CODEWITHSUNDEEP
pythonqt5pyqt5
maldalei
maldalei

Reputation: 13

How to prevent window and widgets in a pyqt5 application from changing size when the visibility of one widget is altered

I want to create a dialog, in which the user should first select one item in a drop down, and for some choices specify an additional parameter. For the sake of the example let's say that the possible choices are A and B and for B the user has to enter a text. The text field should not be visible when A is selected.

Here is a MWE:

#!/usr/bin/env python
import sys
from PyQt5.QtWidgets import QApplication, QComboBox, QDialog, QGridLayout, QLineEdit

class Example(QDialog) :

    def __init__(self, parent=None) :
        super(QDialog, self).__init__(parent)
        self.mainLayout = QGridLayout()
        self.setLayout(self.mainLayout)

        self.comboBox = QComboBox()
        self.comboBox.addItems(['A', 'B'])
        self.mainLayout.addWidget(self.comboBox, 0, 0)

        self.lineEdit = QLineEdit('')
        self.lineEdit.setMinimumWidth(50)
        self.mainLayout.addWidget(self.lineEdit, 0, 1)

        self.comboBox.activated[str].connect(self.update)
        self.update(str(self.comboBox.currentText()))

    def update(self, choice) :
        if 'B' in choice :
            self.lineEdit.setVisible(True)
        else : 
            self.lineEdit.setVisible(False)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    example = Example()
    example.show()
    sys.exit(app.exec_())

The problem is, that when initially choice A is presented, the size of the dialog is just enough for the comboBox. When option B is selected, the window is expanded and everything is as it should be. However, when option A is selected again, the comboBox' width increases, taking up all of the avalaible space, instead of leaving empty space to the right.

How can I have space allocated for the text field, no matter if visible or not? What am I missing here?

EDIT The answer by S.Nick solves the problem of the MWE in a way, but not the way I was hoping for: As soon as the scenario is more complex, widgets get reallocated again, e.g. if a QLabel is added in front of the comboBox

    self.label = QLabel('label')
    self.mainLayout.addWidget(self.label, 0, 0)
    self.comboBox = QComboBox()
    self.comboBox.addItems(['A', 'B'])
    self.mainLayout.addWidget(self.comboBox, 0, 1, alignment=Qt.AlignLeft) 
    self.lineEdit = QLineEdit('', self)
    self.lineEdit.setMinimumWidth(50)
    self.mainLayout.addWidget(self.lineEdit, 0, 2)

then the comboBox is flipped around when changing the selection. What I want is that, once in the beginning space and position is allocated for each widget and that the space and position is permanent no matter if any widget is visible or not.

Upvotes: 1

Views: 225

Answers (1)

Heike
Heike

Reputation: 24420

You could try something like this:

def __init__(self, parent=None) :
    super(QDialog, self).__init__(parent)
    self.mainLayout = QGridLayout()
    self.setLayout(self.mainLayout)

    self.label = QLabel('label')
    self.mainLayout.addWidget(self.label, 0, 0)
    self.comboBox = QComboBox()
    self.comboBox.addItems(['A', 'B'])
    self.mainLayout.addWidget(self.comboBox, 0, 1)
    self.lineEdit = QLineEdit('', self)
    self.lineEdit.setMinimumWidth(200)
    self.mainLayout.addWidget(self.lineEdit, 0, 2)
    self.comboBox.activated[str].connect(self.update)

    self.mainLayout.setColumnStretch(2,1)
    self.adjustSize()

    self.update(str(self.comboBox.currentText()))

self.mainLayout.setColumnStretch(2,1) will make sure that the last column will take up all the extra horizontal space even when the line edit widget is hidden.

self.adjustSize() adjusts the size of the main window to the sum of the sizes of all its child widgets. Since at this point the line edit widget is still visible, its size is taken into account as well when the size of the main window is adjusted.

Screenshots

Initial window:

screenshot A

After selecting B:

screenshot B

Upvotes: 1

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