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 /*
  * Copyright © 1998-2004  David Turner and Werner Lemberg
  * Copyright © 2004,2007,2009  Red Hat, Inc.
  * Copyright © 2011,2012  Google, Inc.
  *
  *  This is part of HarfBuzz, a text shaping library.
  *
  * Permission is hereby granted, without written agreement and without
  * license or royalty fees, to use, copy, modify, and distribute this
  * software and its documentation for any purpose, provided that the
  * above copyright notice and the following two paragraphs appear in
  * all copies of this software.
  *
  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  * DAMAGE.
  *
  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  *
  * Red Hat Author(s): Owen Taylor, Behdad Esfahbod
  * Google Author(s): Behdad Esfahbod
  */
 
 #if !defined(HB_H_IN) && !defined(HB_NO_SINGLE_HEADER_ERROR)
 #error "Include <hb.h> instead."
 #endif
 
 #ifndef HB_BUFFER_H
 #define HB_BUFFER_H
 
 #include "hb-common.h"
 #include "hb-unicode.h"
 #include "hb-font.h"
 
 HB_BEGIN_DECLS
 
 /**
  * hb_glyph_info_t:
  * @codepoint: either a Unicode code point (before shaping) or a glyph index
  *             (after shaping).
  * @cluster: the index of the character in the original text that corresponds
  *           to this #hb_glyph_info_t, or whatever the client passes to
  *           hb_buffer_add(). More than one #hb_glyph_info_t can have the same
  *           @cluster value, if they resulted from the same character (e.g. one
  *           to many glyph substitution), and when more than one character gets
  *           merged in the same glyph (e.g. many to one glyph substitution) the
  *           #hb_glyph_info_t will have the smallest cluster value of them.
  *           By default some characters are merged into the same cluster
  *           (e.g. combining marks have the same cluster as their bases)
  *           even if they are separate glyphs, hb_buffer_set_cluster_level()
  *           allow selecting more fine-grained cluster handling.
  *
  * The #hb_glyph_info_t is the structure that holds information about the
  * glyphs and their relation to input text.
  */
 typedef struct hb_glyph_info_t {
   hb_codepoint_t codepoint;
   /*< private >*/
   hb_mask_t      mask;
   /*< public >*/
   uint32_t       cluster;
 
   /*< private >*/
   hb_var_int_t   var1;
   hb_var_int_t   var2;
 } hb_glyph_info_t;
 
 /**
  * hb_glyph_flags_t:
  * @HB_GLYPH_FLAG_UNSAFE_TO_BREAK: Indicates that if input text is broken at the
  *                 beginning of the cluster this glyph is part of,
  *                 then both sides need to be re-shaped, as the
  *                 result might be different.
  *                 On the flip side, it means that when this
  *                 flag is not present, then it is safe to break
  *                 the glyph-run at the beginning of this
  *                 cluster, and the two sides will represent the
  *                 exact same result one would get if breaking
  *                 input text at the beginning of this cluster
  *                 and shaping the two sides separately.
  *                 This can be used to optimize paragraph
  *                 layout, by avoiding re-shaping of each line
  *                 after line-breaking.
  * @HB_GLYPH_FLAG_UNSAFE_TO_CONCAT: Indicates that if input text is changed on one
  *                 side of the beginning of the cluster this glyph
  *                 is part of, then the shaping results for the
  *                 other side might change.
  *                 Note that the absence of this flag will NOT by
  *                 itself mean that it IS safe to concat text.
  *                 Only two pieces of text both of which clear of
  *                 this flag can be concatenated safely.
  *                 This can be used to optimize paragraph
  *                 layout, by avoiding re-shaping of each line
  *                 after line-breaking, by limiting the
  *                 reshaping to a small piece around the
  *                 breaking position only, even if the breaking
  *                 position carries the
  *                 #HB_GLYPH_FLAG_UNSAFE_TO_BREAK or when
  *                 hyphenation or other text transformation
  *                 happens at line-break position, in the following
  *                 way:
  *                 1. Iterate back from the line-break position
  *                 until the first cluster start position that is
  *                 NOT unsafe-to-concat, 2. shape the segment from
  *                 there till the end of line, 3. check whether the
  *                 resulting glyph-run also is clear of the
  *                 unsafe-to-concat at its start-of-text position;
  *                 if it is, just splice it into place and the line
  *                 is shaped; If not, move on to a position further
  *                 back that is clear of unsafe-to-concat and retry
  *                 from there, and repeat.
  *                 At the start of next line a similar algorithm can
  *                 be implemented. That is: 1. Iterate forward from
  *                 the line-break position until the first cluster
  *                 start position that is NOT unsafe-to-concat, 2.
  *                 shape the segment from beginning of the line to
  *                 that position, 3. check whether the resulting
  *                 glyph-run also is clear of the unsafe-to-concat
  *                 at its end-of-text position; if it is, just splice
  *                 it into place and the beginning is shaped; If not,
  *                 move on to a position further forward that is clear
  *                 of unsafe-to-concat and retry up to there, and repeat.
  *                 A slight complication will arise in the
  *                 implementation of the algorithm above,
  *                 because while our buffer API has a way to
  *                 return flags for position corresponding to
  *                 start-of-text, there is currently no position
  *                 corresponding to end-of-text.  This limitation
  *                 can be alleviated by shaping more text than needed
  *                 and looking for unsafe-to-concat flag within text
  *                 clusters.
  *                 The #HB_GLYPH_FLAG_UNSAFE_TO_BREAK flag will
  *                 always imply this flag.
  *                 To use this flag, you must enable the buffer flag
  *                 @HB_BUFFER_FLAG_PRODUCE_UNSAFE_TO_CONCAT during
  *                 shaping, otherwise the buffer flag will not be
  *                 reliably produced.
  *                 Since: 4.0.0
  * @HB_GLYPH_FLAG_SAFE_TO_INSERT_TATWEEL: In scripts that use elongation (Arabic,
                    Mongolian, Syriac, etc.), this flag signifies
                    that it is safe to insert a U+0640 TATWEEL
                    character before this cluster for elongation.
                    This flag does not determine the
                    script-specific elongation places, but only
                    when it is safe to do the elongation without
                    interrupting text shaping.
                    Since: 5.1.0
  * @HB_GLYPH_FLAG_DEFINED: All the currently defined flags.
  *
  * Flags for #hb_glyph_info_t.
  *
  * Since: 1.5.0
  */
 typedef enum { /*< flags >*/
   HB_GLYPH_FLAG_UNSAFE_TO_BREAK         = 0x00000001,
   HB_GLYPH_FLAG_UNSAFE_TO_CONCAT        = 0x00000002,
   HB_GLYPH_FLAG_SAFE_TO_INSERT_TATWEEL      = 0x00000004,
 
   HB_GLYPH_FLAG_DEFINED             = 0x00000007 /* OR of all defined flags */
 } hb_glyph_flags_t;
 
 HB_EXTERN hb_glyph_flags_t
 hb_glyph_info_get_glyph_flags (const hb_glyph_info_t *info);
 
 #define hb_glyph_info_get_glyph_flags(info) \
     ((hb_glyph_flags_t) ((unsigned int) (info)->mask & HB_GLYPH_FLAG_DEFINED))
 
 
 /**
  * hb_glyph_position_t:
  * @x_advance: how much the line advances after drawing this glyph when setting
  *             text in horizontal direction.
  * @y_advance: how much the line advances after drawing this glyph when setting
  *             text in vertical direction.
  * @x_offset: how much the glyph moves on the X-axis before drawing it, this
  *            should not affect how much the line advances.
  * @y_offset: how much the glyph moves on the Y-axis before drawing it, this
  *            should not affect how much the line advances.
  *
  * The #hb_glyph_position_t is the structure that holds the positions of the
  * glyph in both horizontal and vertical directions. All positions in
  * #hb_glyph_position_t are relative to the current point.
  *
  */
 typedef struct hb_glyph_position_t {
   hb_position_t  x_advance;
   hb_position_t  y_advance;
   hb_position_t  x_offset;
   hb_position_t  y_offset;
 
   /*< private >*/
   hb_var_int_t   var;
 } hb_glyph_position_t;
 
 /**
  * hb_segment_properties_t:
  * @direction: the #hb_direction_t of the buffer, see hb_buffer_set_direction().
  * @script: the #hb_script_t of the buffer, see hb_buffer_set_script().
  * @language: the #hb_language_t of the buffer, see hb_buffer_set_language().
  *
  * The structure that holds various text properties of an #hb_buffer_t. Can be
  * set and retrieved using hb_buffer_set_segment_properties() and
  * hb_buffer_get_segment_properties(), respectively.
  */
 typedef struct hb_segment_properties_t {
   hb_direction_t  direction;
   hb_script_t     script;
   hb_language_t   language;
   /*< private >*/
   void           *reserved1;
   void           *reserved2;
 } hb_segment_properties_t;
 
 /**
  * HB_SEGMENT_PROPERTIES_DEFAULT:
  *
  * The default #hb_segment_properties_t of of freshly created #hb_buffer_t.
  */
 #define HB_SEGMENT_PROPERTIES_DEFAULT {HB_DIRECTION_INVALID, \
                        HB_SCRIPT_INVALID, \
                        HB_LANGUAGE_INVALID, \
                        (void *) 0, \
                        (void *) 0}
 
 HB_EXTERN hb_bool_t
 hb_segment_properties_equal (const hb_segment_properties_t *a,
                  const hb_segment_properties_t *b);
 
 HB_EXTERN unsigned int
 hb_segment_properties_hash (const hb_segment_properties_t *p);
 
 HB_EXTERN void
 hb_segment_properties_overlay (hb_segment_properties_t *p,
                    const hb_segment_properties_t *src);
 
 
 /**
  * hb_buffer_t:
  *
  * The main structure holding the input text and its properties before shaping,
  * and output glyphs and their information after shaping.
  */
 
 typedef struct hb_buffer_t hb_buffer_t;
 
 HB_EXTERN hb_buffer_t *
 hb_buffer_create (void);
 
 HB_EXTERN hb_buffer_t *
 hb_buffer_create_similar (const hb_buffer_t *src);
 
 HB_EXTERN void
 hb_buffer_reset (hb_buffer_t *buffer);
 
 
 HB_EXTERN hb_buffer_t *
 hb_buffer_get_empty (void);
 
 HB_EXTERN hb_buffer_t *
 hb_buffer_reference (hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_destroy (hb_buffer_t *buffer);
 
 HB_EXTERN hb_bool_t
 hb_buffer_set_user_data (hb_buffer_t        *buffer,
              hb_user_data_key_t *key,
              void *              data,
              hb_destroy_func_t   destroy,
              hb_bool_t           replace);
 
 HB_EXTERN void *
 hb_buffer_get_user_data (const hb_buffer_t  *buffer,
              hb_user_data_key_t *key);
 
 
 /**
  * hb_buffer_content_type_t:
  * @HB_BUFFER_CONTENT_TYPE_INVALID: Initial value for new buffer.
  * @HB_BUFFER_CONTENT_TYPE_UNICODE: The buffer contains input characters (before shaping).
  * @HB_BUFFER_CONTENT_TYPE_GLYPHS: The buffer contains output glyphs (after shaping).
  *
  * The type of #hb_buffer_t contents.
  */
 typedef enum {
   HB_BUFFER_CONTENT_TYPE_INVALID = 0,
   HB_BUFFER_CONTENT_TYPE_UNICODE,
   HB_BUFFER_CONTENT_TYPE_GLYPHS
 } hb_buffer_content_type_t;
 
 HB_EXTERN void
 hb_buffer_set_content_type (hb_buffer_t              *buffer,
                 hb_buffer_content_type_t  content_type);
 
 HB_EXTERN hb_buffer_content_type_t
 hb_buffer_get_content_type (const hb_buffer_t *buffer);
 
 
 HB_EXTERN void
 hb_buffer_set_unicode_funcs (hb_buffer_t        *buffer,
                  hb_unicode_funcs_t *unicode_funcs);
 
 HB_EXTERN hb_unicode_funcs_t *
 hb_buffer_get_unicode_funcs (const hb_buffer_t  *buffer);
 
 HB_EXTERN void
 hb_buffer_set_direction (hb_buffer_t    *buffer,
              hb_direction_t  direction);
 
 HB_EXTERN hb_direction_t
 hb_buffer_get_direction (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_script (hb_buffer_t *buffer,
               hb_script_t  script);
 
 HB_EXTERN hb_script_t
 hb_buffer_get_script (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_language (hb_buffer_t   *buffer,
             hb_language_t  language);
 
 
 HB_EXTERN hb_language_t
 hb_buffer_get_language (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_segment_properties (hb_buffer_t *buffer,
                   const hb_segment_properties_t *props);
 
 HB_EXTERN void
 hb_buffer_get_segment_properties (const hb_buffer_t *buffer,
                   hb_segment_properties_t *props);
 
 HB_EXTERN void
 hb_buffer_guess_segment_properties (hb_buffer_t *buffer);
 
 
 /**
  * hb_buffer_flags_t:
  * @HB_BUFFER_FLAG_DEFAULT: the default buffer flag.
  * @HB_BUFFER_FLAG_BOT: flag indicating that special handling of the beginning
  *                      of text paragraph can be applied to this buffer. Should usually
  *                      be set, unless you are passing to the buffer only part
  *                      of the text without the full context.
  * @HB_BUFFER_FLAG_EOT: flag indicating that special handling of the end of text
  *                      paragraph can be applied to this buffer, similar to
  *                      @HB_BUFFER_FLAG_BOT.
  * @HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES:
  *                      flag indication that character with Default_Ignorable
  *                      Unicode property should use the corresponding glyph
  *                      from the font, instead of hiding them (done by
  *                      replacing them with the space glyph and zeroing the
  *                      advance width.)  This flag takes precedence over
  *                      @HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES.
  * @HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES:
  *                      flag indication that character with Default_Ignorable
  *                      Unicode property should be removed from glyph string
  *                      instead of hiding them (done by replacing them with the
  *                      space glyph and zeroing the advance width.)
  *                      @HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES takes
  *                      precedence over this flag. Since: 1.8.0
  * @HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE:
  *                      flag indicating that a dotted circle should
  *                      not be inserted in the rendering of incorrect
  *                      character sequences (such at <0905 093E>). Since: 2.4.0
  * @HB_BUFFER_FLAG_VERIFY:
  *                      flag indicating that the hb_shape() call and its variants
  *                      should perform various verification processes on the results
  *                      of the shaping operation on the buffer.  If the verification
  *                      fails, then either a buffer message is sent, if a message
  *                      handler is installed on the buffer, or a message is written
  *                      to standard error.  In either case, the shaping result might
  *                      be modified to show the failed output. Since: 3.4.0
  * @HB_BUFFER_FLAG_PRODUCE_UNSAFE_TO_CONCAT:
  *                      flag indicating that the @HB_GLYPH_FLAG_UNSAFE_TO_CONCAT
  *                      glyph-flag should be produced by the shaper. By default
  *                      it will not be produced since it incurs a cost. Since: 4.0.0
  * @HB_BUFFER_FLAG_PRODUCE_SAFE_TO_INSERT_TATWEEL:
  *                      flag indicating that the @HB_GLYPH_FLAG_SAFE_TO_INSERT_TATWEEL
  *                      glyph-flag should be produced by the shaper. By default
  *                      it will not be produced. Since: 5.1.0
  * @HB_BUFFER_FLAG_DEFINED: All currently defined flags: Since: 4.4.0
  *
  * Flags for #hb_buffer_t.
  *
  * Since: 0.9.20
  */
 typedef enum { /*< flags >*/
   HB_BUFFER_FLAG_DEFAULT            = 0x00000000u,
   HB_BUFFER_FLAG_BOT                = 0x00000001u, /* Beginning-of-text */
   HB_BUFFER_FLAG_EOT                = 0x00000002u, /* End-of-text */
   HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES    = 0x00000004u,
   HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES  = 0x00000008u,
   HB_BUFFER_FLAG_DO_NOT_INSERT_DOTTED_CIRCLE    = 0x00000010u,
   HB_BUFFER_FLAG_VERIFY             = 0x00000020u,
   HB_BUFFER_FLAG_PRODUCE_UNSAFE_TO_CONCAT   = 0x00000040u,
   HB_BUFFER_FLAG_PRODUCE_SAFE_TO_INSERT_TATWEEL = 0x00000080u,
 
   HB_BUFFER_FLAG_DEFINED            = 0x000000FFu
 } hb_buffer_flags_t;
 
 HB_EXTERN void
 hb_buffer_set_flags (hb_buffer_t       *buffer,
              hb_buffer_flags_t  flags);
 
 HB_EXTERN hb_buffer_flags_t
 hb_buffer_get_flags (const hb_buffer_t *buffer);
 
 /**
  * hb_buffer_cluster_level_t:
  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES: Return cluster values grouped by graphemes into
  *   monotone order.
  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS: Return cluster values grouped into monotone order.
  * @HB_BUFFER_CLUSTER_LEVEL_CHARACTERS: Don't group cluster values.
  * @HB_BUFFER_CLUSTER_LEVEL_DEFAULT: Default cluster level,
  *   equal to @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES.
  * @HB_BUFFER_CLUSTER_LEVEL_GRAPHEMES: Only group clusters, but don't enforce monotone order.
  *
  * Data type for holding HarfBuzz's clustering behavior options. The cluster level
  * dictates one aspect of how HarfBuzz will treat non-base characters
  * during shaping.
  *
  * In @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES, non-base
  * characters are merged into the cluster of the base character that precedes them.
  * There is also cluster merging every time the clusters will otherwise become non-monotone.
  *
  * In @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS, non-base characters are initially
  * assigned their own cluster values, which are not merged into preceding base
  * clusters. This allows HarfBuzz to perform additional operations like reorder
  * sequences of adjacent marks. The output is still monotone, but the cluster
  * values are more granular.
  *
  * In @HB_BUFFER_CLUSTER_LEVEL_CHARACTERS, non-base characters are assigned their
  * own cluster values, which are not merged into preceding base clusters. Moreover,
  * the cluster values are not merged into monotone order. This is the most granular
  * cluster level, and it is useful for clients that need to know the exact cluster
  * values of each character, but is harder to use for clients, since clusters
  * might appear in any order.
  *
  * In @HB_BUFFER_CLUSTER_LEVEL_GRAPHEMES, non-base characters are merged into the
  * cluster of the base character that precedes them. This is similar to the Unicode
  * Grapheme Cluster algorithm, but it is not exactly the same. The output is
  * not forced to be monotone. This is useful for clients that want to use HarfBuzz
  * as a cheap implementation of the Unicode Grapheme Cluster algorithm.
  *
  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES is the default, because it maintains
  * backward compatibility with older versions of HarfBuzz. New client programs that
  * do not need to maintain such backward compatibility are recommended to use
  * @HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS instead of the default.
  *
  * Since: 0.9.42
  */
 typedef enum {
   HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES    = 0,
   HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS   = 1,
   HB_BUFFER_CLUSTER_LEVEL_CHARACTERS        = 2,
   HB_BUFFER_CLUSTER_LEVEL_GRAPHEMES     = 3,
   HB_BUFFER_CLUSTER_LEVEL_DEFAULT = HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES
 } hb_buffer_cluster_level_t;
 
 /**
  * HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE:
  * @level: #hb_buffer_cluster_level_t to test
  *
  * Tests whether a cluster level groups cluster values into monotone order.
  * Requires that the level be valid.
  *
  * Since: 11.0.0
  */
 #define HB_BUFFER_CLUSTER_LEVEL_IS_MONOTONE(level) \
     ((bool) ((1u << (unsigned) (level)) & \
          ((1u << HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES) | \
           (1u << HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS))))
 
 /**
  * HB_BUFFER_CLUSTER_LEVEL_IS_GRAPHEMES:
  * @level: #hb_buffer_cluster_level_t to test
  *
  * Tests whether a cluster level groups cluster values by graphemes. Requires
  * that the level be valid.
  *
  * Since: 11.0.0
  */
 #define HB_BUFFER_CLUSTER_LEVEL_IS_GRAPHEMES(level) \
     ((bool) ((1u << (unsigned) (level)) & \
          ((1u << HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES) | \
           (1u << HB_BUFFER_CLUSTER_LEVEL_GRAPHEMES))))
 
 /**
  * HB_BUFFER_CLUSTER_LEVEL_IS_CHARACTERS
  * @level: #hb_buffer_cluster_level_t to test
  *
  * Tests whether a cluster level does not group cluster values by graphemes.
  * Requires that the level be valid.
  *
  * Since: 11.0.0
  */
 #define HB_BUFFER_CLUSTER_LEVEL_IS_CHARACTERS(level) \
     ((bool) ((1u << (unsigned) (level)) & \
          ((1u << HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARCATERS) | \
           (1u << HB_BUFFER_CLUSTER_LEVEL_CHARACTERS))))
 
 HB_EXTERN void
 hb_buffer_set_cluster_level (hb_buffer_t               *buffer,
                  hb_buffer_cluster_level_t  cluster_level);
 
 HB_EXTERN hb_buffer_cluster_level_t
 hb_buffer_get_cluster_level (const hb_buffer_t *buffer);
 
 /**
  * HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT:
  *
  * The default code point for replacing invalid characters in a given encoding.
  * Set to U+FFFD REPLACEMENT CHARACTER.
  *
  * Since: 0.9.31
  */
 #define HB_BUFFER_REPLACEMENT_CODEPOINT_DEFAULT 0xFFFDu
 
 HB_EXTERN void
 hb_buffer_set_replacement_codepoint (hb_buffer_t    *buffer,
                      hb_codepoint_t  replacement);
 
 HB_EXTERN hb_codepoint_t
 hb_buffer_get_replacement_codepoint (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_invisible_glyph (hb_buffer_t    *buffer,
                    hb_codepoint_t  invisible);
 
 HB_EXTERN hb_codepoint_t
 hb_buffer_get_invisible_glyph (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_not_found_glyph (hb_buffer_t    *buffer,
                    hb_codepoint_t  not_found);
 
 HB_EXTERN hb_codepoint_t
 hb_buffer_get_not_found_glyph (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_not_found_variation_selector_glyph (hb_buffer_t    *buffer,
                           hb_codepoint_t  not_found_variation_selector);
 
 HB_EXTERN hb_codepoint_t
 hb_buffer_get_not_found_variation_selector_glyph (const hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_set_random_state (hb_buffer_t    *buffer,
                 unsigned        state);
 
 HB_EXTERN unsigned
 hb_buffer_get_random_state (const hb_buffer_t *buffer);
 
 /*
  * Content API.
  */
 
 HB_EXTERN void
 hb_buffer_clear_contents (hb_buffer_t *buffer);
 
 HB_EXTERN hb_bool_t
 hb_buffer_pre_allocate (hb_buffer_t  *buffer,
             unsigned int  size);
 
 
 HB_EXTERN hb_bool_t
 hb_buffer_allocation_successful (hb_buffer_t  *buffer);
 
 HB_EXTERN void
 hb_buffer_reverse (hb_buffer_t *buffer);
 
 HB_EXTERN void
 hb_buffer_reverse_range (hb_buffer_t *buffer,
              unsigned int start, unsigned int end);
 
 HB_EXTERN void
 hb_buffer_reverse_clusters (hb_buffer_t *buffer);
 
 
 /* Filling the buffer in */
 
 HB_EXTERN void
 hb_buffer_add (hb_buffer_t    *buffer,
            hb_codepoint_t  codepoint,
            unsigned int    cluster);
 
 HB_EXTERN void
 hb_buffer_add_utf8 (hb_buffer_t  *buffer,
             const char   *text,
             int           text_length,
             unsigned int  item_offset,
             int           item_length);
 
 HB_EXTERN void
 hb_buffer_add_utf16 (hb_buffer_t    *buffer,
              const uint16_t *text,
              int             text_length,
              unsigned int    item_offset,
              int             item_length);
 
 HB_EXTERN void
 hb_buffer_add_utf32 (hb_buffer_t    *buffer,
              const uint32_t *text,
              int             text_length,
              unsigned int    item_offset,
              int             item_length);
 
 HB_EXTERN void
 hb_buffer_add_latin1 (hb_buffer_t   *buffer,
               const uint8_t *text,
               int            text_length,
               unsigned int   item_offset,
               int            item_length);
 
 HB_EXTERN void
 hb_buffer_add_codepoints (hb_buffer_t          *buffer,
               const hb_codepoint_t *text,
               int                   text_length,
               unsigned int          item_offset,
               int                   item_length);
 
 HB_EXTERN void
 hb_buffer_append (hb_buffer_t *buffer,
           const hb_buffer_t *source,
           unsigned int start,
           unsigned int end);
 
 HB_EXTERN hb_bool_t
 hb_buffer_set_length (hb_buffer_t  *buffer,
               unsigned int  length);
 
 HB_EXTERN unsigned int
 hb_buffer_get_length (const hb_buffer_t *buffer);
 
 /* Getting glyphs out of the buffer */
 
 HB_EXTERN hb_glyph_info_t *
 hb_buffer_get_glyph_infos (hb_buffer_t  *buffer,
                unsigned int *length);
 
 HB_EXTERN hb_glyph_position_t *
 hb_buffer_get_glyph_positions (hb_buffer_t  *buffer,
                    unsigned int *length);
 
 HB_EXTERN hb_bool_t
 hb_buffer_has_positions (hb_buffer_t  *buffer);
 
 
 HB_EXTERN void
 hb_buffer_normalize_glyphs (hb_buffer_t *buffer);
 
 
 /*
  * Serialize
  */
 
 /**
  * hb_buffer_serialize_flags_t:
  * @HB_BUFFER_SERIALIZE_FLAG_DEFAULT: serialize glyph names, clusters and positions.
  * @HB_BUFFER_SERIALIZE_FLAG_NO_CLUSTERS: do not serialize glyph cluster.
  * @HB_BUFFER_SERIALIZE_FLAG_NO_POSITIONS: do not serialize glyph position information.
  * @HB_BUFFER_SERIALIZE_FLAG_NO_GLYPH_NAMES: do no serialize glyph name.
  * @HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS: serialize glyph extents.
  * @HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS: serialize glyph flags. Since: 1.5.0
  * @HB_BUFFER_SERIALIZE_FLAG_NO_ADVANCES: do not serialize glyph advances,
  *  glyph offsets will reflect absolute glyph positions. Since: 1.8.0
  * @HB_BUFFER_SERIALIZE_FLAG_DEFINED: All currently defined flags. Since: 4.4.0
  *
  * Flags that control what glyph information are serialized in hb_buffer_serialize_glyphs().
  *
  * Since: 0.9.20
  */
 typedef enum { /*< flags >*/
   HB_BUFFER_SERIALIZE_FLAG_DEFAULT      = 0x00000000u,
   HB_BUFFER_SERIALIZE_FLAG_NO_CLUSTERS      = 0x00000001u,
   HB_BUFFER_SERIALIZE_FLAG_NO_POSITIONS     = 0x00000002u,
   HB_BUFFER_SERIALIZE_FLAG_NO_GLYPH_NAMES   = 0x00000004u,
   HB_BUFFER_SERIALIZE_FLAG_GLYPH_EXTENTS    = 0x00000008u,
   HB_BUFFER_SERIALIZE_FLAG_GLYPH_FLAGS      = 0x00000010u,
   HB_BUFFER_SERIALIZE_FLAG_NO_ADVANCES      = 0x00000020u,
 
   HB_BUFFER_SERIALIZE_FLAG_DEFINED      = 0x0000003Fu
 } hb_buffer_serialize_flags_t;
 
 /**
  * hb_buffer_serialize_format_t:
  * @HB_BUFFER_SERIALIZE_FORMAT_TEXT: a human-readable, plain text format.
  * @HB_BUFFER_SERIALIZE_FORMAT_JSON: a machine-readable JSON format.
  * @HB_BUFFER_SERIALIZE_FORMAT_INVALID: invalid format.
  *
  * The buffer serialization and de-serialization format used in
  * hb_buffer_serialize_glyphs() and hb_buffer_deserialize_glyphs().
  *
  * Since: 0.9.2
  */
 typedef enum {
   HB_BUFFER_SERIALIZE_FORMAT_TEXT   = HB_TAG('T','E','X','T'),
   HB_BUFFER_SERIALIZE_FORMAT_JSON   = HB_TAG('J','S','O','N'),
   HB_BUFFER_SERIALIZE_FORMAT_INVALID    = HB_TAG_NONE
 } hb_buffer_serialize_format_t;
 
 HB_EXTERN hb_buffer_serialize_format_t
 hb_buffer_serialize_format_from_string (const char *str, int len);
 
 HB_EXTERN const char *
 hb_buffer_serialize_format_to_string (hb_buffer_serialize_format_t format);
 
 HB_EXTERN const char **
 hb_buffer_serialize_list_formats (void);
 
 HB_EXTERN unsigned int
 hb_buffer_serialize_glyphs (hb_buffer_t *buffer,
                 unsigned int start,
                 unsigned int end,
                 char *buf,
                 unsigned int buf_size,
                 unsigned int *buf_consumed,
                 hb_font_t *font,
                 hb_buffer_serialize_format_t format,
                 hb_buffer_serialize_flags_t flags);
 
 HB_EXTERN unsigned int
 hb_buffer_serialize_unicode (hb_buffer_t *buffer,
                  unsigned int start,
                  unsigned int end,
                  char *buf,
                  unsigned int buf_size,
                  unsigned int *buf_consumed,
                  hb_buffer_serialize_format_t format,
                  hb_buffer_serialize_flags_t flags);
 
 HB_EXTERN unsigned int
 hb_buffer_serialize (hb_buffer_t *buffer,
              unsigned int start,
              unsigned int end,
              char *buf,
              unsigned int buf_size,
              unsigned int *buf_consumed,
              hb_font_t *font,
              hb_buffer_serialize_format_t format,
              hb_buffer_serialize_flags_t flags);
 
 HB_EXTERN hb_bool_t
 hb_buffer_deserialize_glyphs (hb_buffer_t *buffer,
                   const char *buf,
                   int buf_len,
                   const char **end_ptr,
                   hb_font_t *font,
                   hb_buffer_serialize_format_t format);
 
 HB_EXTERN hb_bool_t
 hb_buffer_deserialize_unicode (hb_buffer_t *buffer,
                    const char *buf,
                    int buf_len,
                    const char **end_ptr,
                    hb_buffer_serialize_format_t format);
 
 
 
 /*
  * Compare buffers
  */
 
 /**
  * hb_buffer_diff_flags_t:
  * @HB_BUFFER_DIFF_FLAG_EQUAL: equal buffers.
  * @HB_BUFFER_DIFF_FLAG_CONTENT_TYPE_MISMATCH: buffers with different
  *     #hb_buffer_content_type_t.
  * @HB_BUFFER_DIFF_FLAG_LENGTH_MISMATCH: buffers with differing length.
  * @HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT: `.notdef` glyph is present in the
  *     reference buffer.
  * @HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT: dotted circle glyph is present
  *     in the reference buffer.
  * @HB_BUFFER_DIFF_FLAG_CODEPOINT_MISMATCH: difference in #hb_glyph_info_t.codepoint
  * @HB_BUFFER_DIFF_FLAG_CLUSTER_MISMATCH: difference in #hb_glyph_info_t.cluster
  * @HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH: difference in #hb_glyph_flags_t.
  * @HB_BUFFER_DIFF_FLAG_POSITION_MISMATCH: difference in #hb_glyph_position_t.
  *
  * Flags from comparing two #hb_buffer_t's.
  *
  * Buffer with different #hb_buffer_content_type_t cannot be meaningfully
  * compared in any further detail.
  *
  * For buffers with differing length, the per-glyph comparison is not
  * attempted, though we do still scan reference buffer for dotted circle and
  * `.notdef` glyphs.
  *
  * If the buffers have the same length, we compare them glyph-by-glyph and
  * report which aspect(s) of the glyph info/position are different.
  *
  * Since: 1.5.0
  */
 typedef enum { /*< flags >*/
   HB_BUFFER_DIFF_FLAG_EQUAL         = 0x0000,
 
   /* Buffers with different content_type cannot be meaningfully compared
    * in any further detail. */
   HB_BUFFER_DIFF_FLAG_CONTENT_TYPE_MISMATCH = 0x0001,
 
   /* For buffers with differing length, the per-glyph comparison is not
    * attempted, though we do still scan reference for dottedcircle / .notdef
    * glyphs. */
   HB_BUFFER_DIFF_FLAG_LENGTH_MISMATCH       = 0x0002,
 
   /* We want to know if dottedcircle / .notdef glyphs are present in the
    * reference, as we may not care so much about other differences in this
    * case. */
   HB_BUFFER_DIFF_FLAG_NOTDEF_PRESENT        = 0x0004,
   HB_BUFFER_DIFF_FLAG_DOTTED_CIRCLE_PRESENT = 0x0008,
 
   /* If the buffers have the same length, we compare them glyph-by-glyph
    * and report which aspect(s) of the glyph info/position are different. */
   HB_BUFFER_DIFF_FLAG_CODEPOINT_MISMATCH    = 0x0010,
   HB_BUFFER_DIFF_FLAG_CLUSTER_MISMATCH      = 0x0020,
   HB_BUFFER_DIFF_FLAG_GLYPH_FLAGS_MISMATCH  = 0x0040,
   HB_BUFFER_DIFF_FLAG_POSITION_MISMATCH     = 0x0080
 
 } hb_buffer_diff_flags_t;
 
 /* Compare the contents of two buffers, report types of differences. */
 HB_EXTERN hb_buffer_diff_flags_t
 hb_buffer_diff (hb_buffer_t *buffer,
         hb_buffer_t *reference,
         hb_codepoint_t dottedcircle_glyph,
         unsigned int position_fuzz);
 
 
 /*
  * Tracing.
  */
 
 /**
  * hb_buffer_message_func_t:
  * @buffer: An #hb_buffer_t to work upon
  * @font: The #hb_font_t the @buffer is shaped with
  * @message: `NULL`-terminated message passed to the function
  * @user_data: User data pointer passed by the caller
  *
  * A callback method for #hb_buffer_t. The method gets called with the
  * #hb_buffer_t it was set on, the #hb_font_t the buffer is shaped with and a
  * message describing what step of the shaping process will be performed.
  * Returning `false` from this method will skip this shaping step and move to
  * the next one.
  *
  * Return value: `true` to perform the shaping step, `false` to skip it.
  *
  * Since: 1.1.3
  */
 typedef hb_bool_t   (*hb_buffer_message_func_t) (hb_buffer_t *buffer,
                              hb_font_t   *font,
                              const char  *message,
                              void        *user_data);
 
 HB_EXTERN void
 hb_buffer_set_message_func (hb_buffer_t *buffer,
                 hb_buffer_message_func_t func,
                 void *user_data, hb_destroy_func_t destroy);
 
 
 HB_END_DECLS
 
 #endif /* HB_BUFFER_H */

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