format PE GUI 4.0 DLL
entry DllMain

include '%fasminc%\win32a.inc'

struct MOUSEHOOKSTRUCT
        .pt             POINT
        .hwnd           dd ?
        .wHitTestCode   dd ?
        .dwExtraInfo    dd ?
ends

WMU_MOUSEHOOK equ WM_USER + 6

section '.data' data readable writeable
        insH            dd ?                    ;handle for instance

section '.sdata' readable writeable shareable
        hookH   dd ?
        wndH    dd ?

section '.code' code readable executable
   proc DllMain, hinstDll, fdwReason, lpvReserved
                push [hinstDll]
                pop  [insH]
                mov  eax,TRUE
                ret
   endp
        
   proc mouse_procedure,nCode,wParam,lParam
        invoke  CallNextHookEx,[hookH],[nCode],[wParam],[lParam]
                mov  edx,[lParam]
        invoke  WindowFromPoint,[edx + MOUSEHOOKSTRUCT.pt.x],[edx + MOUSEHOOKSTRUCT.pt.y]
        invoke  PostMessage,[wndH],WMU_MOUSEHOOK,eax,0
                xor  eax,eax            ;must clear eax here
                ret
   endp
   
   proc mouse_hook_install,wndTempH
                push [wndTempH]
                pop  [wndH]
        invoke  SetWindowsHookEx,WH_MOUSE,mouse_procedure,[insH],NULL
                mov  [hookH],eax
                ret
   endp

   proc mouse_hook_uninstall
        invoke  UnhookWindowsHookEx,[hookH]
                ret
   endp

section '.idata' import data readable
        library USER32, 'USER32.DLL'

        import  USER32,\
                CallNextHookEx,         'CallNextHookEx',\
                WindowFromPoint,        'WindowFromPoint',\
                PostMessage,            'PostMessageA',\
                SetWindowsHookEx,       'SetWindowsHookExA',\
                UnhookWindowsHookEx,    'UnhookWindowsHookEx'

section '.edata' export data readable
        export  'TUT_24A.DLL',\
                mouse_procedure,        'mouse_procedure',\
                mouse_hook_install,     'mouse_hook_install',\
                mouse_hook_uninstall,   'mouse_hook_uninstall'

section '.reloc' fixups data discardable    

        invoke  WindowFromPoint,[edx + MOUSEHOOKSTRUCT..pt.x],[edx + MOUSEHOOKSTRUCT..pt.y]