Blob from bytes? about harfpy HOT 11 CLOSED

It seems I also need to keep a reference to the Face object when calling hb.Face.create_for_tables(..) otherwise I get OSError: exception: privileged instruction when calling hb_shape.

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Still get some access violations after that..

Traceback (most recent call last):
  File "c:\users\admin\downloads\trufont\lib\trufont\controls\glyphCanvasView.py", line 342, in keyPressEvent
    self._redirectEvent(event, self._currentTool.keyPressEvent)
  File "c:\users\admin\downloads\trufont\lib\trufont\controls\glyphCanvasView.py", line 465, in _redirectEvent
    callback(event)
  File "c:\users\admin\downloads\trufont\lib\trufont\drawingTools\textTool.py", line 123, in keyPressEvent
    self.layoutLine.insert(text)
  File "c:\users\admin\downloads\trufont\lib\trufont\objects\layoutLine.py", line 100, in insert
    self.updateView()
  File "c:\users\admin\downloads\trufont\lib\trufont\objects\layoutLine.py", line 170, in updateView
    self._shapeAndSetText()
  File "c:\users\admin\downloads\trufont\lib\trufont\objects\layoutLine.py", line 149, in _shapeAndSetText
    records = self.engine.process(names)
  File "c:\users\admin\downloads\trufont\lib\trufont\objects\layoutEngine.py", line 256, in process
    hb.shape(self._hbFont, buf, list(self._fontFeatures.values()))
  File "c:\users\admin\downloads\harfpy\harfbuzz.py", line 4194, in shape
    hb.hb_shape(font._hbobj, buffer._hbobj, c_features, nr_features)
OSError: exception: access violation reading 0xBEE7AE64

cc @khaledhosny

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Ah, apparently storing a reference to the hb.FontFuncs I use fixes the last access violation.

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In other words, a Font object needs to keep a reference to the parent Face?

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I think so in the create_for_tables case which is similar to create_for_array (a reference to the data source should be kept). It can be left to the user, but in that case it should probably be documented.

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hb_font_t keeps a reference of its hb_face_t, so I think the Python objects should do something similar.

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sgtm. The Font.face method would then return the cached Face object, this would keep the source data alive.

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OK, I have done this in 99b3562. See if it fixes the problem.

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Thanks. I think the same should be done for FontFuncs, a reference to it should be stored when Font.set_funcs is called.

About my question in the first post, would you know how to use the hb.Blob.create rather than create for array? (see first post)

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There is a subtlety to getting the memory address for bytes and bytearray objects. Blob.create_for_array can now accept these as of 5a887d5 (copying the same code I used in Qahirah, thanks to a tip from Eryk Sun). You can just use that, or you can look at the code to figure out how to do it with Blob.create for yourself.

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Font.font_funcs and Buffer.unicode_funcs now have associated references saved to prevent premature disposal as of e5c5fe0.

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