user32 EnumDisplayMonitors rewrite (go style) (#26)

typedef.go

@@ -937,6 +937,8 @@ type HOOKPROC func(int, WPARAM, LPARAM) LRESULT
 // https://msdn.microsoft.com/en-us/library/windows/desktop/ms633498(v=vs.85).aspx
 type WNDENUMPROC func(HWND, LPARAM) LRESULT
 
+type MONITORENUMPROC func(HMONITOR, HDC, RECT, LPARAM) bool
+
 //https://msdn.microsoft.com/en-us/library/windows/desktop/aa366775(v=vs.85).aspx
 type MEMORY_BASIC_INFORMATION struct {
 	BaseAddress       PVOID

user32.go

@@ -1077,12 +1077,18 @@ func GetMonitorInfo(hMonitor HMONITOR, lmpi *MONITORINFO) bool {
 	return ret != 0
 }
 
-func EnumDisplayMonitors(hdc HDC, clip *RECT, fnEnum, dwData uintptr) bool {
+func EnumDisplayMonitors(hdc HDC, clip *RECT, fnEnum MONITORENUMPROC, dwData LPARAM) bool {
 	ret, _, _ := procEnumDisplayMonitors.Call(
 		uintptr(hdc),
 		uintptr(unsafe.Pointer(clip)),
-		fnEnum,
-		dwData,
+		syscall.NewCallback(func(Arg1 HMONITOR, Arg2 HDC, Arg3 uintptr, Arg4 LPARAM) LRESULT {
+			if fnEnum(Arg1, Arg2, *(*RECT)(unsafe.Pointer(Arg3)), Arg4) {
+				return 1
+			} else {
+				return 0
+			}
+		}),
+		uintptr(dwData),
 	)
 	return ret != 0
 }