This message is sent by an application to determine the layout height (in pixels) occupied by the text.
Windows Mobile Classic and Windows Mobile Professional layout height number increases when more lines are added to the page.
The layout height can be 10, 25, 40, ... 1160, and so on. The layout height does not depend on the client area, scroll bars, or any other visual effects.
If there is a blank page or when "blank page" == DTM_CLEAR, both width and height should be 0 and DTM_LAYOUTHEIGHT returns 0.
The following example shows how you might use this message.
lHeight=SendMessage(hWndCtrl, DTM_LAYOUTHEIGHT, 0, 0);