Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!usc!apple!well!brecher
From: brecher@well.sf.ca.us (Steve Brecher)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Need help with bitmaps
Message-ID: <16625@well.sf.ca.us>
Date: 12 Mar 90 02:47:11 GMT
References: <101780003@hpcvlx.cv.hp.com>
Reply-To: brecher@well.sf.ca.us (Steve Brecher)
Organization: Software Supply, Sunnyvale, CA
Lines: 40


In article <101780003@hpcvlx.cv.hp.com>, billf@hpcvlx.cv.hp.com (Bill F.
Faus) writes:
> Can someone give me a mimimal program that illustrates how a bit map
> (say a simple rectangle 2 bytes wide and 100 bytes tall) is put onto
> screen...
> 
> Which command actually writes to the screen?  Is it SetPortBits, or is
> it CopyBits?  Can bitmaps be displayed without the use of windows?
> 
>     char       Blob[200];
>  ...
>     SetRect(&myBlob.bounds, 100, 100, 200, 102);

You're on the right track.  CopyBits can write to the screen, if the
destination BitMap (or PixMap -- IM vol. V) coincides with (part of) the
screen.  SetPortBits just alters the current grafPort data structure; it
does not draw.  BitMaps can displayed without the use of windows, but
you almost never would do that in a real application since the area
outside of your windows is "owned" by system software.  For your
experiments, though, you can draw wherever you want!

You want to think in terms of pixels, not bytes.  The rectangle you
want is 16 pixels wide and 100 pixels tall.  Also note that the
coordinate arguments to SetRect (L,T,R,B) are not in the same order
as the fields of a Rect (T,L,B,R).  Hence, your SetRect should be

SetRect(&myBlob.bounds, 100, 100, 116, 200);

> CopyBits(&myBlob, &myPort.portBits, &myBlob.bounds, &myPort.portRect, 
>          srcCopy, 0L);

Given the change to SetRect, this will draw on the screen.  But, since
CopyBits scales the drawing to fit the destination rectangle, it will
draw a much larger area than you intend.  To draw a 16x100 rectangle,
you will need to change the dstRect argument to such a rectangle, e.g.,
by making it the same as the srcRect argument.
-- 

brecher@well.sf.ca.us (Steve Brecher)