CODEWITHSUNDEEP
delphiwinapi
Mojtaba Tajik
Mojtaba Tajik

Reputation: 1733

Check is current active window Desktop or no

I try to check if current active window is Desktop do something , i wrote below code in a timer but the handle value returned by GetDektopWindow & GetForegroundWindow is not same value :

  if GetForegroundWindow = GetDesktopWindow then
    // Do something

How do this ?

Upvotes: 3

Views: 4176

Answers (3)

Sertac Akyuz
Sertac Akyuz

Reputation: 54792

// not defined in D2007
function GetShellWindow: HWND; stdcall; external user32;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  if GetForegroundWindow = GetShellWindow then
    [..]
end;

With the only non-explorer shell I use (sharpe) it fails though.

update:

Sometimes the window hierarchy of the desktop is different (see Andreas' comments). The below shot is Spy++'s take when Windows 7's desktop picture rotation functionality is activated. Some 'WorkerW' window takes over the screen and it is the one that gets activated when clicked on the desktop. Since GetShellWindow returns the 'Progman's handle, the above test fails.

Spy++.png

At this point it might seem reasonable to test if the foreground window has the shell's default view window as its immediate child, however I saw multiple references that indicate multiple 'WorkerW' windows might get nested. So I think the below would be a more fail-safe approach:

procedure TForm1.Timer1Timer(Sender: TObject);

  function HasDefViewChild(Wnd: HWND): Boolean;
  begin
    Result := Wnd <> 0;
    if Result then begin
      Result := FindWindowEx(Wnd, 0, 'SHELLDLL_DefView', nil) <> 0;
      if not Result then
        Result := HasDefViewChild(FindWindowEx(Wnd, 0, 'WorkerW', nil));
    end;
  end;

begin
  if HasDefViewChild(GetForegroundWindow) then
    [...]
end;

This will work when the foreground window is 'Progman', because then the 'DefView' is 'Progman's child. OTOH when 'WorkerW' is the active window, the code will iterate if the first child is not 'DefView' and yet another 'WorkerW' instead.

Upvotes: 5

Mojtaba Tajik
Mojtaba Tajik

Reputation: 1733

I search about this , GetWindowDesktop return the handle of desktop window but the desktop window is under another window called shell , so when you switch to dektop really you switch to shell window and must get shell handle , if you terminate process of shell window ( explorer.exe ) then you can see the real dektop window .

Upvotes: 0

Chris Thornton
Chris Thornton

Reputation: 15817

A great tool for figuring out the structure of window parent/child relationships, window classes, etc., is WinDowse by Greatis Software. http://www.greatis.com/delphicb/windowse/ I would start there. And I'd output the values of GetForegroundWindow and GetDesktopWindow (etc.,) onto labels in your test app. So you can see what those values are, as you poke around with WinDowse, in real time.

Upvotes: 2

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