  * technical details, using the constants defined above.
 234  *
 235  * x shift and y shift values represent floating point numbers that get
 236  * rounded to multiples of 1/(2^CONTROL_DELTA_SHIFT) pixels.
 237  *
 238  * Values for x and y shifts must be in the range
 239  * [CONTROL_DELTA_SHIFT_MIN;CONTROL_DELTA_SHIFT_MAX].  Values for ppems must
 240  * be in the range [CONTROL_DELTA_PPEM_MIN;CONTROL_DELTA_PPEM_MAX].
 241  *
 242  * The returned error codes are 0 (TA_Err_Ok) or in the range 0x200-0x2FF;
 243  * see `ttfautohint-errors.h' for all possible values.
 244  *
 245  * `TA_control_parse_buffer' stores the parsed result in `font->control', to
 246  * be freed with `TA_control_free' after use.  If there is no control
 247  * instructions data (for example, an empty string or whitespace only)
 248  * nothing gets allocated, and `font->control' is set to NULL.
 249  *
 250  * In case of error, `error_string_p' holds an error message, `errlinenum_p'
 251  * gives the line number in the control instructions buffer where the error
 252  * occurred, `errline_p' the corresponding line, and `errpos_p' the position
 253  * in this line.  After use, `error_string_p' and `errline_p' must be
 254  * deallocated by the user.  Note that `errline_p' and `errpos_p' can be
 255  * NULL even in case of an error.  If there is no error, those four values
 256  * are undefined.
 257  */
 258
 259 TA_Error
 260 TA_control_parse_buffer(FONT* font,
 261                         char** error_string_p,
 262                         unsigned int* errlinenum_p,
 263                         char** errline_p,
 264                         char** errpos_p);
 265
 266
 267 /*
 268  * Free the allocated data in `control'.
 269  */
 270
 271 void
 272 TA_control_free(Control* control);
 273
 274
 275 /*
 276  * Return a string representation of `font->control'.  After use, the string
 277  * should be deallocated with a call to `free'.  In case of an allocation
 278  * error, the return value is NULL.
 279  */
 280
 281 char*
 282 TA_control_show(FONT* font);
 283
 284
 285 /*
 286  * Build a tree providing sequential access to the control instructions data
 287  * in `font->control'.  This also sets `font->control_data_cur' to the first
 288  * element (or NULL if there isn't one).
 289  */
 290
 291 TA_Error
 292 TA_control_build_tree(FONT* font);
 293
 294
 295 /*
 296  * Free the control instructions data tree.
 297  */
 298
 299 void
 300 TA_control_free_tree(FONT* font);
 301
 302
 303 /*
 304  * Get next control instruction and store it in `font->control_data_cur'.
 305  */
 306
 307 void
 308 TA_control_get_next(FONT* font);
 309
 310
 311 /*
 312  * Access control instruction.  Return NULL if there is no more data.
 313  */
 314
 315 const Ctrl*
 316 TA_control_get_ctrl(FONT* font);
 317
 318
 319 /*
 320  * Collect one-point segment data for a given glyph index and store them in
 321  * `font->control_segment_dirs'.
 322  */
 323
 324 TA_Error
 325 TA_control_segment_dir_collect(FONT* font,
 326                                long font_idx,
 327                                long glyph_idx);
 328
 329 /*
 330  * Access next one-point segment data.  Returns 1 on success or 0 if no more
 331  * data.  In the latter case, it resets the internal iterator so that
 332  * calling this function another time starts at the beginning again.
 333  */
 334
 335 int
 336 TA_control_segment_dir_get_next(FONT* font,
 337                                 int* point_idx,
 338                                 TA_Direction* dir,
 339                                 int* left_offset,
 340                                 int* right_offset);
 341
 342
 343 #ifdef __cplusplus
 344 } /* extern "C" */
 345 #endif
 346
 347 #endif /* __TACONTROL_H__ */
 348
 349 /* end of control.h */