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import hashlib |
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from fontTools.pens.basePen import MissingComponentError |
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from fontTools.pens.pointPen import AbstractPointPen |
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class HashPointPen(AbstractPointPen): |
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""" |
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This pen can be used to check if a glyph's contents (outlines plus |
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components) have changed. |
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Components are added as the original outline plus each composite's |
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transformation. |
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Example: You have some TrueType hinting code for a glyph which you want to |
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compile. The hinting code specifies a hash value computed with HashPointPen |
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that was valid for the glyph's outlines at the time the hinting code was |
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written. Now you can calculate the hash for the glyph's current outlines to |
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check if the outlines have changed, which would probably make the hinting |
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code invalid. |
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> glyph = ufo[name] |
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> hash_pen = HashPointPen(glyph.width, ufo) |
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> glyph.drawPoints(hash_pen) |
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> ttdata = glyph.lib.get("public.truetype.instructions", None) |
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> stored_hash = ttdata.get("id", None) # The hash is stored in the "id" key |
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> if stored_hash is None or stored_hash != hash_pen.hash: |
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> logger.error(f"Glyph hash mismatch, glyph '{name}' will have no instructions in font.") |
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> else: |
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> # The hash values are identical, the outline has not changed. |
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> # Compile the hinting code ... |
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> pass |
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""" |
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def __init__(self, glyphWidth=0, glyphSet=None): |
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self.glyphset = glyphSet |
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self.data = ["w%s" % round(glyphWidth, 9)] |
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@property |
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def hash(self): |
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data = "".join(self.data) |
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if len(data) >= 128: |
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data = hashlib.sha512(data.encode("ascii")).hexdigest() |
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return data |
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def beginPath(self, identifier=None, **kwargs): |
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pass |
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def endPath(self): |
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self.data.append("|") |
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def addPoint( |
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self, |
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pt, |
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segmentType=None, |
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smooth=False, |
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name=None, |
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identifier=None, |
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**kwargs, |
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): |
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if segmentType is None: |
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pt_type = "o" |
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else: |
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pt_type = segmentType[0] |
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self.data.append(f"{pt_type}{pt[0]:g}{pt[1]:+g}") |
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def addComponent(self, baseGlyphName, transformation, identifier=None, **kwargs): |
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tr = "".join([f"{t:+}" for t in transformation]) |
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self.data.append("[") |
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try: |
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self.glyphset[baseGlyphName].drawPoints(self) |
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except KeyError: |
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raise MissingComponentError(baseGlyphName) |
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self.data.append(f"({tr})]") |
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