Timed messages in StatusBar

[jonathanrocher]

This PR exposes the ability to control the duration of a StatusBar message (qt only for now). I am creating this PR to start the discussion:

• Would others agree that this is desirable?
• How to handle Wx since its wx.StatusBar doesn't expose the same ability? What's pyface's policy for exposing toolkit specific capabilities? If that's not acceptable, a similar behavior could be implemented using a wx.Timer: https://stackoverflow.com/questions/23188042/wxpython-statusbar-temporary-text . That feels like a lot of complexity brought into pyface though.

[corranwebster]

This generally looks fine as an addition. I would prefer to measure time in seconds and then convert to integer milliseconds at the toolkit level.

For the wx case, we have timers exposed in a toolkit-independent fashion in pyface.timer, so it should be fairly easy to add the capability to remove after a fixed amount of time with a toolkit-independent timer object.

[corranwebster]

I think duration in seconds would be better. That is what pyface.timer uses.

[jonathanrocher]

Changed.

[codecov-commenter]

Codecov Report

Merging #522 into master will increase coverage by 0.95%.
The diff coverage is 62.93%.

@@            Coverage Diff             @@
##           master     #522      +/-   ##
==========================================
+ Coverage   37.08%   38.04%   +0.95%     
==========================================
  Files         470      470              
  Lines       26027    26184     +157     
  Branches     3961     3975      +14     
==========================================
+ Hits         9652     9961     +309     
+ Misses      15948    15788     -160     
- Partials      427      435       +8     

Impacted Files	Coverage Δ
pyface/__init__.py	82.60% <ø> (ø)
pyface/ui/wx/action/status_bar_manager.py	31.91% <31.25%> (+2.36%)	⬆️
pyface/ui/qt4/init.py	62.50% <33.33%> (ø)
pyface/ui/qt4/workbench/split_tab_widget.py	12.47% <50.00%> (ø)
pyface/qt/QtNetwork.py	75.00% <60.00%> (ø)
pyface/qt/QtOpenGL.py	75.00% <60.00%> (ø)
pyface/qt/QtSvg.py	75.00% <60.00%> (ø)
pyface/qt/QtTest.py	75.00% <60.00%> (ø)
pyface/qt/QtWebKit.py	68.42% <60.00%> (ø)
pyface/qt/QtCore.py	77.77% <62.50%> (ø)
... and 36 more

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[jonathanrocher]

This is ready for a second look. WX support added, implementation redone for Qt, unit test added.

[jonathanrocher]

Test failure only happens with pyqt, not pyqt5 and is triggered by the following exception in the listener:

Exception occurred in traits notification handler.
Please check the log file for details.
Exception occurred in traits notification handler for object: <pyface.ui.qt4.action.status_bar_manager.StatusBarManager object at 0x127802888>, trait: messages, old value: ['goodbye world'], new value: []
Traceback (most recent call last):
  File "/Users/jrocher/.edm/envs/bootstrap3/lib/python3.6/site-packages/traits/trait_notifiers.py", line 381, in __call__
    self.handler(*args)
  File "/Users/jrocher/Projects/ETS_source/pyface/pyface/ui/qt4/action/status_bar_manager.py", line 100, in _messages_changed
    self._show_messages()
  File "/Users/jrocher/Projects/ETS_source/pyface/pyface/ui/qt4/action/status_bar_manager.py", line 142, in _show_messages
    self.status_bar.showMessage("  ".join(self.messages))
RuntimeError: wrapped C/C++ object of type QStatusBar has been deleted

Can't make sense of it. Any suggestions?

[kitchoi]

If the UI is closed before the timer gets to run its action, then when the timer's action is run, it would be accessing deleted objects. I think in the remove_status_bar method, we should stop and remove the timer if there is one. See if that resolves the error you saw?

[jonathanrocher]

Thanks for the suggestion @kitchoi . Didn't help with the test failure, but good suggestion anyway, so added.