Global mouse hook in Delphi

Hello everyone!

On my primary job I have changed my mouse. At home I have A4Tech optical mouse with a scroll but on my job I have Genius mouse (optical and with a scroll as well). At home I use my scroll also as a middle button and when I press it the window which is under cursor getting minimized. It was easy to achieve this behavior because software which comes with my A4Tech mouse supports this functionality. Another case is my Genius mouse at work. Software which bundled with it does not allow to minimize the window under the cursor when the scroll button is pressed. Pity!

But solution always can be found! I decided to write 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 = 'Igor_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 < 0 then
begin
  Result := CallNextHookEx(GlobalData^.HookHandle, Code, wParam, lParam);
  exit;
end; // if

if (wParam = WM_NCMBUTTONDOWN) or (wParam = WM_MBUTTONDOWN) then
begin
  CurrWND := PMouseHookStruct(lParam)^.hwnd;
  CurrWND := GetAncestor(CurrWND, GA_ROOTOWNER);
  SendMessage(CurrWND, WM_SYSCOMMAND, SC_MINIMIZE, 0);
end; // if

Result := CallNextHookEx(GlobalData^.HookHandle, Code, wParam, lParam);
end;

procedure CreateGlobalHeap;
begin
MMF:= CreateFileMapping(INVALID_HANDLE_VALUE, nil, PAGE_READWRITE, 0,
  SizeOf(TDLLGlobal), MemMapFile);

if MMF = 0 then begin
  MessageBox(0, 'CreateFileMapping -', '', 0);
  exit;
end;

GlobalData:= MapViewOfFile(MMF, FILE_MAP_ALL_ACCESS, 0, 0, SizeOf(TDLLGlobal));
if GlobalData = nil then begin
// не смогди создать отображение
  CloseHandle(MMF);
  MessageBox(0, 'MapViewOfFile -', '', 0);
end;
end;

procedure DeleteGlobalHeap;
begin
if GlobalData<>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.

If you don't know what is HOOK and how it works at all then you shoulf go and read MSDN.
Good luck! Study hard!