Видеть подсказки все время, пока поле редактирования имеет фокус

FocusHintWindow.Showing := True;
FocusHintWindow.Showing := False;

unit FHintWin;

{ -----------------------------------------------------------

TFocusHintWindow --

Вот пример того, как можно использовать TFocusHintWindow.
Данный пример выводит всплывающую подсказку ниже любого
TEdit, имеющего фокус. В противном случае выводится
стандартная подсказка Windows.

unit Unit1;
interface
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics,
Controls, Forms, Dialogs, StdCtrls, FHintWin;

type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
private
FocusHintWindow: TFocusHintWindow;
procedure AppIdle( Sender: TObject; var Done: Boolean );
procedure AppShowHint( var HintStr: string;
var CanShow: Boolean; var HintInfo: THintInfo );
end;

implementation

procedure TForm1.FormCreate( Sender: TObject );
begin
Application.OnIdle := AppIdle;
Application.OnShowHint := AppShowHint;
FocusHintWindow := TFocusHintWindow.Create( Self );
end;

procedure TForm1.AppIdle(Sender: TObject; var Done: Boolean);
begin
FocusHintWindow.Showing := Screen.ActiveControl is TEdit;
end;

procedure TForm1.AppShowHint( var HintStr: string;
var CanShow: Boolean; var HintInfo: THintInfo );
begin
CanShow := not FocusHintWindow.Showing;
end;

end.
----------------------------------------------------------- }

interface

uses SysUtils, WinTypes, WinProcs, Classes, Controls, Forms;

type
  TFocusHintWindow = class(THintWindow)
  private
    FShowing: Boolean;
    HintControl: TControl;
  protected
    procedure SetShowing(Value: Boolean);
    function CalcHintRect(Hint: string): TRect;
    procedure Appear;
    procedure Disappear;
  public
    property Showing: Boolean read FShowing write SetShowing;
  end;

implementation

function TFocusHintWindow.CalcHintRect(Hint: string): TRect;
var
  Buffer: array[Byte] of Char;
begin
  Result := Bounds(0, 0, Screen.Width, 0);
  DrawText(Canvas.Handle, StrPCopy(Buffer, Hint), -1, Result,
    DT_CALCRECT or DT_LEFT or DT_WORDBREAK or DT_NOPREFIX);

  with HintControl, ClientOrigin do
    OffsetRect(Result, X, Y + Height + 6);
  Inc(Result.Right, 6);
  Inc(Result.Bottom, 2);
end;

procedure TFocusHintWindow.Appear;
var
  Hint: string;
  HintRect: TRect;
begin
  if (Screen.ActiveControl = HintControl) then
    Exit;

  HintControl := Screen.ActiveControl;
  Hint := GetShortHint(HintControl.Hint);
  HintRect := CalcHintRect(Hint);
  ActivateHint(HintRect, Hint);
  FShowing := True;
end;

procedure TFocusHintWindow.Disappear;
begin
  HintControl := nil;
  ShowWindow(Handle, SW_HIDE);
  FShowing := False;
end;

procedure TFocusHintWindow.SetShowing(Value: Boolean);
begin
  if Value then
    Appear
  else
    Disappear;
end;

end.