[visitor] Split TTVisitor into its own module

Lib/fontTools/misc/visitor.py

@@ -1,4 +1,5 @@
-from fontTools.ttLib import TTFont
+"""Generic visitor pattern implementation for Python objects."""
+
 import enum
 
 
@@ -94,21 +95,3 @@ class Visitor(object):
             self.visitObject(obj, *args, **kwargs)
         elif isinstance(obj, list):
             self.visitList(obj, *args, **kwargs)
-
-
-class TTVisitor(Visitor):
-    def visit(self, obj, *args, **kwargs):
-        if hasattr(obj, "ensureDecompiled"):
-            obj.ensureDecompiled(recurse=False)
-        super().visit(obj, *args, **kwargs)
-
-
-@TTVisitor.register(TTFont)
-def visit(visitor, font):
-    if hasattr(visitor, "font"):
-        return False
-    visitor.font = font
-    for tag in font.keys():
-        visitor.visit(font[tag])
-    del visitor.font
-    return False

Lib/fontTools/ttLib/ttVisitor.py

@@ -0,0 +1,22 @@
+"""Specialization of fontTools.misc.visitor to work with TTFont."""
+
+from fontTools.misc.visitor import Visitor
+from fontTools.ttLib import TTFont
+
+
+class TTVisitor(Visitor):
+    def visit(self, obj, *args, **kwargs):
+        if hasattr(obj, "ensureDecompiled"):
+            obj.ensureDecompiled(recurse=False)
+        super().visit(obj, *args, **kwargs)
+
+
+@TTVisitor.register(TTFont)
+def visit(visitor, font):
+    if hasattr(visitor, "font"):
+        return False
+    visitor.font = font
+    for tag in font.keys():
+        visitor.visit(font[tag])
+    del visitor.font
+    return False

Snippets/scale-upem.py

@@ -1,4 +1,4 @@
-from fontTools.misc.visitor import TTVisitor
+from fontTools.ttLib.ttVisitor import TTVisitor
 import fontTools.ttLib as ttLib
 import fontTools.ttLib.tables.otBase as otBase
 import fontTools.ttLib.tables.otTables as otTables