Qt

This page is about the platform-independent C++ library / toolkit Qt.

This page is a stub. I once worked extensively with Qt for several years, all that is left from this time are some handwritten notes that I transcribed here. I'm not even sure whether the information on this page is still correct or relevant.

Layout

QLayout queries widgets according to the following algorithm:

• QSizePolicy comes first
  • Ignore: The widget gets as much space as possible, the only limit is maximumSize
  • Fixed : The widget gets exactly sizeHint() space
  • All others
    • Query sizeHint()
    • Distribute space according to the actual QSizePolicy of all widgets
    • Minimum size
      • If minimumSize() is set, the minimum size the widget gets is minimumSize()
      • If minimumSize() is not set, the minimum size the widget gets is minimumSizeHint()
      • In both cases: If the result is 0 the widget gets no space
    • Maximum size
      • The maximum size the widget gets is maximumSize()
      • If the result is QWIDGETSIZE_MAX, the maximum size the widget gets is unlimited
  • sizeHint() and minimumSizeHint()
    • Widget without a layout
      • The widget must calculate the size hint by itself
      • The default implementation provides a size hint = QSize(), i.e. no size hint
    • Widget with a layout
      • The layout provides the size hints
• After QSizePolicy comes ... what?