Merge pull request #3518 from fonttools/cff-to-cff2-remove-unused-subroutines

[CFFToCFF2] Remove unused subroutines if necessary

Lib/fontTools/cffLib/CFFToCFF2.py

@@ -65,6 +65,7 @@ def _convertCFFToCFF2(cff, otFont):
             program[min(i, j) :] = []
 
     # Clean up glyph charstrings
+    removeUnusedSubrs = False
     nominalWidthXError = _NominalWidthUsedError()
     for glyphName in charStrings.keys():
         cs, fdIndex = charStrings.getItemAndSelector(glyphName)
@@ -86,10 +87,9 @@ def _convertCFFToCFF2(cff, otFont):
             # Program has explicit width. We want to drop it, but can't
             # just pop the first number since it may be a subroutine call.
             # Instead, when seeing that, we embed the subroutine and recurse.
-            # This has the problem that some subroutines might become unused.
-            # We don't currently prune those. Subset module has code for this
-            # kind of stuff, possibly plug it in here if pruning becomes needed.
+            # If this ever happened, we later prune unused subroutines.
             while program[1] in ["callsubr", "callgsubr"]:
+                removeUnusedSubrs = True
                 subrNumber = program.pop(0)
                 op = program.pop(0)
                 bias = extractor.localBias if op == "callsubr" else extractor.globalBias
@@ -103,6 +103,9 @@ def _convertCFFToCFF2(cff, otFont):
         if program and program[-1] == "endchar":
             program.pop()
 
+    if removeUnusedSubrs:
+        cff.remove_unused_subroutines()
+
     # Upconvert TopDict
 
     cff.major = 2

Lib/fontTools/cffLib/transforms.py

@@ -362,8 +362,7 @@ def remove_hints(cff):
         #    we have seen any non-hint operators so far and do the right
         #    thing, recursively... Good luck understanding that :(
         css = set()
-        for g in font.charset:
-            c, _ = cs.getItemAndSelector(g)
+        for c in cs.values():
             c.decompile()
             subrs = getattr(c.private, "Subrs", [])
             decompiler = _DehintingT2Decompiler(
@@ -422,8 +421,7 @@ def remove_unused_subroutines(cff):
         # Renumber subroutines to remove unused ones
 
         # Mark all used subroutines
-        for g in font.charset:
-            c, _ = cs.getItemAndSelector(g)
+        for c in cs.values():
             subrs = getattr(c.private, "Subrs", [])
             decompiler = _MarkingT2Decompiler(subrs, c.globalSubrs, c.private)
             decompiler.execute(c)
@@ -449,8 +447,7 @@ def remove_unused_subroutines(cff):
             subrs._new_bias = calcSubrBias(subrs._used)
 
         # Renumber glyph charstrings
-        for g in font.charset:
-            c, _ = cs.getItemAndSelector(g)
+        for c in cs.values():
             subrs = getattr(c.private, "Subrs", None)
             _cs_subset_subroutines(c, subrs, font.GlobalSubrs)