Question

I am making a custom Panel component which derives TPanel.

I want for my new component to have some code executed on the OnMouseEnter and OnMouseLeave events, however, i do not know how to implement it.

I see that TPanel has published properties OnMouseEnter, OnMouseLeave.

How do i override those and add some of my own code?

The example of my idea:
Default behaviour of TMyPanel which should be in component itself.

on event OnMouseEnter do: Color := NewColor;
on event OnMouseLeave do: Color := OldColor;

And then, i want to be able to assign some function to these events at run time.
This assignment is done in the application.

.. TButton1.Click ..
begin
    MyPanel1.OnMouseEnter := DoSomethingMore;
    MyPanel1.OnMouseLeave := DoSomethingElse;
end;

so in the end, when mouse is over new panel, it should change color AND do some other actions written in DoSomethingMore procedure.

Thanks

Answer 1

Anoher approach is to handle the windows messages yourself:

type
  TMyPanel = class(TPanel)
  private
    procedure CMMouseEnter(var Message: TMessage); message CM_MOUSEENTER;
    procedure CMMouseLeave(var Message: TMessage); message CM_MOUSELEAVE;
  published
  end;

implementation

{ TMyPanel }

procedure TMyPanel.CMMouseEnter(var Message: TMessage);
begin
     // Do whatever your want before the event
     if Assigned(OnMouseEnter) then OnMouseEnter(Self);
end;

procedure TMyPanel.CMMouseLeave(var Message: TMessage);
begin
     // Do whatever your want before the event
     if Assigned(OnMouseLeave) then OnMouseLeave(Self);
end;

EDIT: See below for better VCL compliant version.