[preProcessor] add inplace=False argument

By default, we still make a copy of the input glyphs before applying
filters (e.g. needed when compiling fonts from editors like TruFont).
Sometimes it may be slightly faster to avoid the copy, and apply the
filters in-place. E.g. fontmake reads the UFO from file without
saving the modified Defcon objects.

Lib/ufo2ft/__init__.py

@@ -18,7 +18,8 @@ def compileOTF(ufo, preProcessorClass=OTFPreProcessor,
                featureCompilerClass=FeatureCompiler,
                kernWriterClass=KernFeatureWriter, markWriterClass=MarkFeatureWriter,
                glyphOrder=None, useProductionNames=True, optimizeCFF=True,
-               roundTolerance=None, removeOverlaps=False):
+               roundTolerance=None, removeOverlaps=False,
+               inplace=False):
     """Create FontTools CFF font from a UFO.
 
     *removeOverlaps* performs a union operation on all the glyphs' contours.
@@ -32,7 +33,8 @@ def compileOTF(ufo, preProcessorClass=OTFPreProcessor,
       of 0 completely disables rounding; values in between only round floats
       which are close to their integral part within the tolerated range.
     """
-    preProcessor = preProcessorClass(ufo, removeOverlaps=removeOverlaps)
+    preProcessor = preProcessorClass(
+        ufo, inplace=inplace, removeOverlaps=removeOverlaps)
     glyphSet = preProcessor.process()
 
     outlineCompiler = outlineCompilerClass(
@@ -57,7 +59,8 @@ def compileTTF(ufo, preProcessorClass=TTFPreProcessor,
                kernWriterClass=KernFeatureWriter, markWriterClass=MarkFeatureWriter,
                glyphOrder=None, useProductionNames=True,
                convertCubics=True, cubicConversionError=None,
-               reverseDirection=True, removeOverlaps=False):
+               reverseDirection=True, removeOverlaps=False,
+               inplace=False):
     """Create FontTools TrueType font from a UFO.
 
     *removeOverlaps* performs a union operation on all the glyphs' contours.
@@ -66,7 +69,8 @@ def compileTTF(ufo, preProcessorClass=TTFPreProcessor,
     to quadratic curves should be handled.
     """
     preProcessor = preProcessorClass(
-        ufo, removeOverlaps=removeOverlaps,
+        ufo, inplace=inplace,
+        removeOverlaps=removeOverlaps,
         convertCubics=convertCubics,
         conversionError=cubicConversionError,
         reverseDirection=reverseDirection)

Lib/ufo2ft/preProcessor.py

@@ -12,8 +12,10 @@ class BasePreProcessor(object):
     the UFO glyphs, such as decomposing composites, removing overlaps, or
     applying custom filters.
 
-    The input UFO is **not** modified. The ``process`` method returns a
-    dictionary containing the modified glyphset, keyed by glyph name.
+    By default the input UFO is **not** modified. The ``process`` method
+    returns a dictionary containing the new modified glyphset, keyed by
+    glyph name. If ``inplace`` is True, the input UFO is modified directly
+    without the need to first copy the glyphs.
 
     Subclasses can override the ``initDefaultFilters`` method and return
     a list of built-in filters which are performed in a predefined order,
@@ -26,9 +28,12 @@ class BasePreProcessor(object):
     "com.github.googlei18n.ufo2ft.filters".
     """
 
-    def __init__(self, ufo, **kwargs):
+    def __init__(self, ufo, inplace=False, **kwargs):
         self.ufo = ufo
-        self.glyphSet = {g.name: _copyGlyph(g) for g in ufo}
+        if inplace:
+            self.glyphSet = {g.name: g for g in ufo}
+        else:
+            self.glyphSet = {g.name: _copyGlyph(g) for g in ufo}
         self.defaultFilters = self.initDefaultFilters(**kwargs)
         self.preFilters, self.postFilters = loadFilters(self.ufo)