Spiral Out 2

unit uMain;

interface

uses
  Winapi.Windows, Winapi.Messages,
  System.SysUtils, System.Variants, System.Classes, System.Types,
  Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.ExtCtrls,
  GDIPAPI, GDIPOBJ;

const
  DOT_COUNT = 120;
  DOT_SPACING = 2.5;
  LINE_WIDTH = 1.0;
  SPEED_FACTOR = 0.01;

type
  TSpiralPoint = record
    Degrees: Currency;
    Distance: Currency;
    Speed: Currency;
  end;

  TSpiralPoints = array of TSpiralPoint;

  TfrmMain = class(TForm)
    tmrStart: TTimer;
    tmrMain: TTimer;
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure tmrStartTimer(Sender: TObject);
    procedure tmrMainTimer(Sender: TObject);
    procedure FormPaint(Sender: TObject);
  private
    FPoints: TSpiralPoints;
    FPen: TGPPen;
    function CenterPoint: TGPPointF;
  public
    function CreateCanvas: TGPGraphics;
  end;

var
  frmMain: TfrmMain;

implementation

{$R *.dfm}

function NewPosition(Center: TGPPointF; Distance: Currency; Degrees: Currency): TGPPointF;
var
  Radians: Real;
begin
  //Convert angle from degrees to radians; Subtract 135 to bring position to 0 Degrees
  Radians:= (Degrees - 135) * Pi / 180;
  Result.X:= Trunc(Distance*Cos(Radians)-Distance*Sin(Radians))+Center.X;
  Result.Y:= Trunc(Distance*Sin(Radians)+Distance*Cos(Radians))+Center.Y;
end;

{ TfrmSpiral }

procedure TfrmMain.FormCreate(Sender: TObject);
var
  X: Integer;
begin
  WindowState:= wsMaximized; //Maximize window on startup
  Color:= clBlack; //Set form's background to black
  FPen:= TGPPen.Create(MakeColor(180, 180, 255)); //Create pen and set color to light blue
  FPen.SetWidth(LINE_WIDTH); //Set the width of the line (pen)
  SetLength(FPoints, DOT_COUNT); //Populate array of points
  //Set defaults values for each point
  for X := 0 to Length(FPoints)-1 do begin
    FPoints[X].Degrees:= 0; //Start all at 0 degrees to be straight line
    FPoints[X].Distance:= (X+1) * DOT_SPACING; //Spacing between each point / radius from center point
    FPoints[X].Speed:= (X+1) * SPEED_FACTOR; //Make each one slightly slower than the next
  end;
end;

procedure TfrmMain.FormDestroy(Sender: TObject);
begin
  SetLength(FPoints, 0); //Clear array of points
  FreeAndNil(FPen); //Destroy pen object
end;

procedure TfrmMain.tmrStartTimer(Sender: TObject);
begin
  //One-time timer just to put delay before main animation starts
  tmrStart.Enabled:= False;
  tmrMain.Enabled:= True;
end;

procedure TfrmMain.tmrMainTimer(Sender: TObject);
var
  X: Integer;
begin
  //Increase degrees of each point based its "speed"
  for X := 0 to Length(FPoints)-1 do begin
    FPoints[X].Degrees:= FPoints[X].Degrees + FPoints[X].Speed;
  end;
  Self.Invalidate; //Force form to repaint
end;

function TfrmMain.CenterPoint: TGPPointF;
begin
  //Returns absolute center point of form's client area
  Result.X:= ClientWidth / 2;
  Result.Y:= ClientHeight / 2;
end;

function TfrmMain.CreateCanvas: TGPGraphics;
begin
  //Create GDI+ canvas object
  Result:= TGPGraphics.Create(Canvas.Handle);
  Result.SetInterpolationMode(InterpolationMode.InterpolationModeHighQuality);
  Result.SetSmoothingMode(SmoothingMode.SmoothingModeHighQuality);
  Result.SetCompositingQuality(CompositingQuality.CompositingQualityHighQuality);
end;

procedure TfrmMain.FormPaint(Sender: TObject);
var
  X: Integer;
  P: TGPPointF;
  Last: TGPPointF;
  Can: TGPGraphics;
begin
  Can:= CreateCanvas; //Create GDI+ canvas
  try
    //Iterate through all points
    for X := 0 to Length(FPoints)-1 do begin
      //Calculate position around center point
      P:= NewPosition(CenterPoint, FPoints[X].Distance, FPoints[X].Degrees);
      if X > 0 then begin
        //Only draw line if not the first point (need at least 2 points)
        Can.DrawLine(FPen, Last.X, Last.Y, P.X, P.Y);
      end;
      //Keep track of prior point to draw next line
      Last:= P;
    end;
  finally
    Can.Free; //Destroy GDI+ canvas
  end;
end;

end.