The QFrame class is the base class of widgets that have an (optional) frame. ... A frame widget has three attributes: frame style , a line width and a mid-line width . ... Virtual function that is called when the frame style, line width or mid-line width changes. ... Note that the frame width depends on the frame style , not only the line width and the mid line width. For example, the style NoFrame always has a frame width 0, while the style Panel has a frame width equivalent to the line width. ...