Specifying font feature tags

OpenType fonts may support feature tags that specify alternate glyph shapes or substitutions to be made optionally. The text API now supports setting a list of feature tags to be used with the associated font. Feature tags can be set/get with:

• matplotlib.text.Text.set_fontfeatures / matplotlib.text.Text.get_fontfeatures

• Any API that creates a Text object by passing the fontfeatures argument (e.g., plt.xlabel(..., fontfeatures=...))

Font feature strings are eventually passed to HarfBuzz, and so all string formats supported by hb_feature_from_string() are supported. Note though that subranges are not explicitly supported and behaviour may change in the future.

For example, the default font DejaVu Sans enables Standard Ligatures (the 'liga' tag) by default, and also provides optional Discretionary Ligatures (the dlig tag.) These may be toggled with + or -.

fig = plt.figure(figsize=(7, 3))

fig.text(0.5, 0.85, 'Ligatures', fontsize=40, horizontalalignment='center')

# Default has Standard Ligatures (liga).
fig.text(0, 0.6, 'Default: fi ffi fl st', fontsize=40)

# Disable Standard Ligatures with -liga.
fig.text(0, 0.35, 'Disabled: fi ffi fl st', fontsize=40,
         fontfeatures=['-liga'])

# Enable Discretionary Ligatures with dlig.
fig.text(0, 0.1, 'Discretionary: fi ffi fl st', fontsize=40,
         fontfeatures=['dlig'])

(Source code, 2x.png, png)

Available font feature tags may be found at https://learn.microsoft.com/en-us/typography/opentype/spec/featurelist