The WM_COMMAND message is 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.
WM_COMMAND
wNotifyCode = HIWORD(wParam); // notification code
wID = LOWORD(wParam); // item, control, or accelerator identifier
hwndCtl = (HWND) lParam; // handle of control
Parameters
wNotifyCode
Value of the high-order word of wParam. Specifies the notification code if the message is from a control. If the message is from an accelerator, this parameter is 1. If the message is from a menu, this parameter is 0.
wID
Value of the low-order word of wParam. Specifies the identifier of the menu item, control, or accelerator.
hwndCtl
Value of lParam. Identifies the control sending the message if the message is from a control. Otherwise, this parameter is NULL.
Return Values
If an application processes this message, it should return zero.
Remarks
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.
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.
See Also