1 files changed, 799 insertions, 472 deletions
diff --git a/gfx/harfbuzz/src/hb-buffer.h b/gfx/harfbuzz/src/hb-buffer.h
index bf289c19b3..9cf33c2d7f 100644
--- a/gfx/harfbuzz/src/hb-buffer.h
+++ b/gfx/harfbuzz/src/hb-buffer.h
@@ -1,472 +1,799 @@
-/*
- * 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
- */
-
-#ifndef HB_H_IN
-#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).
- * @mask: 
- * @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;
-  hb_mask_t      mask;
-  uint32_t       cluster;
-
-  /*< private >*/
-  hb_var_int_t   var1;
-  hb_var_int_t   var2;
-} hb_glyph_info_t;
-
-/**
- * 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;
-
-#define HB_SEGMENT_PROPERTIES_DEFAULT {HB_DIRECTION_INVALID, \
-				       HB_SCRIPT_INVALID, \
-				       HB_LANGUAGE_INVALID, \
-				       NULL, \
-				       NULL}
-
-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_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_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 (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).
- */
-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 (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 (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 (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 (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 (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 (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_EOT.
- * @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 (currently done
- *                      by replacing them with the space glyph and zeroing the
- *                      advance width.)
- *
- * 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_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 (hb_buffer_t *buffer);
-
-/*
- * 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_DEFAULT = HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES
-} hb_buffer_cluster_level_t;
-
-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 (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 (hb_buffer_t    *buffer);
-
-
-HB_EXTERN void
-hb_buffer_reset (hb_buffer_t *buffer);
-
-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 hb_bool_t
-hb_buffer_set_length (hb_buffer_t  *buffer,
-		      unsigned int  length);
-
-HB_EXTERN unsigned int
-hb_buffer_get_length (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 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.
- *
- * 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_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 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);
-
-
-/*
- * Debugging.
- */
-
-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 */
+/*
+ * 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 positin 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.
+ * 
+ * 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.
+ *
+ * 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.
+ *
+ * @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_DEFAULT = HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES
+} hb_buffer_cluster_level_t;
+
+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);
+
+
+/*
+ * 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 */