additionally support Qt5

[dirk-thomas]

With these patches the same code base can satisfy both of the following use cases (with only minimal try / except logic:

• continue to work with Qt 4 (in Indigo and Jade) relying on the forward compatibility provided by:
  • add QtWidgets for forward compatibility with Qt5 python_qt_binding#31
• support Qt 5 (in Kinetic) using these changes:
  • switch to Qt5 python_qt_binding#30
  • switch to Qt5 qt_gui_core#64
  • switch to Qt5 rqt#106

The version dependency on python_qt_binding ensures that the packages which use QtWidgets are getting the changes from ros-visualization/python_qt_binding#31.

This is required for a release into Kinetic.

[dirk-thomas]

As a follow up of this PR the package rqt_plot will be moved into a separate repository since it requires a Qt version specific dependency on Qwt. Since I don't want to branch this repo for Kinetic rqt_plot is extracted since it requires branching.

[trainman419]

rqt_bag depends on rqt_plot, so that may need to move as well.

[dirk-thomas]

rqt_bag doesn't need to move. Only rqt_plot needs a different dependency in its manifest. rqt_bag can continue to use it even if it is in a different repo.

[trainman419]

The dependency chain now is rqt_bag_plugins -> rqt_plot -> rqt_py_common. Moving the middle item in that dependency chain out of the repository seems like it will cause confusion for people building from source, and I'm not convinced that tools like bloom or devel jobs are designed for that situation.

[dirk-thomas]

That is true. A circular dependency on the repository level is not fun and should be avoided. I might create a "relay" package then which just chooses the Qwt version. Then that package can be branches and rqt_plot and friends can stay in this repo (without a need to branch).

[dirk-thomas]

I created a "dependency only" package called qwt_dependency which lives outside of this repo and is now being used as a dependency: 3ac086c

That way we can use Qwt 5 for Jade and older and Qwt 6.1 for Kinetic (once it becomes available as a system package or someone creates a custom package which we import into our apt repo).

[dirk-thomas]

With PySide 2 there are no working backends for plotting at the moment. There are either no packages available upstream or the package is too old (in the case of matplotlib it supports PySide 2 only as of the upcoming release 2.1). We would need to create our own package of one of the backend libraries to support it in Kinetic.

[dirk-thomas]

I posted on the SIG and am looking forward for feedback on these changes: https://groups.google.com/forum/#!topic/ros-sig-rqt/1zcA4xlQ3E0