Almost 20 years ago I already worked deeply in some system functionality of Windows OS, even without the Internet, but still with will to knowledge.

CoolHint.pas

unit CoolHint;

interface
uses
  Windows, SysUtils, Classes, Graphics, Controls, Forms, StdCtrls, Hook;

type
  TCoolHint = class(THintWindow)
    bmp: TBitmap;
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
  public
    procedure CreateParams(var Params: TCreateParams); override;
    procedure ActivateHint(Rect: TRect; const AHint: string); override;
    function CalculateHintRect(Point: TPoint; Hint: string): TRect;
  protected
    procedure Paint; override;
  end;

var ColorArrow: TColor = $0040c0ff;
    ColorInformation: TColor = clSkyBlue;
    ColorQuestion: TColor = clGreen;
    ColorWarning: TColor = clRed;
    ColorRadiation: TColor = clGray;
    IsFlat: Boolean = false;


function ShowErrorHintAtControl(Expression: boolean;Control: TWinControl;
  Hint: String; Duration: Cardinal=3000): boolean;

implementation

uses Types;

var R,ControlRect: TRect;
    ContHeight, ContWidth: word;
    HintText: string;
    Handed: boolean;
    C,arrow: char;
    cl: TColor;

{$R hint.res}

function ShowErrorHintAtControl(Expression: boolean;Control: TWinControl;
  Hint: String; Duration: Cardinal=3000): boolean;
var HintWindow: TCoolHint;
    Ticks: Cardinal;
begin
  Result:=Expression;
  if not Expression
    then Exit;
  HintWindow:=TCoolHint.Create(Control);
  ControlRect:=Control.ClientRect;
  Handed:=true;
  ControlRect.TopLeft:=Control.ClientToScreen(ControlRect.TopLeft);
  ControlRect.BottomRight:=Control.ClientToScreen(ControlRect.BottomRight);
  HintWindow.ActivateHint(HintWindow.CalculateHintRect(
    Point(ControlRect.Left,ControlRect.Bottom),Hint),Hint);
  Handed:=false;
  Ticks:=GetTickCount;
  while GetTickCount<Ticks+Duration do
    Application.ProcessMessages;
  HintWindow.Free;
end;

procedure TCoolHint.CreateParams(var Params: TCreateParams);
begin
inherited CreateParams(Params);
  Params.Style := Params.Style and not ws_Border or CS_DROPSHADOW;
end;

function TCoolHint.CalculateHintRect(Point: TPoint; Hint: string): TRect;
var dr: TRect;
begin
  dr:=rect(0,0,Self.Canvas.TextWidth(Hint),0);
  DrawText(Self.Canvas.Handle, PChar(Hint),-1, dr, DT_CALCRECT or DT_LEFT or
    DT_WORDBREAK or DT_NOPREFIX or DT_RTLREADING);
  Inc(dr.Right, 4);
  Inc(dr.Bottom, 2);
  result:=dr;
end;

constructor TCoolHint.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  with Canvas.Font do
  begin
    Name := 'Arial';
    Style := Style + [fsBold];
    Color := clBlack;
  end;
  bmp := TBitmap.Create;
  bmp.Transparent:=true;
  Canvas.Brush.Style := bsClear;
end;

destructor TCoolHint.Destroy;
begin
inherited destroy;
bmp.Free;
end;

procedure TCoolHint.Paint;
begin
  R:=ClientRect;
  with Canvas do
  begin
    Pen.Color := clBlack;
    Brush.Color := clWhite;
    Rectangle(0, 0, r.Right, R.Bottom);
    case c of
      '?': cl:=ColorQuestion;
      '!': cl:=ColorWarning;
      'i': cl:=ColorInformation;
      'r': cl:=ColorRadiation;
    else
      if IsFlat
        then cl:=clBtnFace
        else cl:=ColorArrow;
    end;
    Brush.Color := cl;
    Pen.Color := cl;

    if (c<>'?') and (c<>'!') and (c<>'i') and (c<>'Ё') and (c<>'ш') and (c<>'r')
      then case arrow of
        '1','2','3','4': begin
            Rectangle(1, 1, 17, R.Bottom-1);
            R.Left:=20;
            R.Top:=1;
            Draw(3, 2+(R.Bottom-16)*
              byte((Height>18) and ((arrow='2') or (arrow='4'))), bmp);
          end;
        '5','6': begin
            Rectangle(R.Right-17, 1, R.Right-1, R.Bottom-1);
            R.Left:=4;
            R.Top:=1;
            Draw(R.Right-15, 2+(R.Bottom-16)*
              byte((Height>18) and (arrow='5')), bmp);
          end;
      end else begin
        Rectangle(1+(R.Right-18)*byte((arrow='5') or (arrow='6')), 1,
          17+(R.Right-18)*byte((arrow='5') or (arrow='6')), R.Bottom-1);
        R.Left:=20-17*byte((arrow='5') or (arrow='6'));
        R.Top:=1;
        Draw(3+(R.Right-17)*byte((arrow='5') or (arrow='6')),
          2+(R.Bottom-16)*byte((Height>18) and ((arrow='2')
            or (arrow='4') or (arrow='5'))), bmp);
      end;
  end;
  Canvas.Brush.Color := clWhite;
  DrawText(Canvas.Handle, PChar(HintText), -1, R, DT_LEFT or DT_NOPREFIX or
    DT_WORDBREAK or DrawTextBiDiModeFlagsReadingOnly);
end;

procedure TCoolHint.ActivateHint(Rect: TRect; const AHint: string);
var cont: TControl;
begin
    C:=AHint[1];
    arrow:='1';
    case c of
      '?': bmp.LoadFromResourceName(HInstance,'QUESTION');
      '!': bmp.LoadFromResourceName(HInstance,'WARNING');
      'i','ш': bmp.LoadFromResourceName(HInstance,'INFORMATION');
      'r','Ё': bmp.LoadFromResourceName(HInstance,'RADIATION');
    end;
    if (c<>'?') and (c<>'!') and (c<>'i') and (c<>'Ё') and (c<>'ш') and (c<>'r')
      then HintText:=AHint
      else HintText:=copy(AHint,2,255);
    Rect.Right:=Rect.Right+17;
    if not Handed
      then begin
        cont:=FindDragTarget(Mouse.CursorPos,true);
        ControlRect:=cont.ClientRect;
        ControlRect.TopLeft:=cont.ClientToScreen(ControlRect.TopLeft);
        ControlRect.BottomRight:=cont.ClientToScreen(ControlRect.BottomRight);
      end;
    ContHeight:=ControlRect.Bottom - (ControlRect.Top)*byte(not (ControlRect.Top<0));
    ContWidth:=ControlRect.Right - (ControlRect.Left)*byte(not (ControlRect.Left<0));

    UpdateBoundsRect(Rect);
    Rect.Top:=ControlRect.Bottom+2;
    Rect.Left:=ControlRect.Left;
    Rect.Right:=Rect.Left+Width;
    Rect.Bottom:=Rect.Top+Height;

    if (Rect.Bottom > Screen.ActiveForm.Height+Screen.ActiveForm.Top)
      and (Height<Screen.ActiveForm.Height) then begin
        Rect.Top := Rect.Top - Height - ContHeight -3;
        arrow:='2';
      end;
    if ((Rect.Right > Screen.ActiveForm.Left+Screen.ActiveForm.Width)
      and (Rect.Left-Width-2>Screen.ActiveForm.Left)
      and (Width<Screen.ActiveForm.Width))
      or (Rect.Right>Screen.Width) then begin
        Rect.Left := Rect.Left - Width -2;
        if arrow='1' then arrow:='6';
        if arrow='2' then arrow:='5';
      end;
    if Width < ContWidth then begin
        if arrow='2' then arrow:='4';
        if arrow='1' then arrow:='3';
      end;

    if (c<>'?') and (c<>'!') and (c<>'i') and (c<>'Ё') and (c<>'ш') and (c<>'r')
      then bmp.LoadFromResourceName(HInstance,'ARROW'+arrow);

    SetWindowPos(Handle, HWND_TOPMOST, Rect.Left, Rect.Top, Width, Height,
      SWP_SHOWWINDOW or SWP_NOACTIVATE);
    Repaint;
    Invalidate;
end;

initialization
  HintWindowClass := TCoolHint;
  Handed:=false;    
//  Application.HintPause:=1500;
//  Application.HintHidePause:=3000;
//  Application.HintShortPause:=100;
end.