KNotifications is KDE’s framework for creating popup notifications. It supports Linux, Windows, macOS, and Android, making it, to my knowledge, the most complete cross-platform library for this available in C++. This makes it natually interesting to use for non-KDE Qt application developers.

However there is one aspect that makes it less attractive for third-party developers: It’s number of dependencies. As of KNotifications 5.110 it depends on the following other KDE Frameworks:

• KCoreAddons
• KConfig
• KWindowSystem

as well as some third-party like QtWidgets, X11, libdbusmenu-qt and libcanberra.

While none of these are a hard blocker for usage in most cases the overall impression isn’t very appetizing. During the KF5 time we already weeded out some dependencies that don’t make sense on some platforms, like removing the QtWidgets dependency on Android. We were however somewhat limited in our ability to do large cleanups by our strict API/ABI stability promise. For KF6 we have the opportunity do to larger cleanups.

One larger source of dependencies is the KStatusNotifierItem class, which is part of the KNotifications framework and is used to create system tray icons. Since its functionality is rather independent from creating popup notifications we decided to split it out into a separate, new framework. This significantly reduces the number of dependencies of KNotifications. A number of other changes further reduced the number of dependencies and cleaned up the public API a bit.

As a result what will become KF6 KNotifications on Linux only depends on Qt (QtGui + QtDBus, and optionally QtQml for QML support), KConfig (that would also be feasible to remove if someone is motivated enough) and libcanberra (for playing notification sounds).

Other KDE Frameworks received similar changes, but KNotifications is likely the one where this has the largest impact.

Doing this kind of work is part of my position as KDE Software Platform Engineer. To support my work please consider donating to KDE e.V..