以下成员源于类 QPaintEvent are part of the Qt compatibility layer. We advise against using them in new code.
| QPaintEvent (const QRegion & paintRegion , const QRect & paintRect ) | |
| bool | erased () const |
Constructs a paint event object with both a paintRegion 和 paintRect , both of which represent the area of the widget that needs to be updated.
Returns true if the paint event region (or rectangle) has been erased with the widget's background; otherwise returns false.
Qt 4 always erases regions that require painting. The exception to this rule is if the widget sets the Qt::WA_OpaquePaintEvent or Qt::WA_NoSystemBackground attributes. If either one of those attributes is set and the window system does not make use of subwidget alpha composition (currently X11 and Windows, but this may change), then the region is not erased.
