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layoutEngine.py
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layoutEngine.py
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import weakref
from fontTools.ttLib import TTFont
from fontTools.feaLib.builder import addOpenTypeFeaturesFromString
from defcon.objects.base import BaseObject
try:
import compositor
from defcon.objects.uniData import UnicodeData
from defcon.objects.features import Features
except ImportError:
pass
# ---------
# Factories
# ---------
def _makeCMAP(unicodeData):
mapping = {}
for name, values in unicodeData.items():
mapping[name] = values[0]
return mapping
def _layoutEngineOTLTablesRepresentationFactory(layoutEngine):
font = layoutEngine.font
gdef = gsub = gpos = None
if font.features.text:
otf = TTFont()
otf.setGlyphOrder(sorted(font.keys()))
# compile with fontTools
try:
addOpenTypeFeaturesFromString(otf, font.features.text)
except:
import traceback
print(traceback.format_exc(5))
if "GDEF" in otf:
gdef = otf["GDEF"]
if "GSUB" in otf:
gsub = otf["GSUB"]
if "GPOS" in otf:
gpos = otf["GPOS"]
return gdef, gsub, gpos
# -----------
# Main Object
# -----------
class LayoutEngine(BaseObject):
"""
This object provides a GDEF, GSUB and GPOS OpenType Layout Engine for
the default layer of the given font. The engine uses the ``compositor``
module so you must have that installed to use this object.
**This object posts the following notifications:**
- LayoutEngine.Changed
This object monitors the font's feature text and character mapping. When
those change, the compiled tables will be flagged for recompilation and
the next time the engine is queried the tables will be recompiled. Any
data that you have retrieved, such as the list of feature tags, may no
longer be correct. Thus, the data will need to be retrieved again. To be
notified when this is necessary, subscribe to the ``LayoutEngine.Changed``
notification.
"""
changeNotificationName = "LayoutEngine.Changed"
representationFactories = {
"defcon.layoutEngine.tables" : dict(
factory=_layoutEngineOTLTablesRepresentationFactory,
destructiveNotifications=("LayoutEngine._DestroyCachedTables")
)
}
def __init__(self, font):
self._needsInternalUpdate = True
self._font = weakref.ref(font)
self._layoutEngine = compositor.LayoutEngine()
super(LayoutEngine, self).__init__()
self.beginSelfNotificationObservation()
def _get_font(self):
if self._font is not None:
return self._font()
return None
font = property(_get_font)
def _get_engine(self):
if self._needsInternalUpdate:
self._updateEngine()
return self._layoutEngine
engine = property(_get_engine, doc="The compositor layout engine. This object must always be retrieved from the LayoutEngine for the automatic updating to occur.")
# --------------
# Engine Updates
# --------------
def _updateEngine(self):
font = self.font
cmap = _makeCMAP(font.unicodeData)
self._layoutEngine.setCMAP(cmap)
gdef, gsub, gpos = self.getRepresentation("defcon.layoutEngine.tables")
self._layoutEngine.setFeatureTables(gdef, gsub, gpos)
self._needsInternalUpdate = False
# -------------
# Notifications
# -------------
def beginSelfNotificationObservation(self):
super(LayoutEngine, self).beginSelfNotificationObservation()
self.beginSelfLayersObservation()
self.beginSelfLayerObservation()
self.beginSelfFeaturesObservation()
def endSelfNotificationObservation(self):
self.endSelfLayersObservation()
self.endSelfLayerObservation()
self.endSelfFeaturesObservation()
super(LayoutEngine, self).endSelfNotificationObservation()
self._font = None
# default layer changed (changes cmap)
def beginSelfLayersObservation(self):
layers = self.font.layers
layers.addObserver(observer=self, methodName="_layerSetDefaultLayerWillChange", notification="LayerSet.DefaultLayerWillChange")
layers.addObserver(observer=self, methodName="_layerSetDefaultLayerChanged", notification="LayerSet.DefaultLayerChanged")
def endSelfLayersObservation(self):
layers = self.font.layers
layers.removeObserver(observer=self, notification="LayerSet.DefaultLayerWillChange")
layers.removeObserver(observer=self, notification="LayerSet.DefaultLayerChanged")
def _layerSetDefaultLayerWillChange(self, notification):
self.endSelfLayerObservation()
def _layerSetDefaultLayerChanged(self, notification):
self.beginLayerObservation()
self._postNeedsUpdateNotification()
# cmap change
def beginSelfLayerObservation(self):
layer = self.font.layers.defaultLayer
layer.addObserver(observer=self, methodName="_layerGlyphUnicodesChanged", notification="Layer.GlyphUnicodesChanged")
def endSelfLayerObservation(self):
layer = self.font.layers.defaultLayer
layer.removeObserver(observer=self, notification="Layer.GlyphUnicodesChanged")
def _layerGlyphUnicodesChanged(self):
self._postNeedsUpdateNotification()
# feature text change
def beginSelfFeaturesObservation(self):
features = self.font.features
features.addObserver(observer=self, methodName="_featuresTextChanged", notification="Features.TextChanged")
def endSelfFeaturesObservation(self):
features = self.font.features
features.removeObserver(observer=self, notification="Features.TextChanged")
def _featuresTextChanged(self, notification):
self._destroyCachedTables()
self._postNeedsUpdateNotification()
# posting
def _destroyCachedTables(self):
self.postNotification("LayoutEngine._DestroyCachedTables")
def _postNeedsUpdateNotification(self):
self._needsInternalUpdate = True
self.postNotification(self.changeNotificationName)
# ----------
# Engine API
# ----------
def process(self, stringOrGlyphList, script="latn", langSys=None, rightToLeft=False, case="unchanged"):
"""
Process a string (or list of glyph names) with the current
feature states for the given **script** and **langSys**.
The writing will be left to right unless **rightToLeft**
is set to True.
The case may be changed following the Unicode case conversion
rules by setting **case** to one of the following:
+-----------+
| unchanged |
+-----------+
| upper |
+-----------+
| lower |
+-----------+
"""
self._updateEngine()
glyphRecords = self.engine.process(
stringOrGlyphList,
script=script, langSys=langSys,
rightToLeft=rightToLeft, case=case
)
layer = self.font.layers.defaultLayer
finalGlyphRecords = []
for glyphRecord in glyphRecords:
if glyphRecord.glyphName not in layer:
continue
layerGlyph = layer[glyphRecord.glyphName]
glyphRecord.advanceWidth += layerGlyph.width
glyphRecord.advanceHeight += layerGlyph.height
finalGlyphRecords.append(glyphRecord)
return finalGlyphRecords
def getScriptList(self):
"""
Get a list of defined scripts.
"""
return self.engine.getScriptList()
def getLanguageList(self):
"""
Get a list of defined languages.
"""
return self.engine.getLanguageList()
def getFeatureList(self):
"""
Get a list of defined features.
"""
return self.engine.getFeatureList()
def getFeatureState(self, name):
"""
Get the state for the feature with **name**.
"""
return self.engine.getFeatureState(name)
def setFeatureState(self, name, state):
"""
Set the state for the feature with **name**.
"""
self.engine.setFeatureState(name, state)