[comp.sys.mac.programmer] What would I use ShieldCursor for?

KPURCELL@LIVERPOOL.AC.UK (09/14/90)

I was browsing IM 1 yesterday and came across ShieldCursor() for the first
time (I had not noticed it before). Like all new calls I try to think
what it would be useful for, where I my use it in an application. After
some thought I couldn't come up with any idea of what it would be used
for. So I asked a fellow Mac programmer at the university today, and
after reading the discription through a couple of times he couldn't think
of a use either.

ShieldCursor is defined in the following manner (no IM to hand so this
is a paraphrase):

ShieldCursor(r: Rect; p: Point); IM I 474

If p is in r then the cursor is hidden else if the cursor is stationary
the cursor is hidden when the mouse if moved.

Could somebody give me a suggestion?

Anybody know if it is used in an application I might easily see?

Email or post here.

Kevin Purcell          | kpurcell@liverpool.ac.uk
Surface Science,       |
Liverpool University   | Programming the Macintosh is easy if you understand
Liverpool L69 3BX      | how the Mac works and hard if you don't. -- Dan Allen

wolf@mel.cipl.uiowa.edu (09/16/90)

ShieldCursor would be used if you had a text section and wanted the cursor
hidden while the user was entering text (no need to have it around at that time
possibly).

Or if you were about to do a screen dump and didn't want the cursor to obscure
details of the image.

Or maybe it is an action arcade stile game and you don't need a cursor getting
in the way of the animation until needed (or even during a sequence of images
for a movie perhaps)

Just a few thoughts.

M Wolf

lippin@ragu.berkeley.edu (The Apathist) (09/16/90)

I suspect that ShieldCursor is mainly intended for internal use by the
toolbox: it can be called by QuickDraw to get the cursor out of the
way before writing to the screen.  (For unknown reasons, QD even does
this when drawing to offscreen bitmaps.  Go figure.)  If you want to
write on the screen without smashing the cursor, use it.  Remember
to account for the height and width of the cursor when you do.

For household use, however, ShowCursor, HideCursor, and ObscureCursor
are all you need.

					--Tom Lippincott
					  lippin@math.berkeley.edu

		"It's a multi-purpose shape: a box."
					--David Byrne, "True Stories"

lsr@Apple.COM (Larry Rosenstein) (09/17/90)

In article <1990Sep15.171403.1@mel.cipl.uiowa.edu> wolf@mel.cipl.uiowa.edu writes:
>ShieldCursor would be used if you had a text section and wanted the cursor
>hidden while the user was entering text (no need to have it around at that time

Nope, that's what ObscureCursor is for.

ShieldCursor is used to hide the cursor in case it might interfere with
somthing going on with the screen.  For example, all QuickDraw operations
involving the screen call ShieldCursor with the bounding box of the graphics operation.

The only time you would call ShieldCursor yourself is if you were
reading/writing the screen directly without using QuickDraw, which is
usually not a good idea.

-- 
		 Larry Rosenstein,  Object Specialist
 Apple Computer, Inc.  20525 Mariani Ave, MS 46-B  Cupertino, CA 95014
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