wcomp.pas

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unit WComp;

interface

uses
  Windows, Messages, SysUtils, Classes, Forms;

type
  TWindowedComponent = class(TComponent)
  private
    FHandle : THandle;
    function GetHandle: THandle;
    { Private declarations }
  protected
    procedure WndProc(var Msg : TMessage); virtual;
    { Protected declarations }
  public
    function HandleAllocated: Boolean;
    procedure HandleNeeded;
    procedure DefaultHandler(var Message); override;
    constructor Create(AOwner : TComponent); override;
    destructor Destroy; override;
    property Handle: THandle read GetHandle;
  end;


implementation

{ TWindowedComponent }

constructor TWindowedComponent.Create(AOwner : TComponent);
begin
  inherited Create(AOwner);
  FHandle := 0;
end;

destructor TWindowedComponent.Destroy;
begin
  if HandleAllocated then DeAllocateHWnd(FHandle);
  inherited Destroy;
end;

function TWindowedComponent.HandleAllocated: Boolean;
begin
  Result := FHandle<>0;
end;

procedure TWindowedComponent.HandleNeeded;
begin
  if not HandleAllocated then FHandle := AllocateHWnd(WndProc);
end;

function TWindowedComponent.GetHandle: THandle;
begin
  HandleNeeded;
  Result := FHandle;
end;

procedure TWindowedComponent.WndProc(var Msg : TMessage);
begin
  Dispatch(Msg);
end;

procedure TWindowedComponent.DefaultHandler(var Message);
begin
  if FHandle <> 0 then
   with TMessage(Message) do
    Result := DefWindowProc(FHandle, Msg, wParam, lParam)
  else
    inherited DefaultHandler(Message);
end;

end.