View source for WM CONTROL

This message occurs when a control has a significant event to notify to its owner.

==Syntax==
<PRE>
param1
     USHORT  id             /*  Control-window identity. */
     USHORT  usnotifycode   /*  Notify code. */

param2
     ULONG   ulcontrolspec  /*  Notify control-specific information. */
</PRE>

;in Combination Boxes
<PRE>
param1
     USHORT  usid             /*  Control window identity. */
     USHORT  usnotifycode     /*  Notify code. */

param2
     HWND    hwndcontrolspec  /*  Combination (combo) window handle. */
</PRE>

;in Container Controls

<PRE>
 For the cause of this message, see WM_CONTROL.

param1
     USHORT  id          /*  Container control ID. */
     USHORT  notifycode  /*  Notify code. */

param2
     ULONG   notifyinfo  /*  Notify code information. */

</PRE>

;in Entry Fields
<PRE>
param1
     USHORT  id               /*  Control window identity. */
     USHORT  usnotifycode     /*  Notify code. */

param2
     HWND    hwndcontrolspec  /*  Entry field control window handle. */
</PRE>

==Parameters==
===Default===
;id (USHORT)
:Control-window identity.
:This is either the parameter of the WinCreateWindow function or the identity of an item in a dialog template. 

;usnotifycode (USHORT)
:Notify code.
:The meaning of the notify code depends on the type of the control. For details, refer to the section describing that control. 

:;CSN_SETFOCUS

::This code returns a Boolean indicating whether the circular slider control sending the notification message is gaining or losing the focus.

::param2 contains TRUE if the control is gaining the focus. 

:;CSN_CHANGED

::This code is sent to notify the application that the circular slider value has been changed.

::param2 contains the new value of the circular slider. 

:;CSN_TRACKING

::This code is sent to notify the application that the circular slider is being tracked by the mouse.

::param2 contain the inter-media value of the circular slider.

::Inter-media values are not necessarily contiguous. 

:;CSN_QUERYBACKGROUNDCOLOR
::This code gives the application the opportunity to set the background color of the circular slider. CLR_* or SYSCLR_* values can be returned for the background color.
::param2 is NULL.

;ulcontrolspec (ULONG)
:Control-specific information.
:The meaning of the control-specific information depends on the type of the control. For details, refer to the section describing that control. 

===in Combination Boxes===
;usnotifycode (USHORT)
:Notify code.

    CBN_EFCHANGE
        The content of the entry field control has changed, and the change has been displayed on the screen. 

CBN_MEMERROR
        The entry field control cannot allocate the storage necessary to accommodate window text of the length implied by the EM_SETTEXTLIMIT message. 

CBN_EFSCROLL
        The entry field control is about to scroll horizontally. This can happen in these circumstances:

            The application has issued a WinScrollWindow call. 
                The content of the entry field control has changed. 
                The caret has moved. The entry field control must scroll to show the caret position. 

CBN_LBSELECT
::An item in the list box control has been selected. 

CBN_LBSCROLL
::The list box is about to scroll. 

CBN_SHOWLIST
::The list box is about to be displayed. 

CBN_ENTER
::The user has depressed the ENTER key or double clicked (single clicked in the case of a drop-down list) on an item in the list box control. 

;hwndcontrolspec (HWND)
:Combination (combo) window handle.

===in Container Controls===

;id (USHORT)
:Container control ID. 

;notifycode (USHORT)
:Notify code.

:The container control uses the following notification codes. For the complete description of the specified notifycode, see Container Control Notification Codes.

:;CN_BEGINEDIT
        Container text is about to be edited. 
:;CN_COLLAPSETREE
        A parent item was collapsed in the tree view. 
:;CN_CONTEXTMENU
        The container received a WM_CONTEXTMENU message. 
:;CN_DRAGAFTER
        The container received a DM_DRAGOVER message. The CN_DRAGAFTER notification code is sent only if either the CA_ORDEREDTARGETEMPH or CA_MIXEDTARGETEMPH attribute of the CNRINFO data structure is set and the current view is the name, text, or details view. 
:;CN_DRAGLEAVE
        The container received a DM_DRAGLEAVE message. 
:;CN_DRAGOVER
        The container received a DM_DRAGOVER message. The CN_DRAGOVER notification code is sent only if the CA_ORDEREDTARGETEMPH attribute of the CNRINFO data structure is not set or the current view is the icon view or tree view. 
:;CN_DROP
        The container received a DM_DROP message. 
:;CN_DROPNOTIFY
        The container received a DM_DROPNOTIFY message. 
:;CN_DROPHELP
        The container received a DM_DROPHELP message. 
:;CN_EMPHASIS
        A container record's attributes changed. 
:;CN_ENDEDIT
        Direct editing of container text has ended. 
:;CN_ENTER
        The Enter key is pressed while the container window has the focus, or the select button is double-clicked while the pointer is over the container window. 
:;CN_EXPANDTREE
        A parent item is expanded in the tree view. 
:;CN_GRIDRESIZED
        The grid was resized. This means there are more or fewer squares than previously, and all the squares are now marked CM_AVAIL. CN_HELP
        The container received a WM_HELP message. 
:;CN_INITDRAG
        The drag button was pressed and the pointer was moved while the pointer was over the container control. 
:;CN_KILLFOCUS
        The container is losing the focus. 
:;CN_PICKUP
        The container received a WM_PICKUP message. 
:;CN_QUERYDELTA
        Queries for more data when a user scrolls to a preset delta value. 
:;CN_REALLOCPSZ
        Container text is edited. This message is sent before the CN_ENDEDIT notification code is sent. 
:;CN_SCROLL
        The container window scrolled. 
:;CN_SETFOCUS
        The container is receiving the focus. 

;notifyinfo (ULONG)
:Notify code information.
:For the definition of this parameter, see the description of the specified notifycode in Container Control Notification Codes.

===in Entry Fields===
;id (USHORT)
:Control window identity. 

;usnotifycode (USHORT)
:Notify code.

:;EN_CHANGE
        The content of the entry field control has changed, and the change has been displayed on the screen. 
:;EN_KILLFOCUS
        The entry field control is losing the focus. 
:;EN_MEMERROR
        The entry field control cannot allocate the storage necessary to accommodate window text of the length implied by the EM_SETTEXTLIMIT message. 
:;EN_OVERFLOW
        The entry field control cannot insert more text than the current text limit. The text limit may be changed with the EM_SETTEXTLIMIT message.

        If the recipient of this message returns TRUE, then the entry field control retries the operation, otherwise it terminates the operation. 

:;EN_SCROLL
        The entry field control is about to scroll horizontally. This can happen in these circumstances:

            The application has issued a WinScrollWindow call �
                The content of the entry field control has changed �
                The caret has moved �
                The entry field control must scroll to show the caret position. 
:;EN_SETFOCUS
                The entry field control is receiving the focus. 

;hwndcontrolspec (HWND)
:Entry field control window handle.

==Returns==
;ulReserved (ULONG)
:Reserved value, should be 0.

==Remarks==
This message is sent to the owner of the control, thereby offering it the opportunity to perform some activity before returning to the control. 

;in Circular Slider Controls
:The circular slider control window procedure generates this message and sends it to its owner, informing the owner of this event.

;in Combination Boxes
:The entry field control window procedure generates this message and sends it to its owner, informing the owner of the event. 

;in Container Controls
:The container control window procedure generates this message and sends it to its owner, informing the owner of this event. 

==Default Processing==
The default window procedure takes no action on this message, other than to set ulReserved to 0. 

==Related Messages==