Letterforms

What happens automatically

Text is shaped with a full OpenType shaping engine before any line breaking happens: standard ligatures form (fi, fl, ffi), kerning pairs apply, and marks attach where the font puts them. There is nothing to switch on; the sections below are about deviating from those defaults.

OpenType features

font-feature-settings toggles the optional features a font carries, by four-letter tag:

.figures  { font-feature-settings: "onum" 1; }         /* oldstyle figures */
.plain    { font-feature-settings: "liga" 0; }         /* no ligatures */
.combined { font-feature-settings: "onum" 1, "liga" 0; }

Which tags do something depends entirely on the font: the built-in Crimson Pro carries oldstyle figures (onum) and ligatures (liga), but no small caps (smcp), so asking for small caps changes nothing. Consult the feature list of your font; typical candidates are smcp (small caps), onum/lnum (oldstyle/lining figures), tnum/pnum (tabular/proportional figures, the difference that makes numbers in tables line up), and the discretionary sets dlig and ss01 ff. Features declared in @font-face via font-feature-settings apply to every use of that face; the property on an element adds to them.

Letter spacing

letter-spacing adds tracking between glyphs. Its classic use is spaced capitals or small caps in headings; running lowercase text is better left untracked:

h1 { letter-spacing: 0.12em; }

Text decoration

text-decoration-line (underline, overline, line-through), text-decoration-style (solid, double, dotted, dashed, wavy) and text-decoration-color compose freely. Without an explicit colour the line follows the text colour, as CSS’s currentColor initial value specifies:

Italic correction

An italic glyph leans into the space of an upright neighbour: a closing parenthesis after an italic f collides visibly. OpenType has no metric for text italic correction, so glu offers a heuristic that inserts a small compensating kern at italic-to-upright boundaries:

body { -bag-italic-correction: auto; }

The property is inherited; none switches the heuristic off again for a subtree.