Code of Web Version of PixelSort

Introduction

Note the following points relating to our adaptations of the code to run in Smart Mobile Studio.

• We have changed some of the variable names to be more meaningful.
• With the constant len set to 2, two for loops are unnecessary and have been removed.
• The with keyword is not accepted by Smart, so some of the code looks more cumbersome than the original.
• In the Canvas.StrokeStyle assignment at the end of the program it was necessary to concatenate small strings to build up the colour string.

The Program

unit PixelSortJS;

interface

uses 
  W3System, W3Components, W3Application, W3Game, W3GameApp, W3Graphics;

type
  Ttrail = record
   x, y : array[1 .. 200] of integer;
   colr, colg, colb : integer;
   realx, realy, targx, targy, speed, angle : real;
  end;

  TApplication = class(TW3CustomGameApplication)
  private
  const len : integer = 2;
    num_trails, mouse_x, mouse_y : integer;
    trails : array[1..10000] of Ttrail;
    tri : array[1 .. 3, 1 .. 3] of real;
    mouse_down : Boolean := false;
  protected
    procedure ApplicationStarting; override;
    procedure ApplicationClosing; override;
    procedure PaintView(Canvas: TW3Canvas); override;
    procedure AddNewColour;
  end;

implementation

procedure TApplication.AddNewColour;
begin
  if num_trails < 5000 then
    begin
      inc(num_trails);
      for var i := 1 to len do
        begin
          trails[num_trails].x[i] := mouse_x;
          trails[num_trails].y[i] := mouse_y;
        end;
      trails[num_trails].realx := mouse_x;
      trails[num_trails].realy := mouse_y;
      trails[num_trails].colr := trunc(256 * random);
      trails[num_trails].colg := trunc(256 * random);
      trails[num_trails].colb := trunc(256 * random);
      trails[num_trails].speed := 7;
      trails[num_trails].angle := 0;
    end;
end;

procedure TApplication.ApplicationStarting;
begin
  inherited;
  GameView.Width := 700;
  GameView.Height := 700;
  GameView.OnMouseMove := procedure(o : TObject; ss : TShiftState; x, y : integer)
    begin
      mouse_x := x;
      mouse_y := y;
      if mouse_down then
        AddNewColour;
    end;

  GameView.OnMouseUp := procedure(o : TObject; b : TMouseButton; ss : TShiftState; x, y : integer)
    begin
      mouse_down := false;
    end;

  GameView.OnMouseDown := procedure(o : TObject; b : TMouseButton; ss : TShiftState; x, y : integer)
    begin
      mouse_x := x;
      mouse_y := y;
      mouse_down := true;
      AddNewColour;
    end;
  num_trails := 0;
  tri[1, 1] := 0;
  tri[2, 1] := 2 * pi / 3;
  tri[3, 1] := 4 * pi / 3;
  GameView.Delay := 1;
  GameView.StartSession(True);
end;

procedure TApplication.ApplicationClosing;
begin
  GameView.EndSession;
  inherited;
end;
 
procedure TApplication.PaintView(Canvas: TW3Canvas);
var
  r, g, b : integer;
begin
  for var i := 1 to 3 do
    begin
      tri[i, 1] := tri[i, 1] + pi / 180;
      if tri[i, 1] > 2 * pi then
        tri[i, 1] := tri[i, 1] - 2 * pi;
      if tri[i, 1] < 0 then
        tri[i, 1] := tri[i, 1] + 2 * pi;
      tri[i, 2] := 350 + round(sin(tri[i, 1]) * 200);
      tri[i, 3] := 350 + round(cos(tri[i, 1]) * 200);
    end;
  if num_trails > 0 then
    for var i := 1 to num_trails do
      begin
        trails[i].angle := trails[i].angle + pi / 360;
        if trails[i].colr + trails[i].colb + trails[i].colg <> 0 then
          begin
            trails[i].targx := (trails[i].colr * tri[1, 2] + trails[i].colg * tri[2, 2] + trails[i].colb * tri[3, 2])/(trails[i].colr + trails[i].colb + trails[i].colg);
            trails[i].targy := (trails[i].colr * tri[1, 3] + trails[i].colg * tri[2, 3] + trails[i].colb * tri[3, 3]) / (trails[i].colr + trails[i].colb + trails[i].colg);
          end;
        if (trails[i].targy - trails[i].realy) < 0 then
          trails[i].angle := arctan((trails[i].targx - trails[i].realx) / (trails[i].targy - trails[i].realy)) + pi;
        if (trails[i].targy-trails[i].realy) > 0 then
          trails[i].angle := arctan((trails[i].targx - trails[i].realx) / (trails[i].targy - trails[i].realy));
        if ((trails[i].targy - trails[i].realy) = 0) then
          if (trails[i].targx - trails[i].realx) > 0 then
            trails[i].angle := pi / 2
          else
            trails[i].angle := 3 * pi / 2;
        if trails[i].angle > 2 * pi then
          trails[i].angle := trails[i].angle - 2 * pi;
        if trails[i].angle < 0 then
          trails[i].angle := trails[i].angle + 2 * pi;
        trails[i].realx := trails[i].realx + sin(trails[i].angle) * trails[i].speed;
        trails[i].realy := trails[i].realy + cos(trails[i].angle) * trails[i].speed;
        trails[i].x[2] := trails[i].x[1];
        trails[i].y[2] := trails[i].y[1];
        trails[i].x[1] := round(trails[i].realx);
        trails[i].y[1] := round(trails[i].realy);
        r := trails[i].colr;
        g := trails[i].colg;
        b := trails[i].colb;
        Canvas.StrokeStyle := 'rgb(' +intToStr(r)+ ',' + intToStr(g) + ',' + intToStr(b) + ')';
        Canvas.BeginPath;
        Canvas.LineF(trails[i].x[1], trails[i].y[1], trails[i].x[2], trails[i].y[2]);
        Canvas.Stroke;
        Canvas.ClosePath;
      end;
end;

end.

Remarks

Could you write a similar program constructing objects from polygons?