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From: chiu@princeton.UUCP (Kenneth Chiu)
Newsgroups: net.micro.amiga
Subject: clearing a window
Message-ID: <1964@princeton.UUCP>
Date: Sun, 12-Oct-86 00:39:56 EDT
Article-I.D.: princeto.1964
Posted: Sun Oct 12 00:39:56 1986
Date-Received: Sun, 12-Oct-86 13:27:18 EDT
Reply-To: chiu@princeton.UUCP (Kenneth Chiu)
Distribution: net
Organization: Princeton University Computer Science Department
Lines: 54


Is there a simple, efficient, reliable way to clear a window?  What I did was
something like this:

	pen = window->RPort->FgPen;
	mode = window->RPort->DrawMode;

	SetAPen(window->RPort, 0L);
	SetDrMd(window->RPort, JAM1);

	xmin = window->BorderLeft;
	ymin = window->BorderTop;
	xmax = window->Width - window->BorderRight - 1;
	ymax = window->Height - window->BorderBottom - 1;

	RectFill(window->RPort, xmin, ymin, xmax, ymax);

	window->RPort->FgPen = pen;
	window->RPort->DrawMode = mode;

Now, as I understand the manual, the RectFill function doesn't use any of the
fancy area fill data structures (like AreaInfo, or TmpRas), so I don't have to
worry about these.  The only thing wrong with this fragment is that the
AreaPtrn is NOT guaranteed to be all 1's, am I correct?  So if I save the
AreaPtrn information, do SetAfPt, then the Rectfill, and restore the AreaPtrn
information, then will this be robust?

But do I need to save and restore any of the old information at all?  In other
words, does Intuition expect that nobody will change this data, or does it
reset it everytime it does something?  (Will it possibly "lose" the AreaPtrn
array somewhere in my measly 512K?)

Lastly, I don't quite understand the intention of the Designers with regard
to some of these functions.  More specifically, is it necessary, or even
desireable to use SetAPen(rp, color) instead of rp->FgPen = color.  Some
of the "functions" are implemented as macros (e.g. SetAfPt).  SetAPen seems
to be a function, however, since I can't find it in any of the graphics
include files.  Perhaps they want us to use these functions/macros to maintain
compatibility, but they haven't provided a complementary set of
functions/macros to extract the information.

What I really want to do is to refresh a window's gadgets.  RefreshGadgets
redraws them, and RemoveGadget takes them out of the list, but no function
seems to >erase< the ones that are no longer.  So I am resorting to clearing
the window and then calling RefreshGadgets.  Alternativeely, if I could find
some way to redraw a window's borders and system gadgets, then I could use
SetRast, which is probably fast as lightning.  Perhaps I can't see the forest
for the trees, and there is some really easy way to do this.  Surely other
people have wanted to do this same thing.

Hope I have not been too verbose.
-- 
Kenneth Chiu                                              UUCP: princeton!chiu
Princeton University Computer Science Department        BITNET: 6031801@PUCC