clean up of Qt namespace breaks PySides

[tacaswell]

00aae5f breaks some of the compatibility bindings.

PySides does not export pyqtSignature or pyqtProperty so importing matplotlib fails. There may be more issues, but after those two I gave up and started to revert commits until it worked again ;)

By reverting both f7bee43 and 00aae5f I could get master to work with PySides again.

@mspacek can you take a look at this? I probably won't be able to look at this in detail until next week.

[dmcdougall]

@tacaswell Am I missing something? 1f3d871 appears to not be a valid commit.

[tacaswell]

@dmcdougall Sorry, I apparently fail at copy-paste. Updated the issue with the correct sha1 (f7bee43)

[mspacek]

Oops, sorry about that. Unfortunately, I don't have any experience at all with PySide. To be honest, I didn't even know what pyqtSignature and pyqtProperty are for, I just stopped importing them directly into the namespace, along with everything else. A quick search seems to indicate they're some kind of a relic specific to PyQt4 that maybe shouldn't be used any more.

According to this, pyqtSignature decorators should be replaced with Slot decorators:
http://www.qtrac.eu/pyqtbook.html

QStrings are also apparently a relic of PyQt4's API 1. For API 2, they're gone, replaced with Python strings. PySide uses only API 2. So we'll have to force the use of API 2. I would guess there's already some machinery in MPL to do that:
http://qt-project.org/wiki/Differences_Between_PySide_and_PyQt

I'll try installing PySide and see if I can fix things up in master.

[dmcdougall]

@mspacek Thanks. If no immediate solution can be implemented or you come across difficulties then let me know and those commits can be reverted.

[tacaswell]

@mspacek There is also https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/backends/qt4_compat.py which smooths over most of the differences.

This had been in the back of my head to check, but I never got to it. Sorry for not catching this before it got merged.

[tacaswell]

As a note, reverting just those two commits breaks the menu functionality altogether.

[mspacek]

Sorry, still haven't gotten around to it. I should be able to tomorrow though.

[mspacek]

@tacaswell this is now fixed by #2328, and can be closed.