notepad NOTIFICATIONS seem to cause deadlocks

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Ben Morgan
2012-04-23
2013-01-25
  • Ben Morgan
    Ben Morgan
    2012-04-23

    I have code which does automatic styling every couple of seconds after changes in a SCINTILLANOTIFICATION.PAINTED handler. However, I found if I registered for notepad notifications (e.g. NOTIFICATION.BUFFERACTIVATED or NOTIFICATION.FILESAVED), and these arrived while I was styling the text, notepad++ would lock up and need killing and restarting.

    I managed to simulate BUFFERACTIVATED and FILESAVED by using PAINTED as an idle loop and looking for changes, and my script seems fine now.

    Is this because of multi-threading in notepad++ and which Python thread messages are dispatched on?

     
  • I would guess it was.  Although theoretically, it should be fine, as all scintilla notifications are processed on a consumer thread, and the event returns before the callback is complete, so the scintilla events can occur however they like.  Notepad++ events like BUFFERACTIVATED are processed inline, so do not return until the callback is completed. 

    I can imagine that this is something along the lines of the BUFFERACTIVATED causing a PAINT, which causes your script to set a style, which causes another PAINT, and so on.  With enough layers and locks and waits, there's a deadlock hidden in there somewhere.

    I will try to reproduce this when I get some time, but with the Python GIL stamping its size 12s around at the same time, it makes for a complex issue, and can't guarantee a fix in the near future (or possibly at all…)

    Incidentally, doesn't the MODIFIED notification do what you want - seems a shame to style after every paint, when you really want to style after a modification has been made - I can see that you might be fighting with the real lexer though - in which case, would your own lexer /language definition be a better idea?  Just a thought.

    Sorry I can't be of more help.

    Cheers,
    Dave.

     
  • Ben Morgan
    Ben Morgan
    2012-04-24

    The reason I didn't use MODIFIED was because it tended to crash in odd places. If you just have a basic script which prints out the arguments for an exception, it crashes (I put in a bug report for that). Note that I am using PAINT not for doing styling every time, but as my idle loop. I have a timer which updates it three seconds or so after it was last modified or when it is saved. I basically use a md5 checksum to see when the text has changed.

    I have created a follow-up bug from this with a test case as sourceforge won't let me attach here:
    https://sourceforge.net/tracker/?func=detail&aid=3520784&group_id=337487&atid=1413747

    Basically, what I am doing in my script is the equivalent of pyflakes-vim - a little bit of extra checking of Python code on top of the regular python syntax highlighting. So it needs to still use the basic python lexer.

    Thanks for your time,
    Ben.