This is a higher level update on what has been going on with the current focus topic for Arcan releases, that is the network transparency (2020). It comes as a companion to the upcoming release post as a way to give it more context.
A12 is our network protocol that lets applications written against libarcan-shmif communicate remotely. A12 and SHMIF share most of the same data and event model, but they have very different approaches to transmission, queuing, compression, authentication, confidentiality and so on.
Just as SHMIF consolidates a forest of IPC systems with an untapped common ground into one system around this common ground, A12 consolidates a forest of protocols into one. The history for this part spans many years, starting way before the naughty bits of protocol design and implementation.
The preparations cover everything from decoupling command line and shell from the terminal; due diligence decomposing expectations of features from existing solutions and their respective flaws; working in crash resilience to transition from local to networked operation and back; making sure it fits the security and accessibility story; that it is observable and debuggable; that it meshes with obscure input devices and as many varied windowing schemes as possible — on a foundation presented over a decade ago as a dissertation on the traditional and future role of networked display servers for surveillance and control in critical infrastructure.