Drop SWT in favor of Swing.
The SWT frontend should be removed and be replaced with Swing, for the simple reason that Swing does not rely on an unreliable toolkit, namely GTK+. Downloading the current build of jMathPaper and running it on newer systems, for example Ubuntu 18.04, will lead to the GUI not starting because the GTK+3 version that SWT is build against is incompatible with newer ones. An upgrade of SWT could solve that, but would make jMathPaper not start on older systems. That is unacceptable.
The SWT developers have done an amazing job at creating a cross-platform, native GUI library. However, GTK+3 is unstable and the moment it becomes stable it will be deprecated, that is absolutely beyond stupidity when it comes to providing a basic GUI framework. Additionally, there are only major versions anymore and no guarantee that version x will be compatible with x+1, API breakage is a part of the GTK+3 development now. This is absolutely unacceptable for downstream developers, and therefor SWT should be dropped and be replaced with Swing.