kerning: Support for accessing kerning data

fontTools.ufoLib.kerning.lookupKerningValue(pair, kerning, groups, fallback=0, glyphToFirstGroup=None, glyphToSecondGroup=None)[source]

Retrieve the kerning value (if any) between a pair of elements.

The elments can be either individual glyphs (by name) or kerning groups (by name), or any combination of the two.

Parameters:

  • pair – A tuple, in logical order (first, second) with respect to the reading direction, to query the font for kerning information on. Each element in the tuple can be either a glyph name or a kerning group name.

  • kerning – A dictionary of kerning pairs.

  • groups – A set of kerning groups.

  • fallback – The fallback value to return if no kern is found between the elements in pair. Defaults to 0.

  • glyphToFirstGroup – A dictionary mapping glyph names to the first-glyph kerning groups to which they belong. Defaults to None.

  • glyphToSecondGroup – A dictionary mapping glyph names to the second-glyph kerning groups to which they belong. Defaults to None.

Returns:

The kerning value between the element pair. If no kerning for the pair is found, the fallback value is returned.

Note: This function expects the kerning argument to be a flat dictionary of kerning pairs, not the nested structure used in a kerning.plist file.

Examples:

>>> groups = {
...     "public.kern1.O" : ["O", "D", "Q"],
...     "public.kern2.E" : ["E", "F"]
... }
>>> kerning = {
...     ("public.kern1.O", "public.kern2.E") : -100,
...     ("public.kern1.O", "F") : -200,
...     ("D", "F") : -300
... }
>>> lookupKerningValue(("D", "F"), kerning, groups)
-300
>>> lookupKerningValue(("O", "F"), kerning, groups)
-200
>>> lookupKerningValue(("O", "E"), kerning, groups)
-100
>>> lookupKerningValue(("O", "O"), kerning, groups)
0
>>> lookupKerningValue(("E", "E"), kerning, groups)
0
>>> lookupKerningValue(("E", "O"), kerning, groups)
0
>>> lookupKerningValue(("X", "X"), kerning, groups)
0
>>> lookupKerningValue(("public.kern1.O", "public.kern2.E"),
...     kerning, groups)
-100
>>> lookupKerningValue(("public.kern1.O", "F"), kerning, groups)
-200
>>> lookupKerningValue(("O", "public.kern2.E"), kerning, groups)
-100
>>> lookupKerningValue(("public.kern1.X", "public.kern2.X"), kerning, groups)
0