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From: atchison@hpindda.HP.COM (Lee Atchison)
Newsgroups: comp.sys.mac
Subject: Need help with drawing icons
Message-ID: <6500008@hpindda.HP.COM>
Date: 19 Jan 88 18:25:32 GMT
Organization: HP Information Networks, Cupertino, CA
Lines: 83

Hi!  I have a programming question.  I've tried looking in IM, but it
doesn't seem to give me the help I am looking for.

What I am trying to do is draw icons, invert them (using the icon mask,
like the finder does), and erase them.  I want to be able to do this both
in a window and on the desktop (like the disk icons, and the trashcan
in the finder).

The routine DrawIcon (I think that is what it is called, I don't have IM
handy) doesn't help, as it assumes a white background when it draws the icon
(the icon square is drawn white as well as the icon itself, ie. it uses a
srcCopy transfer mode).

I have tried the following routine to draw an icon in a window, and this
works fine:

    port:GrafPtr;
    pos:Rect; { location to draw icon }

    GetPort(port);
    CopyBits(myicon.iconmask,port^.portBits,
	     myicon.iconmask.bounds,pos,
	     SrcBic,Nil);  { clears mask space for icon }
    CopyBits(myicon.icon,port^.portBits,
	     myicon.icon.bounds,pos,
	     SrcOr,Nil);   { draw icon }

and this to invert the icon:

    GetPort(port);
    CopyBits(myicon.iconmask,port^.portBits,
	     myicon.iconmask.bounds,pos,
	     SrcXor,Nil);  { invert the icon }

Both of these work fine in a window.  I simply use EraseRect to erase the icon.
Is this the best way to do this?  Will this work on all Macs?

Now, for drawing on the desktop, I used the following:

    CopyBits(ScreenBits,myicon.hold,
	     pos,myicon.hold.bounds,
	     SrcCopy,Nil);  { save a copy of the background at this point }
    CopyBits(myicon.iconmask,ScreenBits,
	     myicon.iconmask.bounds,pos,
	     SrcBic,Nil);   { clear mask for icon }
    CopyBits(myicon.icon,ScreenBits,
	     myicon.icon.bounds,pos,
	     SrcOr,Nil);    { draw icon }

My EraseIcon is:

    CopyBits(myicon.hold,ScreenBits,
	     myicon.hold.bounds,pos,
	     SrcCopy,Nil);  { restore background at this point }

My InvertIcon is the same as the invericon for in a window.

Now, these routines work fine UNTIL I start having an overlapping window.
Then these routines fail.  If I draw an icon that is supposedly hidden (either
partially or completely) by a window, the icon draws on top of the window.

Obviously, my problem is that I shouldn't be using ScreenBits, but what should
I use instead?

Now the real question.  Is this the way I'm suppose to do it?  Will this work
on all Macs?  Will this work under (gulp) Multifinder?  Am I allowed to write
on the desktop AT ALL under Multifinder?  Am I conforming to the Macintosh
Guidelines correctly?

A related question.  How to I know when I need to update these icons stored
on the desktop?  Obviously, I don't get an update event for the desktop, but
there has to be someway.  I've thought about updating anytime a window was
moved, or anytime one of my windows became active.  The later will allow me
to redraw these icons after coming back from a DA (or another application
under MultiFinder).  Is there a better or more complete way of doing this?

Thanks in advance for any help you can give to me.

			-lee
--------------
Lee Atchison
Hewlett Packard, Information Networks Division
atchison%hpindda@hplabs.hp.com