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Draws in Paintbox

Posted on 2006-06-29
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Last Modified: 2010-04-05
Hello,

I'm trying to do a buttin that when pressed, using a paintbox, draw a big triangle, and inside of this triangle another one but with half of the size and so on... until it makes just one point... When I tryed to do this PaintBox1.Canvas.MoveTo(x/2,0); it encountered an error "Incompatible types: 'Integer' and 'Extended'"...
Can anyone help me plz??
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Question by:plinho
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6 Comments
 
LVL 26

Accepted Solution

by:
Russell Libby earned 50 total points
Comment Utility
You need to use  one of the following to return an integer result (you can't use floating point math on a canvas)

x div 2, 0
Round(x / 2)
Trunc(x / 2)

Regards,
Russell


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Author Comment

by:plinho
Comment Utility
=], thanks rllibby!!
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Author Comment

by:plinho
Comment Utility
by the way.... do you know how to make a triangle that has all the sides the same size, 60°, I don't know the name in english =/, using paintbox?
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LVL 26

Expert Comment

by:Russell Libby
Comment Utility

procedure TForm1.PaintBox1Paint(Sender: TObject);
var  ptTriangle:    Array [0..3] of TPoint;
     dwSize:        Integer;
     dwX:           Integer;
     dwY:           Integer;
begin

  // Need to form a square
  if (PaintBox1.Width > PaintBox1.Height) then
     dwSize:=PaintBox1.Height
  else
     dwSize:=PaintBox1.Width;

  // Leave a small border of 5px each side
  Dec(dwSize, 10);

  // Calculate the remaining borders
  dwX:=(PaintBox1.Width - dwSize) div 2;
  dwY:=(PaintBox1.Height - dwSize) div 2;

  // Triangle with equal angles
  ptTriangle[0]:=Point(dwX, dwY + dwSize);
  ptTriangle[1]:=Point(dwX + (dwSize div 2), dwY);
  ptTriangle[2]:=Point(dwX + dwSize, dwY + dwSize);
  ptTriangle[3]:=Point(dwX, dwY + dwSize);

  // Use polygon function
  PaintBox1.Canvas.Polygon(ptTriangle);

end;
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LVL 26

Expert Comment

by:Russell Libby
Comment Utility

Btw, its an "equilateral triangle", You will also find that by decrementing the size, you can draw triangles within the triangle (like your original question)

procedure TForm1.PaintBox1Paint(Sender: TObject);
var  ptTriangle:    Array [0..3] of TPoint;
     dwSize:        Integer;
     dwX:           Integer;
     dwY:           Integer;
begin

  // Fill canvas with white brush
  PaintBox1.Canvas.Brush.Color:=clWhite;
  PaintBox1.Canvas.FillRect(Rect(0, 0, PaintBox1.Width, PaintBox1.Height));

  // Need to form a square
  if (PaintBox1.Width > PaintBox1.Height) then
     dwSize:=PaintBox1.Height
  else
     dwSize:=PaintBox1.Width;

  // Leave a small border of 5px each side
  Dec(dwSize, 10);

  // While size > 0
  while (dwSize > 20) do
  begin
     // Calculate the remaining borders
     dwX:=(PaintBox1.Width - dwSize) div 2;
     dwY:=(PaintBox1.Height - dwSize) div 2;
     // Triangle with equal angles
     ptTriangle[0]:=Point(dwX, dwY + dwSize);
     ptTriangle[1]:=Point(dwX + (dwSize div 2), dwY);
     ptTriangle[2]:=Point(dwX + dwSize, dwY + dwSize);
     ptTriangle[3]:=Point(dwX, dwY + dwSize);
     // Use polygon function
     PaintBox1.Canvas.Polygon(ptTriangle);
     // Cut size in half
     dwSize:=dwSize div 2;
  end;

end;

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Author Comment

by:plinho
Comment Utility
thanks ;)
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