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From: jackiw@cs.swarthmore.edu (Nick Jackiw)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Arrows at the end of lines...
Message-ID: <Q33N0BC@cs.swarthmore.edu>
Date: 16 Aug 90 15:38:22 GMT
References: <1320@sirius.ucs.adelaide.edu.au>
Reply-To: jackiw@cs.swarthmore.edu (Nick Jackiw)
Organization: Visual Geometry Project, Swarthmore College, PA
Lines: 58

legg@sirius.ucs.adelaide.edu.au (Christian Legg) writes:
> 
>   Hello fellow programmers.
> 
>   I'd like to be able to draw arrow heads on the end of lines, just as
> Mac Draw allows one to do. 

Try this.

  procedure DrawArrow (fromPt, toPt: Point);

{By Nick Jackiw}

{Given two quickdraw points, DrawArrow draws an arrowhead pointing to toPt}
{in the direction facing away from fromPt.}

const
 ArrowShaftLength=10;	{How many pixels "long" the arrow-head is}
 ArrowHeadWidth=49;     {# of degrees "wide" the arrow-head is...should be odd}

   var
    myAngle, dX, dY: integer;
    aRect: Rect;

  begin
   fromPt := PrimalToLocal(fromPt);
   toPt := PrimalToLocal(toPt);

   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
      top := v - ArrowShaftLength;
      right := h + ArrowShaftLength;
      bottom := v + ArrowShaftLength;
      left := h - ArrowShaftLength
     end;

   PaintArc(aRect, (myAngle + 180) - arrowHeadWidth div 2, arrowHeadWidth)
  end;


-- 
-----Nick Jackiw [jackiw@cs.swarthmore.edu|jackiw@swarthmr.bitnet------
"This orbe of starres fixed infinitely vp extendeth hitself in altitvde 
sphericallye, and therefore immovable the pallace of foelicity garnished
with perpetvall shining glorious lightes innvmerable." - Thomas Digges