GetClientRect(&rect); 是取得客户区矩形区域,客户区是相对设备坐标说的,还是逻辑坐标啊?请教一下.

是相对的，
当前窗口的左上角x，y为0
右下角为当前窗口的宽度、高度

Pointer to a RECT structure that receives the client coordinates. The left and top members are zero. The right and bottom members contain the width and height of the window.
Because client coordinates are relative to the upper-left corner of a window's client area, the coordinates of the upper-left corner are (0,0).

就是获得当前的窗口的大小，左上（0，0），右下就是窗口结束的地方。