void Hook(IntPtr hookHandle, EnumWindowEvent @event, IntPtr hWnd, int @object, int child, int threadId,
int timestampMs)
{
EventHandler <WindowEventArgs> handler;
switch (@event)
{
case EnumWindowEvent.FOREGROUND_CHANGED:
handler = _activated;
break;
case EnumWindowEvent.NAME_CHANGED:
handler = _textChanged;
break;
case EnumWindowEvent.MINIMIZED:
handler = _minimized;
break;
case EnumWindowEvent.UNMIMINIZED:
handler = _unminimized;
break;
default:
Debug.Write($"Unexpected event {@event}");
return;
}
handler?.Invoke(this, new WindowEventArgs(hWnd));
}
void EnsureHook(EnumWindowEvent @event)
{
if (!_hooksDictionary.TryGetValue(@event, out var hookId))
{
hookId = SetHook(@event);
_hooksDictionary.Add(@event, hookId);
}
}
void EventAdd(ref EventHandler <WindowEventArgs> handler, EventHandler <WindowEventArgs> user,
EnumWindowEvent @event)
{
lock (_hooksDictionary)
{
handler += user;
this.EnsureHook(@event);
}
}
IntPtr SetHook(EnumWindowEvent @event)
{
IntPtr hookId = DllUser32.SetWinEventHook(
hookMin: @event, hookMax: @event,
moduleHandle: IntPtr.Zero, callback: _eventProc,
processId: 0, threadId: 0,
flags: EnumHookFlags.OUT_OF_CONTEXT);
if (hookId == IntPtr.Zero)
{
throw new Win32Exception();
}
return(hookId);
}
void EventRemove(ref EventHandler <WindowEventArgs> handler, EventHandler <WindowEventArgs> user,
EnumWindowEvent @event)
{
lock (_hooksDictionary)
{
if (handler != null && handler - user == null)
{
if (!DllUser32.UnhookWinEvent(_hooksDictionary[@event]))
{
throw new Win32Exception();
}
bool existed = _hooksDictionary.Remove(@event);
Debug.Assert(existed);
}
handler -= user;
}
}
internal static extern IntPtr SetWinEventHook(EnumWindowEvent hookMin, EnumWindowEvent hookMax, IntPtr moduleHandle, WinEventProc callback, int processId, int threadId, EnumHookFlags flags);