Author: Mike Shkolnik 

How can I add the hot track effect to my component?

Answer:

If you want to add a useful feature to your component (like URL in html or 
PageControl/TabControl.HotTrack) you must handle the CM_MOUSEENTER and 
CM_MOUSELEAVE messages: 

1   type
2     TyourControl = class(TDescControl)
3     private
4       { Private declarations }
5       FLinkFont: TFont;
6       FPassiveFont: TFont;
7   
8       procedure CMMouseEnter(var Msg: TMessage); message CM_MOUSEENTER;
9       procedure CMMouseLeave(var Msg: TMessage); message CM_MOUSELEAVE;
10    end;
11  
12  implementation
13  
14  procedure TyourControl.CMMouseEnter(var Msg: TMessage);
15  begin
16    //Change color when mouse is over control
17    Font.Assign(FLinkFont);
18  end;
19  
20  procedure TyourControl.CMMouseLeave(var Msg: TMessage);
21  begin
22    //Change color when mouse leaves control
23    Font.Assign(FPassiveFont);
24  end;


As example, you can view a sources of the TURLLabel and/or THighLightLabel components on my site (http://www.geocities.com/mshkolni