Making Qt Application that work with different System Font Sizes

Question

I am working on a Qt application targeting Windows and Mac OS X. I have lots of dialogs with text in my application. I created the application on Windows, where I sized the dialogs to fit all of my text neatly. As soon as I compiled on Mac OS X, I realised all of the text doesn't fit properly. Furthermore, setting a different system font size in the Windows Control Panel causes all of dialog sizes to be incorrect.

How are you supposed to handle different system font sizes in Qt?

Answer 1

You don't: you let Qt do the job for you. Use layouts to arrange your widgets; avoid setting fixed sizes. Last point: I recommend to use Qt-Designer to create your interfaces.

Edit for Dmitry: here are Python files from 2 ui files (generated with pyuic4) each one with 2 QLabel. 1 Qlabel font is huge (72), the other is the default one (10).

1. Min and Max size are constrained: here if max font size is 10, the label is correctly displayed.

   from PyQt4 import QtCore, QtGui
   
   class Ui_Dialog(object):
       def setupUi(self, Dialog):
           Dialog.setObjectName("Dialog")
           Dialog.resize(115, 160)
           sizePolicy = QtGui.QSizePolicy(QtGui.QSizePolicy.Fixed, QtGui.QSizePolicy.Fixed)
           sizePolicy.setHorizontalStretch(0)
           sizePolicy.setVerticalStretch(0)
           sizePolicy.setHeightForWidth(Dialog.sizePolicy().hasHeightForWidth())
           Dialog.setSizePolicy(sizePolicy)
           Dialog.setMinimumSize(QtCore.QSize(115, 160))
           Dialog.setMaximumSize(QtCore.QSize(115, 160))
           self.verticalLayout = QtGui.QVBoxLayout(Dialog)
           self.verticalLayout.setObjectName("verticalLayout")
           self.label = QtGui.QLabel(Dialog)
           font = QtGui.QFont()
           font.setFamily("Andale Mono")
           font.setPointSize(72)
           self.label.setFont(font)
           self.label.setObjectName("label")
           self.verticalLayout.addWidget(self.label)
           self.label_2 = QtGui.QLabel(Dialog)
           self.label_2.setObjectName("label_2")
           self.verticalLayout.addWidget(self.label_2)
   
           self.retranslateUi(Dialog)
           QtCore.QMetaObject.connectSlotsByName(Dialog)
   
       def retranslateUi(self, Dialog):
           Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None, QtGui.QApplication.UnicodeUTF8))
           self.label.setText(QtGui.QApplication.translate("Dialog", "UGLY", None, QtGui.QApplication.UnicodeUTF8))
           self.label_2.setText(QtGui.QApplication.translate("Dialog", "Not ugly", None, QtGui.QApplication.UnicodeUTF8))
   
   
   if __name__ == "__main__":
       import sys
       app = QtGui.QApplication(sys.argv)
       Dialog = QtGui.QDialog()
       ui = Ui_Dialog()
       ui.setupUi(Dialog)
       Dialog.show()
       sys.exit(app.exec_())
   

2. No more constraint on size: the label with font size 72 can be displayed.

   from PyQt4 import QtCore, QtGui
   
   class Ui_Dialog(object):
       def setupUi(self, Dialog):
           Dialog.setObjectName("Dialog")
           Dialog.resize(495, 140)
           self.verticalLayout = QtGui.QVBoxLayout(Dialog)
           self.verticalLayout.setObjectName("verticalLayout")
           self.label = QtGui.QLabel(Dialog)
           font = QtGui.QFont()
           font.setFamily("Andale Mono")
           font.setPointSize(72)
           self.label.setFont(font)
           self.label.setObjectName("label")
           self.verticalLayout.addWidget(self.label)
           self.label_2 = QtGui.QLabel(Dialog)
           self.label_2.setObjectName("label_2")
           self.verticalLayout.addWidget(self.label_2)
   
           self.retranslateUi(Dialog)
           QtCore.QMetaObject.connectSlotsByName(Dialog)
   
       def retranslateUi(self, Dialog):
           Dialog.setWindowTitle(QtGui.QApplication.translate("Dialog", "Dialog", None, QtGui.QApplication.UnicodeUTF8))
           self.label.setText(QtGui.QApplication.translate("Dialog", "less UGLY", None, QtGui.QApplication.UnicodeUTF8))
           self.label_2.setText(QtGui.QApplication.translate("Dialog", "Not ugly", None, QtGui.QApplication.UnicodeUTF8))
   
   
   if __name__ == "__main__":
       import sys
       app = QtGui.QApplication(sys.argv)
       Dialog = QtGui.QDialog()
       ui = Ui_Dialog()
       ui.setupUi(Dialog)
       Dialog.show()
       sys.exit(app.exec_())