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{ Downloaded from The Coder's Knowledge Base                         }
{ http://www.netalive.org/ckb/                                       }
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{ @ CKB Header Version.: 1.01                                        }
{ @ Category ID........: delphi_misc                                 }
{ @ Added to database..: 10.11.98                                    }
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{ @ Title..............: Mouse move                                  }
{ @ Original Filename..: mousemove.txt                               }
{ @ Author.............: Bent Normann Olsen (normann@greennet.gl)    }
{ @ Description........: Highlight a comp by mouse move              }
{ @ Tested w. Compiler.: not tested yet                              }
{ @ Submitted by.......: Unofficial Delphi Developers FAQ (uddf@gnomehome.demon.nl) }
{~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~}


I want to write a component which highlights when the user moves the
mouse over the comp.

Use CM_MOUSEENTER and CM_MOUSELEAVE messages like: 


  TYourObject = class(TAnyControl)
  private
    FMouseInPos : Boolean;
    procedure CMMouseEnter(var AMsg: TMessage); message CM_MOUSEENTER;
    procedure CMMouseLeave(var AMsg: TMessage); message CM_MOUSELEAVE;
  end;

implementation

  procedure TYourObject.CMMouseEnter(var AMsg: TMessage);
  begin
    FMouseInPos := True;
    Refresh;
  end;

  procedure TYourObject.CMMouseLeave(var AMsg: TMessage);
  begin
    FMouseInPos := False;
    Refresh;
  end;

...and then read FMouseInPos when painting the control, or in any way you like to change the highlightning.