/**
This function must be overloaded in the derived class for a control with
- @c wxLC_VIRTUAL style having an @ref SetImageList() "image list"
- (if the control doesn't have an image list, it is not necessary to overload it).
+ @c wxLC_VIRTUAL style having an "image list" (see SetImageList(); if the
+ control doesn't have an image list, it is not necessary to overload it).
It should return the index of the items image in the controls image list
or -1 for no image.