QR codes containing a large amount of data (for example an EU Digital COVID Certificate) make the dialog window sized extremely wide, apparently without any upper limit. Often beyond the size of the screen, to the point, where neither, the "Copy" / "Cancel" buttons are visible, nor the full content, which should be copied or discarded.

Perhaps the width of the dialog could be limited to the screen width, and perhaps a content area GtkBox could have a scrollable widget, to show the content in a width constrained manner?