DefDlgProcW function (winuser.h)

Article
02/22/2024

Calls the default dialog box window procedure to provide default processing for any window messages that a dialog box with a private window class does not process.

Syntax

LRESULT LRESULT DefDlgProcW(
  [in] HWND   hDlg,
  [in] UINT   Msg,
  [in] WPARAM wParam,
  [in] LPARAM lParam
);

Parameters

[in] hDlg

Type: HWND

A handle to the dialog box.

[in] Msg

Type: UINT

The message.

[in] wParam

Type: WPARAM

Additional message-specific information.

[in] lParam

Type: LPARAM

Additional message-specific information.

Return value

Type: LRESULT

The return value specifies the result of the message processing and depends on the message sent.

Remarks

The DefDlgProc function is the window procedure for the predefined class of dialog box. This procedure provides internal processing for the dialog box by forwarding messages to the dialog box procedure and carrying out default processing for any messages that the dialog box procedure returns as FALSE. Applications that create custom window procedures for their custom dialog boxes often use DefDlgProc instead of the DefWindowProc function to carry out default message processing.

Applications create custom dialog box classes by filling a WNDCLASS structure with appropriate information and registering the class with the RegisterClass function. Some applications fill the structure by using the GetClassInfo function, specifying the name of the predefined dialog box. In such cases, the applications modify at least the lpszClassName member before registering. In all cases, the cbWndExtra member of WNDCLASS for a custom dialog box class must be set to at least DLGWINDOWEXTRA.

The DefDlgProc function must not be called by a dialog box procedure; doing so results in recursive execution.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll