Common controls, custom controls, and their parent windows use the WM_NOTIFYFORMAT message to determine whether the control should use ANSI or Unicode structures in the WM_NOTIFY notification messages that the control uses to communicate with its parent window. WM_NOTIFYFORMAT messages are sent from a control to its parent window, and from the parent window to the control.
hwndFrom = (HWND) wParam; // handle of the window sending this message
Command = lParam; // command value specifying the nature of this message
Parameters
hwndFrom
Value of wParam. Handle of the window that is sending the WM_NOTIFYFORMAT message. If Command is NF_QUERY, hwndFrom is the handle of a control. If Command is NF_REQUERY, this is the handle of the parent window of a control.
Command
Value of lParam. A command value that specifies the nature of the WM_NOTIFYFORMAT message. The following values are defined:
| Value | Meaning |
| NF_QUERY | The message is a query to determine whether ANSI or Unicode structures should be used in WM_NOTIFY messages. This command is sent from a control to its parent window. This command is sent during the creation of a control, and in response to an NF_REQUERY command. |
| NF_REQUERY | The message is a request that a control send an NF_QUERY form of this message to its parent window. This command is sent from a control's parent window to the control. The parent window is asking the control to requery it about the type of structures to use in WM_NOTIFY messages. |
Return Values
The return value is one of the following :
| Value | Meaning |
| NFR_ANSI | ANSI structures should be used in WM_NOTIFY messages sent by the control. |
| NFR_UNICODE | Unicode structures should be used in WM_NOTIFY messages sent by the control. |
| 0 | An error occurred. |
If Command is NF_REQUERY, the return value is the result of the requery operation.
Remarks
When a common control is created, the control sends a WM_NOTIFYFORMAT message to its parent window to determine the type of structures to use in WM_NOTIFY messages. If the parent window does not handle this message, the DefWindowProc function responds according to the type of the parent window. That is, if the parent window is a Unicode window, DefWindowProc returns NFR_UNICODE, and if the parent window is an ANSI window, DefWindowProc returns NFR_ANSI. If the parent window is a dialog box and does not handle this message, the DefDlgProc function similarly responds according to the type of the dialog box (Unicode or ANSI).
A parent window can change the type of structures a common control uses in WM_NOTIFY messages by setting lParam to NF_REQUERY and sending a WM_NOTIFYFORMAT message to the control. This causes the control to send an NF_QUERY form of the WM_NOTIFYFORMAT message to the parent window.
See Also