{
Пример рисует две горизонтальные линии на экране используя TDesktopCanvas.
}  
program TrinitronTraining;  

uses  
  Messages, Windows, Graphics, Forms;  

type
  TDesktopCanvas = class(TCanvas)  
  private  
    DC : hDC;  
    function     GetWidth:Integer;  
    function     GetHeight:Integer;  
  public  
    constructor  Create;  
    destructor   Destroy; override;
  published
    property Width: Integer read GetWidth;  
    property Height: Integer read GetHeight;  
  end;  

{ Объект TDesktopCanvas }  
function TDesktopCanvas.GetWidth:Integer;  
begin  
  Result:=GetDeviceCaps(Handle,HORZRES);  
end;  

function TDesktopCanvas.GetHeight:Integer;  
begin  
  Result:=GetDeviceCaps(Handle,VERTRES);  
end;

constructor TDesktopCanvas.Create;  
begin  
  inherited Create;  
  DC := GetDC(0);  
  Handle := DC;  
end;  

destructor TDesktopCanvas.Destroy;  
begin  
  Handle := 0;  
  ReleaseDC(0, DC);  
  inherited Destroy;  
end;  


Const  
  YCount    = 2;  

Var  
  desktop         : TDesktopCanvas;  
  dx,dy           : Integer;  
  i                : Integer;  
  F                : Array[1..YCount] of TForm;  


function CreateLine(Y : Integer) : TForm;  
begin  
  Result := TForm.Create(Application);  
  with Result do begin
    Left      := 0;
    Top       := y;  
    Width     := dx;  
    Height    := 1;  
    BorderStyle := bsNone;  
    FormStyle   := fsStayOnTop;  
    Visible     := True;  
  end;
end;

procedure ProcessMessage;
var
  Msg     : TMsg;
begin
  if PeekMessage(Msg, 0, 0, 0, PM_REMOVE) then
    if Msg.Message = WM_QUIT then Application.Terminate;
end;


begin
  desktop := TDesktopCanvas.Create;
  try
    dx := desktop.Width;
    dy := desktop.Height div (YCount+1);
  finally
    desktop.free;
  end;
  for i:=1 to YCount do F[i]:=CreateLine(i*dy);
  Application.NormalizeTopMosts;
  ShowWindow(Application.Handle, SW_Hide);

  for i:=1 to YCount do
  SetWindowPos(F[i].Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE+SWP_NOMOVE+SWP_NOSIZE);

{ следующие строки используются для того, чтобы не останавливаться
  repeat
    ProcessMessage;
  until false;
{}
  Sleep(1500);

  for i:=1 to YCount do F[i].Free;  
end. 