QGraphicsLayoutItem Class Reference
[QtGui module]

Subclassing QGraphicsLayoutItem

If you create a subclass of QGraphicsLayoutItem and reimplement its virtual functions, you will enable the layout to resize and position your item along with other QGraphicsLayoutItems including QGraphicsWidget and QGraphicsLayout.

You can start by reimplementing important functions: the protected sizeHint() function, as well as the public setGeometry() function. If you want your items to be aware of immediate geometry changes, you can also reimplement updateGeometry().

The geometry, size hint, and size policy affect the item's size and position. Calling setGeometry() will always resize and reposition the item immediately. Normally, this function is called by QGraphicsLayout after the layout has been activated, but it can also be called by the item's user at any time.

The sizeHint() function returns the item' minimum, preferred and maximum size hints. You can override these properties by calling setMinimumSize(), setPreferredSize() or setMaximumSize(). You can also use functions such as setMinimumWidth() or setMaximumHeight() to set only the width or height component if desired.

The effectiveSizeHint() function, on the other hand, returns a size hint for any given Qt::SizeHint, and guarantees that the returned size is bound to the minimum and maximum sizes and size hints. You can set the item's vertical and horizontal size policy by calling setSizePolicy(). The sizePolicy property is used by the layout system to describe how this item prefers to grow or shrink.