Graphics.Polygon code not working - what am I missing? - delphi

Question

My little code creates modern art to the full screen size Form canvas with different kind of shapes.
I can make ellipse, rectangle and line work but not the polycon. Can any one help me? (Version: Delphi community edition )
uses .... GDIPAPI, GDIPOBJ, GDIPUTIL;
procedure TForm1.Button1Click(Sender: TObject);
var
graphics: TGPGraphics;
SolidPen: TGPPen;
SolidBrush : TGPBrush;
x,y,x2,y2,x3,y3 : integer;
begin
graphics := TGPGraphics.Create(Canvas.Handle);
graphics.SetSmoothingMode(SmoothingModeAntiAlias);
SolidPen := TGPPen.Create(MakeColor(255, random(255), random(255), random(255)), random(4)+1);
SolidBrush := TGPSolidBrush.Create(MakeColor(255, random(255), random(255), random(255)));
SolidPen.SetStartCap(LineCapRound);
SolidPen.SetEndCap(LineCapRound);
//POLYCON, not working.------------------
// PROBLEM HERE: it's complaining: 'Oridinal type required' ,
// 'incompatible type: integer and TPoint'
x:= 150; y := 50; x2 := 50; y2 := 250; x3 := 250; y3 := 250;
graphics.FillPolygon(SolidBrush, [Point(x, y), Point(x2, y2), Point(x3, y3)]);
graphics.DrawPolygon(SolidPen, [Point(x, y), Point(x2, y2), Point(x3, y3)]);
//--------------------------------------------
// ELLIPSE, ok
x := random(Form1.width); y := random(Form1.height); x2 := random(200); y2 := random(200);
graphics.FillEllipse(SolidBrush,x, y, x2, y2);
graphics.DrawEllipse(SolidPen,x, y, x2, y2);
// RECTANGLE, ok
x := random(Form1.width); y := random(Form1.height); x2 := random(200); y2 := random(200);
graphics.FillRectangle(SolidBrush, x, y, x2, y2);
graphics.DrawRectangle(SolidPen, x, y, x2, y2);
// LINE, ok
x := random(Form1.width); y := random(Form1.height); x2 := random(Form1.width); y2 := random(Form1.height);
graphics.DrawLine(SolidPen, x, y, x2, y2);
procedure TForm1.FormCreate(Sender: TObject);
begin
Form1.Height := Screen.Height;
Form1.Width := Screen.Width;
end;

Answer 1

You are not passing the points of the polygon correctly.
Looking at the two overloaded DrawPolygon() declarations:
function TGPGraphics.DrawPolygon(pen: TGPPen; points: PGPPointF; count: Integer): TStatus;
function TGPGraphics.DrawPolygon(pen: TGPPen; points: PGPPoint; count: Integer): TStatus;
you can see that the points are passed as a PGPPointF or PGPPoint. The definitions of these types are found in Winapi.GDIPAPI and there we see that the coordinates are either single or integer
Since you are using integer coordinates look at the definition of PGPPoint in Winapi.GDIPAPI
type
PGPPoint = ^TGPPoint;
TGPPoint = record
X : Integer;
Y : Integer;
end;
TPointDynArray = array of TGPPoint;
function MakePoint(X, Y: Integer): TGPPoint; overload;
{$EXTERNALSYM MakePoint}
So, declare a variable
ArrOfPoint: TPointDynArray;
and fill it with your points:
SetLength(ArrOfPoint, 3);
ArrOfPoint[0] := MakePoint(x, y);
ArrOfPoint[1] := MakePoint(x2, y2);
ArrOfPoint[2] := MakePoint(x3, y3);
Finally replace your call to e.g. DrawPolygon() with
graphics.DrawPolygon(SolidPen, PGPPoint(#ArrOfPoint[0]), 3);
meaning you pass the address of the first point as a PGPPoint type.

Answer 2

So, the corrected working code for the polygon is following (at the moment):
uses
... GDIPAPI, GDIPOBJ, GDIPUTIL;
procedure TForm1.Button1Click(Sender: TObject);
var
graphics: TGPGraphics;
SolidPen: TGPPen;
SolidBrush : TGPBrush;
ArrOfPoint: TPointDynArray;
x, y, x2, y2, x3, y3 : integer;
begin
graphics := TGPGraphics.Create(Canvas.Handle);
graphics.SetSmoothingMode(SmoothingModeAntiAlias);
SolidPen := TGPPen.Create(MakeColor(255, random(255), random(255), random(255)), random(4)+1);
SolidBrush := TGPSolidBrush.Create(MakeColor(255, random(255), random(255), random(255)));
x := random(Form1.Width); y := random(Form1.Height);
x2 := random(Form1.Width); y2 := random(Form1.Height);
x3 := random(Form1.Width); y3 := random(Form1.Height);
SetLength(ArrOfPoint, 3);
ArrOfPoint[0] := MakePoint(x, y);
ArrOfPoint[1] := MakePoint(x2, y2);
ArrOfPoint[2] := MakePoint(x3, y3);
graphics.FillPolygon(SolidBrush,PGPPoint(#ArrOfPoint[0]), 3);
graphics.DrawPolygon(SolidPen, PGPPoint(#ArrOfPoint[0]), 3);
end;