There are so many tag options available with screens it can be a bit
overwhelming.  Before discussing more details, it may be helpful to look
at a simple example.  The code below opens a new, custom screen using the
openscreentags() call.  the example uses just two tag items (sa_depth and
sa_pens) which provide the minimum attributes needed to make a screen that
uses the new 3D look of Intuition available in Release 2.  (See the
section on "drawinfo and the 3d look" below for more information.)

     newlookscreen.c 

The example above runs only under Release 2 (V36) and later versions of
the OS.  To make a custom screen that works under both release 2 and
earlier versions of the operating system, use the original openscreen()
function.

The newscreen structure used with openscreen() has been extended with a
tag list in V36 to form an extnewscreen.  this is done by setting the
NS_EXTENDED bit in the Type field of the NewScreen structure and adding a
pointer to an array of tags to the end of the structure.  The NS_EXTENDED
bit is ignored in older versions of the operating system, so the tags can
be transparently added to existing applications and the features will
appear when executed in a system running V36 or greater.  See the
openscreen() autodocs and the include file <intuition/screens.h> for more
information on NS_EXTENDED and the ExtNewScreen structure.