Why a component inherited from TCustomFrame looks different from TFrame?

Question

I wrote a TCustomFrame's child class which has been exactly copied from TFrame (Forms.pas unit):

  TMyFrame = class(TCustomFrame)
  private
    { Private declarations }
  public
    { Public declarations }
  published
    property Align;
    property Anchors;
    property AutoScroll;
    property AutoSize;
    property BiDiMode;
    property Constraints;
    property DockSite;
    property DragCursor;
    property DragKind;
    property DragMode;
    property Enabled;
    property Color nodefault;
    property Ctl3D;
    property Font;
    property Padding;
    property ParentBackground default True;
    property ParentBiDiMode;
    property ParentColor;
    property ParentCtl3D;
    property ParentFont;
    property ParentShowHint;
    property PopupMenu;
    property ShowHint;
    property TabOrder;
    property TabStop;
    property Visible;
    property OnAlignInsertBefore;
    property OnAlignPosition;
    property OnCanResize;
    property OnClick;
    property OnConstrainedResize;
    property OnContextPopup;
    property OnDblClick;
    property OnDockDrop;
    property OnDockOver;
    property OnDragDrop;
    property OnDragOver;
    property OnEndDock;
    property OnEndDrag;
    property OnEnter;
    property OnExit;
    property OnGetSiteInfo;
    property OnMouseActivate;
    property OnMouseDown;
    property OnMouseEnter;
    property OnMouseLeave;
    property OnMouseMove;
    property OnMouseUp;
    property OnMouseWheel;
    property OnMouseWheelDown;
    property OnMouseWheelUp;
    property OnResize;
    property OnStartDock;
    property OnStartDrag;
    property OnUnDock;
  end;

As described here, I've initially defined a TFrame's child class, then I've switched to TCustomFrame and removed the TabOrder property from the DFM in order to be able to open the file in the IDE and recompile the package.

object MyFrame: TMyFrame
  Left = 0
  Top = 0
  Width = 296
  Height = 31
  TabOrder = 0 //this line has been deleted
end

Everything seemed to be ok but after opening and saving the source file, there were several new properties in the DFM and a titlebar appears:

object MyFrame: TMyFrame
  Left = 0
  Top = 0
  ClientHeight = 0
  ClientWidth = 280
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'Tahoma'
  Font.Style = []
  OldCreateOrder = True
  PixelsPerInch = 96
  TextHeight = 13
end

Why is this happened and how should I do it for avoiding these problems?

I also do not understand why this question is downwoted. It has a good problem description and formatted pretty well. — Ari0nhh
I can guess that you might be getting down-votes because instead of working with Delphi's framework, you're fighting it. And basically you seem to have started what's likely to become a never-ending chain of: Got the previous problem fixed, now here's the next ... — Disillusioned
What if you change the object MyFrame: TMyFrame in your DFM to inherited MyFrame: TMyFrame? — Günther the Beautiful
@GünthertheBeautiful: I tried to do that but after replacing object MyFrame: TMyFrame with inherited MyFrame: TMyFrame I get an error Error creating form: Ancestor for 'TCustomFrame' not found. on opening the source file using the IDE. — Fabrizio

Ken Bourassa Ken Bourassa · Accepted Answer · 2016-11-14T14:16:52

I believe all you need to do is register your frame class as a custom module.

In your package's register procedure, add something like this :

procedure Register;
begin
[...]
  RegisterCustomModule(TMyFrame, TCustomMyFrameModule)
end;

And TCustomMyFrameModule is defined as

TCustomMyFrameModule = class(TCustomModule)
  function Nestable: Boolean; override;
end;

function TCustomMyFrameModule.Nestable: Boolean;
begin
  Result := True;
end;

EDIT: For it to work, you need to register a custom module for the parent class of the class your are editing in the IDE.

TFrame1 = class(TMyFrame)
end;
RegisterCustomModule(TMyFrame, TCustomMyFrameModule)

If you want to edit your TMyFrame in the IDE, you will need to register a custom module for TCustomFrame.

TMyFrame = class(TCustomFrame)
end;
RegisterCustomModule(TCustomFrame, TCustomMyFrameModule)

Why a component inherited from TCustomFrame looks different from TFrame?

1 Answers