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From: urlichs@smurf.sub.org (Matthias Urlichs)
Newsgroups: comp.sys.mac.programmer
Subject: Re: An itsy bitsy question...
Message-ID: <hf"2h2."b2@smurf.sub.org>
Date: 7 Jan 91 20:16:29 GMT
References: <La6cV1w164w@questor.wimsey.bc.ca> <27725.2787e3d0@kuhub.cc.ukans.edu>
Organization: University of Karlsruhe, FRG
Lines: 57

In comp.sys.mac.programmer, article <27725.2787e3d0@kuhub.cc.ukans.edu>,
  mlab2@kuhub.cc.ukans.edu writes:
< 
< When in line-drawing-mode, a mouseDown event in the drawing window should call
< a procedure similar to the below:
< 
Modify at will for drawing other shapes, of course...

I'd suggest some enhancements:
- drawing the rubberbanded line in gray
  (QD pattern for monochrome Macs, real gray for Color QD)
- drawing only when the mouse position has changed
- autoscrolling the new endpoint into the window
- invalidating the old line rather than simply erasing it;
  there might be other shapes behind it.

This will make the routine slightly more complicated, of course, but all the
add-ons should already be present in your program anyway. ;-)

< procedure RubberBand;
<   var
<     originalPt, lastPt, newPt : Point;
< begin
<   GetMouse(originalPoint);
<   PenMode(patXOr);
    PenPat(gray);
    (* you might also want to make the pen bigger, maybe one point bigger
       than the line you're drawing, so that it doesn't tend to vanish
       for near-45 degree angles *)
<   GetMouse(lastPt);
<   MoveTo(originalPt.h, originalPt.v);
<   LineTo(lastPt.h, lastPt.v);
<   repeat
     GetMouse(newPt);
     if newPt <> lastPt then begin
<     MoveTo(originalPt.h, originalPt.v);
<     LineTo(lastPt.h, lastPt);
<     (* GetMouse(newPt); *)
      ScrollIntoView(newPt);
      UpdateWindow;
<     MoveTo(originalPt.h,originalPt.v);
<     LineTo(newPt.h, newPt.v);
<     lastPt:=newPt;
     end;
<   until (not Button);
<   PenNormal;
    PenPat(black);
    (* reset pen size? *)
    MoveTo(originalPt.h, originalPt.v);
    LineTo(lastPt.h, lastPt.v);
    (* now erase and invalidate the location of the old line as there might
       have been bits behind it, probably by calling Pt2Rect and InvalRect *)
< end; 

-- 
Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de     /(o\
Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(0700-2330)   \o)/