Find out what process registered a global hotkey? (Windows API)

As far as I've been able to find out, Windows doesn't offer an API function to tell what application has registered a global hotkey (via RegisterHotkey). I can only find out that a hotkey is registered if RegisterHotkey returns false, but not who "owns" the hotkey.

In the absence of a direct API, could there be a roundabout way? Windows maintains the handle associated with each registred hotkey - it's a little maddening that there should be no way of getting at this information.

Example of something that likely wouldn't work: send (simulate) a registered hotkey, then intercept the hotkey message Windows will send to the process that registered it. First, I don't think intercepting the message would reveal the destination window handle. Second, even if it were possible, it would be a bad thing to do, since sending hotkeys would trigger all sorts of potentially unwanted activity from various programs.

It's nothing critical, but I've seen frequent requests for such functionality, and have myself been a victim of applications that register hotkeys without even disclosing it anywhere in the UI or docs.

(Working in Delphi, and no more than an apprentice at WinAPI, please be kind.)

Solution

Your question piqued my interest, so I've done a bit of digging and while, unfortunately I don't have a proper answer for you, I thought I'd share what I have.

I found this example of creating keyboard hook (in Delphi) written in 1998, but is compilable in Delphi 2007 with a couple of tweaks.

It's a DLL with a call to SetWindowsHookEx that passes through a callback function, which can then intercept key strokes: In this case, it's tinkering with them for fun, changing left cursor to right, etc. A simple app then calls the DLL and reports back its results based on a TTimer event. If you're interested I can post the Delphi 2007 based code.

It's well documented and commented and you potentially could use it as a basis of working out where a key press is going. If you could get the handle of the application that sent the key strokes, you could track it back that way. With that handle you'd be able to get the information you need quite easily.

Other apps have tried determining hotkeys by going through their Shortcuts since they can contain a Shortcut key, which is just another term for hotkey. However most applications don't tend to set this property so it might not return much. If you are interested in that route, Delphi has access to IShellLink COM interface which you could use to load a shortcut up from and get its hotkey:

uses ShlObj, ComObj, ShellAPI, ActiveX, CommCtrl;

procedure GetShellLinkHotKey;
var
  LinkFile : WideString;
  SL: IShellLink;
  PF: IPersistFile;

  HotKey : Word;
  HotKeyMod: Byte;
  HotKeyText : string;
begin
  LinkFile := 'C:\Temp\Temp.lnk';

  OleCheck(CoCreateInstance(CLSID_ShellLink, nil, CLSCTX_INPROC_SERVER, IShellLink, SL));

  // The IShellLink implementer must also support the IPersistFile
  // interface. Get an interface pointer to it.
  PF := SL as IPersistFile;

  // Load file into IPersistFile object
  OleCheck(PF.Load(PWideChar(LinkFile), STGM_READ));

  // Resolve the link by calling the Resolve interface function.
  OleCheck(SL.Resolve(0, SLR_ANY_MATCH or SLR_NO_UI));

  // Get hotkey info
  OleCheck(SL.GetHotKey(HotKey));

  // Extract the HotKey and Modifier properties.
  HotKeyText := '';
  HotKeyMod := Hi(HotKey);

  if (HotKeyMod and HOTKEYF_ALT) = HOTKEYF_ALT then
    HotKeyText := 'ALT+';
  if (HotKeyMod and HOTKEYF_CONTROL) = HOTKEYF_CONTROL then
    HotKeyText := HotKeyText + 'CTRL+';
  if (HotKeyMod and HOTKEYF_SHIFT) = HOTKEYF_SHIFT then
    HotKeyText := HotKeyText + 'SHIFT+';
  if (HotKeyMod and HOTKEYF_EXT) = HOTKEYF_EXT then
    HotKeyText := HotKeyText + 'Extended+';

  HotKeyText := HotKeyText + Char(Lo(HotKey));

  if (HotKeyText = '') or (HotKeyText = #0) then
    HotKeyText := 'None';

  ShowMessage('Shortcut Key - ' + HotKeyText);
end;

If you've got access to Safari Books Online, there is a good section about working with shortcuts / shell links in the Borland Delphi 6 Developer's Guide by Steve Teixeira and Xavier Pacheco. My example above is a butchered version from there and this site.

Hope that helps!