Author: Jonas Bilinkevicius 

How to determine the size of the Windows taskbar

Answer:

Solve 1:

You need to get the Rect in the rc member of the APPBARData structure and subtract 
the top from the bottom.

1   procedure TForm1.Button1Click(Sender: TObject);
2   var
3     appbardata: TAppBarData;
4     Rect: TRect;
5     taskBarHeight: Integer;
6   begin
7     AppBarData.cbSize := 0;
8     AppBarData.hWnd := 0;
9     AppBarData.rc.Left := 0;
10    AppBarData.rc.Top := 0;
11    AppBarData.rc.Bottom := 0;
12    AppBarData.rc.Right := 0;
13    SHAppBarMessage(ABM_GETTASKBARPOS, appbardata);
14    Rect := appbardata.rc;
15    taskBarHeight := Rect.Bottom - Rect.Top;
16    ShowMessage(IntToStr(taskBarHeight));
17  end;



Solve 2:

18  function GetTaskBarSize: TRect;
19  var
20    wnd: HWND;
21  begin
22    wnd := FindWindow('Shell_TrayWnd', nil);
23    if wnd > 0 then
24      GetWindowRect(wnd, Result)
25    else
26      Result := Rect(0, 0, 0, 0);
27  end;



Solve 3:

This is one way to get the height of the taskbar:

28  function GetTaskBarRect: TRect;
29  var
30    TBData: TAppBarData;
31  begin
32    TBData.cbSize := sizeof(TAppBarData);
33    SHAppBarMessage(ABM_GETTASKBARPOS, TBData);
34    Result := TBData.rc;
35  end;