TrMemo控件

unit TrMemo;

{$R-}
interface

uses
  Windows, Messages, Controls, StdCtrls, Classes;

const
  TMWM__SpecialInvalidate = WM_USER + 1111;

type
  TTransparentMemo = class(TMemo)
  private
    procedure SpecialInvalidate(var Message:TMessage); message TMWM__SpecialInvalidate;
    procedure WMHScroll(var Message: TWMHScroll); message WM_HSCROLL;
    procedure WMVScroll(var Message: TWMVScroll); message WM_VSCROLL;
    procedure WMSetText(var Message:TWMSetText); message WM_SETTEXT;
    procedure CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT); message CN_CTLCOLOREDIT;
    procedure WMKeyDown(var Message: TWMKeyDown); message WM_KEYDOWN;
    procedure WMEraseBkgnd(var Message: TWMEraseBkgnd); message WM_ERASEBKGND;
  protected
    procedure CreateParams(var Params: TCreateParams); override;
  public
    constructor Create(AOwner: TComponent); override;
  end;

procedure Register;

implementation

{ TTransparentMemo }
procedure TTransparentMemo.WMHScroll(var Message: TWMHScroll);
begin
  inherited;
  PostMessage(Handle,TMWM__SpecialInvalidate,0,0);
end;

procedure TTransparentMemo.WMVScroll(var Message: TWMVScroll);
begin
  SendMessage(Handle,TMWM__SpecialInvalidate,0,0);
  inherited;
  PostMessage(Handle,TMWM__SpecialInvalidate,0,0);
end;

procedure TTransparentMemo.CNCTLCOLOREDIT(var Message:TWMCTLCOLOREDIT);
begin
  with Message do
    begin
      SetBkMode(ChildDC,TRANSPARENT);
      Result:=GetStockObject(HOLLOW_BRUSH)
    end
end;

procedure TTransparentMemo.WMSetText(var Message:TWMSetText);
begin
  inherited;
  if not (csDesigning in ComponentState) then
    PostMessage(Handle,TMWM__SpecialInvalidate,0,0)
end;

procedure TTransparentMemo.SpecialInvalidate(var Message:TMessage);
var r:TRect;
begin
  if Parent<>nil then
  begin
    r:=ClientRect;
    r.TopLeft:=Parent.ScreenToClient(ClientToScreen(r.TopLeft));
    r.BottomRight:=Parent.ScreenToClient(ClientToScreen(r.BottomRight));
    InvalidateRect(Parent.Handle,@r,true);
    RedrawWindow(Handle,nil,0,RDW_FRAME+RDW_INVALIDATE)
  end;
end;

procedure TTransparentMemo.WMKeyDown(var Message: TWMKeyDown);
begin
  SendMessage(Handle,TMWM__SpecialInvalidate,0,0);
  inherited;
  PostMessage(Handle,TMWM__SpecialInvalidate,0,0);
end;

procedure TTransparentMemo.WMEraseBkgnd(var Message: TWMEraseBkgnd);
begin
  Message.Result := 1;
end;

constructor TTransparentMemo.Create(AOwner: TComponent);
begin
  inherited;
  ControlStyle := [csCaptureMouse, csDesignInteractive, csClickEvents,
    csSetCaption, csOpaque, csDoubleClicks, csReplicatable, csNoStdEvents];
end;

procedure TTransparentMemo.CreateParams(var Params: TCreateParams);
begin
  inherited CreateParams(Params);
  with Params do
  begin
    ExStyle:=ExStyle or WS_EX_TRANSPARENT and not WS_EX_WINDOWEDGE
      and not WS_EX_STATICEDGE and not WS_EX_DLGMODALFRAME and not WS_EX_CLIENTEDGE;
  end;
end;

procedure Register;
begin
  RegisterComponents('cool!', [tTransparentMemo]);
end;

end.