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
|
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. |
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.
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.