ID 448081 - setFixedHeight() and setMaximumHeight() functions behave differently with QGroupBox objects in Hiero/Nuke 12.1, and later, compared to 12.0

Problem summary
setFixedHeight() and setMaximumHeight() functions behave differently with QGroupBox objects in Hiero/Nuke 12.1, and later, compared to 12.0 

Customer reported version
Hiero 12.1v4

Customer reported platform
Windows 10

Steps to reproduce

1) Open Hiero or Nuke

2) Run the following code in the Script Editor

from PySide2 import QtWidgets

class Hero(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        QtWidgets.QMainWindow .__init__(self, parent)
        mainWidget = QtWidgets.QWidget()
        self.setCentralWidget(mainWidget)
        self.mainWidgetLayout = QtWidgets.QVBoxLayout()
        mainWidget.setLayout(self.mainWidgetLayout)
        self.populate()

    def populate(self):
        buttonsGroupBox = QtWidgets.QGroupBox()
        buttonsGroupBox.setFixedHeight(48)
        buttonsHLayout = QtWidgets.QHBoxLayout()
        buttonsHLayout.setSpacing(0)
        buttonsGroupBox.setLayout(buttonsHLayout)

        self.someButton = QtWidgets.QPushButton()
        self.someButton.setObjectName('someButton')
        self.someButton.setText("Save Project")
        buttonsHLayout.addWidget(self.someButton)

        self.mainWidgetLayout.addWidget(QtWidgets.QWidget())
        self.mainWidgetLayout.addWidget(buttonsGroupBox)

mainWindow = Hero()
mainWindow.show()

RESULT:

​

Changing setFixedHeight() to setMaximumHeight() (line 14 in the above example) also reproduces this problem.

Expected behaviour
The result of running the above code should look the same as it does in Hiero/Nuke 12.0
​

​

Actual behaviour
As of Nuke 12.1v1, the above code produces the following result, and the QPushButton object looks squashed.

Workaround
You may be able to change the value of the argument given to the setFixedHeight()/setMaximumHeight() function, or by removing the function completely. In this case, the following line (line 14):

buttonsGroupBox.setFixedHeight(48)

Reproduced by support
This bug has been reproduced in:
Nuke 12.2v2 - Windows 10 - Linux CentOS 7
Nuke 12.1v1 - Windows 10 - Linux CentOS 7 - Regression

Unable to reproduce bug in:
Nuke 12.0v7 - Windows 10 - Linux CentOS 7

Earliest version tested
Nuke 12.0v7
- This issue doesn't appear in this version and has regressed