WM_COMMAND message

Article
2021-03-22

Sent when the user selects a command item from a menu, when a control sends a notification message to its parent window, or when an accelerator keystroke is translated.

#define WM_COMMAND                      0x0111

Parameters

wParam: For a description of this parameter, see Remarks.
lParam: For a description of this parameter, see Remarks.

Return value

If an application processes this message, it should return zero.

Example

BOOL AboutDlg (
    HWND hDlg, 
    UINT message, 
    WPARAM wParam, 
    LPARAM lParam)
{
    BOOL bRet = FALSE;
    
    switch (message) 
    {
        case WM_INITDIALOG:
            bRet = TRUE;
            break;

        case WM_COMMAND:
            if (wParam == IDOK ||
                wParam == IDCANCEL) 
            {
                EndDialog(hDlg, TRUE);
                bRet = TRUE;
            }
            break;
    }

    return bRet;
}

Example taken from Windows classic samples on GitHub.

Remarks

Use of the wParam and lParam parameters are summarized here.

Message Source	wParam (high word)	wParam (low word)	lParam
Menu	0	Menu identifier (IDM_*)	0
Accelerator	1	Accelerator identifier (IDM_*)	0
Control	Control-defined notification code	Control identifier	Handle to the control window

Menus

If an application enables a menu separator, the system sends a WM_COMMAND message with the low-word of the wParam parameter set to zero when the user selects the separator.

If a menu is defined with a MENUINFO.dwStyle value of MNS_NOTIFYBYPOS, WM_MENUCOMMAND is sent instead of WM_COMMAND.

Accelerators

Accelerator keystrokes that select items from the window menu are translated into WM_SYSCOMMAND messages.

If an accelerator keystroke occurs that corresponds to a menu item when the window that owns the menu is minimized, no WM_COMMAND message is sent. However, if an accelerator keystroke occurs that does not match any of the items in the window's menu or in the window menu, a WM_COMMAND message is sent, even if the window is minimized.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Winuser.h (include Windows.h)

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