Keyboard Handling for Controls

A control responds to keyboard accelerators so the end-user can initiate actions performed by the control. The container manages keyboard activity for all its embedded controls. With compound documents, keyboard accelerators apply only to the currently active object. With controls, a mechanism has been added so that a control can respond to its keyboard mnemonics even if it is not currently UI-active.

The IOleControl::GetControlInfo and IOleControl::OnMnemonic methods and the IOleControlSite::OnControlInfoChanged method handle a control's keyboard mnemonics. A CONTROLINFO structure describes a control's mnemonic accelerators, and the flags passed back with it through the GetControlInfo method describe the controls behavior with the Enter and Esc keys. When a control changes its mnemonics, it calls OnControlInfoChanged so the container can reload the structure if necessary.

When a control is UI active, it is also the control with the focus. As controls are activated and deactivated between the in-place active and the UI active states, the control calls IOleControlSite::OnFocus to tell the container of such changes.

In addition, when a control is UI active, it will have first chance to process any keystrokes. To give a container the opportunity to process the keystroke before the control, the control calls IOleControlSite::TranslateAccelerator. If the container does not handle the keystroke, the control then processes it.

Related topics

ActiveX Controls