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

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.

I updated mpl pull request #390 and added ipython pull request #550 with a strawman plan based on mpl rcParams. A quick test indicates that it makes qtconsole work with pylab=qt with either PyQt4 or PySide selected in mpl, and it also works with the ipython console with PyQt4, but not with PySide. I don't know why the latter does not work.

Eric

···

On 07/04/2011 06:51 PM, MinRK wrote:

On Mon, Jul 4, 2011 at 20:57, Eric Firing<efiring@...229...> wrote:

On 07/04/2011 04:26 PM, Darren Dale wrote:

On Mon, Jul 4, 2011 at 9:17 PM, Fernando Perez<fperez.net@...149...> wrote:

-MinRK

Eric
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That should have been ipython pull request #556.

Eric

···

On 07/04/2011 09:42 PM, Eric Firing wrote:

I updated mpl pull request #390 and added ipython pull request #550 with