2389: Validate text/int/float inputs within the preferences panel

[krzywon]

Description

A validator method was added to the preferences widget to check that text input boxes are valid before staging any changes. If the value becomes invalid, any previously staged value for that input is removed.

Fixes #2389
Fixes #2521

How Has This Been Tested?

New (but minimal) unit tests and locally running the GUI to ensure invalid entries are not stored in the config.

Review Checklist (please remove items if they don't apply):

• Code has been reviewed
• Functionality has been tested
• Windows installer (GH artifact) has been tested (installed and worked)
• MacOSX installer (GH artifact) has been tested (installed and worked)
• User documentation is available and complete (if required)
• Developers documentation is available and complete (if required)
• The introduced changes comply with SasView license (BSD 3-Clause)

[butlerpd]

This needs to wait for the pyside merge which will require some more changes.

[wpotrzebowski]

@krzywon to look at it again

[krzywon]

This should be ready for review now

[wpotrzebowski]

@rozyczko to look at it

[rozyczko]

The code looks good, minor questions raised to address outside the scope of this review.

Functionality:

• leaving a textbox in yellow state stil allows Apply and OK. Clicking either button updates the staging stack with the incorrect value

Additionally, I am getting failures on clicking "Accept" on the Preferences panel. This seems to be a leftover from merging the PySide6 branch into main. We might as well create a separate ticket for this.

09:02:11 - sas.qtgui.Perspectives.Fitting.FittingWidget - ERROR - Traceback (most recent call last):
  File "D:\projects\sasview\src\sas\qtgui\Utilities\Preferences\PreferencesPanel.py", line 100, in _okClicked
    self._saveStagedChanges()
  File "D:\projects\sasview\src\sas\qtgui\Utilities\Preferences\PreferencesPanel.py", line 106, in _saveStagedChanges
    self.stackedWidget.widget(i).applyNonConfigValues()
  File "D:\projects\sasview\src\sas\qtgui\Perspectives\Fitting\FittingOptions.py", line 177, in applyNonConfigValues
    color = line_edit.palette().color(QtGui.QPalette.Background).name()
AttributeError: type object 'PySide6.QtGui.QPalette' has no attribute 'Background'

Also, the Default Fit Algorithm combobox is squashed.

[krzywon]

I went ahead and covered all of your suggestions here. They are all related to validation and made the system better

[rozyczko]

Thanks! The code and widgets look good now.

The functionality is almost there.

1. The Fit Optimizers page: changing its parameters doesn't trigger the OK/Apply check. I can modify the Fit Algorithms combobox and any numerical value and OK/Apply buttons don't enable.

2. Moving away from an invalid textbox leaves the textbox in an invalid state. Having yellow bg for the users is good, but maybe the control should revert to its original content when focus is lost on bad content?
   Yes - the bad value isn't saved but when the widget is closed and reopened, the invalid textbox is still shown, despite the underlying value (in the model) being correct.

[wpotrzebowski]

@krzywon and @rozyczko to double check if it works

[butlerpd]

@rozyczko to check

[rozyczko]

There are still some minor glitches but we need this functionality.