[Lazarus] Drawing angle boundaries

[Howard Page-Clark]

On 23/6/11 1:11, Leonardo M. Ramé wrote:
> Hi, I need to draw the angle(s) formed by any given four points.
>
> As you can see in the attached image, there are two crossed lines and an
> skewed-rotated ellipse that touches all four points, then between each
> two points and the cross point I would like to draw the angle formed (in
> the example filled in blue).
>
> Does anyone knows how can I do this?.

Try the attached unit, for which the .lpr is as follows:

program pAngleDrawing;

{$mode objfpc}{$H+}

uses
   {$IFDEF UNIX}{$IFDEF UseCThreads}
   cthreads,
   {$ENDIF}{$ENDIF}
   Interfaces, // this includes the LCL widgetset
   Forms, uAngleDrawing;

{$R *.res}

begin
   RequireDerivedFormResource := True;
   Application.Initialize;
   Application.CreateForm(TForm1, Form1);
   Application.Run;
end.

It's a bit buggy and has no error checking for impossible point values, 
but should give you some ideas (uAngleDrawing.lfm is just an empty form).

Howard
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