{"id":902,"date":"2009-11-06T11:08:05","date_gmt":"2009-11-06T10:08:05","guid":{"rendered":"http:\/\/www.navision-blog.de\/2009\/11\/06\/observing-global-shortcuts\/"},"modified":"2009-11-06T11:12:51","modified_gmt":"2009-11-06T10:12:51","slug":"observing-global-shortcuts","status":"publish","type":"post","link":"http:\/\/www.navision-blog.de\/blog\/2009\/11\/06\/observing-global-shortcuts\/","title":{"rendered":"Observing global hotkeys in C# \/ F#"},"content":{"rendered":"

I recently had the problem to register a global hotkey, but my \u201cold\u201d Win32-API calls didn\u2019t work with WPF. I looked around the web and found the \u201cManaged Windows API<\/a>\u201d, but I didn\u2019t want to add another external dependency to my project, so I extracted the core functions for registering hotkeys and condensed the code to a new version. <\/p>\n

As the original \u201cManaged Windows API\u201d is licensed by the GNU Lesser General Public License (LGPL) I want to provide my modifications here.<\/p>\n

First we need a Window which can dispatch the window messages to our event handlers:<\/p>\n

\n

\/\/\/<\/span> <\/span><summary><\/span><\/p>\n

\/\/\/<\/span> A Win32 native window that delegates window messages to <\/span><\/p>\n

\/\/\/<\/span> <\/span>handlers. So several<\/span><\/p>\n

\/\/\/<\/span> components can use the same native window to save <\/span><\/p>\n

\/\/\/<\/span> <\/span>"USER resources". This class<\/span><\/p>\n

\/\/\/<\/span> is useful when writing your own components.<\/span><\/p>\n

\/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

public<\/span> sealed<\/span> class<\/span> EventDispatchingNativeWindow<\/span> : NativeWindow<\/span><\/p>\n

{<\/p>\n

    private<\/span> static<\/span> readonly<\/span> Object<\/span> MyLock = new<\/span> Object<\/span>();<\/p>\n

    private<\/span> static<\/span> EventDispatchingNativeWindow<\/span> _instance;<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Create your own event dispatching window.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> EventDispatchingNativeWindow()<\/p>\n

    {<\/p>\n

        CreateHandle(new<\/span> CreateParams<\/span>());<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> A global instance which can be used by components <\/span><\/p>\n

    \/\/\/<\/span> <\/span>that do not need<\/span> their own window.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> static<\/span> EventDispatchingNativeWindow<\/span> Instance<\/p>\n

    {<\/p>\n

        get<\/span><\/p>\n

        {<\/p>\n

            lock<\/span> (MyLock)<\/p>\n

            {<\/p>\n

                return<\/span> <\/p>\n

                  _instance ?? <\/p>\n

                     (_instance = <\/p>\n

                       new<\/span> EventDispatchingNativeWindow<\/span>());<\/p>\n

            }<\/p>\n

        }<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Attach your event handlers here.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> event<\/span> WndProcEventHandler<\/span> EventHandler;<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Parse messages passed to this window and send <\/span><\/p>\n

    \/\/\/<\/span> <\/span>them to the event handlers.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="m"><\/span>A System.Windows.Forms.Message <\/span><\/p>\n

    \/\/\/<\/span> <\/span>that is associated with the <\/span><\/p>\n

    \/\/\/<\/span> current Windows message.<\/span><\/param><\/span><\/p>\n

    protected<\/span> override<\/span> void<\/span> WndProc(ref<\/span> Message<\/span> m)<\/p>\n

    {<\/p>\n

        bool<\/span> handled = false<\/span>;<\/p>\n

        if<\/span> (EventHandler != null<\/span>)<\/p>\n

            EventHandler(ref<\/span> m, ref<\/span> handled);<\/p>\n

        if<\/span> (!handled)<\/p>\n

            base<\/span>.WndProc(ref<\/span> m);<\/p>\n

    }<\/p>\n

}<\/p>\n<\/p><\/div>\n

Now we can write our global hotkey handler class:<\/p>\n

\n

\/\/\/<\/span> <\/span><summary><\/span><\/p>\n

\/\/\/<\/span> Specifies a class that creates a global keyboard hotkey.<\/span><\/p>\n

\/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

public<\/span> class<\/span> GlobalHotkey<\/span><\/p>\n

{<\/p>\n

    private<\/span> static<\/span> readonly<\/span> Object<\/span> MyStaticLock = new<\/span> Object<\/span>();<\/p>\n

    private<\/span> static<\/span> int<\/span> _hotkeyCounter = 0xA000;<\/p>\n

 <\/p>\n

    private<\/span> readonly<\/span> int<\/span> _hotkeyIndex;<\/p>\n

    private<\/span> readonly<\/span> IntPtr<\/span> _hWnd;<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Initializes a new instance of this class.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="keys"><\/span>The keys.<\/span><\/param><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="ctrl"><\/span>if <\/span><c><\/span>true<\/span><\/c><\/span> [CTRL].<\/span><\/param><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="alt"><\/span>if <\/span><c><\/span>true<\/span><\/c><\/span> [alt].<\/span><\/param><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="shift"><\/span>if <\/span><c><\/span>true<\/span><\/c><\/span> [shift].<\/span><\/param><\/span><\/p>\n

    \/\/\/<\/span> <\/span><param name="winKey"><\/span>if <\/span><c><\/span>true<\/span><\/c><\/span> [win key].<\/span><\/param><\/span><\/p>\n

    public<\/span> GlobalHotkey(Keys<\/span> keys, bool<\/span> ctrl, <\/p>\n

               bool<\/span> alt, bool<\/span> shift, bool<\/span> winKey)<\/p>\n

    {<\/p>\n

        KeyCode = keys;<\/p>\n

        Ctrl = ctrl;<\/p>\n

        Alt = alt;<\/p>\n

        Shift = shift;<\/p>\n

        WindowsKey = winKey;<\/p>\n

        EventDispatchingNativeWindow<\/span>.Instance.EventHandler <\/p>\n

                += NwEventHandler;<\/p>\n

        lock<\/span> (MyStaticLock)<\/p>\n

        {<\/p>\n

            _hotkeyIndex = ++_hotkeyCounter;<\/p>\n

        }<\/p>\n

        _hWnd = EventDispatchingNativeWindow<\/span>.Instance.Handle;<\/p>\n

        Enable();<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> The key code of the hotkey.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> Keys<\/span> KeyCode { get<\/span>; private<\/span> set<\/span>; }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Whether the shortcut includes the Control modifier.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> bool<\/span> Ctrl { get<\/span>; private<\/span> set<\/span>; }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Whether this shortcut includes the Alt modifier.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> bool<\/span> Alt { get<\/span>; private<\/span> set<\/span>; }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Whether this shortcut includes the shift modifier.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> bool<\/span> Shift { get<\/span>; private<\/span> set<\/span>; }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Whether this shortcut includes the Windows key modifier.<\/span><\/p>\n

\n

<\/span><\/p>\n

      \/\/\/<\/span> <\/span><\/summary><\/span> <\/p>\n

    public<\/span> bool<\/span> WindowsKey { get<\/span>; private<\/span> set<\/span>; }<\/p>\n

 <\/p>\n

    ~GlobalHotkey()<\/p>\n

    {<\/p>\n

        Disable();<\/p>\n

        EventDispatchingNativeWindow<\/span>.Instance.EventHandler <\/p>\n

            -= NwEventHandler;<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Enables the hotkey. When the hotkey is enabled, <\/span><\/p>\n

    \/\/\/<\/span> <\/span>pressing it causes a<\/span><\/p>\n

    \/\/\/<\/span> <\/span><c><\/span>HotkeyPressed<\/span><\/c><\/span> event instead of being <\/span><\/p>\n

    \/\/\/<\/span> <\/span>handled by the active<\/span> application.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    private<\/span> void<\/span> Enable()<\/p>\n

    {<\/p>\n

        \/\/ register hotkey<\/span><\/p>\n

        int<\/span> fsModifiers = 0;<\/p>\n

        if<\/span> (Shift) fsModifiers += ModShift;<\/p>\n

        if<\/span> (Ctrl) fsModifiers += ModControl;<\/p>\n

        if<\/span> (Alt) fsModifiers += ModAlt;<\/p>\n

        if<\/span> (WindowsKey) fsModifiers += ModWin;<\/p>\n

        bool<\/span> success = <\/p>\n

           RegisterHotKey(_hWnd, _hotkeyIndex, <\/p>\n

                fsModifiers, (int<\/span>) KeyCode);<\/p>\n

 <\/p>\n

        if<\/span> (!success)<\/p>\n

            throw<\/span> new<\/span> <\/p>\n

              <\/font>Exception<\/span>(<\/p>\n

                "Could not register hotkey (already in use)."<\/span>);<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Disables this instance.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    private<\/span> void<\/span> Disable()<\/p>\n

    {<\/p>\n

        \/\/ unregister hotkey<\/span><\/p>\n

        UnregisterHotKey(_hWnd, _hotkeyIndex);<\/p>\n

    }<\/p>\n

 <\/p>\n

    \/\/\/<\/span> <\/span><summary><\/span><\/p>\n

    \/\/\/<\/span> Occurs when the hotkey is pressed.<\/span><\/p>\n

    \/\/\/<\/span> <\/span><\/summary><\/span><\/p>\n

    public<\/span> event<\/span> EventHandler<\/span> HotkeyPressed;<\/p>\n

 <\/p>\n

    private<\/span> void<\/span> NwEventHandler(ref<\/span> Message<\/span> m, ref<\/span> bool<\/span> handled)<\/p>\n

    {<\/p>\n

        if<\/span> (handled) return<\/span>;<\/p>\n

        if<\/span> (m.Msg != WmHotkey || <\/p>\n

                m.WParam.ToInt32() != _hotkeyIndex)<\/p>\n

            return<\/span>;<\/p>\n

        if<\/span> (HotkeyPressed != null<\/span>)<\/p>\n

            HotkeyPressed(this<\/span>, EventArgs<\/span>.Empty);<\/p>\n

        handled = true<\/span>;<\/p>\n

    }<\/p>\n

 <\/p>\n

    #region<\/span> PInvoke Declarations<\/p>\n

 <\/p>\n

    private<\/span> const<\/span> int<\/span> ModAlt = 0x0001;<\/p>\n

    private<\/span> const<\/span> int<\/span> ModControl = 0x0002;<\/p>\n

    private<\/span> const<\/span> int<\/span> ModShift = 0x0004;<\/p>\n

    private<\/span> const<\/span> int<\/span> ModWin = 0x0008;<\/p>\n

    private<\/span> const<\/span> int<\/span> WmHotkey = 0x0312;<\/p>\n

 <\/p>\n

    [DllImport<\/span>("user32.dll"<\/span>, SetLastError = true<\/span>)]<\/p>\n

    private<\/span> static<\/span> extern<\/span> bool<\/span> RegisterHotKey(IntPtr<\/span> hWnd, <\/p>\n

          int<\/span> id, int<\/span> fsModifiers, int<\/span> vlc);<\/p>\n

 <\/p>\n

    [DllImport<\/span>("user32.dll"<\/span>, SetLastError = true<\/span>)]<\/p>\n

    private<\/span> static<\/span> extern<\/span> bool<\/span> UnregisterHotKey(IntPtr<\/span> hWnd, <\/p>\n

          int<\/span> id);<\/p>\n

 <\/p>\n

    #endregion<\/span><\/p>\n

}<\/p>\n<\/p><\/div>\n

Now we can easily register a global hotkey or use it as an observable in F#:<\/p>\n

\n

\/\/\/ system-wide keyboard hook<\/span><\/p>\n

let<\/span> hotkey = new<\/span> GlobalHotkey(Keys.Q,true<\/span>,false<\/span>,false<\/span>,false<\/span>)<\/p>\n

let<\/span> hookObserver =<\/p>\n

  hotkey.HotkeyPressed  <\/p>\n

    |> Observable.subscribe (fun<\/span> _ -><\/span> printfn "Hotkey pressed"<\/span>)<\/p>\n<\/p><\/div>\n","protected":false},"excerpt":{"rendered":"

I recently had the problem to register a global hotkey, but my \u201cold\u201d Win32-API calls didn\u2019t work with WPF. I looked around the web and found the \u201cManaged Windows API\u201d, but I didn\u2019t want to add another external dependency to my project, so I extracted the core functions for registering hotkeys and condensed the code […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[12,448],"tags":[81,664,584,583,585],"_links":{"self":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/902"}],"collection":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/comments?post=902"}],"version-history":[{"count":2,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/902\/revisions"}],"predecessor-version":[{"id":904,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/posts\/902\/revisions\/904"}],"wp:attachment":[{"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/media?parent=902"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/categories?post=902"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.navision-blog.de\/blog\/wp-json\/wp\/v2\/tags?post=902"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}