Racket Tray🔗ℹ

1 Creating a Tray Icon🔗ℹ

action-spec is mandatory and must contain exactly two values: (list callback default-action-id). callback must accept one argument and default-action-id must be a symbol. Every action generated by the tray is passed to callback as a symbol.

The default action must occur in the menu later installed with tray-set-menu!. Windows maps normal tray activation to this action. Ayatana AppIndicator 0.6 or newer can do the same on Linux. Older AppIndicator 0.5.x implementations open the menu on primary activation instead. A native macOS status item with an attached menu also opens its menu instead of invoking the default action directly.

When hide-on-minimize? is true, Racket Tray periodically checks is-iconized?. When the frame changes to the iconized state it is hidden with (send frame show #f). This implementation is entirely platform independent and does not use a Win32, GTK or AppKit minimize hook.

The returned value represents the tray icon and is accepted by the other procedures in this library.

2 Tray Actions and Menus🔗ℹ

For example:

(tray-set-menu!

tray

(list

(list 'open "Open")

'separator

(list 'exit "Exit")))

Choosing "Open" invokes the callback as (callback 'open). The same callback receives every other menu action.

3 Changing and Closing a Tray Icon🔗ℹ

4 Closing a Window to the Tray🔗ℹ

Racket already provides on-close for handling the close button of a frame. A tray application normally overrides it and hides the frame:

(define tray-frame%

(class frame%

(super-new)

(define/override (on-close)

(send this show #f))))

This is intentionally separate from #:hide-on-minimize?. Closing a window already has a portable public Racket callback; minimizing does not.

5 Platform Behaviour🔗ℹ

On Windows, the backend uses the native HWND returned by Racket GUI, Shell_NotifyIconW and SetWindowSubclass. A normal tray activation invokes the configured default action. No additional native library is needed.

On Linux, the backend uses Ayatana AppIndicator and GTK3. AppIndicator 0.6 or newer provides primary activation, which Racket Tray maps to the default action. With AppIndicator 0.5.x, primary activation opens the menu instead. Menu choices have the same symbolic callback behaviour on both library versions.

On macOS, the backend uses AppKit NSStatusItem, NSStatusBarButton and NSMenu through Racket’s Objective-C FFI. A status item with an attached menu opens that menu when activated. Menu choices invoke the common symbolic callback. No additional native library is needed.

6 Linux Runtime Dependency🔗ℹ

The Linux backend requires the Ayatana AppIndicator GTK3 runtime library. If it cannot be loaded, mk-tray reports the missing dependency and suggests the native package to install.

Debian and Ubuntu use libayatana-appindicator3-1. Fedora uses libayatana-appindicator-gtk3. Arch Linux uses libayatana-appindicator.

7 Example🔗ℹ

The package contains "examples/simple.rkt". It demonstrates symbolic tray actions, hiding a frame on minimize and close, restoring it from the tray, and terminating the application only through the 'exit action.