empty parameter list constructor - for usage by factory
create with ID parameter
Draw widget at its position to buffer
returns number of children of this widget
returns child by index
adds child, returns added item
inserts child at given index, returns inserted item
removes child, returns removed item
removes child by ID, returns removed item
removes child, returns removed item
returns index of widget in child list, -1 if passed widget is not a child of this widget
replace child with other child
WidgetGroup with default drawing of children (just draw all children)