unit MainForm;

interface

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.Menus, Vcl.StdCtrls, Vcl.ExtDlgs,
  Vcl.ExtCtrls;

type
    TMainForm = class(TForm)
    MainMenu: TMainMenu;
    FileItem: TMenuItem;
    HelpItem: TMenuItem;
    ExitItem: TMenuItem;
    AboutItem: TMenuItem;
    MainPanel: TPanel;
    PaintBox: TPaintBox;
    procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
    procedure ExitItemClick(Sender: TObject);
    procedure AboutItemClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormPaint(Sender: TObject);
    procedure FormKeyDown(Sender: TObject; var Key: Word; Shift: TShiftState);

    private
        Shift: ShortInt;

        SkyBmp, PlaneBmp, PlaneLeft, PlaneRight: TBitmap;

        procedure Right;
        procedure Up;
        procedure Down;
        procedure Left;
    end;

resourcestring
    QuitMessage = 'Are you sure you want to exit?';
    AboutMessage = 'This program';
    InvalidExtensionMessage = 'Invalid file type. Text file expected';

var
    _MainForm: TMainForm;

implementation

{$R *.dfm}

procedure TMainForm.AboutItemClick(Sender: TObject);
begin
    MessageDlg(AboutMessage, mtInformation, [mbOk], 0);
end;

procedure TMainForm.Down;
var
    TempBmp: TBitmap;
begin
    TempBmp := TBitmap.Create;
    TempBmp.Width := 640;
    TempBmp.Height := 480;
    TempBmp.Canvas.CopyRect(Rect(0, 0, 640, 480 - Shift), SkyBmp.Canvas, Rect(0, Shift, 640, 480));
    TempBmp.Canvas.CopyRect(Rect(0, 480 - Shift, 640, 480), SkyBmp.Canvas, Rect(0, 0, 640, Shift));

    SkyBmp.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Canvas.Draw(0, 0, SkyBmp);
    TempBmp.Canvas.Draw(200, 200, PlaneBmp);

    PaintBox.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Free;
end;

procedure TMainForm.ExitItemClick(Sender: TObject);
begin
    Close;
end;

procedure TMainForm.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
    if MessageDlg(QuitMessage, mtConfirmation, mbYesNo, 0) = mrNo then
        CanClose := False;
end;

procedure TMainForm.FormCreate(Sender: TObject);
begin
    Shift := 10;

    SkyBmp := TBitmap.Create;
    SkyBmp.LoadFromResourceName(HInstance, 'sky');

    PlaneLeft := TBitmap.Create;
    PlaneLeft.LoadFromResourceName(HInstance, 'plane_left');
    PlaneLeft.Transparent := True;

    PlaneRight := TBitmap.Create;
    PlaneRight.LoadFromResourceName(HInstance, 'plane_right');
    PlaneRight.Transparent := True;

    PlaneBmp := PlaneRight;
end;

procedure TMainForm.FormKeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
begin
    case Key of
        VK_RIGHT: Right;
        VK_UP: Up;
        VK_DOWN: Down;
        VK_LEFT: Left;
    end;

end;

procedure TMainForm.FormPaint(Sender: TObject);
begin
    PaintBox.Canvas.Draw(0, 0, SkyBmp);
    PaintBox.Canvas.Draw(200, 200, PlaneBmp);
end;

procedure TMainForm.Left;
var
    TempBmp: TBitmap;
begin
    PlaneBmp := PlaneLeft;
    TempBmp := TBitmap.Create;
    TempBmp.Width := 640;
    TempBmp.Height := 480;
    TempBmp.Canvas.CopyRect(Rect(Shift, 0, 640, 480), SkyBmp.Canvas, Rect(0, 0, 640 - Shift, 480));
    TempBmp.Canvas.CopyRect(Rect(0, 0, Shift, 480), SkyBmp.Canvas, Rect(640 - Shift, 0, 640, 480));

    SkyBmp.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Canvas.Draw(0, 0, SkyBmp);
    TempBmp.Canvas.Draw(200, 200, PlaneBmp);

    PaintBox.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Free;
end;

procedure TMainForm.Up;
var
    TempBmp: TBitmap;
begin
    TempBmp := TBitmap.Create;
    TempBmp.Width := 640;
    TempBmp.Height := 480;
    TempBmp.Canvas.CopyRect(Rect(0, Shift, 640, 480), SkyBmp.Canvas, Rect(0, 0, 640, 480 - Shift));
    TempBmp.Canvas.CopyRect(Rect(0, 0, 640, Shift), SkyBmp.Canvas, Rect(0, 480 - Shift, 640, 480));

    SkyBmp.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Canvas.Draw(0, 0, SkyBmp);
    TempBmp.Canvas.Draw(200, 200, PlaneBmp);

    PaintBox.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Free;
end;

procedure TMainForm.Right;
var
    TempBmp: TBitmap;
begin
    PlaneBmp := PlaneRight;
    TempBmp := TBitmap.Create;
    TempBmp.Width := 640;
    TempBmp.Height := 480;
    TempBmp.Canvas.CopyRect(Rect(0, 0, 640 - Shift, 480), SkyBmp.Canvas, Rect(Shift, 0, 640, 480));
    TempBmp.Canvas.CopyRect(Rect(640 - Shift, 0, 640, 480), SkyBmp.Canvas, Rect(0, 0, Shift, 480));

    SkyBmp.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Canvas.Draw(0, 0, SkyBmp);
    TempBmp.Canvas.Draw(200, 200, PlaneBmp);

    PaintBox.Canvas.Draw(0, 0, TempBmp);

    TempBmp.Free;
end;

end.