1 files changed, 189 insertions, 0 deletions
diff --git a/misc/pylib/fontbuild/features.py b/misc/pylib/fontbuild/features.py
new file mode 100755
index 000000000..fe6eca012
--- /dev/null
+++ b/misc/pylib/fontbuild/features.py
@@ -0,0 +1,189 @@
+# Copyright 2015 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import re
+
+from feaTools import parser
+from feaTools.writers.fdkSyntaxWriter import FDKSyntaxFeatureWriter
+
+
+class FilterFeatureWriter(FDKSyntaxFeatureWriter):
+    """Feature writer to detect invalid references and duplicate definitions."""
+
+    def __init__(self, refs=set(), name=None, isFeature=False):
+        """Initializes the set of known references, empty by default."""
+        self.refs = refs
+        self.featureNames = set()
+        self.lookupNames = set()
+        self.tableNames = set()
+        self.languageSystems = set()
+        super(FilterFeatureWriter, self).__init__(
+            name=name, isFeature=isFeature)
+
+        # error to print when undefined reference is found in glyph class
+        self.classErr = ('Undefined reference "%s" removed from glyph class '
+            'definition %s.')
+
+        # error to print when undefined reference is found in sub or pos rule
+        subErr = ['Substitution rule with undefined reference "%s" removed']
+        if self._name:
+            subErr.append(" from ")
+            subErr.append("feature" if self._isFeature else "lookup")
+            subErr.append(' "%s"' % self._name)
+        subErr.append(".")
+        self.subErr = "".join(subErr)
+        self.posErr = self.subErr.replace("Substitution", "Positioning")
+
+    def _subwriter(self, name, isFeature):
+        """Use this class for nested expressions e.g. in feature definitions."""
+        return FilterFeatureWriter(self.refs, name, isFeature)
+
+    def _flattenRefs(self, refs, flatRefs):
+        """Flatten a list of references."""
+        for ref in refs:
+            if type(ref) == list:
+                self._flattenRefs(ref, flatRefs)
+            elif ref != "'":  # ignore contextual class markings
+                flatRefs.append(ref)
+
+    def _checkRefs(self, refs, errorMsg):
+        """Check a list of references found in a sub or pos rule."""
+        flatRefs = []
+        self._flattenRefs(refs, flatRefs)
+        for ref in flatRefs:
+            # trailing apostrophes should be ignored
+            if ref[-1] == "'":
+                ref = ref[:-1]
+            if ref not in self.refs:
+                print errorMsg % ref
+                # insert an empty instruction so that we can't end up with an
+                # empty block, which is illegal syntax
+                super(FilterFeatureWriter, self).rawText(";")
+                return False
+        return True
+
+    def classDefinition(self, name, contents):
+        """Check that contents are valid, then add name to known references."""
+        if name in self.refs:
+            return
+        newContents = []
+        for ref in contents:
+            if ref not in self.refs and ref != "-":
+                print self.classErr % (ref, name)
+            else:
+                newContents.append(ref)
+        self.refs.add(name)
+        super(FilterFeatureWriter, self).classDefinition(name, newContents)
+
+    def gsubType1(self, target, replacement):
+        """Check a sub rule with one-to-one replacement."""
+        if self._checkRefs([target, replacement], self.subErr):
+            super(FilterFeatureWriter, self).gsubType1(target, replacement)
+
+    def gsubType4(self, target, replacement):
+        """Check a sub rule with many-to-one replacement."""
+        if self._checkRefs([target, replacement], self.subErr):
+            super(FilterFeatureWriter, self).gsubType4(target, replacement)
+
+    def gsubType6(self, precedingContext, target, trailingContext, replacement):
+        """Check a sub rule with contextual replacement."""
+        refs = [precedingContext, target, trailingContext, replacement]
+        if self._checkRefs(refs, self.subErr):
+            super(FilterFeatureWriter, self).gsubType6(
+                precedingContext, target, trailingContext, replacement)
+
+    def gposType1(self, target, value):
+        """Check a single positioning rule."""
+        if self._checkRefs([target], self.posErr):
+            super(FilterFeatureWriter, self).gposType1(target, value)
+
+    def gposType2(self, target, value, needEnum=False):
+        """Check a pair positioning rule."""
+        if self._checkRefs(target, self.posErr):
+            super(FilterFeatureWriter, self).gposType2(target, value, needEnum)
+
+    # these rules may contain references, but they aren't present in Roboto
+    def gsubType3(self, target, replacement):
+        raise NotImplementedError
+
+    def feature(self, name):
+        """Adds a feature definition only once."""
+        if name not in self.featureNames:
+            self.featureNames.add(name)
+            return super(FilterFeatureWriter, self).feature(name)
+        # we must return a new writer even if we don't add it to this one
+        return FDKSyntaxFeatureWriter(name, True)
+
+    def lookup(self, name):
+        """Adds a lookup block only once."""
+        if name not in self.lookupNames:
+            self.lookupNames.add(name)
+            return super(FilterFeatureWriter, self).lookup(name)
+        # we must return a new writer even if we don't add it to this one
+        return FDKSyntaxFeatureWriter(name, False)
+
+    def languageSystem(self, langTag, scriptTag):
+        """Adds a language system instruction only once."""
+        system = (langTag, scriptTag)
+        if system not in self.languageSystems:
+            self.languageSystems.add(system)
+            super(FilterFeatureWriter, self).languageSystem(langTag, scriptTag)
+
+    def table(self, name, data):
+        """Adds a table only once."""
+        if name in self.tableNames:
+            return
+        self.tableNames.add(name)
+        self._instructions.append("table %s {" % name)
+        self._instructions.extend(["  %s %s;" % line for line in data])
+        self._instructions.append("} %s;" % name)
+
+
+def compileFeatureRE(name):
+    """Compiles a feature-matching regex."""
+
+    # this is the pattern used internally by feaTools:
+    # https://github.com/typesupply/feaTools/blob/master/Lib/feaTools/parser.py
+    featureRE = list(parser.featureContentRE)
+    featureRE.insert(2, name)
+    featureRE.insert(6, name)
+    return re.compile("".join(featureRE))
+
+
+def updateFeature(font, name, value):
+    """Add a feature definition, or replace existing one."""
+    featureRE = compileFeatureRE(name)
+    if featureRE.search(font.features.text):
+        font.features.text = featureRE.sub(value, font.features.text)
+    else:
+        font.features.text += "\n" + value
+
+
+def readFeatureFile(font, text, prepend=True):
+    """Incorporate valid definitions from feature text into font."""
+    writer = FilterFeatureWriter(set(font.keys()))
+    if prepend:
+        text += font.features.text
+    else:
+        text = font.features.text + text
+    parser.parseFeatures(writer, text)
+    font.features.text = writer.write()
+
+
+def writeFeatureFile(font, path):
+    """Write the font's features to an external file."""
+    fout = open(path, "w")
+    fout.write(font.features.text)
+    fout.close()