Qt is a cross-platform application framework that is used for developing application software that can be run on various software and hardware platforms with little or no change in the underlying codebase, while still being a native application with native capabilities and speed. It is sort of a SDL sort of thing, but now also available for AmigaOS 4 and its all written in C++.

AmigaOS 4 version runs Qt apps
With AmigaOS 4.1 Final Edition installed, you can run this app from Alfkil Thorbjørn Wennermark. Download it for free from OS4Depot.net website! Here is more information from the author himself:

This is the minimal distribution of Qt for AmigaOS4.
This archive will enable you to run Qt apps on your Amiga
system. It will not make it possible for you to develop Qt apps and compile existing Qt code. For this purpose, you will need to either upgrade your Qt install with the
examples, docs and development tools. You can find this
upgrade, along with a full distribution of Qt, at the
sourceforge page for Qt AmigaOS4:

www.sourceforge.net/projects/qtamigaosnative

It is really nice and cool to see new code frameworks coming to the Amigascene and we thant Alfkil a lot for this work.

Source
OS4Depot