How to get detailed information about the Windows taskbar programmatically

Problem/Question/Abstract:

I'm trying to determine the edge and rectangle of the Windows taskbar, using the SHAppBarMessage API - but how do I get the Windows taskbar handle?

Answer:

I put a procedure together that gets all the information one would want to get about the TaskBar: Pos (Rect), Edge, window handle, and whether it's set to be AutoHide or AlwaysOnTop. I got the parameter and return information by following the parameter value entries within the Win32 Programmers' reference Online Help file. I also used a 1 second timer to fire the ButtonClick, so that I could test dragging and resizing the TaskBar. I'm not sure if the "Edge section" of code (ABM_GETAUTOHIDEBAR) will work properly if there are other AppBars on the system.

procedure GetTaskBarData(var AppBarInfo: TAppBarData; var AutoHide, AlwaysOnTop:
  boolean);
var
  i, RetVal: Cardinal;
begin
  fillchar(AppBarInfo, sizeof(AppBarInfo), 0);
  AppBarInfo.cbSize := sizeof(AppBarInfo);
  RetVal := ShAppBarMessage(ABM_GETSTATE, AppBarInfo);
  AutoHide := RetVal and ABS_AUTOHIDE > 0;
  AlwaysOnTop := RetVal and ABS_ALWAYSONTOP > 0;
  for i := 0 to 3 do
  begin {ask all the edges}
    AppBarInfo.uEdge := i; {then drop the Taskbar Handle into AppBarInfo}
    AppBarInfo.hWnd := ShAppBarMessage(ABM_GETAUTOHIDEBAR, AppBarInfo);
    if AppBarInfo.hWnd <> 0 then
      break;
    {the Taskbar's edge value is left in uEdge by the break}
  end;
  SHAppBarMessage(ABM_GETTASKBARPOS, AppBarInfo);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  ABI: TAppBarData;
  AHide, AlOnTop: Boolean;
  s: string;
begin
  GetTaskBarData(ABI, AHide, AlOnTop);
  with ABI do
  begin
    caption := format('%d %d %d %d', [rc.left, rc.top, rc.right, rc.bottom]);
    case uEdge of
      ABE_BOTTOM: s := 'Bottom';
      ABE_LEFT: s := 'Left';
      ABE_RIGHT: s := 'Right';
      ABE_TOP: S := 'Top';
    end;
    if AHide then
      s := s + ' AutoHide';
    if AlOnTop then
      s := s + ' AlwaysOnTop';
    caption := caption + ' ' + s;
  end;
end;