Microsoft KB Archive/66248

PRB: WM_PARENTNOTIFY Message lParam Documented Incorrectly

PSS ID Number: Q66248 Article last modified on 04-26-1993

3.00 WINDOWS

Summary: Page 6-93 of the “Microsoft Windows Software Development Kit Reference Volume 1” version 3.0 incorrectly documents the value of lParam sent with each WM_PARENTNOTIFY message. The WM_PARENTNOTIFY message is sent to the parent of a child window when the child window is created, destroyed, or clicked with any mouse button. When the message is sent, wParam contains WM_CREATE, WM_DESTROY, or WM_''BUTTONDOWN for these situations, respectively. (Note that, in this context, '' replaces one of L, M, and R, representing the left, middle, and right mouse buttons, respectively.) The lParam parameter for this message is documented as follows: lParam Contains the window handle of the child window in its low-order word and the ID of the child window in its high-order word. This documentation is correct when wParam contains WM_CREATE or WM_DESTROY. However, when wParam contains a WM_*BUTTONDOWN message, lParam contains the coordinates of the mouse click in the parent window’s client coordinates. The low-order word of lParam contains the x-coordinate and the high-order word contains the y-coordinate.

Additional reference words: 3.00 KBCategory: KBSubcategory: UsrWinGeneral Copyright Microsoft Corporation 1993.