WM_PARENTNOTIFY

WM_PARENTNOTIFY

The WM_PARENTNOTIFY message is sent to the parent of a child window when the child window is created or destroyed, or when the user clicks a mouse button while the cursor is over the child window. When the child window is being created, the system sends WM_PARENTNOTIFY just before the CreateWindow or CreateWindowEx function that creates the window returns. When the child window is being destroyed, Windows sends the message before any processing to destroy the window takes place.

WM_PARENTNOTIFY

fwEvent = LOWORD(wParam); // event flags

idChild = HIWORD(wParam); // identifier of child window

lValue = lParam; // child handle, or cursor coordinates

Parameters

fwEvent

Value of the low-order word of wParam. Specifies the event for which the parent is being notified. This parameter can be one of the following values:

Value	Meaning
WM_CREATE	The child window is being created.
WM_DESTROY	The child window is being destroyed.
WM_LBUTTONDOWN	The user has placed the cursor over the child window and has clicked the left mouse button.
WM_MBUTTONDOWN	The user has placed the cursor over the child window and has clicked the middle mouse button.
WM_RBUTTONDOWN	The user has placed the cursor over the child window and has clicked the right mouse button.

idChild

Value of the high-order word of wParam. If the fwEvent parameter is the WM_CREATE or WM_DESTROY value, idChild specifies the identifier of the child window. Otherwise, idChild is undefined.

lValue

Contains the handle of the child window, if the fwEvent parameter is the WM_CREATE or WM_DESTROY value; otherwise, lValue contains the x- and y-coordinates of the cursor. The x-coordinate is in the low-order word and the y-coordinate is in the high-order word.

Return Values

If an application processes this message, it should return zero.

Remarks

This message is also sent to all ancestor windows of the child window, including the top-level window.

All child windows, except those that have the WS_EX_NOPARENTNOTIFY extended window style, send this message to their parent windows. By default, child windows in a dialog box have the WS_EX_NOPARENTNOTIFY style, unless the CreateWindowEx function is called to create the child window without this style.