Should be able to close document explicitly

[rk700]

Currently we cannot close an opened doc explicitly, and it blocks us from removing the file. Should make the document destruction available to user.

[rk700]

The problem is harder than I thought. Some other object, for example, Page, also holds a reference to the Document. But the stream is not closed until there's no reference at all.

[JorjMcKie]

@rk700, I realized that all classes do already have methods called .delete_<class>, which obviously invoke the respective drop functions (fz_drop_page, fz_drop_document, etc.) in MuPDF.
What do you think of the following idea:

• make those delete functions available to Python, e.g. as additional close() methods
• inform the user that he has to invoke a delete for every class he has created, before he can hope that a delete_Document is successfull
• additionally provide a new "quit()" method which performs a "dirty close" for the underlying file. To be used in case the user is lazy / does not care, etc. In that case additional code could be inserted, to delete / invalidate the Document object on the Python level, to make sure it cannot be used anymore.

[JorjMcKie]

tested - works!

[rk700]

I made a use-after-free mistake myself...Let's see if 6578922 would fix the issue.

Moreover, I strongly suggest that this feature should be something "experimental", since the use-after-free flaw is really easy to trigger.

[JorjMcKie]

Ok, I will test it - this time more thoroughly ... ;-)

[JorjMcKie]

The above closing of the issue may have seemd premature, but:

In the meantime I have run several tests, opening a document, doing all sorts of stuff with, closing it, re-opening it, closing it again, renaming it, opening the renamed version, etc. etc.

So I do believe the problem is resolved this time.

I also updated the documentation to now contain cautioning remarks about using this close method.