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jklymak opened this issue Aug 12, 2018 · 8 comments · Fixed by #11850
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macosx backend won't load #11846

jklymak opened this issue Aug 12, 2018 · 8 comments · Fixed by #11850
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GUI: MacOSX Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions.
Milestone
v3.0.0

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@jklymak
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jklymak commented Aug 12, 2018 •
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Bug report

#11600 (3479481) appears to have broken the macosx backend.

% git checkout 34794819d8
% cd lib
% git clean -xdf
% cd ..
% pip install -e .
% pythonw testMac.py

Traceback (most recent call last):
  File "testMac.py", line 3, in <module>
    import matplotlib.pyplot as plt
  File "/Users/jklymak/matplotlib/lib/matplotlib/pyplot.py", line 2410, in <module>
    switch_backend(rcParams["backend"])
  File "/Users/jklymak/matplotlib/lib/matplotlib/pyplot.py", line 246, in switch_backend
    backend_mod = importlib.import_module(backend_name)
  File "/Users/jklymak/anaconda3/envs/matplotlibdev/lib/python3.6/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/Users/jklymak/matplotlib/lib/matplotlib/backends/backend_macosx.py", line 14, in <module>
    from matplotlib.backends import _macosx
ImportError: Python is not installed as a framework. The Mac OS X backend will not be able to function correctly if Python is not installed as a framework. See the Python documentation for more information on installing Python as a framework on Mac OS X. Please either reinstall Python as a framework, or try one of the other backends. If you are using (Ana)Conda please install python.app and replace the use of 'python' with 'pythonw'. See 'Working with Matplotlib on OSX' in the Matplotlib FAQ for more information.

import matplotlib
matplotlib.use('macosx')

No error on the previous commit (f4ae5d1). #11600 had a bunch of changes in the _src/macosx.h....
@jklymak jklymak added Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions. GUI: MacOSX labels Aug 12, 2018
@jklymak jklymak added this to the v3.0 milestone Aug 12, 2018
@anntzer
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anntzer commented Aug 12, 2018

In _macosx.m verify_framework, there is a block that reads

    NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
    NSRunningApplication* app = [NSRunningApplication currentApplication];
    NSApplicationActivationPolicy activationPolicy = [app activationPolicy];
    [pool release];
    switch (activationPolicy) {
        case NSApplicationActivationPolicyRegular:
        case NSApplicationActivationPolicyAccessory:
            return true;
        case NSApplicationActivationPolicyProhibited:
            break;
    }

This block is present both in 2.2.3 and in 3.0.0rc1.

Can you printf the value of activationPolicy in both versions when you try to import the module?

@jklymak
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jklymak commented Aug 13, 2018 •
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printing as a %d, activationPolicy is -1 in v3.0.0rc1 and doesn't trigger the break or return below.

In v2.2.3 it activationPolicy is 0, and returns true out of the ActivationPolicyAccessory case.

Sorry, I have no idea what [app activationPolicy] does, or I could try and fix, but right now its broken on 3.0, and works 2.2.3...

@jklymak
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jklymak commented Aug 13, 2018 •
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I think NSApp = [NSApplication sharedApplication]; moved into lazy_init but verify_framework() needs the app to have started?

UPDATE: Yep - if I move verify_framework() into lazy_init() the Framwork version works fine. OTOH if i use the non-framework python I get a segfault instead of the nice error message, primarily because I don't know how to pass the fact that the verify_framework failed back to something at a higher level.

@anntzer
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anntzer commented Aug 13, 2018

Just jotting down some notes:

  • [foo bar] is basically objC for foo.bar().
  • Looks like the issue was known since when the code came in: Fix for issue4372 #4452 (comment).
  • We can't afford to start an app unless we're going to commit to the osx backed because otherwise trying to use another backend can cause a segfault when the other GUI toolkit tries itself to start an app (that was caught by the unit test that went in backend switching -- don't create a public fallback API #11600 and is what motivated the refactor in _macosx.m to start with)

@jklymak
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jklymak commented Aug 13, 2018

That all sounds correct. I think the check should go into lazy_init, but lazy_init needs to return something in failure and the higher functions need to bail on failure so the python interpreter can throw the error. I wasn’t familiar enough with the c++ to get that to happen.

@anntzer
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anntzer commented Aug 13, 2018

Also, does it work if you switch back to using the osx<10.6 #ifdef?

@jklymak
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jklymak commented Aug 13, 2018 •
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Yep, that works fine - if I remove the ifdefs and just have:

static bool verify_framework(void)
{
    ProcessSerialNumber psn;
    if (CGMainDisplayID()!=0
     && GetCurrentProcess(&psn)==noErr
     && SetFrontProcess(&psn)==noErr) return true;
    PyErr_SetString(PyExc_ImportError,
        "Python is not installed as a framework. The Mac OS X backend will "
        "not be able to function correctly if Python is not installed as a "
        "framework. See the Python documentation for more information on "
        "installing Python as a framework on Mac OS X. Please either reinstall "
        "Python as a framework, or try one of the other backends. If you are "
        "using (Ana)Conda please install python.app and replace the use of "
        "'python' with 'pythonw'. See 'Working with Matplotlib on OSX' in the "
        "Matplotlib FAQ for more information.");
    return false;
}

and if I'm using pythonw it works, and if I just use python it gives the correct error message about needing to use the framework. Why are both versions of the check in there?

This was referenced Aug 13, 2018
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@dstansby
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Feel free to ping me in pull requests if anyone wants someone with a mac to test stuff.

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GUI: MacOSX Release critical For bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions.
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FIX: macosx framework check jklymak/matplotlib
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