renderer: implement correct error estimation for stroking

[libass] / Changelog

libass (unreleased)
 * Treat invalid nested \t tags like VSFilter
 * Fix stack overflow on deeply nested \t tags

libass (0.14.0)
 * Brand new, faster and better outline stroker (replaces FreeType stroker)
 * Remove option to use the FreeType rasterizer
 * Fix spots of missing border around self-intersecting shapes
 * Switch from Yasm to NASM for building hand-written assembler code
 * Support Core Text font provider on Mac OS X 10.6 and 10.7
 * Clear font cache in ass_set_fonts(). This fixes potentially incorrect
   font choices and an occasional crash if this function is called midway
   through rendering a file.

libass (0.13.7)
 * Fix invalid memory accesses with BorderStyle=4
 * Fix change detection bug on frame resizes
 * Fix cache bugs with border size
 * Reduce precision of border width in font outline caching
 * Don't treat :;<=>? as hexadecimal digits in color headers
 * Fix parsing of unusual Alignment values in ASS style definitions
 * Fix potential truncation in timestamp parsing
 * Treat negative PlayResX/PlayResY like VSFilter
 * Fixes to parsing of embedded fonts
 * Remove arbitrary bitmap limit (fixes issues with subtitle rendering at 4K)
 * Allow using shadow offset to adjust size of background with BorderStyle=4
 * Fix TrueType/OpenType font collection handling with the DirectWrite backend

libass (0.13.6)
 * Bump ABI version to account for the new Justify field in ASS_Style
   that was added in 0.13.5.

libass (0.13.5)
 * Add Justify style override that changes text justification
   (left/right/center) without affecting event positioning.
 * Fix ass_set_cache_limits() to affect total bitmap cache size
   including composite bitmap cache.
 * Number parsing fixes
   * Fix illegal read when parsing some numbers in scientific notation
     with huge exponents.
   * Correctly evaluate numbers in scientific notation with large exponents.
   * Correctly evaluate numbers with many leading zeros.
 * Bug fixes found with fuzzing
   * Fix a small memory leak in the parser.
   * Fix illegal read in the parser on specially crafted input with \t tags.

libass (0.13.4)
 * Bug fixes found with fuzzing
   * Fix memory reallocation in the shaper. (CVE-2016-7972)
   * Fix two small memory leaks in the parser and test program.
   * Fix illegal read in Gaussian blur coefficient calculations.
     (CVE-2016-7970)
   * Fix mode 0/3 line wrapping equalization in specific cases which could
     result in illegal reads while laying out and shaping text.
     (CVE-2016-7969)

libass (0.13.3)
 * Improve compatibility/portablility of build system,
   should fix e.g. compilation on Solaris.
 * Fix memory leak in DirectWrite font provider.
 * Fix the rasterizer when rendering some large outlines.
 * Remove hack that forced RTL base direction depending on font encoding.
 * Greatly improve the internal caches with refcounting and gradual clearing.

libass (0.13.2)
 * Add ass_set_check_readorder() API function to disable use of the ReadOrder
   field for duplicate checking in ass_process_chunk().
 * ass_step_sub(track, now, 0) now finds the start of the subtitle at "now".
 * Bug fixes
   * Fix an issue with the new duplicate checking, which could lead to
     missing subtitles after seeking.
   * Fix a crash with CoreText under specific circumstances

libass (0.13.1)
 * Much faster duplicate event check in ass_process_chunk. This can
   bring a large speedup for embedded subtitles with lots of events.
   To make this possible, it is now forbidden to combine calls to
   ass_process_chunk with any other method of manipulating the event
   list, namely, manual manipulation and calls to ass_process_data,
   ass_read_memory and ass_read_file.
 * Interpret negative timestamp components as actual negative numbers.
   This change increases compatibility with VSFilter.
 * Font matching changes for VSFilter compatibility
   * Look up fonts that contain PostScript outlines by their PostScript
     name instead of their full names. Family names continue to be used
     for all fonts.
   * Keep spaces in font names
 * Drop support for Fontconfig < 2.10.92 to ensure correct font matching
 * Bug fixes
   * Fix building the assembler code for the x32 ABI (GH #200)
   * Fix static linking against libass through pkg-config when libass
     uses libiconv
   * Fix some small memory leaks, potential crashes and bad data uses

libass (0.13.0)
 * Add native font selection backends for OSX (CoreText) and Windows
   (DirectWrite). You can now run libass without fontconfig on these
   platforms. This fixes problems with fontconfig behaving badly on
   these platforms (it could take minutes to scan all system fonts).
   Even on Linux, this speeds up loading of embedded fonts (such as
   provided by ass_add_font()).
   The DirectWrite backend only works on Windows Vista and later. On
   XP, fontconfig is still needed. libass can be compiled with both
   DirectWrite and fontconfig, and then it will fallback to fontconfig
   automatically if DirectWrite is not available at runtime.
 * Add ass_get_available_font_providers() API function.
 * Change the 4th parameter of ass_set_fonts(). This now selects the
   font provider. This is somewhat backwards compatible with the old
   behavior, but if you ever passed values other than 0 or 1, your
   application might break with this libass release.
 * The ass_fonts_update() function now does nothing. It's kept for
   backward compatibility only.
 * Much faster gaussian blur. This can bring a large speedup with big
   blurred signs and such.
 * Drop ENCA support
 * Bug fixes
   * Fix compilation of the freetype rasterizer (disabled by default)
   * Fix rendering with some cases of consecutive line breaks (\N\N).
   * Fix some memory allocation failure checks
   * Avoid system locale dependent behavior by reinventing some standard
     C functions
   * Fix rendering errors with strikes (GH #193)
   * MSVC compilation fixes

libass (0.12.3)
 * VSFilter blur compatibility changes
 * VSFilter color/alpha parsing compatibility changes
 * Bugfixes
   * Fix some potential memory leaks and crashes
   * Fix large timestamps (larger than about 600 hours)
   * Fix a potential crash with the new rasterizer and complex fonts
   * Do not apply user-configured line position to non-dialog events
   * Strictly clip non-dialog events to the video rectangle

libass (0.12.2)
 * Add extern "C" guards to the public headers for C++ compatibility
 * Improvements to style override API and implementation
 * Bugfixes
   * Fix some rasterizer bugs of unknown severity
   * Fix a broken memset() of unknown severity
   * Make timestamp parsing more lenient, which makes libass accept invalid
     files accepted by most other ASS parsers
   * Increase compatibility with broken ASS drawings accepted by VSFilter

libass (0.12.1)
 * Make ASS drawings with an extremely high number of control points work
   This change increases compatibility with VSFilter.
 * Bugfixes
   * Fix a crash when using newer harfbuzz versions (GH #155)
   * Load embedded memory fonts correctly
   * Large shadow offsets rendered incorrectly (GH #142)
   * Fix incorrect closing of last drawing contour
   * Fix issues with undefined behavior in shifts
   * Lots of of malloc() error checking

libass (0.12.0)
 * Implement fast quad-tree rasterizer in C and SSE2/AVX2 assembly
 * Make \be animatable
 * Add BorderStyle=4 (GH #105)
 * Add selective style override functionality
   * ass_set_selective_style_override()
   * ass_set_selective_style_override_enabled()
 * Support for assembly on DragonFly BSD
 * Bugfixes
   * Various parser fixes
   * Fix premature parser exit on }{ in drawing mode (GH #75)
   * Reset clipping mode on every rectangle clip
   * Improved error handling for FriBidi and FreeType (GH #131)
   * Fix bitmap combining cache

libass (0.11.2)
 * Improve yasm version check
 * Fix \fscx0 crashes
 * Actually export ass_library_version
 * Fix change detection with vector clips
 * SIMD assembly bugfixes
 * Parse drawing numbers as floats (GH #63)
 * Fix shaper sign bug (GH #68)
 * Initialize \pbo correctly (GH #74)

libass (0.11.1)
 * Fix distfile generation
 * No functional changes

libass (0.11.0)
 * Add bitmap run combining/compositing
   This changes the text rendering model and increases compatibility with
   VSFilter. It may make rendering faster or slower in certain cases.
 * Add AVX/SSE2 implementations for \be and compositing
   This adds yasm as (optional) build dependency.
 * Add ass_library_version() API funcion (GC #113)
 * Add 'profile' program for benchmarks
 * Improve gaussian blur
 * Fix compilation with MSVC 2013
 * Speed up HarfBuzz shaper
 * Speed up cache
 * Notable compatibility bugfixes
   * Reset origin on \fay changes (GC #88)
   * Tons of parser fixes
   * Fix ascender/descender metrics (GH #8)
   * Fix \pbo sign and scaling
   * Don't reset wrap style on \r (GC #116, GH #45)
 * Notable bugfixes:
   * Correctly handle @font advance (GC #94)
   * Disable ligatures for non-zero \fsp
   * Make sure to release vector clip (GH #22)

libass (0.10.2)
 * API additions and some ABI changes, bumped SONAME
 * Expose header field for VSFilter color mangling (GC #87)
 * Add functions for explicit scaling hints (GC #6)
 * Add 'type' field to ASS_Image (GC #31)
 * Workaround Freetype's font size grid-fitting where appropriate
 * Apply blur to both glyph and border when using opaque box
 * Parser bugfixes
   * Parse angles in style as number
   * Fix fallback event formats
   * Make closing ')' optional for some tags
   * Fix crazy VSFilter behaviour for \move (GC #90)
   * Make \r fall back to line style (GC #104)
   * Parse style name like VSFilter
   * Ignore junk in nested \t tags
   * Make \clip tag arguments mandatory
 * Properly handle script and language in the HarfBuzz shaper
 * Allow ASS_Track and ASS_Renderer to have different ASS_Library
 * Fix stroking in some rare cases
 * Correctly handle @font advance (GC #94)
 * Fix ascent/descent for some fonts (GC #106)
 * Fix ass_step_sub to not require sorted events
 * Fix blur scaling
 * Don't mutate input strings (GC #88)
 * Remove/change some error messages
 * Fix various small memory leaks

libass (0.10.1)
 * Fix letter spacing
 * Add \rSTYLENAME syntax support (GC #43)
 * Fix border generation and border style reset (GC #56)
 * Fix various issues with bug-for-bug compatibility of
   transformations (\fax, \fay, etc.) to VSFilter (GC #46, GC #42)
 * Fix drawing parsing (GC #47)
 * Various fixes to shaper (GC #54, GC #55, GC#59)
 * Fix change detection
 * Add ass_set_line_position API to set a vertical subtitle offset
 * Fix scaling of drawing baseline offset (\pbo) values
 * Fix skipping of zero-width characters for FriBiDi shaper
 * Use LTR text base direction by default, similar to VSFilter

libass (0.10.0)
 * Bidirectional layout and Arabic shaping via FriBidi (GC #13)
 * OpenType shaping via HarfBuzz-ng (GC #13)
 * Add API for shaper configuration
 * Add support for `Language' Script Info property, this can be used for
   hinting the text language
 * Vertical layout improvements
   * Use `vert' and `vkna' OpenType features for vertical glyph variants
   * Position rotated glyphs onto baseline
 * Parse font encoding property for base text direction hinting
 * Refactor cache system
 * Use generic outlines in place of FreeType glyphs
 * Direct outline bitmap rendering
 * Fix whitespace trimming (GC #35)
 * Do not render border if there's no shadow or glyph (GC #29)
 * Adjust spacing after a italic to non-italic style change (GC #37)
 * Fix fade timing
 * Fix x positioning with borders (GC #27)
 * Build system tweaks

libass (0.9.12)
 * Switch to permissive (ISC) license
 * Support \fs+ and \fs- syntax for modifying font size
 * Fix word-wrapping
 * Improved charmap fallback matching
 * Handle a few more VSFilter quirks correctly
 * Add a sensible default style
 * Fix compilation against libpng 1.5

libass (0.9.11)
 * Fix serious memory leaks
 * Reduce frame/drawing initialization overhead

libass (0.9.10)
 * Basic (incorrect, but working) support for @font vertical text layout
 * Fix multiple faces per font attachment
 * charmap selection fixes
 * Add ass_flush_events API function
 * Improve fullname font matching
 * Better PAR correction if text transforms are used
 * Calculate drawing bounding box like VSFilter
 * Performance improvements
   * Cache vector clip masks
   * Avoid unnecessary glyph copies
 * Various rendering fixes

libass (0.9.9)
 * Parse numbers in a locale-independent way
 * Remove support for freetype < 2.2.1, fontconfig < 2.4.1; this especially
   means libass will not extract fonts into the file system anymore
 * Disable script file size limit
 * Match fonts against the full name ("name for humans")
 * Reset clip mode after \iclip
 * Improve VSFilter compatibility
 * Update API documentation
 * A couple of smaller fixes and cleanups

libass (0.9.8)
 * Support \q override tag
 * Support wrap style 1 (i.e. wrap, but do not equalize line lengths)
 * Support border style 3 (opaque box)
 * Use the event bounding box (instead of vertical position and height) for
   collision detection
 * Embold glyphs if no bold variant is available, but was requested
 * Modify \fax to be similar to VSFilter
 * Trim spaces after line wrapping
 * Fix border/shadow overlap combining in some cases
 * Disable kerning by default.  Use "Kerning=yes" style override or
   "Kerning: yes" in [Script Info] to enable it
 * Slight bitmap handling optimizations
 * Various bugfixes

libass (0.9.7)
 * Build system fixes
 * Fixed cache lookup and overload problems
 * All globals have been eliminated, libass is reentrant
 * Dynamically allocate glyph and line buffers
 * Fix up stroking of big borders
 * Support empty lines (\N\N)
 * Support for the following override tags:
   \fax, \fay, \xshad, \yshad, \ybord, \xbord, \iclip, \u, \s, \p, \pbo
 * Full subpixel accuracy for positioning
 * PAR and rotation correction for EOSD rendering
 * Drawing mode (including vector \clip and \iclip)
 * Fixed a few memory leaks
 * Removed MPlayer compatibility code
 * Introduced message handling callback
 * Various fixes to match VSFilter quirks and Windows font metrics
 * Lots of bugfixes

LibASS (0.9.6)
 * Various fixes and updates to match VSFilter renderer.
 * Support \blur tag and ScaledBordersAndShadow property.
 * Fractional arguments and subpixel accuracy.
 * Keep positions when pan-and-scan is used.
 * Lots of bugfixes and other changes.

LibASS (0.9.5)
 * Support '=' and '.' in style name in arguments to ass_set_style_overrides().
 * Allow overriding [Script Info] parameters with ass_set_style_overrides().
 * Add workarounds for some buggy fonts.
 * Remove buggy workarounds for some other fonts.
 * Fixed ass_set_line_spacing() (was broken before).
 * Negative margin sizes are now used for image cropping.
 * Better handling of behind-the-camera objects.
 * Case insensitive parsing of SSA/ASS section headers.
 * Improved font matching.
 * When 2 styles have the same name, the later one is used.
 * Fixed several other bugs.