此程序实现停靠窗口QDockWidget类的使用，窗口一在主窗口的左边和右边停靠，窗口2只可浮动和右部停靠两种状态间切换，并且不可移动；窗口2可实现停靠窗口的各个状态。-Dock the window QDockWidget class use of this program, the window in the left and right of the main window docked window 2 can only switch between the floating and t