[VC++] Adding icon to system tray

Here is how to create a tray icon for your application and showing system tray menu. For this you need to add an icon to the system tray using Shell_NotifyIcon() and you need to handle the tray message for the added icon. Below is the code for adding tray icon and showing a menu saying Test Tray Icon on clicking the tray icon.
Modify dialog class header creating a member variable for system tray menu and adding declaration of shell tray icon message handler.

protected:
...
afx_msg HRESULT OnSystemTrayIconClick( WPARAM wParam_i, LPARAM lParam_i );

private:
...
CMenu m_TrayMenu;

Modify dialog class Cpp file adding global constants for tray icon message handling and tray icon id

const UINT SHELL_TRAY_ICON = 2001; // Shell Tray icon ID
const UINT SHELL_TRAY_MSG = (WM_APP+2000); // Message name for tray icon messages
const UINT SHELL_TRAY_TEST_ID = 2100; // ID of shell tray menuitem

Modify dialog class Cpp file adding tray icon adding code in OnInitdialog

void CSampleDlg::OnInitDialog()
{
    ...
    NOTIFYICONDATA stNotifyIconData;
    stNotifyIconData.cbSize = sizeof( NOTIFYICONDATA );
    stNotifyIconData.hWnd = GetSafeHwnd();
    stNotifyIconData.uID = SHELL_TRAY_ICON;
    stNotifyIconData.uFlags = NIF_MESSAGE  NIF_ICON  NIF_TIP;
    stNotifyIconData.uCallbackMessage = SHELL_TRAY_MSG;
    stNotifyIconData.hIcon = AfxGetApp()->LoadIcon( IDR_MAINFRAME );
    strncpy( stNotifyIconData.szTip, "TestShellTrayIcon",sizeof"TestShellTrayIcon"));
    Shell_NotifyIcon( NIM_ADD, &stNotifyIconData );
    m_TrayMenu.CreatePopupMenu();
    m_TrayMenu.InsertMenu( 0, MF_BYCOMMAND|MF_POPUP,SHELL_TRAY_TEST_ID, "Test Tray Icon" );
    return TRUE;
}

Add entry to message map for mapping tray icon message

BEGIN_MESSAGE_MAP( CSampleDlg, CDialog )
...
ON_MESSAGE ( SHELL_TRAY_MSG, OnSystemTrayIconClick )
END_MESSAGE_MAP()

Now implement the tray icon message handler which will handle mouse LButton and RButton down by showing a menu

HRESULT CSampleDlg::OnSystemTrayIconClick( WPARAM wParam_i, LPARAM lParam_i )
{
    switch( wParam_i )
    {
    case SHELL_TRAY_ICON:
        {
            switch( lParam_i )
            {
            case WM_LBUTTONDOWN:
            case WM_RBUTTONDOWN:
                {
                    POINT CurPos ;
                    GetCursorPos( &CurPos );
                    SetForegroundWindow();
                    TrackPopupMenu( m_TrayMenu, TPM_LEFTBUTTON, CurPos.x, CurPos.y, 0, GetSafeHwnd(), 0 );
                    PostMessage( WM_NULL, 0, 0 );
                }
                break ;
            }
        }
        break ;
    default:
            OutputDebugString ("invalid icon id from tray\n");
            break ;
    }
    return TRUE ;
}