UpdtControl
UpdtControl Draw all controls in specified region [128K ROMs]
#include <Controls.h> Control Manager
void UpdtControl( theWindow, theRgn );
WindowPtr theWindow ; window owning controls needing update
RgnHandle theRgn ; region of window to update
UpdtControl is a more efficient version of DrawControls. It draws only
those controls intersecting a specified region - typically the visRgn of the
window's port. This should have been named "UpdtControls".
theWindow is a pointer to a 108-byte GrafPort structure (actually a 156-byte
WindowRecord). It is typically a value obtained from
EventRecord. message after calling WaitNextEvent.
theRgn is a handle leading to a variable-length Region structure. Controls
having contrlRects that intersect this region are drawn. Typical
usage is to pass the visRgn of theWindow .
Returns: none

Notes: For the 128K ROMs and later, UpdtControl is the preferred method for
drawing controls after detecting an update event. A typical usage is:
UpdtControl( updtWin, updtWin -> visRgn );
Where "updtWin" is the value of message in an update EventRecord. This
sequence would replace the call to DrawControls in the example listed
under that topic. It is normally surrounded by BeginUpdate and