changes:
You have to include <QtAVWidgets/QtAVWidgets.h> to use built-in widget
renderers
Link against QtAVWidgets
TODO:
QT += avwidgets not available
move ids to widgets module?
BUG:
parent widget's paint engine must be qpainter, otherwise children may
not update
TODO:
subclass of QSlider. press slider can not change value
auto hide slider
HAVE_FEATURE should be used in library internally for building the
library. Those macros are not provided for users. Users can choose a
FEATURE in runtime. If the FEATURE is compiled into library, then you
can.