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

[Eric Firing]

On 07/04/2011 06:51 PM, MinRK wrote:
> On Mon, Jul 4, 2011 at 20:57, Eric Firing<efiring at hawaii.edu>  wrote:
>> On 07/04/2011 04:26 PM, Darren Dale wrote:
>>> On Mon, Jul 4, 2011 at 9:17 PM, Fernando Perez<fperez.net at gmail.com>    wrote:
>>>> Hi folks,
>>>>
>>>> Eric Firing, Darren Dale and others in the MPL team are trying to work
>>>> out the Qt API selection issues after our own updates, but there are
>>>> some technical questions in there that require more knowledge about Qt
>>>> than I have.  The MPL pull request is:
>>>>
>>>> https://github.com/matplotlib/matplotlib/pull/390
>>>>
>>>> which follows our own recent changes:
>>>>
>>>> https://github.com/ipython/ipython/pull/550#issuecomment-1490217
>>>>
>>>> Evan has already done the lion's share of the work on this topic, but
>>>> I figured I'd ping the list in case someone else can also jump in,
>>>> since I myself am kind of useless on the details of Qt itself.
>>>
>>> Note that this is probably not specific to matplotlib, but rather
>>> IPython's qt gui support. IPython.external.qt is setting the sip api
>>> level for PyQt4 to api version 2. Version 2 is not the default for
>>> python-2, which means that ipython would not be able to run PyQt4 apps
>>> or scripts that use QString or QVariant, both of which are officially
>>> supported in the default PyQt4 api. It will impact a lot of users and
>>> a lot of projects.
>>
>> Reference:
>>
>> http://developer.qt.nokia.com/wiki/Differences_Between_PySide_and_PyQt
>>
>> It seems that the mpl qt4 backend works with Version 1 or 2 (and with
>> PyQt4 or PySide) given just a little bit of compatibility shimming.  If
>> ipython can similarly get by with a few shims, so that it does not need
>> to set the Version, then the problem is solved once those shims are
>> identified and installed.
>>
>> 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.

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?

Eric

>
> -MinRK
>
>>
>> Eric
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