Question

I have this sample of code:

import sys
from PyQt4.QtGui import (QApplication, QHBoxLayout, QVBoxLayout, QDialog,
                                          QFrame, QPushButton, QComboBox)

class Form(QDialog):
    def __init__(self, parent=None):
        super(Form, self).__init__(parent)

        moreButton = QPushButton('moreButton')
        moreButton.setCheckable(True)
        resizeButton = QPushButton('Resize')
        combo = QComboBox()
        combo.addItems(['item1', 'item2'])

        layout1 = QHBoxLayout()
        layout1.addWidget(moreButton)
        layout1.addWidget(resizeButton)

        layout2 = QHBoxLayout()
        layout2.addWidget(combo)
        self.frame = QFrame()
        self.frame.setLayout(layout2)
        self.frame.hide()

        layout3 = QVBoxLayout()
        layout3.addLayout(layout1)
        layout3.addWidget(self.frame)

        moreButton.toggled.connect(self.frame.setVisible)
        moreButton.clicked.connect(self.method)
        resizeButton.clicked.connect(self.method)

        self.setLayout(layout3)
        self.resize(630, 50)

    def method(self):
        if self.frame.isVisible():           
            self.resize(630, 150)
        else:
            self.resize(630, 250)

app = QApplication(sys.argv)
form = Form()
form.show()
app.exec_()

I run it and when moreButton clicked the ComboBox appears or disappears. Dialog’s size also changes. But if I change the method to:

def method(self):
    if self.frame.isVisible():           
        self.resize(630, 150)
    else:
        self.resize(630, 50)

(in order to set the initial size when combo is hidden) the resizing does not work. However, if I click resizeButton -which is connected to the same method- the resizing works properly.

I know that there are other ways to achieve such a result (eg. layout.setSizeConstraint(QLayout.SetFixedSize)), but I want to declare size explicitly.

What am I doing wrong?

Answer 1

My guess is that you are trying to resize the QDialog before it has time to re-adjust its size after you hide stuff. So at the time resize is called it has a minimumSize that makes sure the buttons and the combobox visible. When you call it after some time, it now has proper miminumSize and responds properly.

A quick fix is manually overriding minimumSize before resizing:

def method(self):
    if self.frame.isVisible():
        # uncomment below, if you like symmetry :)
        # self.setMinimumSize(630, 150)
        self.resize(630, 150)
    else:
        self.setMinimumSize(630, 50)
        self.resize(630, 50)

But, if I were to tackle this, I’d just leave managing resizing to the layout and use sizeConstraint. That’s what these layouts for anyways.