Author: Jonas Bilinkevicius

I want to add a menu item to the menu, which pops up when you right-click on the 
taskbar button for your application. I know how to add item to form system menu, 
but it doesn't change the popup menu on the taskbar.

Answer:

Solve 1:

1   unit Unit1;
2   
3   interface
4   
5   uses
6     Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
7     StdCtrls, ExtCtrls;
8   
9   const
10    idSysAbout = 100;
11  
12  type
13    TForm1 = class(TForm)
14      procedure FormCreate(Sender: TObject);
15    public
16      procedure AppMessage(var Msg: TMsg; var Handled: Boolean);
17    end;
18  
19  var
20    Form1: TForm1;
21  
22  implementation
23  
24  {$R *.DFM}
25  
26  procedure TForm1.AppMessage(var Msg: TMsg; var Handled: Boolean);
27  begin
28    if (Msg.message = WM_SYSCOMMAND) and (Msg.WParam = idSysAbout) then
29    begin
30      ShowMessage('This is a test');
31      Handled := True;
32    end;
33  end;
34  
35  procedure TForm1.FormCreate(Sender: TObject);
36  begin
37    AppendMenu(GetSystemMenu(Application.Handle, False), MF_SEPARATOR, 0, '');
38    AppendMenu(GetSystemMenu(Application.Handle, False), MF_STRING, idSysAbout, 
39  'Test');
40    Application.OnMessage := AppMessage;
41  end;
42  
43  end.



Solve 2:

The popup menu for a Taskbar button is the Application windows system menu. To add 
items to it you need to use API functions.

44  { ... }
45  var
46    hSysMenu: HMENU;
47  begin
48    hSysMenu := getSystemMenu(Application.handle, false);
49    AppendMenu(hSysmenu, MF_STRING, $100, 'My Item');
50  
51  The item IDs you use ($100 in this example) need to be multiples of 16, in hex 
52  notation that means the last digit is 0. Take care not to conflict with the 
53  predefined SC_ menu constants for the system menu. All of these have values above 
54  61000.
55  
56  to get informed when the user selects your new item you need to hande the 
57  WM_SYSCOMMAND message send to the Application window. for this you attach a hook to 
58  it, using Application.HookMainWindow.
59  
60  procedure TForm1.FormCreate(Sender: TObject);
61  var
62    hSysMenu: HMENU;
63  begin
64    hSysMenu := getSystemMenu(application.handle, false);
65    AppendMenu(hSysmenu, MF_STRING, $100, 'My Item');
66    Application.HookMainWindow(AppHook);
67  end;
68  
69  function Tform1.AppHook(var message: TMessage): Boolean;
70  begin
71    if (message.Msg = WM_SYSCOMMAND) and ((message.WParam and $FFF0) = $100) then
72    begin
73      Result := true;
74      ShowMessage('Hi, folks');
75    end
76    else
77      Result := false;
78  end;