There’s nothing secret about it, it’s well known and discussed in the dev forums.
The whole UI system, from front end to aircraft, is html.
That said, it’s undocumented (mainly) and quite the interesting technical challenge to piece together how it works for both FE and aircraft. One of the harder ones I’ve encountered actually, there’s nothing quite like analysing a complex codebase from scratch to understand how it works, with no docs to guide you.
Never underestimate the importance and value of good documentation, so kudo’s to the SDK team for continuing to improve this area. It’s a critical part of the SDK, and technical writing is part science and part art to do well, having worn that hat a couple of times.
SonantAlpaca commented • Jun 25 2021 at 11:47 PM
Hello,
Our new documentation website is constantly evolving, and while our tech writer has already done a great job on many various topics, he still has a LOT to do (as the SDK is big ) The HTML/JS/CoherentGT topic has been on his list for quite a while now, but as you may imagine, it’s a massive one and we need time to do something good. We’ll probably have more time this summer to work on that, so hopefully we’ll be able to provide you a lot more information in the upcoming months.
We already added model behaviour documentation on the next update, including the new input events.
I’m not sure they want people poking around in the main interface, so what ModernUI and I are doing is a bit bleeding edge, which is why I’m taking a very tightly scoped approach and trying to limit my changes to one area that can add utility and value in a bigger way without potentially disrupting the wider FE. Also easier from a maintenance & support perspective, which is the big elephant in the room developing things for MSFS.
SU12 will see more documentation coming on the aircraft side of this.
See
https://devsupport.flightsimulator.com/idea/584/add-jshtml-documentation-to-the-sdk.html
Nocturne Simbol commented · Dec 21 2022 at 6:42 PM
Hello!
Just to update on this… SU12 will see the release of the initial draft of documentation covering HTML/JS/CSS instruments. It’ll be a work in progress, with some things needing fleshed out still, but it will cover the entire panel.xml file, as well as the most important methods from the base JS files (BaseInstruments, coherent, etc…) and the Aircraft Tutorial will have new sections covering creating simple gauges and debugging them. Hopefully this will address some of the primary problems people have been having!
All the best!