1,如何得到当前选择集, 2,如何创建 当前选择集 反应器 3,AcEdInputContextReactor能否实现 当前选择集反应器 功能? AcEdInputContextReactor的两个函数 AcEdInputContextReactor::beginSSGet, This function provides notification for the start of an AutoCAD selection set
acquisition operation. AcEdInputContextReactor::beginEntsel This function provides notification for the start of an AutoCAD entity selection
operation. selection set acquisition 与 entity selection 有何区别?