[SOLVED] Win32: Problems with aero screen snap

Hi All,
I'm posting this because I -know- that someone will run into this problem when writing code.

The Problem: How to move a Window (form) around the screen by dragging it by its' client area.

Seasoned programmers will think they know the solution to this, and typically, they'd suggest handling the WM_NCHITTEST
message. However, by doing this, you buy into Microsofts aero screen snap bug.

What I have found that Windows dragged using the WM_NCHITTEST message will clip when dragged off of the top of the screen. I have tested this under Delphi 7, Lazarus (latest version, and TDM-GCC)

Well...Here's a workaround for anyone who runs into this problem:

Instead of responding to the WM_NCHITTEST message, use the WM_LBUTTONDOWN, WM_MOUSEMOVE, and WM_MOUSEUP messages.

Here's the code in pascal, but the same thing applies to just about every programming language that supports Windows messages.

Code:

unit Unit1;

{$mode objfpc}{$H+}

interface

uses
 Windows,LCLType, Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs;

type
{ TForm1 }
  TForm1 = class(TForm)
 procedure FormMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
 procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
 procedure FormMouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
  private
  public
end;

var
  Form1: TForm1;

implementation

var
  OldCoords: TPoint;
  bMouseDown: Boolean = False;

{$R *.lfm}

{ TForm1 }

procedure TForm1.FormMouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
Windows.GetCursorPos(OldCoords);
Windows.ScreenToClient(Self.Handle,OldCoords);
Windows.SetCapture(Self.Handle);
bMouseDown := True;
end;

procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
var
  ptMouse,pt: TPoint;
begin
inherited;
GetCursorPos(ptMouse);
Windows.ScreenToClient(Self.Handle,ptMouse);

//
// A trick to capture the 'delta' that the mouse moved...
// This is best done in client coordinates.
//

if bMouseDown = True then
begin
     pt.x := (ptMouse.x - OldCoords.x);
     pt.y := (ptMouse.y - OldCoords.y);

     Self.Left := Self.Left + pt.x;
     Self.Top := Self.Top + pt.y;
end;
end;


procedure TForm1.FormMouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
bMouseDown := False;
Windows.ReleaseCapture;
end;
end.

I hope this saves someone time, grief, and aggravation.