Qt widget wrapper

[MarcusZuber]

First attempt to write a qt-widget-wrapper that can be applied to a Parameterizable.

The code is still quite chaotic but in the first tests it did what it should be.

An example session:

import logging
from inspect import iscoroutinefunction
import concert
concert.require("0.30.1")

from concert.quantities import q
from concert.session.utils import ddoc, dstate, pdoc, code_of

from concert.devices.motors.dummy import LinearMotor
from concert.gui.parameterizable import ParameterizableWidget

LOG = logging.getLogger(__name__)

lin_motor = await LinearMotor()
lin_motor_widget = ParameterizableWidget(lin_motor)

Then lin_motor_widget.show() opens the widget. Can be also used as a general widget in qt layouts etc.

TODOs / Questions:

• How to handle Properties with arbitrary data types? Maybe add a string-to-property function to the property?
  -> I will add a string-to-property function to the Property-Widget
• How to add functions? Create subclasses for each device?
  This would require a subclass for each device and would lead to a bridge like implementation (if seen from the gui side).
  Maybe a simple way to add buttons connected to functions and a factory that sets this for the most common devices/experiments would be a more clean solution (also with less work...)
• Test performance of (ugly manual) event-loop. (In a standard experimental setup no problems where found.)

In concert.gui.parameterizable there is ParameterWidget (+ StateWidget QuantityWidget SelectionWidget that inherit from ParameterWidget). This widget implements a Widget for a (async) setter/getter for a Parameter (Quantitiy....). The setting/getting runs detatched (with the qasynv.asyncSlot). It also features the signals

setter_started = pyqtSignal()
setter_finished = pyqtSignal()
setter_error = pyqtSignal(Exception)

getter_started = pyqtSignal()
getter_finished = pyqtSignal()
getter_error = pyqtSignal(Exception)

that are emitted when a setter/getter is called, finished and when an Exception is raised within.

The ParameterizableWidget adds all parameter (etc.) widgets to a new Widget. The paramter-widgets are in the dictionary params. This allows to connect the setter/getter signals to any arbitrary function.
(E.g. in the example session above)

def print_done():
   print("done")

lin_motor_widget.params['position'].setter_finished.connect(print_done)

All widgets are "functional" and there are many options to make the look more appealing.

[MarcusZuber]

With the Widgets one can build a standalone application like (maybe the setting of the asyncio-eventloop is required)

from PyQt5.QtGui import QApplication
from concert.devices.samplechangers.dummy import SampleChanger
from concert.gui.parameterizable import ParameterizableWidget

if __name__ == '__main__':
   app = QApplication([]) # or args etc.
   changer = SampleChanger()
   changer_widget = ParameterizableWidget(changer)
   changer_widget.show() # or an arbitrary combination in layouts etc.
   app.exec()

I also wanted to have the possibility to open a Widget from a running concert session. Therefore, I added this manual "qt event loop". The possibility to open a widget in a running session is required, if devices do not allow access from multiple connections (or when parameters/state is handled in concert -> that's why I don't like the transition decorator).
Also for checking within a running session if a device is working correctly (without setting up a special session) is a feature that I would like to have. (With some physical devices I have serious trust issues 😉 and to have a small window where state/parameters are polled from time to time can help a lot)

So far I wrapped all async slots that qt sees only non-asyncio blocking functions. I didn't test qt-asyncio compatible event loops like asyncqt or quamash with tango etc. But changing the event loop within a running concert session (not a standalone python program) does not work.

[tfarago]

Before we continue here this will require a discussion with the others, we could try to chat in the week after Easter.

[MarcusZuber]

Sure. I just wanted to dump everything from my mind here, otherwise I can not remember until the next discussions 😉

I just played with it in the lab and it feels quite nice and responsive.

[tfarago]

When I exit python bin/gui_standalone.py I get a segmentation fault 😨

[tfarago]

This should be history after #482 if we manage to have the widget like this:

class ParameterWidget(QWidget, AsyncObject):
   def __ainit__(self, param):
        super().__init__()
        await super().__ainit__()

[MarcusZuber]

When I exit python bin/gui_standalone.py I get a segmentation fault 😨

I'm quite satisfied in this state, that I only get this when exiting...

I already think to know the cause. When the full-async stuff is working I will fix it.

[codecov]

Codecov Report

Patch coverage: 0.90% and project coverage change: -2.96 ⚠️

Comparison is base (4f2027c) 88.36% compared to head (ba5d6a3) 85.41%.

❗ Current head ba5d6a3 differs from pull request most recent head f0739e6. Consider uploading reports for the commit f0739e6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #480      +/-   ##
==========================================
- Coverage   88.36%   85.41%   -2.96%     
==========================================
  Files         120      117       -3     
  Lines        8306     8151     -155     
==========================================
- Hits         7340     6962     -378     
- Misses        966     1189     +223     

Impacted Files	Coverage Δ
concert/_ipython_setup.py	0.00% <0.00%> (ø)
concert/gui/__init__.py	0.00% <0.00%> (ø)
concert/gui/parameterizable.py	0.00% <0.00%> (ø)
concert/config.py	100.00% <100.00%> (ø)

... and 17 files with indirect coverage changes

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[MarcusZuber]

So far I'm quite happy with the functionality and interface. We should discuss how to proceed.