TLinkLabel background on a TPageControl

Question

I am trying to use a TLinkLabel on a TPageControl, and I can't find a way to make it use it's parent's background.

// Image removed because the website doesn't exist any more 
// and I can't find it anywhere... Sorry.

As you can see, the parent tab sheet's lovely gradient is not preserved behind the link text.

I would like the functionality of having multiple links in a flowing block of text (the functionality that TLinkLabel provides) and have the background of the parent showing behind the text.

TLinkLabel does not have a ParentBackground property. I have tried creating a derived class that adds csParentBackground to the control style, to no avail:

TMyLinkLabel = class (TLinkLabel)
public
  constructor Create(AOwner: TComponent); override;
end;

...

constructor TMyLinkLabel.Create(AOwner: TComponent); 
begin
  inherited;
  ControlStyle := ControlStyle - [csOpaque] + [csParentBackground]
end;

Anyone have any ideas?

Answer 1

Nat, you are nearly there with your changes to the ControlStyle of the TLinkLabel. What you have to do in addition is to make sure that the parent of the standard Windows static control (that's what the TLinkLabel is) handles the WM_CTLCOLORSTATIC message correctly.

The VCL has a nice redirection mechanism to let controls handle messages that are sent as notifications to their parent windows for themselves. Making use of this a completely self-contained transparent link label can be created:

type
  TTransparentLinkLabel = class(TLinkLabel)
  private
    procedure CNCtlColorStatic(var AMsg: TWMCtlColorStatic);
      message CN_CTLCOLORSTATIC;
  public
    constructor Create(AOwner: TComponent); override;
  end;

constructor TTransparentLinkLabel.Create(AOwner: TComponent);
begin
  inherited;
  ControlStyle := ControlStyle - [csOpaque] + [csParentBackground];
end;

procedure TTransparentLinkLabel.CNCtlColorStatic(var AMsg: TWMCtlColorStatic);
begin
  SetBkMode(AMsg.ChildDC, TRANSPARENT);
  AMsg.Result := GetStockObject(NULL_BRUSH);
end;

Answer 2

Normally I hate it when people offer a third-party component as an answer, but I'll mention the TMS THTMLabel as an alternative for what you want to do. It has the Transparent property of the TLabel, and allows you to use HTML as the caption, and so you can do multiple links as per your example.