delphi - How do you remove a property from a descendent component

Question

I have created a TListView descendent component... It functions flawlessly, but I wonder if it is possible to remove a TListView property that I do not want in the descendent. The properties I do not want to appear in the object inspector are LargeImages, RowSelect, ShowColumnHeader, ShowWorkAreas, ViewStyle, OwnerData, OnData and OnDataFind. The descendent only has one viewstyle vsIcon.

This is the interface part of the component:

  TImageEnListView = class(TListView)
  private
    FImageList: TImageList;
    FImageIndex: integer;
    FStringList: TStringList;
    FThumbnailWidth: integer;
    FThumbnailHeight: integer;
    FIconVerticalSpacing: integer;
    FIconHorzontalSpacing: integer;
    FFolder: string;
    FShadowedThumbnail: boolean;
    FShowCaptions: boolean;
    FShowTips: boolean;
    FBackgroundWorker: TBackgroundWorker;
    FTaskDialog: TTaskDialog;
    procedure BackgroundWorkerWork(Worker: TBackgroundWorker);
    { Event after threading is complete }
    procedure BackgroundWorkerWorkComplete(Worker: TBackgroundWorker; Cancelled: Boolean);
    { Event for feedback to GUI }
    procedure BackgroundWorkerWorkFeedback(Worker: TBackgroundWorker; FeedbackID,
      FeedbackValue: Integer);
  public
   { Public declarations }
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    { Clears thumbnails, fileList and imageList }
    procedure ClearThumbnails;
    procedure InfoTip(Sender: TObject; Item: TListItem; var InfoTip: string);
    procedure Data(Sender: TObject; Item: TListItem);
    procedure DataFind(Sender: TObject; Find: TItemFind; const FindString: string;
      const FindPosition: TPoint; FindData: Pointer; StartIndex: Integer; Direction:
      TSearchDirection;
      Wrap: Boolean; var Index: Integer);
    procedure FillItems;
    property BackgroundWorker: TBackgroundWorker read FBackgroundWorker;
  published
    { Published declarations }
    property Folder: string read FFolder write FFolder;
    property FileList: TStringList read FStringList write FStringList;
    property ImageList: TImageList read FImageList write FImageList;
    property ThumbnailWidth: integer read FThumbnailWidth write FThumbnailWidth default 170;
    property ThumbnailHeight: integer read FThumbnailHeight write FThumbnailHeight default 120;
    property ShadowedThumbnail: boolean read FShadowedThumbnail write FShadowedThumbnail default
      True;
    property ShowTips: boolean read FShowTips write FShowTips default False;
    property ShowCaptions: boolean read FShowCaptions write FShowCaptions default True;
  end;

Answer 1

Create your class from TTCustomListView instead of TListView, and just expose the properties and events you want to make visible. You can use the VCL source (in the ComCtrls unit) to see how it was done for TListView in exactly the same way (except TListView exposes them all, of course). Here's a (very useless) example of how to do so:

TImageEnListView = class(TCustomListView)
... other code
published
  // Only expose some of the properties that are protected
  // in TCustomListView. Meaningless from a use standpoint,
  // but demonstrates the technique
  property Columns;
  property ColumnClick;
  property Constraints;
  property DragCursor;
  property DragKind;
  property DragMode;
  property Enabled;
  property Font;
  property FlatScrollBars;
  property FullDrag;
  property GridLines;
  property HideSelection;
end;

For classes where you don't have a TCustom ancestor, you can create a wrapper class and include the class you want to alter as a private field within it, and only expose the functionality you want through new properties you publish. Something like this should get you started (I'll just expose a property or two, and you can take it from there):

type
  TMySpecialListView=class(TComponent)
  private
    FEnListView: TImageEnListView;
    function GetThumbnailHeight: Integer;
    function GetThumbnailWidth: Integer;
    procedure SetThumbnailHeight(Value: Integer);
    procedure SetThumbnailWidth(Value: Integer);
  public
    constructor Create(AOwner: TComponent); override;
  published
    property ThumbnailHeight: Integer read GetThumbnailHeight
      write SetThumbnailHeight;
    property ThumbnailWidth: Integer read GetThumbnailWidth
      write SetThumbnailWidth;
  end;

implementation

{ TMySpecialListView }

constructor TMySpecialListView.Create(AOwner: TComponent);
begin
  inherited;
  FEnhListView := TImageEnListView.Create(Self);
  FEnhListView.Parent := Self.Parent;
  // Set other properties needed like width and height. You
  // can get the ones you need from your current .dfm values
  // for a new blank form with your TImageEnListView dropped
  // on it.
end;

function TMySpecialListView.GetThumbnailHeight: Integer;
begin
  Result := FEnhListView.ThumbnailHeight;
end;

function TMySpecialListView.GetThumbnailWidth: Integer;
begin
  Result := FEnhListView.ThumbnailWidth;
end;

procedure TMySpecialListView.SetThumbnailHeight(Value: Integer);
begin
  if Value <> FEnhListView.ThumbnailHeight then
    FEnhListView.ThumbnailHeight := Value;
end;

procedure TMySpecialListView.SetThumbnailWidth(Value: Integer);
begin
  if Value <> FEnhListView.ThumbnailWidth then
    FEnhListView.ThumbnailWidth := Value;
end;