对话框编辑器中使用的单位是Dialog Units（DLU）——一种设备无关的长度单位。MSDN中对此的解释如下： The system defines the size and location of user interface elements in a window based on dialog units (DLUs), not pixels. A dialog unit is the device-independent measure to use for layout. One horizontal dialog unit is equal to one-fourth of the average character width for the current system font. One vertical dialog unit is equal to one-eighth of an average character height for the current system font. The default height for most single-line controls is 14 DLUs. Be careful if you use a pixel-based drawing program, because it may not provide an accurate representation when you translate your design into dialog units. If you do use a pixel-based drawing tool, you may want to take screen snapshots from a development tool that supports dialog units and use those images.
有逻辑坐标，设备坐标等说法
CWnd的成员函数接收的都是设备坐标，也就是以屏幕左上角为原点
逻辑坐标是相对窗口的左上角为原点
在dialog editor 里面和 程序动态生成的时候一样。
全是从dialog 的client area的左上角开始算(0,0)点，
只是似乎他们的(1,1)点并不重合……
The system defines the size and location of user interface elements in a window based on dialog units (DLUs), not pixels. A dialog unit is the device-independent measure to use for layout. One horizontal dialog unit is equal to one-fourth of the average character width for the current system font. One vertical dialog unit is equal to one-eighth of an average character height for the current system font. The default height for most single-line controls is 14 DLUs. Be careful if you use a pixel-based drawing program, because it may not provide an accurate representation when you translate your design into dialog units. If you do use a pixel-based drawing tool, you may want to take screen snapshots from a development tool that supports dialog units and use those images.