From b438dbeee555606b9b045ed3b9b965cab9bafd6e Mon Sep 17 00:00:00 2001
From: Cosimo Lupo <cosimo.lupo@daltonmaag.com>
Date: Thu, 23 Mar 2017 14:03:15 +0000
Subject: [PATCH] [basePen] add LoggingPen and DecomposingPen, subclass BasePen
 from DecomposingPen

This is so we can reuse addComponent with the recording pen, without having to
inherit from the BasePen (which also splits curveTo and qCurveTo commands).

Log warning message on missing glyphs by default, optionally raise KeyError
if skipMissingComponents = False
---
 Lib/fontTools/pens/basePen.py | 61 ++++++++++++++++++++++++++---------
 1 file changed, 46 insertions(+), 15 deletions(-)

diff --git a/Lib/fontTools/pens/basePen.py b/Lib/fontTools/pens/basePen.py
index ed8ce3939..e0d3ae06d 100644
--- a/Lib/fontTools/pens/basePen.py
+++ b/Lib/fontTools/pens/basePen.py
@@ -38,6 +38,7 @@ sequence of length 2 will do.
 
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
+from fontTools.misc.loggingTools import LogMixin
 
 __all__ =  ["AbstractPen", "NullPen", "BasePen",
 			"decomposeSuperBezierSegment", "decomposeQuadraticSegment"]
@@ -141,7 +142,50 @@ class NullPen(object):
 		pass
 
 
-class BasePen(AbstractPen):
+class LoggingPen(LogMixin, AbstractPen):
+	"""A pen with a `log` property (see fontTools.misc.loggingTools.LogMixin)
+	"""
+	pass
+
+
+class DecomposingPen(LoggingPen):
+
+	""" Implements a 'addComponent' method that decomposes components
+	(i.e. draws them onto self as simple contours).
+	It can also be used as a mixin class (e.g. see ContourRecordingPen).
+
+	You must override moveTo, lineTo, curveTo and qCurveTo. You may
+	additionally override closePath, endPath and addComponent.
+	"""
+
+	# By default a warning message is logged when a base glyph is missing;
+	# set this to False if you want to raise a 'KeyError' exception
+	skipMissingComponents = True
+
+	def __init__(self, glyphSet):
+		""" Takes a single 'glyphSet' argument (dict), in which the glyphs
+		that are referenced as components are looked up by their name.
+		"""
+		super(DecomposingPen, self).__init__()
+		self.glyphSet = glyphSet
+
+	def addComponent(self, glyphName, transformation):
+		""" Transform the points of the base glyph and draw it onto self.
+		"""
+		from fontTools.pens.transformPen import TransformPen
+		try:
+			glyph = self.glyphSet[glyphName]
+		except KeyError:
+			if not self.skipMissingComponents:
+				raise
+			self.log.warning(
+				"glyph '%s' is missing from glyphSet; skipped" % glyphName)
+		else:
+			tPen = TransformPen(self, transformation)
+			glyph.draw(tPen)
+
+
+class BasePen(DecomposingPen):
 
 	"""Base class for drawing pens. You must override _moveTo, _lineTo and
 	_curveToOne. You may additionally override _closePath, _endPath,
@@ -150,7 +194,7 @@ class BasePen(AbstractPen):
 	"""
 
 	def __init__(self, glyphSet=None):
-		self.glyphSet = glyphSet
+		super(BasePen, self).__init__(glyphSet)
 		self.__currentPoint = None
 
 	# must override
@@ -186,19 +230,6 @@ class BasePen(AbstractPen):
 		mid2y = pt2y + 0.66666666666666667 * (pt1y - pt2y)
 		self._curveToOne((mid1x, mid1y), (mid2x, mid2y), pt2)
 
-	def addComponent(self, glyphName, transformation):
-		"""This default implementation simply transforms the points
-		of the base glyph and draws it onto self.
-		"""
-		from fontTools.pens.transformPen import TransformPen
-		try:
-			glyph = self.glyphSet[glyphName]
-		except KeyError:
-			pass
-		else:
-			tPen = TransformPen(self, transformation)
-			glyph.draw(tPen)
-
 	# don't override
 
 	def _getCurrentPoint(self):