procedure TForm1.Panel1MouseDown(Sender: TObject; Button: TMouseButton;
 Shift: TShiftState; X, Y: Integer);
begin
 if Button = mbLeft then
 begin
   ReleaseCapture;
   TControl(Sender).Perform(WM_SYSCOMMAND, $F008 , 0); // $F012
 end;
end;

procedure TForm1.Panel1MouseMove(Sender: TObject; Shift: TShiftState; X,
 Y: Integer);
begin
 Caption := IntToStr(x) + ' ' + IntToStr(y);
end;

procedure TForm1.Panel1Resize(Sender: TObject);
begin
 Caption := FloatToStr(Panel1.Width) + ' ' + FloatToStr(Panel1.Height);
end;

object Form1: TForm1
 Left = 192
 Top = 114
 Width = 602
 Height = 374
 Caption = 'Form1'
 Color = clBtnFace
 Font.Charset = DEFAULT_CHARSET
 Font.Color = clWindowText
 Font.Height = -11
 Font.Name = 'MS Sans Serif'
 Font.Style = []
 OldCreateOrder = False
 OnResize = FormResize
 PixelsPerInch = 96
 TextHeight = 13
 object Panel1: TPanel
   Left = 164
   Top = 100
   Width = 185
   Height = 61
   BorderWidth = 2
   Caption = 'Panel1'
   TabOrder = 0
   OnMouseDown = Panel1MouseDown
   OnMouseMove = Panel1MouseMove
   object Memo1: TMemo
     Left = 3
     Top = 3
     Width = 179
     Height = 55
     Align = alClient
     Lines.Strings = (
       'Memo1')
     TabOrder = 0
   end
 end
end

unit Unit1;
interface
uses
 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, StdCtrls;

type
 TPosMouseRect = (pmNone, pmRect, pmLU, pmU, pmRU, pmR, pmRD, pmD, pmLD, pmL);

 TForm1 = class(TForm)
   Panel1: TPanel;
   Memo1: TMemo;
   procedure Panel1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
   procedure Panel1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
   procedure FormResize(Sender: TObject);
 private { Private declarations }
   OldX, OldY: Integer; PMDown: TPosMouseRect;
 public { Public declarations }
 end;

var Form1: TForm1;

implementation

{$R *.dfm}

function GetPosMouseInRect(Rct: TRect; MP: TPoint; AVal: Integer): TPosMouseRect;
function XLeft: Boolean; begin Result:=MP.X<Rct.Left+AVal; end;
function XRight: Boolean; begin Result:=MP.X>Rct.Right-Rct.Left-AVal; end;
function XCentr: Boolean; begin Result:=(MP.X>=Rct.Left+AVal) and (MP.X<=Rct.Right-Rct.Left-AVal) end;
function YTop: Boolean; begin Result:=MP.Y<Rct.Top+AVal; end;
function YBottom: Boolean; begin Result:=MP.Y>Rct.Bottom-Rct.Top-AVal end;
function YCenter: Boolean; begin Result:=(MP.Y>=Rct.Top+AVal) and (MP.Y<=Rct.Bottom-Rct.Top-AVal) end;
begin
 Result:=pmNone;
 if not PtInRect(Rct, MP) then Exit;
 if XLeft and YTop then Result:=pmLU else
 if XLeft and YCenter then Result:=pmL else
 if XLeft and YBottom then Result:=pmLD else
 if XCentr and YTop then Result:=pmU else
 if XRight and YTop then Result:=pmRU else
 if XRight and YCenter then Result:=pmR else
 if XRight and YBottom then Result:=pmRD else
 if XCentr and YBottom then Result:=pmD else
 Result:=pmRect;
end;

procedure TForm1.Panel1MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
 OldX:=X; OldY:=Y; PMDown:=GetPosMouseInRect(Panel1.ClientRect, Point(X, Y), 4);
end;

procedure TForm1.Panel1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var NewX, NewY: Integer;
begin
 case GetPosMouseInRect(Panel1.ClientRect, Point(X, Y), 4) of
  pmRect, pmNone: Panel1.Cursor:=crDefault;
  pmU, pmD: Panel1.Cursor:=crSizeNS;
  pmLU, pmRD: Panel1.Cursor:=crSizeNWSE;
  pmLD, pmRU: Panel1.Cursor:=crSizeNESW;
  pmL, pmR: Panel1.Cursor:=crSizeWE;
 end;
 if not (ssLeft in Shift) then Exit;
 NewX:=X-OldX;
 NewY:=Y-OldY;
 with (Sender as TControl) do
  case PMDown of
   pmRect: SetBounds(Left + NewX, Top + NewY, Width, Height); //В принципе в данной задаче не нужно.
   pmL:  SetBounds(Left + NewX, Top, Width+-NewX*2, Height);
   pmLU: SetBounds(Left + NewX, Top + NewY, Width+-NewX*2, Height+-NewY*2);
   pmU:  SetBounds(Left, Top + NewY, Width, Height+-NewY*2);
   //pmR: Sorry...
   //pmD: Sorry...
   //pmRD: Sorry...
   //pmLD: Sorry...
  end;
end;

procedure TForm1.FormResize(Sender: TObject);
begin
 Panel1.Left:=(ClientWidth-Panel1.Width) div 2;
 Panel1.Top:=(ClientHeight-Panel1.Height) div 2;
end;

end.

pmR: SetBounds(Left + NewX, Top, Width - NewX*2, Height);

if (NewX>=Panel1.Width-20) or (NewY>=Panel1.Height-20) then Exit; //20 это минимальный размер

   pmR:    begin
            SetBounds(Left - StepX, Top, Width + StepX*2, Height);
            OldX:=X+StepX;
           end;
   pmD:    begin
            SetBounds(Left, Top - StepY, Width, Height + StepY*2);
            OldY:=Y+StepY;
           end;
   pmRD:   begin
            SetBounds(Left - StepX, Top - StepY, Width + StepX*2, Height + StepY*2);
            OldX:=X+StepX; OldY:=Y+StepY;
           end;
   pmLD:   begin
            SetBounds(Left + StepX, Top - StepY, Width + -StepX*2, Height + StepY*2);
            OldY:=Y+StepY;
           end;
   pmRU:   begin
            SetBounds(Left - StepX, Top + StepY, Width + StepX*2, Height + -StepY*2);
            OldX:=X+StepX;
           end;
  end;

if (Panel1.Width<=20+StepX) or (Panel1.Height<=20+StepY) then Exit;