Refactor our Qt plugin to make use of the original colors from Qt widget styles

[paulolieuthier]

Before:

After:

Looking reeeally nicer now. Credits for qt5ct's and KDE's developers. Fixes lxde/lxqt#695.

[paulolieuthier]

This is a really nice feature, as Qt apps will turn beautiful again. Please, @jleclanche, @luis-pereira, @palinek, @agaida, @pmattern test this. It will be a very good addition to 0.10.

[jleclanche]

@paulolieuthier this is very hard to review because of all the unrelated changes....

[paulolieuthier]

Filelight is segfaulting on start.

[agaida]

qupzilla segfaults on start, keyboard panel plugin don't work as expected with this patch

[paulolieuthier]

Ok, taking a different approach now. Filelight and Qupzilla are not segfaulting anymore. @agaida, please test the keyboard plugin.

@jleclanche I hope it's better to review it now. :smile:

[agaida]

@paulolieuthier - looks good, works as expected, open a new issue for the keyboard plugin Edit: not a new issue - lxde/lxqt#729

[paulolieuthier]

Konversation is crashing with the patch. It really looks like a bug in Konversation, but I'll try to work on it.

[paulolieuthier]

OK, it's ready. No Qt application sefgault when opening. Unfortunately, both Qupzilla and Konversation crash when changing the Qt widget style, but they also crash with current master, so it's not something introduced in this patch. Besides, Konversation also crashes in Plasma (as reported), so I believe it's not our fault.

The patch is very simple now and testing it is also very simple.

[luis-pereira]

@paulolieuthier I didn't report (sorry). It worked Ok to me. GTM.