Help from the Mouse - Win32 Programmer's Reference (win32.hlp)

Help from the Mouse

Windows provides user access to help information from the mouse by notifying the application whenever the user clicks the right mouse button or clicks a window, control, or menu after clicking the Question (?) button. The application responds by displaying help information associated with the given window, control, or menu.

The system sends a WM_CONTEXTMENU message when the user clicks the right mouse button. The window that was clicked receives the message. If the window is a child window, such as a control, the DefWindowProc function passes the message to the parent window. The WM_CONTEXTMENU message specifies the coordinates of the mouse cursor. The x-coordinate is in the low-order word of the lParam parameter, and the y-coordinate is in the high-order word. If the user clicked a control, the wParam parameter is the handle of the control that received the button click.

The system sends a WM_HELP message when the user clicks an item in a window after clicking the Question (?) button that appears in the title bar of the window. You can add a Question button to a title bar by specifying the WS_EX_CONTEXTHELP style in the CreateWindowEx function when creating the window. The lParam parameter of WM_HELP is a pointer to a HELPINFO structure that contains detailed information about the item for which help is requested, including the coordinates of the mouse cursor at the time the user clicked the mouse button.

The Question button is recommended for use in dialog boxes only. In the past, applications have provided user access to help information about a dialog box by providing a Help button in the dialog box. This method is no longer recommended. Use the Question button instead.

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