Inside Macintosh: Mac OS 8 Toolbox Reference /

Chapter 2 - Control Manager Reference / Control Manager Functions

Defining Your Own Action Functions

When your action function is called for a control part, your action function is passed a handle to the control and the control's part code. Your action function should then respond as is appropriate. For an example of such an action function, see MyActionProc. The only exception to this is for indicators that don't support live feedback.

If the mouse-down event occurs in an indicator of a control that does not support live feedback, your action function should take no parameters, because the user may move the cursor outside the indicator while dragging it. For an example of such an action function, see MyIndicatorActionProc.