Trapping-messages-in-non-client-area-of-a-form


            Question:
How can I trap messages in the non client areas of my form,
such as the title bar?
Answer:
Create a message handler for one of the variety of WM_NC
(non client) messages available to trap. (search the Windows
API help file for WM_NC). This example shows how to track 
mouse movement in all of the non client areas of the form.
Example:
unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
 Dialogs, StdCtrls;
type
 TForm1 = class(TForm)
 private
 procedure WMNCMOUSEMOVE(var Message: TMessage);
 message WM_NCMOUSEMOVE;
 { Private declarations }
 public
 { Public declarations }
 end;
var
 Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.WMNCMOUSEMOVE(var Message: TMessage);
var
 s : string;
begin
 case Message.wParam of
 HTERROR : s := 'HTERROR';
 HTTRANSPARENT : s := 'HTTRANSPARENT';
 HTNOWHERE : s := 'HTNOWHERE';
 HTCLIENT : s := 'HTCLIENT';
 HTCAPTION : s := 'HTCAPTION';
 HTSYSMENU : s := 'HTSYSMENU';
 HTSIZE : s := 'HTSIZE';
 HTMENU : s := 'HTMENU';
 HTHSCROLL : s := 'HTHSCROLL';
 HTVSCROLL : s := 'HTVSCROLL';
 HTMINBUTTON : s := 'HTMINBUTTON';
 HTMAXBUTTON : s := 'HTMAXBUTTON';
 HTLEFT : s := 'HTLEFT';
 HTRIGHT : s := 'HTRIGHT';
 HTTOP : s := 'HTTOP';
 HTTOPLEFT : s := 'HTTOPLEFT';
 HTTOPRIGHT : s := 'HTTOPRIGHT';
 HTBOTTOM : s := 'HTBOTTOM';
 HTBOTTOMLEFT : s := 'HTBOTTOMLEFT';
 HTBOTTOMRIGHT : s := 'HTBOTTOMRIGHT';
 HTBORDER : s := 'HTBORDER';
 HTOBJECT : s := 'HTOBJECT';
 HTCLOSE : s := 'HTCLOSE';
 HTHELP : s := 'HTHELP';
 else s := '';
 end;
 Form1.Caption := s;
 Message.Result := 0;
end;
end.
VCL Delphi
