Floating point division causes Qt error

[g5t]

For the latest v3.1 release available for (at least) x86_64 linux and macOS, attempting to interactively configure an instrument via mcgui raises a TypeError.

Steps to reproduce the error

1. Start mcgui and load an instrument *.instr file with user-configurable parameters.
2. Click on Run...

This results in an error message printed to stderr and a seemingly-hung GUI with the status message Getting instrument params....

Commandline output showing the error traceback

[~]$ mcgui 
loading system configuration
QSocketNotifier: Can only be used with threads started with QThread
Traceback (most recent call last):
  File "/usr/local/mcstas/3.1/bin/../tools/Python/mcgui/mcgui.py", line 596, in handleRunOrInterruptSim
    fixed_params, new_instr_params, inspect, mcdisplay, autoplotter = self.view.showStartSimDialog(
  File "/usr/local/mcstas/3.1/tools/Python/mcgui/viewclasses.py", line 157, in showStartSimDialog
    self.__ssd.createParamsWidgets(params)
  File "/usr/local/mcstas/3.1/tools/Python/mcgui/viewclasses.py", line 798, in createParamsWidgets
    self.ui.gridGrid.addWidget(lbl, y, x, 1, 1)
TypeError: arguments did not match any overloaded call:
  addWidget(self, QWidget): too many arguments
  addWidget(self, QWidget, int, int, alignment: Union[Qt.Alignment, Qt.AlignmentFlag] = Qt.Alignment()): argument 2 has unexpected type 'float'
  addWidget(self, QWidget, int, int, int, int, alignment: Union[Qt.Alignment, Qt.AlignmentFlag] = Qt.Alignment()): argument 2 has unexpected type 'float'

Source of error

The layout-defining division https://github.com/McStasMcXtrace/McCode/blob/0c15352d0d01015e96da2e93aa8c7e86a4e20833/tools/Python/mcgui/viewclasses.py#L792 results in a floating point value but an integer is required by addWidget.

Proposed solution

Switch the floating point division for integer division, e.g., y = i // (int(mccode_config.configuration["GUICOLS"])*2).

Implementing the proposed solution in the insitu viewclasses.py removes the TypeError and allows the Start simulation dialog box to appear as expectred.

[willend]

Hi @g5t, thanks for both issue and proposed solution. :)

I OK with you, I might come by for a "demo" at your desk also, I think there may be (system/user) specifics to it alongside the evident code-problem.

[willend]

@g5t now reproduced on vanilla Ubuntu 22.04 Arm. As we discussed, likely related to exact version of Qt/pyqt.

Will fix on master and mccode-3 branches toward next set of stable releases. Thanks!

[willend]

[g5t]

A similar error appears via the pyqtgraph variant of mcplot at https://github.com/McStasMcXtrace/McCode/blob/0c15352d0d01015e96da2e93aa8c7e86a4e20833/tools/Python/mccodelib/pqtgfrontend.py#L80-L82 where w and h are expected to be int valued in the call to resize.

And in the contained function add_plot which used floating point division https://github.com/McStasMcXtrace/McCode/blob/0c15352d0d01015e96da2e93aa8c7e86a4e20833/tools/Python/mccodelib/pqtgfrontend.py#L384