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From: smoke@well.sf.ca.us (Nicholas Jackiw)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Arrowheads anyone?
Message-ID: <23497@well.sf.ca.us>
Date: 8 Mar 91 18:25:33 GMT
References: <2867@krafla.rhi.hi.is> <1991Mar5.190538.778@csn.org>
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 51

In article <1991Mar5.190538.778@csn.org> bernard@cs.colorado.edu (Bernie Bernstein) writes:
> * ArrowPoints
>I wrote this in Think C a long time ago.  I would be interested in hearing
>from others who have faster ways to do this.
>      o,  ,,   ,      | Bernie Bernstein                      | ,    ,,

This Pascal frag cuts down on all the trig (or rather, delegates it
to the Toolbox):

 procedure DrawArrow (fromPt, toPt: Point);

{Given two points, DrawArrow draws an arrowhead pointing to toPt.}
{The pixel-length of the arrowhead is specified by ELineInset.}

const ELineInset=10;
  var
   myAngle, dX, dY: integer;
   aRect: Rect;

 begin

  with fromPt do
   begin
    with aRect do
     begin
      left := h - 100;
      top := v - 100;
      right := h + 100;
      bottom := v + 100
     end;
    PtToAngle(aRect, toPt, myAngle)
   end;

  with toPt do
   with aRect do
    begin
     dX := ELineInset;
     top := v - dX;
     right := h + dX;
     bottom := v + dX;
     left := h - dX;
    end;

  PaintArc(aRect, (myAngle + 180) - 24, 49)  ; Total Arrow Arc=50 degrees
 end;

-- 
                              --- * ---
Nicholas Jackiw                Smoke@well.sf.ca.us | Jackiw@cs.swarthmore.edu
Key Curriculum Press, Inc.     Applelink: D3970    | (415) 548-2304
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