Minimize-to-SysTray for Dialog-Based Applications

Minimize-to-systray is a common UI idiom these days, but Windows doesn’t
make this task easy.

Another
article
here at CodeGuru by Dominik Filipp explains one way to
implement this. That technique uses the “make your main window
owned by an invisible window” trick, and also involves messing
with the WS_EX_APPWINDOW style bit. This comes straight out of
the MSDN docs, so you’d think it’d work right. Heh.

A minor problem with Filipp’s article is that the code relies on
CWnd::PreCreateWindow() being called to set up a critical
window ownership relation, but this doesn’t get called for CDialog-based
windows. You can set this relation up another way, but then you hit
another problem: when you minimize, the taskbar button disappears,
but then you get an MDI-like “minimized window” icon on your desktop
just above the taskbar.

I have no doubt that Filipp’s code works fine if your main window
is derived from CWnd, but it fails for CDialog-based windows. Small
utility apps are the most likely to use this idiom, and such apps are
usually easiest to build as a dialog-based program. You could use
CFormView, as it is derived from CWnd yet lets
you use a dialog template. But, that’s a lot harder than a true
dialog-based app. What we need instead is a technique that works
with CDialog-based apps without a lot of trickery.

My technique works with dialog-based applications, and presumably
also with regular CWnd-based apps, though I haven’t tested it. Instead
of all that trickery with invisible “owner” windows and twiddling
style bits, we just hide the main dialog when we get minimized.
Windows sees that we’re invisible and minimized, so it removes our
button from the taskbar. We show the window again when we get
restored.

The code accompanying this article also illustrates how to
integrate this technique with a systray icon. It follows the usual
pattern: you minimize the main window, it disappears from the
taskbar and puts an icon in the systray. Then when you double-click
on the systray icon, the icon disappears and the main dialog window
is restored.

The sample project (16 KB) is a
basic AppWizard-generated dialog-based app with a few modifications.
This list will tell you what you need to cut-and-paste out of the
sample project to add this feature to your own apps:

  1. Add a handler for WM_SYSCOMMAND, for handling the “you’re being
    minimized” event. You
    may just be able to copy CTBHideDlg’s OnSysCommand() handler
    and the SetupTaskBarButton() and SetupTrayIcon()
    functions into your CDialog class.

  2. I use Chris Maunder’s
    CSystemTray
    class (included in the zip file) to handle the systray icon. You may
    need to #include <afxdisp.h> in your stdafx.h file in
    order to get CSystemTray to compile. Alternatively, you can yank out
    all the animated icon stuff, which is what I do in my own projects.
    (I can’t distribute that version, though, due to the license
    CSystemTray is distributed under.)

  3. Create a simple popup menu for attaching to the systray icon, and add
    command handlers for the menu items. (E.g. Restore, About, Exit, etc.)

  4. Override DestroyWindow(). In it, manually get rid
    of the systray icon since Windows won’t do it for you.

  5. You may want to add code to handle the case where the user
    wants to start the app minimized. MFC won’t handle this case for
    CDialog-based apps, so you have to do it yourself. Note that this
    only works right if the dialog you want to minimize has the WS_VISIBLE
    style set when you create it. If not, Windows ignores you when you
    say ShowWindow(SW_HIDE) in the minimize handler, and you get a
    systray icon and a taskbar button.

Downloads

Download demo project – 15 Kb

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