Prince supports typographic ligatures found in OpenType fonts, i.e. Prince will replace certain characters that appear next to each other with other special glyphs that join those two characters together into one single glyph.
A prominent example of a typographic ligature is fi, which replaces the two characters fi with a single glyph.
Prince automatically enables ligatures declared by the OpenType fonts with the
liga feature (see OpenType Features in Prince). This feature
covers the "standard ligatures" which the font manufacturer thinks should be used
in normal conditions. Microsoft has a list of the OpenType feature names
here.
Other special ligatures need to be explicitly enabled in Prince to take effect.
This is achieved by using the font-variant CSS property with
the prince-opentype() function (see Prince Specific Functions).
Care must be taken in which order the features are enabled! And please note that
enabling one feature will disable all the default features. To see which OpenType
features are enabled by default, see the OpenType Features in Prince section.
@page {
font-variant: prince-opentype(dlig, liga);
}Unlike other ligature features, the clig feature specifies the context
in which the ligature is recommended. "Contextual ligatures" are important in some
script designs.
The dlig feature covers the "discretionary ligatures" which may be
used for special effects.
Some ligatures were in common use in the past, such as ligatures with the so-called
"long s" - but they appear anachronistic today. Some fonts include the historical
forms as alternates, so the "historical ligatures", covered by the hlig
feature, can be used for a 'period' effect. This feature replaces the default (current)
forms with the historical alternates.
Some scripts, most notably Arabic and Syriac scripts, require certain ligatures
to be used in normal conditions. These "required ligatures" are covered by the
rlig feature. Prince enables this feature by default in Arabic script.