Looper
I like the elegant way that CycleJS uses Reactive Programming to build web interfaces and I wanted to see if it would be a good fit for a game I'm working on in F#.
Fortunately, Andre Staltz, creator of CycleJS did a great set of videos on egghead.io where he builds a simple version of CycleJS to explain how it works.
So I built this toy version of CycleJS in F# using Silk.NET OpenGL library to handle mouse input.
Windows usage
./run
Mac/Linux usage (not tested)
./run.sh
Tested on Windows 10 .NET Core 3.1.
This version starts counting up in 1 second intervals in the shell. If you click with the left mouse button you'll also see a click count.
As Silk.NET is all based on events these can be turned into streams (with a bit of boilerplate) and seem to work quite nicely.
Thoughts so far
OpenGL is obviously not component based like the DOM and I think drivers will mostly be either input or output rather than the dual role the DOM, and therefore CycleJS has. Still, it's a neat way to get your head into streams.
The only difference in CycleFS compared with the toy CycleJS code is that instead
of a drivers object that gets passed into Cycle.run we have a function so that
we can pass in the Silk.NET window and input objects in order to create some of
the drivers but manage the creation of these in the library
Final thoughts
The core premise of CycleJS is that you attach events to components and return these from your main function. Your main function receives events as inputs from those components. Hence the Cycle name. In the DOM, inputs are directly related to outputs.
OpenGL doesn't really work this way. You don't have components. Inputs and outputs are global. You're free to design how you want. I don't think it's necessary to create this relationship in an engine.
However, it has given me some insights into how I might further develop my game engine. Drivers are a nice analogy and really helps to separate responsibilities, isolate effects and keep the logic pure functions. It's also pushed me to try out Subjects such as Broadcast for converting the Action based events in Silk.NET to Observables and using Behaviour for managing state.