MSDN中对该函数的说明 Call this function to do rubber-band selection. It is usually called from inside the function of your application that handles the WM_LBUTTONDOWN message (typically OnLButtonDown).This function will capture the mouse until the user releases the left mouse button, presses the ESC key, or presses the right mouse button. As the user moves the mouse cursor, the feedback is updated by calling DrawTrackerRect and OnChangedRect.Tracking is performed with a rubber-band-type selection from the lower-right handle. If inverting is allowed, the rectangle can be sized by dragging either up and to the left or down and to the right. 这个函数只用来追踪鼠标的移动，最后并不保留痕迹。
Call this function to do rubber-band selection. It is usually called from inside the function of your application that handles the WM_LBUTTONDOWN message (typically OnLButtonDown).This function will capture the mouse until the user releases the left mouse button, presses the ESC key, or presses the right mouse button. As the user moves the mouse cursor, the feedback is updated by calling DrawTrackerRect and OnChangedRect.Tracking is performed with a rubber-band-type selection from the lower-right handle. If inverting is allowed, the rectangle can be sized by dragging either up and to the left or down and to the right.
这个函数只用来追踪鼠标的移动，最后并不保留痕迹。