Global mouse hook

Here is a global mouse hook on Delphi which will intercept middle (scroll) button click (WM_NCMBUTTONDOWN and WM_MBUTTONDOWN messages), check if any top level window is under the cursor and if yes then minimize that window.

The code is pretty simple.

We need two projects: one - which runs the hook and then kills it; the other - the hook itself (it is supposed to be a DLL because it is a global hook). Nothing difficult (at least if you what is DLL and how to use them)!

Here is the mouse hook (WH_MOUSE) implementation:

library MiddleButton;

uses
Windows,
Messages;

const
MemMapFile = 'temp_thief';
type
PDLLGlobal = ^TDLLGlobal;
TDLLGlobal = packed record
HookHandle: HHOOK;
end;

var
GlobalData: PDLLGlobal;
MMF: THandle;

{$R *.res}

function HookProc(Code: integer; wParam: WPARAM; lParam: LPARAM): LRESULT; stdcall;
var
CurrWND: THandle;
begin
if Code < wparam =" WM_NCMBUTTONDOWN)" wparam =" WM_MBUTTONDOWN)" mmf =" 0" globaldata =" nil">nil then
UnmapViewOfFile(GlobalData);

if MMF<> INVALID_HANDLE_VALUE then
CloseHandle(MMF);
end;

procedure RunHook; stdcall;
begin
GlobalData^.HookHandle:= SetWindowsHookEx(WH_MOUSE, @HookProc, HInstance, 0);
if GlobalData^.HookHandle = INVALID_HANDLE_VALUE then
begin
MessageBox(0, 'Error :)' , '' , MB_OK);
Exit;
end;
end;

procedure KillHook; stdcall;
begin
if (GlobalData<>nil) and (GlobalData^.HookHandle<>INVALID_HANDLE_VALUE) then
UnhookWindowsHookEx(GlobalData^.HookHandle);
end;

procedure DLLEntry(dwReason: DWORD);
begin
case dwReason of
DLL_PROCESS_ATTACH: CreateGlobalHeap;
DLL_PROCESS_DETACH: DeleteGlobalHeap;
end;
end;

exports
KillHook,
RunHook;

begin
DLLProc:= @DLLEntry;
DLLEntry(DLL_PROCESS_ATTACH);
end.And here is an implementation of the hook launcher:
unit RunMiddleButton;

interface

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

type
TfrmMain = class(TForm)
btnRunHook: TButton;
btnKillHook: TButton;
procedure btnRunHookClick(Sender: TObject);
procedure btnKillHookClick(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

procedure RunHook; stdcall; external 'MiddleButton.dll' name 'RunHook';
procedure KillHook; stdcall; external 'MiddleButton.dll' name 'KillHook';

var
frmMain: TfrmMain;

implementation

{$R *.dfm}

procedure TfrmMain.btnRunHookClick(Sender: TObject);
begin
RunHook;
end;

procedure TfrmMain.btnKillHookClick(Sender: TObject);
begin
KillHook;
end;

end.