Crate ttf_parser

A high-level, safe, zero-allocation TrueType font parser.

Features

• A high-level API.
• Zero allocations.
• Zero unsafe.
• Zero dependencies.
• Fast.
• Stateless.
• Simple and maintainable code (no magic numbers).

Supported TrueType features

• (cmap) Character to glyph index mapping using glyph_index() method.
  All subtable formats except Mixed Coverage (8) are supported.
• (cmap) Character variation to glyph index mapping using glyph_variation_index() method.
• (glyf) Glyph outlining using outline_glyph() method.
• (hmtx) Retrieving a glyph's horizontal metrics using glyph_hor_metrics() method.
• (vmtx) Retrieving a glyph's vertical metrics using glyph_ver_metrics() method.
• (kern) Retrieving a glyphs pair kerning using glyphs_kerning() method.
• (maxp) Retrieving a total number of glyphs using number_of_glyphs() method.
• (name) Listing all name records using names() method.
• (name) Retrieving a font's family name using family_name() method.
• (name) Retrieving a font's PostScript name using post_script_name() method.
• (post) Retrieving a font's underline metrics name using underline_metrics() method.
• (head) Retrieving a font's units per EM value using units_per_em() method.
• (hhea) Retrieving a generic font info using: ascender(), descender(), height() and line_gap() methods.

Supported OpenType features

• (CFF ) Glyph outlining using outline_glyph() method.
• (OS/2) Retrieving a font kind using is_regular(), is_italic(), is_bold() and is_oblique() methods.
• (OS/2) Retrieving a font's weight using weight() method.
• (OS/2) Retrieving a font's width using width() method.
• (OS/2) Retrieving a font's X height using x_height() method.
• (OS/2) Retrieving a font's strikeout metrics using strikeout_metrics() method.
• (OS/2) Retrieving a font's subscript metrics using subscript_metrics() method.
• (OS/2) Retrieving a font's superscript metrics using superscript_metrics() method.

Methods' computational complexity

TrueType fonts designed for fast querying, so most of the methods are very fast. The main exception is glyph outlining. Glyphs can be stored using two different methods: using Glyph Data format and Compact Font Format (pdf). The first one is fairly simple which makes it faster to process. The second one is basically a tiny language with a stack-based VM, which makes it way harder to process. Currently, it takes 40% more time to outline all glyphs in SourceSansPro-Regular.otf (which uses CFF) rather than in SourceSansPro-Regular.ttf.

test outline_cff  ... bench:   1,651,557 ns/iter (+/- 2,751)
test outline_glyf ... bench:     977,046 ns/iter (+/- 4,973)

Here is some methods benchmarks:

test outline_glyph_276_from_cff  ... bench:       1,247 ns/iter (+/- 2)
test outline_glyph_276_from_glyf ... bench:         817 ns/iter (+/- 15)
test outline_glyph_8_from_cff    ... bench:         521 ns/iter (+/- 2)
test family_name                 ... bench:         445 ns/iter (+/- 4)
test from_data_otf               ... bench:         435 ns/iter (+/- 1)
test outline_glyph_8_from_glyf   ... bench:         360 ns/iter (+/- 7)
test from_data_ttf               ... bench:         133 ns/iter (+/- 0)

Some methods are too fast, so we execute them 1000 times to get better measurements.

test glyph_index_u41     ... bench:      24,648 ns/iter (+/- 256)
test glyph_2_hor_metrics ... bench:       8,421 ns/iter (+/- 18)
test units_per_em        ... bench:         564 ns/iter (+/- 2)
test x_height            ... bench:         568 ns/iter (+/- 1)
test strikeout_metrics   ... bench:         564 ns/iter (+/- 0)
test width               ... bench:         422 ns/iter (+/- 0)
test ascender            ... bench:         279 ns/iter (+/- 1)
test subscript_metrics   ... bench:         279 ns/iter (+/- 0)

family_name is expensive, because it allocates a String and the original data is stored as UTF-16 BE.

Safety

• The library must not panic. Any panic considered as a critical bug and should be reported.
• The library forbids unsafe code.

Structs

Font	A font data handle.
GlyphId	A type-safe wrapper for glyph ID.
HorizontalMetrics	A horizontal metrics of a glyph.
LineMetrics	A line metrics.
Name	A Name Record.
Names	An iterator over font's names.
Rect	Rectangle.
ScriptMetrics	A script metrics used by subscript and superscript.
VerticalMetrics	A vertical metrics of a glyph.

Enums

CFFError	A list of errors that can occur during a CFF table parsing.
Error	A font parsing error.
NameId	A name ID.
PlatformId	A platform ID.
TableName	A table name.
Weight	A font weight.
Width	A font width.

Traits

OutlineBuilder

A trait for glyph outline construction.

Functions

fonts_in_collection

Returns a number of fonts stored in a TrueType font collection.