stopping a while loop

[Zolko]

Hello,

I have made an animation command that changes a variable between 2 values, and updates the assembly at each step. The code is extremely trivial:

Code: Select all

def onRun(self):
    # the selected variable
    varName = self.varList.currentText()
    begin   = self.minValue.value()
    end     = self.maxValue.value()
    step    = self.stepValue.value()
    varValue = begin
    while varValue <= end:
        setattr( self.Variables, varName, varValue )
        App.ActiveDocument.Model.recompute('True')
        Gui.updateGui()
        varValue += step
    return

It is launched when clicking on the button "Run" which is connected to the function by :

Code: Select all

self.OKButton.clicked.connect(self.onRun)

This all works well. Except that if I have made a mistake in the values, this loop can be very slow and long, so I have foreseen a Stop button to stop the loop in the middle. I imagined to connect the Stop button to a "break" in the while loop but Python (or Qt) doesn't accept that.

Is there a way to use this Stop button to halt that while loop ?

self.StopButton.clicked.connect(self.onStop)

[DeepSOIC]

You can call QtGui.QApplication.processEvents() from within the loop. That requires instance of qApp, and I have not been able to reliably obtain one from PySide2. Apparently it's buggy.

Another option is to use progress window. An example can be found in Macro Recompute Profiler. I don't know, but likely it is possible to use FreeCAD's progress bar in status window for this purpose as well.

[DeepSOIC]

Another approach (better, but more difficult/less readable code) is to use a timer and a state machine to drive your animation.

[Zolko]

Another approach (better, but more difficult/less readable code) is to use a timer and a state machine to drive your animation.

I don't know what a state machine is, but that gave me an idea: I added a variable self.Run which is initialized to True, and I connect the Stop button to a function that sets it to False, and I check that variable in the while loop:

Code: Select all

while varValue <= end and self.Run:
   ...

def onStop(self):
    self.Run = False
    return
...
self.StopButton.clicked.connect(self.onStop)

And that does it. Thank-you

[DeepSOIC]

I added a variable self.Run which is initialized to True, and I connect the Stop button to a function that sets it to False, and I check that variable in the while loop … And that does it.

Good to know, so Gui.updateGui is likely just a call to QApplication.processEvents, I persume. Otherwise, the button should not be pressable while your loop is running, because the event loop is blocked.

[openBrain]

You can call QtGui.QApplication.processEvents() from within the loop. That requires instance of qApp, and I have not been able to reliably obtain one from PySide2. Apparently it's buggy.

This is quite easily circumvent using QtGui.QApplication.instance().processEvents()

I don't know what a state machine is, but that gave me an idea: I added a variable self.Run which is initialized to True, and I connect the Stop button to a function that sets it to False, and I check that variable in the while loop:

You posted while I was compiling the small below example, but yes, you need to use a state variable.
However, running processEvents() as described by DeePSOIC should also be done. Try the simple below example, once as is and once with processEvents() line commented out (beware to save your data before)

Code: Select all

from PySide import QtGui

class Infinite(QtGui.QMessageBox):

    def __init__(self):
        super(Infinite, self).__init__()
        self.run = False
        self.brun = self.addButton("Run", QtGui.QMessageBox.ActionRole)
        self.brun.clicked.disconnect()
        self.bstop = self.addButton("Stop", QtGui.QMessageBox.ActionRole)
        self.bstop.clicked.disconnect()
        self.addButton("Quit", QtGui.QMessageBox.ActionRole)
        self.setWindowTitle("Test")
        self.setText("Click on run")
        self.brun.clicked.connect(self.infiniteLoop)
        self.bstop.clicked.connect(self.stopLoop)

    def infiniteLoop(self):
        self.run = True
        while self.run:
            self.setText("Running...")
            QtGui.QApplication.instance().processEvents()
        self.setText("Stopped")

    def stopLoop(self):
        self.run = False

Infinite().exec_()

[openBrain]

Good to know, so Gui.updateGui is likely just a call to QApplication.processEvents, I persume. Otherwise, the button should not be pressable while your loop is running, because the event loop is blocked.

Fully agree with this !

[DeepSOIC]

QtGui.QApplication.instance()

thanks, will try it next time I need it.