up follow livre

venv/lib/python3.13/site-packages/fontTools/ufoLib/kerning.py

@@ -0,0 +1,121 @@
+def lookupKerningValue(
+    pair, kerning, groups, fallback=0, glyphToFirstGroup=None, glyphToSecondGroup=None
+):
+    """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.
+
+    Args:
+      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
+    """
+    # quickly check to see if the pair is in the kerning dictionary
+    if pair in kerning:
+        return kerning[pair]
+    # create glyph to group mapping
+    if glyphToFirstGroup is not None:
+        assert glyphToSecondGroup is not None
+    if glyphToSecondGroup is not None:
+        assert glyphToFirstGroup is not None
+    if glyphToFirstGroup is None:
+        glyphToFirstGroup = {}
+        glyphToSecondGroup = {}
+        for group, groupMembers in groups.items():
+            if group.startswith("public.kern1."):
+                for glyph in groupMembers:
+                    glyphToFirstGroup[glyph] = group
+            elif group.startswith("public.kern2."):
+                for glyph in groupMembers:
+                    glyphToSecondGroup[glyph] = group
+    # get group names and make sure first and second are glyph names
+    first, second = pair
+    firstGroup = secondGroup = None
+    if first.startswith("public.kern1."):
+        firstGroup = first
+        first = None
+    else:
+        firstGroup = glyphToFirstGroup.get(first)
+    if second.startswith("public.kern2."):
+        secondGroup = second
+        second = None
+    else:
+        secondGroup = glyphToSecondGroup.get(second)
+    # make an ordered list of pairs to look up
+    pairs = [
+        (first, second),
+        (first, secondGroup),
+        (firstGroup, second),
+        (firstGroup, secondGroup),
+    ]
+    # look up the pairs and return any matches
+    for pair in pairs:
+        if pair in kerning:
+            return kerning[pair]
+    # use the fallback value
+    return fallback
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()