Fix chained contextual builder overflow
diff --git a/Lib/fontTools/otlLib/builder.py b/Lib/fontTools/otlLib/builder.py
index bfb9d41..64cbc5e 100644
--- a/Lib/fontTools/otlLib/builder.py
+++ b/Lib/fontTools/otlLib/builder.py
@@ -377,6 +377,12 @@
candidates = [None, None, None, []]
for rule in ruleset.rules:
candidates[3].append(self.buildFormat3Subtable(rule, chaining))
+ # Check we can build it
+ try:
+ self.getCompiledSize_(candidates[3])
+ except Exception as e:
+ log.warning("Contextual format 3 at %s overflowed" % str(self.location))
+ candidates[3] = None
# Can we express the whole ruleset as a format 2 subtable?
classdefs = ruleset.format2ClassDefs()
@@ -384,11 +390,26 @@
candidates[2] = [
self.buildFormat2Subtable(ruleset, classdefs, chaining)
]
+ # Check we can build it
+ try:
+ self.getCompiledSize_(candidates[2])
+ except Exception as e:
+ log.warning("Contextual format 2 at %s overflowed (%s)" % (str(self.location), e))
+ candidates[2] = None
if not ruleset.hasAnyGlyphClasses:
candidates[1] = [self.buildFormat1Subtable(ruleset, chaining)]
+ # Check we can build it
+ try:
+ self.getCompiledSize_(candidates[1])
+ except Exception as e:
+ log.warning("Contextual format 1 at %s overflowed" % str(self.location))
+ candidates[1] = None
candidates = [x for x in candidates if x is not None]
+ if not candidates:
+ raise OpenTypeLibError("All candidates overflowed", self.location)
+
winner = min(candidates, key=self.getCompiledSize_)
subtables.extend(winner)
