Liste ohne dahinterliegende Items

[Bjoerk]

Oje, ob das so stimmt?

Delphi-Quellcode:

type
  TGraphicHistoryStatusChanged = procedure(CanUndo, CanRedo: boolean) of object;

  TGraphicHistory = class
  private
    FCurrent: integer;
    FList: TGraphicList;
    FEnterValue: TGraphicList;
    FExitValue: TGraphicList;
    FEnabled: boolean;
    FOnHistoryStatusChanged: TGraphicHistoryStatusChanged;
    FItem: TGraphicList;
    FPath: string;
    FFileNames: TStringList;
    procedure SetCurrent(const Value: integer);
    procedure AddExitValue;
    function Changed: boolean;
    function GetItems(Index: integer): TGraphicList;
    property FItems[Index: integer]: TGraphicList read GetItems;
    property Current: integer read FCurrent write SetCurrent;
    function CanUndo: boolean;
    function CanRedo: boolean;
    function Count: integer;
  public
    property OnHistoryStatusChanged: TGraphicHistoryStatusChanged
      read FOnHistoryStatusChanged write FOnHistoryStatusChanged;
    property Enabled: boolean read FEnabled write FEnabled;
    procedure Enter;
    procedure Exit;
    procedure UnDo;
    procedure ReDo;
    procedure Clear;
    procedure Refresh(List: TGraphicList);
    constructor Create(Path: string; List: TGraphicList);
    destructor Destroy; override;
  end;

implementation

{ TGraphicHistory }

constructor TGraphicHistory.Create(Path: string; List: TGraphicList);
begin
  inherited Create;
  FEnterValue := TGraphicList.Create;
  FExitValue := TGraphicList.Create;
  FList := List;
  FEnabled := true;
  FCurrent := -1;
  FItem := TGraphicList.Create;
  FPath := Path;
  FFileNames := TStringList.Create;
end;

destructor TGraphicHistory.Destroy;
begin
  FEnterValue.Free;
  FExitValue.Free;
  FFileNames.Free;
  FItem.Free;
  inherited Destroy;
end;

function TGraphicHistory.GetItems(Index: integer): TGraphicList;
begin
  FItem.LoadFromFile(FFileNames[Index]);
  Result := FItem;
end;

procedure TGraphicHistory.Clear;
begin
  Current := -1;
  FEnterValue.Clear;
  FFileNames.Clear;
  Tui.RecycleFile(FPath, FOF_NOCONFIRMATION or FOF_SILENT);
end;

function TGraphicHistory.Count: integer;
begin
  Result := FFileNames.Count;
end;

procedure TGraphicHistory.AddExitValue;
begin
  FFileNames.Add(FPath + IntToStr(Count));
  FExitValue.SaveToFile(FFileNames[Count - 1]);
  FItem.Assign(FExitValue); // Last;
  Current := Count - 1;
end;

function TGraphicHistory.Changed: boolean;
begin
  Result := not FEnterValue.Compare(FExitValue);
end;

function TGraphicHistory.CanUndo: boolean;
begin
  Result := FEnabled and (Count > 1) and (FCurrent > 0);
end;

function TGraphicHistory.CanRedo: boolean;
begin
  Result := FEnabled and (Count > 1) and (FCurrent < Count - 1);
end;

procedure TGraphicHistory.UnDo;
begin
  if CanUnDo then
  begin
    Current := Current - 1;
    FList.Assign(FItems[FCurrent]);
  end;
end;

procedure TGraphicHistory.ReDo;
begin
  if CanReDo then
  begin
    Current := Current + 1;
    FList.Assign(FItems[FCurrent]);
  end;
end;

procedure TGraphicHistory.Refresh(List: TGraphicList);
begin
  Clear;
  FFileNames.Add(FPath + IntToStr(Count));
  List.SaveToFile(FFileNames[Count - 1]);
  FItem.Assign(List); // Last;
end;

procedure TGraphicHistory.Enter;
begin
  FEnterValue.Assign(FList);
end;

procedure TGraphicHistory.Exit;
begin
  FExitValue.Assign(FList);
  if Changed then
    AddExitValue;
end;

procedure TGraphicHistory.SetCurrent(const Value: integer);
begin
  FCurrent := Value;
  if Assigned(FOnHistoryStatusChanged) then
    FOnHistoryStatusChanged(CanUndo, CanRedo);
end;

[Bjoerk]

Jo läuft. Wenn man noch eine kleine Klasse vorschaltet wird‘s noch einfacher. Und wie Sir Rufo ja auch schon anmerkte es kann quasi immer nur einen geben, List[I].Assign(List[J]) geht z.B. nicht wie auch die Funktionalität dieser Klasse insgesamt stark eingeschränkt ist, für eine History aber eben völlig ausreichend und auch sinnvoll, wenn man dem User den RAM nicht "zumüllen" will, weil er z.B. gerade DIN A0 große Metafiles 20 fach gezoomt auf einem Paintbox.Canvas darstellt.

Delphi-Quellcode:

constructor TGraphicListFiles.Create(Path: string);
begin
  FItems := TGraphicList.Create;
  FPath := IncludeTrailingPathDelimiter(Path);
  if not SysUtils.DirectoryExists(FPath) then
    SysUtils.CreateDir(FPath);
end;

destructor TGraphicListFiles.Destroy;
begin
  FItems.Free;
  Clear;
  if SysUtils.DirectoryExists(FPath) then
    SysUtils.RemoveDir(FPath);
  inherited;
end;

procedure TGraphicListFiles.Clear;
var
  I: integer;
begin
  for I := 0 to FCount - 1 do
    if SysUtils.FileExists(FileName(I)) then
      SysUtils.DeleteFile(FileName(I));
  FCount := 0;
end;

function TGraphicListFiles.FileName(Index: integer): string;
begin
  Result := FPath + IntToStr(Index) + '.dat';
end;

function TGraphicListFiles.GetItems(Index: integer): TGraphicList; // ReadOnly;
begin
  FItems.LoadFromFile(FileName(Index));
  Result := FItems;
end;

function TGraphicListFiles.Add(Value: TGraphicList): integer; // WriteOnly;
begin
  Result := FCount;
  Value.SaveToFile(FileName(Result));
  Inc(FCount);
end;

[Sir Rufo]

Doch das würde schon gehen, wenn du ein Interface zurückgibst