[IPython-dev] Qt api selection re. ipython and matplotlib

[MinRK]

On Tue, Jul 5, 2011 at 09:45, Eric Firing <efiring at hawaii.edu> wrote:
> On 07/05/2011 01:36 AM, Darren Dale wrote:
>>
>> On Tue, Jul 5, 2011 at 2:22 AM, Eric Firing<efiring at hawaii.edu>  wrote:
>>>
>>> On 07/04/2011 06:51 PM, MinRK wrote:
>>>>
>>>> On Mon, Jul 4, 2011 at 20:57, Eric Firing<efiring at hawaii.edu>    wrote:
>>>>>
>>>>> If I remove the version-setting from qt.py, then ipython still works
>>>>> with mpl and PyQt4 via "ipython pylab=qt", but it does not work with
>>>>> qtconsole or with PySide.
>>>>
>>>> I don't think we are going to rewrite the whole qtconsole to support
>>>> version 1 for 0.11 this week.  What we can do is change the default
>>>> behavior in qt_for_kernel,
>>>>
>>>>
>>>> (https://github.com/ipython/ipython/blob/master/IPython/external/qt_for_kernel.py)
>>>> which is where code that interacts with other applications gets
>>>> imported.  Currently, we use our v2 import unless matplotlib<= 1.0.1
>>>> is detected.  However, we can change that default to be more
>>>> conservative.  User code (e.g. matplotlib code, integration with other
>>>> apps) is not in the same process as the QtConsole, so we can have v1
>>>> code in the kernel with v2 in the frontend.
>>
>> Good point.
>>
>>> If ipython and mpl have to be synchronized, and if we want to be able to
>>> choose to use pyside or pyqt4, then I think we need more than a change in
>>> the ipython default.  It looks like this calls for yet another pesky
>>> rcParams entry in mpl.  Then that can be used for figuring out what to
>>> import in both matplotlib and ipython.  The default, if there is no
>>> rcParams
>>> entry, would be PyQt4 with the platform default API version.
>>>
>>> Darren, does this sound like a solution that would work for you?
>>
>> If ipython changes its qt_for_kernel to not set the api level, then it
>> seems to me that either the environment variable approach or the
>> rcParams approach will work for pylab/pyplot. The rcParams approach is
>> a little awkward for folks using the OO interface, but it looks like
>> it would work. You mentioned that it does not work with the ipython
>> console and pyside though, what doesn't work?
>
> No figure is displayed after plotting, and then there is an error upon
> exiting ipython if the figure (which was never displayed) is not closed.
>
> Eric
>
>

I think the logic should be something along the lines of:

if matplotlib:
    if matplotlib <= 1.0.1:
         use PyQt+v1 # old matplotlib can't support v2, if I
understand correctly
    else:
         ask matplotlib
if no answer or no matplotlib:
    if QT_API defined:
        if QT_API=pyqt:
                use PyQt+v2 #because this is an ETS env variable, and
ETS requires v2
        elif QT_API=pyside:
           use pyside
    else:
        try pyqt+v1
        if no pyqt:
             try pyside

gist: QT_API should be respected if set, and use v2 unless matplotlib
is too old to allow it.  If nothing is specified, the default is
pyqt+v1, the safest option, but PySide should still be chosen if it's
the only Qt installed.

Does this make sense?

-MinRK