Fix tabbar issue in OSX

[goanpeca]

Fixes #2598

Description

I think now the user can switch the tab when clicking, however when moving tabs the displaced tab will retain a weird color until it has been selected again. I am not sure why, but at least this PR will fix the main issue.

[goanpeca]

@blink1073 can you test?

[blink1073]

Nope, it doesn't actually switch tabs, it just highlights them.

[blink1073]

Traceback (most recent call last):
  File "/Users/ssilvester/workspace/spyder-ide/spyderlib/plugins/__init__.py", line 121, in eventFilter
    self.tab_pressed(event)
  File "/Users/ssilvester/workspace/spyder-ide/spyderlib/plugins/__init__.py", line 135, in tab_pressed
    self.dock_tabbar.mousePressEvent(self, event)
TypeError: QTabBar.mousePressEvent(QMouseEvent): argument 1 has unexpected type 'TabFilter'

[goanpeca]

f*ck, I pushed the wrong change give me asec...

[goanpeca]

Ok can you try again @blink1073 ?

[blink1073]

Flawless!

[blink1073]

I see what you mean about the weird color when dragging them around.

[goanpeca]

Ok I have no idea what is the issue with that weird tab...

There is a thing called document mode that can be applied to OSx, @blink1073

Would you mind adding this line in spyderlib/plugins/__init__py

Line 65 or similar (the init method of the TabFilter)

    def __init__(self, dock_tabbar, main):
        QObject.__init__(self)
        self.dock_tabbar = dock_tabbar
        self.main = main
        self.moving = False
        self.from_index = None
        self.to_index = None

        self.dock_tabbar.setDocumentMode(True)   # New line

This will change the overall look and in this mode the problem is no longer there... but it looks different...
http://doc.qt.io/qt-4.8/qtabbar.html#documentMode-prop

[blink1073]

Ha, that "fixes" the issue, at the expense of looking terrible all the time 😄

[blink1073]

Prob takes a different set of css.

[goanpeca]

Hahahahah yes... I have tried resetting css refreshing, updating... meh...

Well will be a minor hiccup for now,

@ccordoba12 this can be merged I believe

[ccordoba12]

Thanks for the fix @goanpeca!

One thing about documentMode: activating it makes Spyder crash when you undock panes (at least in Qt 4). That's why we don't use it and instead have a huge qss file to compensate for it :-)