In this article, I wish to describe the useful undocumented function
GetTaskmanWindow. The GetTaskmanWindow function returns a handle to
the window that ownes the taskbar buttons.
Here is the quoting about taskbar from Microsoft MSDN:
“The Microsoft® Windows® interface includes a special application desktop
toolbar called the taskbar.
The taskbar can be used for such tasks as switching between open
windows and starting new applications…”
and “The taskbar includes the Start menu, taskbar buttons,
a shortcut menu, and a status area…”.
Unfortunately, Win32 API doesn’t contain documented
function that can be used for accessing to the
taskbar so we should again use an undocumented way.

Here is the prototype for GetTaskmanWindow:

function GetTaskmanWindow (): HWND;

As always, Microsoft doesn’t provide us with the exports symbols
in the User32.lib for this function, so we should load them dynamically using the
GetProcAddress and GetModuleHandle functions:

// getaskmanwnd.cpp (Windows NT/2000)
//
// This example will show you how you can obtain a handle to the
// Windows Taskbar window.
// Translated from C to Delphi by Thomas Stutz
// Original Code:
// (c)1999 Ashot Oganesyan K, SmartLine, Inc
// mailto:ashot@aha.ru, http://www.protect-me.com, http://www.codepile.com

function TaskmanWindow: HWND;
type
  TGetTaskmanWindow = function(): HWND; stdcall;
var
  hUser32: THandle;
  GetTaskmanWindow: TGetTaskmanWindow;
begin
  Result := 0;
  hUser32 := GetModuleHandle('user32.dll');
  if (hUser32 > 0) then
  begin
    @GetTaskmanWindow := GetProcAddress(hUser32, 'GetTaskmanWindow');
    if Assigned(GetTaskmanWindow) then
    begin
      Result := GetTaskmanWindow;
    end;
  end;
end;

procedure ShowTaskmanWindow(bValue: Boolean);
var
  hTaskmanWindow: Hwnd;
begin
  hTaskmanWindow := TaskmanWindow;
  if hTaskmanWindow <> 0 then
  begin
    ShowWindow(GetParent(hTaskmanWindow), Ord(bValue));
  end;
end;

UsageExample to Hide the Taskman Window

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShowTaskmanWindow(False);
end;