View source for WinSetClassMsgInterest

This function ''sets the message interest of a window class''.

==Syntax==
 WinSetClassMsgInterest(hab, pszClassName, ulMsgClass, lControl)

==Parameters==
;hab ([[HAB]]) - Input: Anchor-block handle.
;pszClassName ([[PSZ]]) - Input: Window-class name.
;ulMsgClass ([[ULONG]]) - Input: Message class to set interest for. Can be a specific message ID (e.g., [[WM_SHOW]]) or SMIM_ALL (all messages except [[WM_QUIT]] under certain lControl values).
;lControl ([[LONG]]) - Input: Interest identifier.
:;SMI_INTEREST
::Interested in the message(s).
:;SMI_NOINTEREST
::Not interested in the message(s).
:;SMI_AUTODISPATCH
::Interested, but messages should be automatically dispatched to the window procedure.
;rc ([[BOOL]]) - Returns: TRUE if interest was successfully changed, FALSE otherwise.

==Returns==
;rc (BOOL) - returns :Interest-changed indicator.
:;TRUE
::Interest successfully changed
:;FALSE
::Interest not successfully changed.

==Remarks==
This function only works if the [[MsgControlHook]] hook has been set.

The interest for [[WM_QUIT]] cannot be set to SMI_AUTODISPATCH using SMIM_ALL, as [[WM_QUIT]] is the standard way to terminate an application. It can be set specifically if needed.

==Errors==
Possible returns from [[WinGetLastError]]:
:* PMERR_INVALID_HWND (0x1001) - An invalid window handle was specified.

==Example Code==
<Pre>
#define INCL_WINMESSAGEMGR /* Or use INCL_WIN, INCL_PM, */
#include <os2.h>

HAB   hab;          /* Anchor-block handle. */
PSZ   pszClassName; /* Window-class name. */
ULONG ulMsgClass;   /* Message class to have interest level set. */
LONG  lControl;     /* Interest identifier for the message class. */
BOOL  rc;           /* Interest-changed indicator. */

rc = WinSetClassMsgInterest(hab, pszClassName,
                            ulMsgClass, lControl);
</Pre>
This example sets the message interest for the WC_MENU window class, allowing its messages to be processed in the MsgControlHook procedure.
<Pre>
#define INCL_WINMESSAGEMGR
#define INCL_WINHOOKS
#define INCL_WINMENUS   /* for WC_MENU parameter definition. */
#include <OS2.H>
main()
{
  /* Hook Procedure Prototype */

BOOL MsgControlHook(HAB hab,LONG  idContext,     /* this hook can */
           HWND hwnd, PSZ pszClassname,      /* be given any */
           ULONG  ulMsgclass,                /* name.           */
           LONG  idControl, PBOOL fSuccess);
HWND hwnd;
HAB hab;
BOOL fSuccess;


/* This function passes the hook procedure address to the system. */

WinSetHook(hab,
          (HMQ)0,
          MCHK_CLASSMSGINTEREST,
          (PFN)MsgControlHook,
          (HMODULE)0); /* hook is into application queue. */

 /*
 This function sets the message interest of a window class.
 */
WinSetClassMsgInterest(hab,
                       WC_MENU,   /* menu window class.           */
                       SMIM_ALL,  /* set interest level for all */
                                  /* messages.                    */
                       SMI_AUTODISPATCH); /* interested in the */
                                  /* messages, but they are to  */
                                  /* be automatically dispatched */
                                  /* to the window procedure.    */
}
/*
 This hook allows the call which determine the flow of messages to be
 intercepted. It must be present for the WinSetClassMsgInterest
 call to have an effect.
*/

BOOL MsgControlHook(HAB hab,LONG  idContext,     /* this hook can */
           HWND hwnd, PSZ pszClassname,      /* be given any */
           ULONG  ulMsgclass,                /* name.           */
           LONG  idControl, PBOOL fSuccess)
{
/* ... */
}
</PRE>

==Related Messages==
* [[WM_QUIT]]

==Related Functions==
* [[WinBroadcastMsg]]
* [[WinCreateMsgQueue]]
* [[WinDestroyMsgQueue]]
* [[WinDispatchMsg]]
* [[WinGetDlgMsg]]
* [[WinGetMsg]]
* [[WinInSendMsg]]
* [[WinPeekMsg]]
* [[WinPostMsg]]
* [[WinPostQueueMsg]]
* [[WinQueryMsgPos]]
* [[WinQueryMsgTime]]
* [[WinQueryQueueInfo]]
* [[WinQueryQueueStatus]]
* [[WinSendDlgItemMsg]]
* [[WinSendMsg]]
* [[WinSetMsgInterest]]
* [[WinSetMsgMode]]
* [[WinSetSynchroMode]]
* [[WinWaitMsg]]
[[Category:Win]]