In the Presentation Manager, parent and child windows are active at the same time. Therefore, when a help instance is associated with a window, its descendants are included in the association. However, only the parent window is the active help window.
Note: Do not confuse child windows with dialog, message boxes, and other windows which the application may own but are actually children of the desktop.
For IPF to process help requests for a child window, an application must send IPF HM_SET_ACTIVE_WINDOW messages to set the active help window. Until this happens, IPF continues to satisfy help requests for the child window from the help subtable for the parent window.
The HM_SET_ACTIVE_WINDOW message should be sent by ALL windows in response to the WM_ACTIVATE and WM_INITMENU messages as shown in the following example.
switch( usMsg )
{
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case WM_ACTIVATE:
if( SHORT1FROMMP( mp1 ) )
{
/*
* Set active help window to this window's parent when
* activated
*/
WinSendMsg( WinQueryHelpInstance( hWnd ),
HM_SET_ACTIVE_WINDOW,
WinQueryWindow( hWnd, QW_PARENT ),
WinQueryWindow( hWnd, QW_PARENT ) );
}
else
{
/*
* Clear active help window when this window is
* deactivated - necessary for message box help, etc.
* to work properly.
*/
WinSendMsg( WinQueryHelpInstance( hWnd ),
HM_SET_ACTIVE_WINDOW,
NULL,
NULL );
}
break;
case WM_INITMENU:
/*
* Set active window to this window's parent here so that
* the menu id will be found in the proper subtable.
* Activation and deactivation of the help window will
* take care of setting the help window back to the
* active window.
*/
WinSendMsg( WinQueryHelpInstance( hWnd ),
HM_SET_ACTIVE_WINDOW,
WinQueryWindow( hWnd, QW_PARENT ),
WinQueryWindow( hWnd, QW_PARENT ) );
break;
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}