unit2.~pas

then control for change set of pb

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs;

type
  TForm2 = class(TForm)
  private
    { Private declarations }
  public
    { Public declarations }
    function ComputeDockingRect(var DockRect: TRect; MousePos: TPoint): TAlign;    
  end;

var
  Form2: TForm2;

implementation

uses Unit3;

{$R *.dfm}

function TForm2.ComputeDockingRect(var DockRect: TRect;
  MousePos: TPoint): TAlign;
var
  DockTopRect,
  DockLeftRect,
  DockBottomRect,
  DockRightRect,
  DockCenterRect: TRect;
begin
  Result := alNone;
  //divide form up into docking "Zones"
  DockLeftRect.TopLeft := Point(0, 0);
  DockLeftRect.BottomRight := Point(ClientWidth div 5, ClientHeight);

  DockTopRect.TopLeft := Point(ClientWidth div 5, 0);
  DockTopRect.BottomRight := Point(ClientWidth div 5 * 4, ClientHeight div 5);

  DockRightRect.TopLeft := Point(ClientWidth div 5 * 4, 0);
  DockRightRect.BottomRight := Point(ClientWidth, ClientHeight);

  DockBottomRect.TopLeft := Point(ClientWidth div 5, ClientHeight div 5 * 4);
  DockBottomRect.BottomRight := Point(ClientWidth div 5 * 4, ClientHeight);

  DockCenterRect.TopLeft := Point(ClientWidth div 5, ClientHeight div 5);
  DockCenterRect.BottomRight := Point(ClientWidth div 5 * 4, ClientHeight div 5 * 4);

  //Find out where the mouse cursor is, to decide where to draw dock preview.
  if PtInRect(DockLeftRect, MousePos) then
    begin
      Result := alLeft;
      DockRect := DockLeftRect;
      DockRect.Right := ClientWidth div 2;
    end
  else
    if PtInRect(DockTopRect, MousePos) then
      begin
        Result := alTop;
        DockRect := DockTopRect;
        DockRect.Left := 0;
        DockRect.Right := ClientWidth;
        DockRect.Bottom := ClientHeight div 2;
      end
    else
      if PtInRect(DockRightRect, MousePos) then
        begin
          Result := alRight;
          DockRect := DockRightRect;
          DockRect.Left := ClientWidth div 2;
        end
      else
        if PtInRect(DockBottomRect, MousePos) then
          begin
            Result := alBottom;
            DockRect := DockBottomRect;
            DockRect.Left := 0;
            DockRect.Right := ClientWidth;
            DockRect.Top := ClientHeight div 2;
         end
        else
          if PtInRect(DockCenterRect, MousePos) then
          begin
            Result := alClient;
            DockRect := DockCenterRect;
          end;
  if Result = alNone then Exit;

  //DockRect is in screen coordinates.
  DockRect.TopLeft := ClientToScreen(DockRect.TopLeft);
  DockRect.BottomRight := ClientToScreen(DockRect.BottomRight);
end;

end.