The SetCaretPos function is an example of a system function you can use to indicate focus location. For more information about this function, see the documentation included in the Win32 SDK.
Many accessibility aids must follow where the user is working. For example, a screen review utility conveys to users where the input focus is; a screen enlarger pans its viewport to ensure that users' focus is always kept on the visible portion of the screen. Most utilities give users the ability to manually move the viewport, but this becomes a laborious process, especially if it has to be repeated each time the input focus moves.
When the system handles the move of the input focus, such as when the user selects a menu, navigates between controls in a dialog box, or activates a window, an accessibility utility can track the change. However, the utility may not detect when an application moves the input focus within its own window. Therefore, whenever possible, use standard system functions to place the input focus, such as the text insertion point. Even when you provide your own implementation of focus, you can use the system functions to indicate focus location without making the standard input focus indicator visible.
Note
The SetCaretPos function is an example of a system function you can use to indicate focus location. For more information about this function, see the documentation included in the Win32 SDK.