Fonts

Pango supports a flexible architecture where a particular rendering architecture can supply an implementation of fonts. The PangoFont structure represents an abstract rendering-system-independent font. Pango provides routines to list available fonts, and to load a font matching a given description.

Conceptually, Pango groups fonts into faces and families which are identified by a name. A font face provides the different sizes of a single font style. A font family provides the available styles of a font.

As an example, “Helvetica” is a family, “Helvetica Bold” is a face of this family, and “Helvetica Bold 12pt” is a concrete font of this face.

Font Enumeration

The central object for dealing with the available fonts on a system and caching loaded fonts is a PangoFontMap. An application typically uses a single font map.

Since the font map depends on the rendering architecture in use, you’ll need to use the backend function pango_cairo_font_map_get_default() to obtain the default fontmap. Depending on the platform, it will return a PangoCairoFcFontMap, a PangoCairoWin32FontMap or a PangoCairoCoreTextFontMap.

Once you have a fontmap, you can enumerate the available font families with pango_font_map_list_families(). To enumerate the faces of a font family, use pango_font_family_list_faces().

Font Descriptions

Since loading fonts uses system resources, Pango provides a way to describe a font without loading it. A PangoFontDescription is a struct that contains enough information to load a concrete font with pango_font_map_load_font() or pango_context_load_font(). You can obtain a font description from a font face using pango_font_face_describe(), or by parsing a string such as

Helvetica Bold 12pt

with pango_font_description_from_string().

Glyphs

A font provides information about glyphs and how to position and render them. The Pango rendering pipeline uses this information to create a PangoGlyphString, which contains the glyphs corresponding to the characters in the text and related information such as glyph positions and sizes, and clustering information (i.e. which glyphs correspond to which characters).

A glyph is identified by a PangoGlyph, which is a numeric ID. Note that glyph IDs are font-specific: the same character can be represented by diffferent glyph IDs in different fonts.

The mapping between characters and glyphs is in general neither 1-1 nor a map: a single glyph may represent multiple characters (as is the case with ligatures), a single character may be represented by multiple glyphs (for example, when combining accents and base character), and in complex scripts, multiple characters may form clusters that get rearranged and represented by multiple glyphs.