Help from the Keyboard

Windows provides user access to help information from the keyboard by notifying the application whenever the user presses the F1 key. The system sends WM_HELP to the window that has the keyboard focus when the user presses the F1 key. If the window is child window (for example, a control in a dialog box), the DefWindowProc function passes the message to the parent window. If a menu is active when F1 is pressed, the system sends the message to the window associated with the menu. The application responds by displaying help information associated with the window, control, or menu that has the focus or is active. For example, if the user selects a control in a dialog box and presses F1, the application displays help information for that control.

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. You use this information to determine the help topic to display. The HELPINFO structure also includes the coordinates of the mouse cursor at the time the user pressed the F1 key. You can use this information to provide help based on the location of the mouse cursor.

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