harfbuzz/NEWS

Overview of changes leading to 0.9.34
Saturday, August 2, 2014
=====================================

- hb_feature_from_string() now accepts CSS font-feature-settings format.
- As a result, hb-shape / hb-view --features also accept CSS-style strings.
  Eg, "'liga' off" is accepted now.
- Add old-spec Myanmar shaper:
  https://bugs.freedesktop.org/show_bug.cgi?id=81775
- Don't apply 'calt' in Hangul shaper.
- Fix mark advance zeroing for Hebrew shaper:
  https://bugs.freedesktop.org/show_bug.cgi?id=76767
- Implement Windows-1256 custom Arabic shaping.  Only built on Windows,
  and requires help from get_glyph().  Used by Firefox.
  https://bugzilla.mozilla.org/show_bug.cgi?id=1045139
- Disable 'liga' in vertical text.
- Build fixes.
- API changes:

  * Make HB_BUFFER_FLAG_BOT/EOT easier to use.

    Previously, we expected users to provide BOT/EOT flags when the
    text *segment* was at paragraph boundaries.  This meant that for
    clients that provide full paragraph to HarfBuzz (eg. Pango), they
    had code like this:

      hb_buffer_set_flags (hb_buffer,
                           (item_offset == 0 ? HB_BUFFER_FLAG_BOT : 0) |
                           (item_offset + item_length == paragraph_length ?
                            HB_BUFFER_FLAG_EOT : 0));

      hb_buffer_add_utf8 (hb_buffer,
                          paragraph_text, paragraph_length,
                          item_offset, item_length);

    After this change such clients can simply say:

      hb_buffer_set_flags (hb_buffer,
                           HB_BUFFER_FLAG_BOT | HB_BUFFER_FLAG_EOT);

      hb_buffer_add_utf8 (hb_buffer,
                          paragraph_text, paragraph_length,
                          item_offset, item_length);

    Ie, HarfBuzz itself checks whether the segment is at the beginning/end
    of the paragraph.  Clients that only pass item-at-a-time to HarfBuzz
    continue not setting any flags whatsoever.

    Another way to put it is: if there's pre-context text in the buffer,
    HarfBuzz ignores the BOT flag.  If there's post-context, it ignores
    EOT flag.


Overview of changes leading to 0.9.33
Tuesday, July 22, 2014
=====================================

- Turn off ARabic 'cswh' feature that was accidentally turned on.
- Add HB_TAG_MAX_SIGNED.
- Make hb_face_make_immutable() really make face immutable!
- Windows build fixes.


Overview of changes leading to 0.9.32
Thursday, July 17, 2014
=====================================

- Apply Arabic shaping features in spec order exactly.
- Another fix for Mongolian free variation selectors.
- For non-Arabic scripts in Arabic shaper apply 'rlig' and 'calt'
  together.
- Minor adjustment to U+FFFD logic.
- Fix hb-coretext build.


Overview of changes leading to 0.9.31
Wednesday, July 16, 2014
=====================================

- Only accept valid UTF-8/16/32; we missed many cases before.
- Better shaping of invalid UTF-8/16/32.  Falls back to
  U+FFFD REPLACEMENT CHARACTER now.
- With all changes in this release, the buffer will contain fully
  valid Unicode after hb_buffer_add_utf8/16/32 no matter how
  broken the input is.  This can be overriden though.  See below.
- Fix Mongolian Variation Selectors for fonts without GDEF.
- Fix minor invalid buffer access.
- Accept zh-Hant and zh-Hans language tags.  hb_ot_tag_to_language()
  now uses these instead of private tags.
- Build fixes.
- New API:
  * hb_buffer_add_codepoints().  This does what hb_buffer_add_utf32()
    used to do, ie. no validity check on the input at all.  add_utf32
    now replaces invalid Unicode codepoints with the replacement
    character (see below).
  * hb_buffer_set_replacement_codepoint()
  * hb_buffer_get_replacement_codepoint()
    Previously, in hb_buffer_add_utf8 and hb_buffer_add_utf16, when
    we detected broken input, we replaced that with (hb_codepoint_t)-1.
    This has changed to use U+FFFD now, but can be changed using these
    new API.


Overview of changes leading to 0.9.30
Wednesday, July 9, 2014
=====================================

- Update to Unicode 7.0.0:
  * New scripts Manichaean and Psalter Pahlavi are shaped using
    Arabic shaper.
  * All the other new scripts to through the generic shaper for
    now.
- Minor Indic improvements.
- Fix graphite2 backend cluster mapping [crasher!]
- API changes:
  * New HB_SCRIPT_* values for Unicode 7.0 scripts.
  * New function hb_ot_layout_language_get_required_feature().
- Build fixes.


Overview of changes leading to 0.9.29
Thursday, May 29, 2014
=====================================

- Implement cmap in hb-ot-font.h.  No variation-selectors yet.
- Myanmar: Allow MedialYa+Asat.
- Various Indic fixes:
  * Support most characters in Extended Devanagary and Vedic
    Unicode blocks.
  * Allow digits and a some punctuation as consonant placeholders.
- Build fixes.


Overview of changes leading to 0.9.28
Monday, April 28, 2014
=====================================

- Unbreak old-spec Indic shaping. (bug 76705)
- Fix shaping of U+17DD and U+0FC6.
- Add HB_NO_MERGE_CLUSTERS build option.  NOT to be enabled by default
  for shipping libraries.  It's an option for further experimentation
  right now.  When we are sure how to do it properly, we will add
  public run-time API for the functionality.
- Build fixes.


Overview of changes leading to 0.9.27
Tuesday, March 18, 2014
=====================================

- Don't use "register" storage class specifier
- Wrap definition of free_langs() with HAVE_ATEXIT
- Add coretext_aat shaper and hb_coretext_face_create() constructor
- If HAVE_ICU_BUILTIN is defined, use hb-icu Unicode callbacks
- Add Myanmar test case from OpenType Myanmar spec
- Only do fallback Hebrew composition if no GPOS 'mark' available
- Allow bootstrapping without gtk-doc
- Use AM_MISSING_PROG for ragel and git
- Typo in ucdn's Makefile.am
- Improve MemoryBarrier() implementation


Overview of changes leading to 0.9.26
Thursday, January 30, 2014
=====================================

- Misc fixes.
- Fix application of 'rtlm' feature.
- Automatically apply frac/numr/dnom around U+2044 FRACTION SLASH.
- New header: hb-ot-shape.h
- Uniscribe: fix scratch-buffer accounting.
- Reorder Tai Tham SAKOT to after tone-marks.
- Add Hangul shaper.
- New files:
  hb-ot-shape-complex-hangul.cc
  hb-ot-shape-complex-hebrew.cc
  hb-ot-shape-complex-tibetan.cc
- Disable 'cswh' feature in Arabic shaper.
- Coretext: better handle surrogate pairs.
- Add HB_TAG_MAX and _HB_SCRIPT_MAX_VALUE.


Overview of changes leading to 0.9.25
Wednesday, December 4, 2013
=====================================

- Myanmar shaper improvements.
- Avoid font fallback in CoreText backend.
- Additional OpenType language tag mappiongs.
- More aggressive shape-plan caching.
- Build with / require automake 1.13.
- Build with libtool 2.4.2.418 alpha to support ppc64le.


Overview of changes leading to 0.9.24
Tuesday, November 13, 2013
=====================================

- Misc compiler warning fixes with clang.
- No functional changes.


Overview of changes leading to 0.9.23
Monday, October 28, 2013
=====================================

- "Udupi HarfBuzz Hackfest", Paris, October 14..18 2013.
- Fix (Chain)Context recursion with non-monotone lookup positions.
- Misc Indic bug fixes.
- New Javanese / Buginese shaping, similar to Windows 8.1.


Overview of changes leading to 0.9.22
Thursday, October 3, 2013
=====================================

- Fix use-after-end-of-scope in hb_language_from_string().
- Fix hiding of default_ignorables if font doesn't have space glyph.
- Protect against out-of-range lookup indices.

- API Changes:

  * Added hb_ot_layout_table_get_lookup_count()


Overview of changes leading to 0.9.21
Monday, September 16, 2013
=====================================

- Rename gobject-introspection library name from harfbuzz to HarfBuzz.
- Remove (long disabled) hb-old and hb-icu-le test shapers.
- Misc gtk-doc and gobject-introspection annotations.
- Misc fixes.
- API changes:

  * Add HB_SET_VALUE_INVALID

Overview of changes leading to 0.9.20
Thursday, August 29, 2013
=====================================

General:
- Misc substitute_closure() fixes.
- Build fixes.

Documentation:
- gtk-doc boilerplate integrated.  Docs are built now, but
  contain no contents.  By next release hopefully we have
  some content in.  Enable using --enable-gtk-doc.

GObject and Introspection:
- Added harfbuzz-gobject library (hb-gobject.h) that has type
  bindings for all HarfBuzz objects and enums.  Enable using
  --with-gobject.
- Added gobject-introspection boilerplate.  Nothing useful
  right now.  Work in progress.  Gets enabled automatically if
  --with-gobject is used.  Override with --disable-introspection.

OpenType shaper:
- Apply 'mark' in Myanmar shaper.
- Don't apply 'dlig' by default.

Uniscribe shaper:
- Support user features.
- Fix loading of fonts that are also installed on the system.
- Fix shaping of Arabic Presentation Forms.
- Fix build with wide chars.

CoreText shaper:
- Support user features.

Source changes:
- hb_face_t code moved to hb-face.h / hb-face.cc.
- Added hb-deprecated.h.

API changes:
- Added HB_DISABLE_DEPRECATED.
- Deprecated HB_SCRIPT_CANADIAN_ABORIGINAL; replaced by
  HB_SCRIPT_CANADIAN_SYLLABICS.
- Deprecated HB_BUFFER_FLAGS_DEFAULT; replaced by
  HB_BUFFER_FLAG_DEFAULT.
- Deprecated HB_BUFFER_SERIALIZE_FLAGS_DEFAULT; replaced by
  HB_BUFFER_SERIALIZE_FLAG_DEFAULT.


Overview of changes leading to 0.9.19
Tuesday, July 16, 2013
=====================================

- Build fixes.
- Better handling of multiple variation selectors in a row.
- Pass on variation selector to GSUB if not consumed by cmap.
- Fix undefined memory access.
- Add Javanese config to Indic shaper.
- Misc bug fixes.

Overview of changes leading to 0.9.18
Tuesday, May 28, 2013
=====================================

New build system:

- All unneeded code is all disabled by default,

- Uniscribe and CoreText shapers can be enabled with their --with options,

- icu_le and old shapers cannot be enabled for now,

- glib, freetype, and cairo will be detected automatically.
  They can be force on/off'ed with their --with options,

- icu and graphite2 are default off, can be enabled with their --with
  options,

Moreover, ICU support is now build into a separate library:
libharfbuzz-icu.so, and a new harfbuzz-icu.pc is shipped for it.
Distros can enable ICU now without every application on earth
getting linked to via libharfbuzz.so.

For distros I recommend that they make sure they are building --with-glib
--with-freetype --with-cairo, --with-icu, and optionally --with-graphite2;
And package harfbuzz and harfbuzz-icu separately.


Overview of changes leading to 0.9.17
Monday, May 20, 2013
=====================================

- Build fixes.
- Fix bug in hb_set_get_min().
- Fix regression with Arabic mark positioning / width-zeroing.

Overview of changes leading to 0.9.16
Friday, April 19, 2013
=====================================

- Major speedup in OpenType lookup processing.  With the Amiri
  Arabic font, this release is over 3x faster than previous
  release.  All scripts / languages should see this speedup.

- New --num-iterations option for hb-shape / hb-view; useful for
  profiling.

Overview of changes leading to 0.9.15
Friday, April 05, 2013
=====================================

- Build fixes.
- Fix crasher in graphite2 shaper.
- Fix Arabic mark width zeroing regression.
- Don't compose Hangul jamo into Unicode syllables.


Overview of changes leading to 0.9.14
Thursday, March 21, 2013
=====================================

- Build fixes.
- Fix time-consuming sanitize with malicious fonts.
- Implement hb_buffer_deserialize_glyphs() for both json and text.
- Do not ignore Hangul filler characters.
- Indic fixes:
  * Fix Malayalam pre-base reordering interaction with post-forms.
  * Further adjust ZWJ handling.  Should fix known regressions from
    0.9.13.


Overview of changes leading to 0.9.13
Thursday, February 25, 2013
=====================================

- Build fixes.
- Ngapi HarfBuzz Hackfest in London (February 2013):
  * Fixed all known Indic bugs,
  * New Win8-style Myanmar shaper,
  * New South-East Asian shaper for Tai Tham, Cham, and New Tai Lue,
  * Smartly ignore Default_Ignorable characters (joiners, etc) wheb
    matching GSUB/GPOS lookups,
  * Fix 'Phags-Pa U+A872 shaping,
  * Fix partial disabling of default-on features,
  * Allow disabling of TrueType kerning.
- Fix possible crasher with broken fonts with overlapping tables.
- Removed generated files from git again.  So, one needs ragel to
  bootstrap from the git tree.

API changes:
- hb_shape() and related APIs now abort if buffer direction is
  HB_DIRECTION_INVALID.  Previously, hb_shape() was calling
  hb_buffer_guess_segment_properties() on the buffer before
  shaping.  The heuristics in that function are fragile.  If the
  user really wants the old behvaior, they can call that function
  right before calling hb_shape() to get the old behavior.
- hb_blob_create_sub_blob() always creates sub-blob with
  HB_MEMORY_MODE_READONLY.  See comments for the reason.


Overview of changes leading to 0.9.12
Thursday, January 18, 2013
=====================================

- Build fixes for Sun compiler.
- Minor bug fix.

Overview of changes leading to 0.9.11
Thursday, January 10, 2013
=====================================

- Build fixes.
- Fix GPOS mark attachment with null Anchor offsets.
- [Indic] Fix old-spec reordering of viramas if sequence ends in one.
- Fix multi-threaded shaper data creation crash.
- Add atomic ops for Solaris.

API changes:
- Rename hb_buffer_clear() to hb_buffer_clear_contents().


Overview of changes leading to 0.9.10
Thursday, January 3, 2013
=====================================

- [Indic] Fixed rendering of Malayalam dot-reph
- Updated OT language tags.
- Updated graphite2 backend.
- Improved hb_ot_layout_get_size_params() logic.
- Improve hb-shape/hb-view help output.
- Fixed hb-set.h implementation to not crash.
- Fixed various issues with hb_ot_layout_collect_lookups().
- Various build fixes.

New API:

hb_graphite2_face_get_gr_face()
hb_graphite2_font_get_gr_font()
hb_coretext_face_get_cg_font()

Modified API:

hb_ot_layout_get_size_params()


Overview of changes leading to 0.9.9
Wednesday, December 5, 2012
====================================

- Fix build on Windows.
- Minor improvements.


Overview of changes leading to 0.9.8
Tuesday, December 4, 2012
====================================


- Actually implement hb_shape_plan_get_shaper ().
- Make UCDB data tables const.
- Lots of internal refactoring in OTLayout tables.
- Flesh out hb_ot_layout_lookup_collect_glyphs().

New API:

hb_ot_layout_collect_lookups()
hb_ot_layout_get_size_params()


Overview of changes leading to 0.9.7
Sunday, November 21, 2012
====================================


HarfBuzz "All-You-Can-Eat-Sushi" (aka Vancouver) Hackfest and follow-on fixes.

- Fix Arabic contextual joining using pre-context text.
- Fix Sinhala "split matra" mess.
- Fix Khmer shaping with broken fonts.
- Implement Thai "PUA" shaping for old fonts.
- Do NOT route Kharoshthi script through the Indic shaper.
- Disable fallback positioning for Indic and Thai shapers.
- Misc fixes.


hb-shape / hb-view changes:

- Add --text-before and --text-after
- Add --bot / --eot / --preserve-default-ignorables
- hb-shape --output-format=json


New API:

hb_buffer_clear()

hb_buffer_flags_t

HB_BUFFER_FLAGS_DEFAULT
HB_BUFFER_FLAG_BOT
HB_BUFFER_FLAG_EOT
HB_BUFFER_FLAG_PRESERVE_DEFAULT_IGNORABLES

hb_buffer_set_flags()
hb_buffer_get_flags()

HB_BUFFER_SERIALIZE_FLAGS
hb_buffer_serialize_glyphs()
hb_buffer_deserialize_glyphs()
hb_buffer_serialize_list_formats()

hb_set_add_range()
hb_set_del_range()
hb_set_get_population()
hb_set_next_range()

hb_face_[sg]et_glyph_count()

hb_segment_properties_t
HB_SEGMENT_PROPERTIES_DEFAULT
hb_segment_properties_equal()
hb_segment_properties_hash()

hb_buffer_set_segment_properties()
hb_buffer_get_segment_properties()

hb_ot_layout_glyph_class_t
hb_ot_layout_get_glyph_class()
hb_ot_layout_get_glyphs_in_class()

hb_shape_plan_t
hb_shape_plan_create()
hb_shape_plan_create_cached()
hb_shape_plan_get_empty()
hb_shape_plan_reference()
hb_shape_plan_destroy()
hb_shape_plan_set_user_data()
hb_shape_plan_get_user_data()
hb_shape_plan_execute()
hb_shape_plan_get_shaper()

hb_ot_shape_plan_collect_lookups()


API changes:

- Remove "mask" parameter from hb_buffer_add().
- Rename hb_ot_layout_would_substitute_lookup() and hb_ot_layout_substitute_closure_lookup().
- hb-set.h API const correction.
- Renamed hb_set_min/max() to hb_set_get_min/max().
- Rename hb_ot_layout_feature_get_lookup_indexes() to hb_ot_layout_feature_get_lookups().
- Rename hb_buffer_guess_properties() to hb_buffer_guess_segment_properties().



Overview of changes leading to 0.9.6
Sunday, November 13, 2012
====================================

- Don't clear pre-context text if no new context is provided.
- Fix ReverseChainingSubstLookup, which was totally borked.
- Adjust output format of hb-shape a bit.
- Include config.h.in in-tree.  Makes it easier for alternate build systems.
- Fix hb_buffer_set_length(buffer, 0) invalid memory allocation.
- Use ICU LayoutEngine's C API instead of C++.  Avoids much headache.
- Drop glyphs for all of Unicode Default_Ignorable characters.
- Misc build fixes.

Arabic shaper:
- Enable 'dlig' and 'mset' features in Arabic shaper.
- Implement 'Phags-pa shaping, improve Mongolian.

Indic shaper:
- Decompose Sinhala split matras the way old HarfBuzz / Pango did.
- Initial support for Consonant Medials.
- Start adding new-style Myanmar shaping.
- Make reph and 'pref' logic introspect the font.
- Route Meetei-Mayek through the Indic shaper.
- Don't apply 'liga' in Indic shaper.
- Improve Malayalam pre-base reordering Ra interaction with Chillus.



Overview of changes leading to 0.9.5
Sunday, October 14, 2012
====================================

- Synthetic-GSUB Arabic fallback shaping.

- Misc Indic improvements.

- Add build system support for pthread.

- Imported UCDN for in-tree Unicode callbacks implementation.

- Context-aware Arabic joining.

- Misc other fixes.

- New API:

  hb_feature_to/from-string()
  hb_buffer_[sg]et_content_type()



Overview of changes leading to 0.9.4
Tuesday, Sep 03, 2012
====================================

- Indic improvements with old-spec Malayalam.

- Better fallback glyph positioning, specially with Thai / Lao marks.

- Implement dotted-circle insertion.

- Better Arabic fallback shaping / ligation.

- Added ICU LayoutEngine backend for testing.  Call it by the 'icu_le' name.

- Misc fixes.



Overview of changes leading to 0.9.3
Friday, Aug 18, 2012
====================================

- Fixed fallback mark positioning for left-to-right text.

- Improve mark positioning for the remaining combining classes.

- Unbreak Thai and fallback Arabic shaping.

- Port Arabic shaper to shape-plan caching.

- Use new ICU normalizer functions.



Overview of changes leading to 0.9.2
Friday, Aug 10, 2012
====================================

- Over a thousand commits!  This is the first major release of HarfBuzz.

- HarfBuzz is feature-complete now!  It should be in par, or better, than
  both Pango's shapers and old HarfBuzz / Qt shapers.

- New Indic shaper, supporting main Indic scripts, Sinhala, and Khmer.

- Improved Arabic shaper, with fallback Arabic shaping, supporting Arabic,
  Sinhala, N'ko, Mongolian, and Mandaic.

- New Thai / Lao shaper.

- Tibetan / Hangul support in the generic shaper.

- Synthetic GDEF support for fonts without a GDEF table.

- Fallback mark positioning for fonts without a GPOS table.

- Unicode normalization shaping heuristic during glyph mapping.

- New experimental Graphite2 backend.

- New Uniscribe backend (primarily for testing).

- New CoreText backend (primarily for testing).

- Major optimization and speedup.

- Test suites and testing infrastructure (work in progress).

- Greatly improved hb-view cmdline tool.

- hb-shape cmdline tool.

- Unicode 6.1 support.

Summary of API changes:

o Changed API:

  - Users are expected to only include main header files now (ie. hb.h,
    hb-glib.h, hb-ft.h, ...)

  - All struct tag names had their initial underscore removed.
    Ie. "struct _hb_buffer_t" is "struct hb_buffer_t" now.

  - All set_user_data() functions now take a "replace" boolean parameter.

  - hb_buffer_create() takes zero arguments now.
    Use hb_buffer_pre_allocate() to pre-allocate.

  - hb_buffer_add_utf*() now accept -1 for length parameteres,
    meaning "nul-terminated".

  - hb_direction_t enum values changed.

  - All *_from_string() APIs now take a length parameter to allow for
    non-nul-terminated strings. A -1 length means "nul-terminated".

  - Typedef for hb_language_t changed.

  - hb_get_table_func_t renamed to hb_reference_table_func_t.

  - hb_ot_layout_table_choose_script()

  - Various renames in hb-unicode.h.

o New API:

  - hb_buffer_guess_properties()
    Automatically called by hb_shape().

  - hb_buffer_normalize_glyphs()

  - hb_tag_from_string()

  - hb-coretext.h

  - hb-uniscribe.h

  - hb_face_reference_blob()
  - hb_face_[sg]et_index()
  - hb_face_set_upem()

  - hb_font_get_glyph_name_func_t
    hb_font_get_glyph_from_name_func_t
    hb_font_funcs_set_glyph_name_func()
    hb_font_funcs_set_glyph_from_name_func()
    hb_font_get_glyph_name()
    hb_font_get_glyph_from_name()
    hb_font_glyph_to_string()
    hb_font_glyph_from_string()

  - hb_font_set_funcs_data()

  - hb_ft_font_set_funcs()
  - hb_ft_font_get_face()

  - hb-gobject.h (work in progress)

  - hb_ot_shape_glyphs_closure()
    hb_ot_layout_substitute_closure_lookup()

  - hb-set.h

  - hb_shape_full()

  - hb_unicode_combining_class_t

  - hb_unicode_compose_func_t
    hb_unicode_decompose_func_t
    hb_unicode_decompose_compatibility_func_t
    hb_unicode_funcs_set_compose_func()
    hb_unicode_funcs_set_decompose_func()
    hb_unicode_funcs_set_decompose_compatibility_func()
    hb_unicode_compose()
    hb_unicode_decompose()
    hb_unicode_decompose_compatibility()

o Removed API:

  - hb_ft_get_font_funcs()

  - hb_ot_layout_substitute_start()
    hb_ot_layout_substitute_lookup()
    hb_ot_layout_substitute_finish()
    hb_ot_layout_position_start()
    hb_ot_layout_position_lookup()
    hb_ot_layout_position_finish()



Overview of changes leading to 0.6.0
Friday, May 27, 2011
====================================

- Vertical text support in GPOS
- Almost all API entries have unit tests now, under test/
- All thread-safety issues are fixed

Summary of API changes follows.


* Simple Types API:

  o New API:
    HB_LANGUAGE_INVALID
    hb_language_get_default()
    hb_direction_to_string()
    hb_direction_from_string()
    hb_script_get_horizontal_direction()
    HB_UNTAG()

  o Renamed API:
    hb_category_t renamed to hb_unicode_general_category_t

  o Changed API:
    hb_language_t is a typed pointers now

  o Removed API:
    HB_TAG_STR()


* Use ISO 15924 tags for hb_script_t:

  o New API:
    hb_script_from_iso15924_tag()
    hb_script_to_iso15924_tag()
    hb_script_from_string()

  o Changed API:
    HB_SCRIPT_* enum members changed value.


* Buffer API streamlined:

  o New API:
    hb_buffer_reset()
    hb_buffer_set_length()
    hb_buffer_allocation_successful()

  o Renamed API:
    hb_buffer_ensure() renamed to hb_buffer_pre_allocate()
    hb_buffer_add_glyph() renamed to hb_buffer_add()

  o Removed API:
    hb_buffer_clear()
    hb_buffer_clear_positions()

  o Changed API:
    hb_buffer_get_glyph_infos() takes an out length parameter now
    hb_buffer_get_glyph_positions() takes an out length parameter now


* Blob API streamlined:

  o New API:
    hb_blob_get_data()
    hb_blob_get_data_writable()

  o Renamed API:
    hb_blob_create_empty() renamed to hb_blob_get_empty()

  o Removed API:
    hb_blob_lock()
    hb_blob_unlock()
    hb_blob_is_writable()
    hb_blob_try_writable()

  o Changed API:
    hb_blob_create() takes user_data before destroy now


* Unicode functions API:

  o Unicode function vectors can subclass other unicode function vectors now.
    Unimplemented callbacks in the subclass automatically chainup to the parent.

  o All hb_unicode_funcs_t callbacks take a user_data now.  Their setters
    take a user_data and its respective destroy callback.

  o New API:
    hb_unicode_funcs_get_empty()
    hb_unicode_funcs_get_default()
    hb_unicode_funcs_get_parent()

  o Changed API:
    hb_unicode_funcs_create() now takes a parent_funcs.

  o Removed func getter functions:
    hb_unicode_funcs_get_mirroring_func()
    hb_unicode_funcs_get_general_category_func()
    hb_unicode_funcs_get_script_func()
    hb_unicode_funcs_get_combining_class_func()
    hb_unicode_funcs_get_eastasian_width_func()


* Face API:

  o Renamed API:
    hb_face_get_table() renamed to hb_face_reference_table()
    hb_face_create_for_data() renamed to hb_face_create()

  o Changed API:
    hb_face_create_for_tables() takes user_data before destroy now
    hb_face_reference_table() returns empty blob instead of NULL
    hb_get_table_func_t accepts the face as first parameter now

* Font API:

  o Fonts can subclass other fonts now.  Unimplemented callbacks in the
    subclass automatically chainup to the parent.  When chaining up,
    scale is adjusted if the parent font has a different scale.

  o All hb_font_funcs_t callbacks take a user_data now.  Their setters
    take a user_data and its respective destroy callback.

  o New API:
    hb_font_get_parent()
    hb_font_funcs_get_empty()
    hb_font_create_sub_font()

  o Removed API:
    hb_font_funcs_copy()
    hb_font_unset_funcs()

  o Removed func getter functions:
    hb_font_funcs_get_glyph_func()
    hb_font_funcs_get_glyph_advance_func()
    hb_font_funcs_get_glyph_extents_func()
    hb_font_funcs_get_contour_point_func()
    hb_font_funcs_get_kerning_func()

  o Changed API:
    hb_font_create() takes a face and references it now
    hb_font_set_funcs() takes user_data before destroy now
    hb_font_set_scale() accepts signed integers now
    hb_font_get_contour_point_func_t now takes glyph first, then point_index
    hb_font_get_glyph_func_t returns a success boolean now


* Changed object model:

  o All object types have a _get_empty() now:
    hb_blob_get_empty()
    hb_buffer_get_empty()
    hb_face_get_empty()
    hb_font_get_empty()
    hb_font_funcs_get_empty()
    hb_unicode_funcs_get_empty()

  o Added _set_user_data() and _get_user_data() for all object types:
    hb_blob_get_user_data()
    hb_blob_set_user_data()
    hb_buffer_get_user_data()
    hb_buffer_set_user_data()
    hb_face_get_user_data()
    hb_face_set_user_data()
    hb_font_funcs_get_user_data()
    hb_font_funcs_set_user_data()
    hb_font_get_user_data()
    hb_font_set_user_data()
    hb_unicode_funcs_get_user_data()
    hb_unicode_funcs_set_user_data()

  o Removed the _get_reference_count() from all object types:
    hb_blob_get_reference_count()
    hb_buffer_get_reference_count()
    hb_face_get_reference_count()
    hb_font_funcs_get_reference_count()
    hb_font_get_reference_count()
    hb_unicode_funcs_get_reference_count()

  o Added _make_immutable() and _is_immutable() for all object types except for buffer:
    hb_blob_make_immutable()
    hb_blob_is_immutable()
    hb_face_make_immutable()
    hb_face_is_immutable()


* Changed API for vertical text support

  o The following callbacks where removed:
    hb_font_get_glyph_advance_func_t
    hb_font_get_kerning_func_t

  o The following new callbacks added instead:
    hb_font_get_glyph_h_advance_func_t
    hb_font_get_glyph_v_advance_func_t
    hb_font_get_glyph_h_origin_func_t
    hb_font_get_glyph_v_origin_func_t
    hb_font_get_glyph_h_kerning_func_t
    hb_font_get_glyph_v_kerning_func_t

  o The following API removed as such:
    hb_font_funcs_set_glyph_advance_func()
    hb_font_funcs_set_kerning_func()
    hb_font_get_glyph_advance()
    hb_font_get_kerning()

  o New API added instead:
    hb_font_funcs_set_glyph_h_advance_func()
    hb_font_funcs_set_glyph_v_advance_func()
    hb_font_funcs_set_glyph_h_origin_func()
    hb_font_funcs_set_glyph_v_origin_func()
    hb_font_funcs_set_glyph_h_kerning_func()
    hb_font_funcs_set_glyph_v_kerning_func()
    hb_font_get_glyph_h_advance()
    hb_font_get_glyph_v_advance()
    hb_font_get_glyph_h_origin()
    hb_font_get_glyph_v_origin()
    hb_font_get_glyph_h_kerning()
    hb_font_get_glyph_v_kerning()

  o The following higher-leve API added for convenience:
    hb_font_get_glyph_advance_for_direction()
    hb_font_get_glyph_origin_for_direction()
    hb_font_add_glyph_origin_for_direction()
    hb_font_subtract_glyph_origin_for_direction()
    hb_font_get_glyph_kerning_for_direction()
    hb_font_get_glyph_extents_for_origin()
    hb_font_get_glyph_contour_point_for_origin()


* OpenType Layout API:

  o New API:
    hb_ot_layout_position_start()
    hb_ot_layout_substitute_start()
    hb_ot_layout_substitute_finish()


* Glue code:

  o New API:
    hb_glib_script_to_script()
    hb_glib_script_from_script()
    hb_icu_script_to_script()
    hb_icu_script_from_script()


* Version API added:

  o New API:
    HB_VERSION_MAJOR
    HB_VERSION_MINOR
    HB_VERSION_MICRO
    HB_VERSION_STRING
    HB_VERSION_CHECK()
    hb_version()
    hb_version_string()
    hb_version_check()