I am the author of WireframeSketcher wireframing tool. It’s a Java based Eclipse RCP application. It is already packaged and distributed as a deb/rpm/tgz package, but I wanted to try to provide a snap package too.
WireframeSketcher at its heart is a reduced version of Eclipse IDE. There is a snapcraft.yaml for Eclipse already, and I’ve used it as a reference for creating the snapcraft.yaml for WireframeSketcher. Since Eclipse uses classic confinement, I believe the same arguments apply to WireframeSketcher to prefer the same confinement. In any case the application works well with classic.
I did try to see what would it take to make strict confinement work, but honestly I don’t have enough know how to do it. Using gnome-3-28 extension I could launch the application. However there are several things that didn’t work out of the gate: printing, launching files in external viewer (for example opening a PDF) using SWT API, installing new plugins break the application completely. There are various dbus errors in the console that probably have something to do with the way dbus is being used in SWT. Printing wireframes and exporting them to various formats is the main task of WireframeSketcher so fixing these issues is a must.
As I see it, to make strict work might requires a deeper understanding of snap, and also might require some changes in the Eclipse platform which I am not in position to make. I believe that once Eclipse IDE can be made to use strict confinement, all others Eclipse RCP/SWT apps can follow and be made to work the same way too. But until then classic is probably the way to go.