Meziantou.Framework

Introduction

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Meziantou.Framework.Fonts reads font files and turns text into glyphs. It is the font engine that Meziantou.Framework.Imaging uses to draw text, and that the WebPlatform and Pdf libraries use to lay out and embed text. It is written entirely in C#, without native dependency, and is trimmable and compatible with NativeAOT.

Do you need this package?

To draw text on images, use the text API of Meziantou.Framework.Imaging: it loads fonts, lays out paragraphs in any script and direction, and draws them. Use this package directly when you write your own text renderer or document writer and need what is under that API:

  • the names, metrics and tables of a font, and the outlines of its glyphs;
  • the glyphs of a text and their positions, after the substitutions and the positioning of the font;
  • the fonts installed on the machine;
  • a subset of a font to embed in a document;
  • the metrics of PostScript fonts from AFM files, such as the 14 standard fonts of PDF.

The public API is low level: it is the one these libraries need. Update the packages that use it together.

What it supports

Supported
ContainersTrueType and OpenType fonts and collections, WOFF 1.0 and WOFF 2.0
OutlinesTrueType, CFF and CFF2
Variable fontsThe axes and named instances, and the variations of the outlines, the metrics and the layout tables
Color fontsCOLR versions 0 and 1, CPAL, and glyphs that are images (sbix, CBDT)
MetricsHorizontal and vertical metrics, BASE baselines, the constants and glyph constructions of the MATH table
HintingOutlines fitted to the pixel grid of a size, with or without the TrueType instructions of the font
ShapingThe GSUB and GPOS tables, and the shaping models of complex scripts: Arabic, Hebrew, Indic, Khmer, Myanmar, Thai and Lao, Hangul, and the universal shaping engine
Installed fontsWindows, macOS and Linux
OtherSubsets of TrueType and CFF outlines, AFM files

The types are in the Meziantou.Framework.Fonts namespace.

Principles

  • Fonts are untrusted input. Every read is bounds-checked, and the work of loading a font, decoding a glyph and shaping a text is bounded by limits you choose: a hostile font cannot make the application run out of memory or time.
  • A face is immutable and thread-safe. It keeps the bytes of its file and reads its tables in place. It has no cache and no state: the working storage of a glyph is yours.
  • Explicit errors. A file that is not a font, a malformed font, an unsupported feature and an exceeded limit throw distinct exceptions.

Next steps