How do I auto-adjust the size of a QDialog depending on the text length of one of its children?

Question

I have a QDialog I'm working with. It is made somewhat like a QMessageBox. I noticed that the size of the QMessageBox (and the size of its label) depends on the size of the message displayed.

How would I make the size of my QDialog adjust automatically like a QMessageBox? Presently my QDialog contains a button box and a label, and the QDialog is layout Vertical.

(I know I could just use the message box directly but eventually I will have more complex dialogs.)

Answer 1

Automatic solution:

Use layouts and set size policies to QSizePolicy::Expanding. In QtDesigner, once all your children are placed on your QDialog, then click on the Adjust Size button next layout ones. Your QDialog will be automatically resized at runtime.

Manual solution:

The QWidget class has a method adjustSize that resize the QWidget to fit its content. Just call it when all children are set.

Answer 2

Set your dialog to be expanding, and very small. Then, be sure to set your message before showing the dialog. When shown, it will try to find its proper size, based on the size of the objects it contains. (This happens recursively, so if the dialog isn't the direct parent of the label in which you show your message, make sure everything between the label and the dialog is set to use layouts.)