A way to ensure that a system tray icon is removed... guaranteed

Question

Is there a way to guarantee that your system tray icon is removed?

To add the system tray icon you do:

Shell_NotifyIcon(NIM_ADD, &m_tnd);

To remove the system tray icon you do:

Shell_NotifyIcon(NIM_DELETE, &m_tnd);

What I want to know: what if you application crashes? The icon stays in your system tray until you mouse over. Is there a way to guarantee that the icon will be removed, even when the application crashes? I would prefer not to use structured exception handling for various reasons.

Another case that I want to handle is when the process is killed, but doesn't necessarily crash.

Answer 1

There are many ways to ensure the call to Shell_NotifyIcon(NIM_DELETE, &m_tnd); in C++ for the case of the application crhashing; using a RAII wrapper over the NOTIFYICONDATA you're using will do the work, for example:

struct NID
{
    NID() : icon_data() { icon_data.cbSize = sizeof(icon_data); }
    ~NID() { Shell_NotifyIcon(NIM_DELETE, &icon_data); }
    void Show(HWND w) { icon_data.hWnd = w; Shell_NotifyIcon(NIM_ADD, &icon_data); }
    NOTIFYICONDATA icon_data;
};

This is a simplified version of the wrapper but it will illustrate the main idea: if you create an instance of NID in static storage it will be initialized before the WinMain or main call and its destructor will be called on the program cleanup, even if this cleanup is due an abnormal termination.

So, we can use this NOTIFYICONDATA resource wrapped in struct NID this way:

NID nid; // <--- automatic storage duration, cleared after WinMain return
         // even if it returns normal or abnormally

int CALLBACK WinMain(HINSTANCE, HINSTANCE, LPSTR, int)
{
    try
    {
        // GetMessage(&message, NULL, 0, 0) loop ...
        // ...
        // use nid.icon_data as you please
    }
    catch (...)
    {
        // something bad happened...
    }

    return 0;
}

The example above calls the ~NID() when the program terminates (after an exception or after closing the program), the destructor will call Shell_NotifyIcon(NIM_DELETE, &icon_data); and the icon is deleted from the notification area; this code covers the normal termination and the exception termination, you can read more about this topic in this good answer from NPE:

As for the kill the process case there's no simple way to do this.

I've already tested that std::atexit and std::at_quick_exit functions aren't called after killing the program through the task manager so I guess that you must hook the termination call... it seems a pretty complex task but is explained in this answer from BSH:

When a process is terminated (not closed) nothing realy can be done unless you start do some hooking, either by hooking TerminateProcess or NtTerminateProcess in the Task Manger process

Hope it helps (though is an answer 6 years later lol)

Answer 2

Another thing most programmers forget to check for is if the explorer restarts/crashes. Its nice if the application handle this and recreate its own icon.

Just check for Message WM_TASKBARCREATED and recreate the icon.

Answer 3

You could have a separate, simpler (and thus presumably more robust) program which monitors your application. This program could actually launch your program and then monitor the process. Yeah, this is a very ugly solution.

Answer 4

Personally I would use a Vectored Exception Handler. Yes, it's based on SEH, but you don't have to deal with all the different stack that you might need to unwind.

TerminateProcess() is must more destructive. You really can't guard yourself against that; when it happens your process is dead. No ore instructions are processed, so it does not matter what code there is in your application.

An external application wouldn't really help, would it? It too could crash, or be killed.