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Live Control Channel & Shader Hot-Reload

Control/, Shaders/ShaderModule.cs

Shader hot-reload

ShaderModule tracks, per compiled pass, the full set of files it pulled in via #include (transitively — GlavaPreprocessor.Process returns that set alongside the preprocessed source). A FileSystemWatcher over the shader tree (RootDir, plus a second watcher over the sibling glavasharp/ directory for modules resolved via that fallback — see GlavaSharp-Original Modules) marks a file dirty on save; ShaderModule.ReloadIfDirty(), called once per frame from the render thread (never from the watcher's own callback thread — no GL context there), recompiles every pass whose dependency set contains a dirty file. Editing a module's own .frag recompiles just that pass; editing a shared file like util/smooth.glsl or aurora.glsl recompiles every pass across the module that included it. A failed recompile logs an error and leaves the previous, still-working GL program running rather than tearing anything down.

Live-tweakable per-module properties

A pass can declare #request property "name" float default min max (a GlavaSharp extension to GLava's #request convention, parsed the same way #request uniform already was) right next to the uniform float name; it already needs — see shaders/glavasharp/aurora/1.frag's amplify for the worked example (replaced what used to be a #define AMPLIFY 2.6 in aurora.glsl). ShaderModule re-applies the current value to every pass that declared it on each Render() call, so a change takes effect on the very next frame with no recompile involved.

Feed-driven properties

A property can also declare #request feed "name" source (a second, separate line from #request property — feed-eligibility is an orthogonal annotation on an already-complete property declaration, not a different kind of property) to opt into being driven by a named built-in data source instead of manual slider input — e.g. shaders/glavasharp/clock/2.frag's #request feed "seconds_since_midnight" clock. Control/FeedRegistry.cs is a small, deliberately non-pluggable name → Func<float> lookup (one entry today: "clock" → DateTime.Now.TimeOfDay.TotalSeconds). PropertyStore tracks a mutable enabled flag per feed-eligible property, on by default (a clock with its time feed off at startup would just show frozen hands, never what you want), and the control page renders a checkbox (auto: clock) next to the slider, disabling the slider while the feed is active. AppWindow.Run calls PropertyStore.ApplyFeeds once per frame, right after DrainPending, which samples every enabled feed and routes it through the exact same ApplyPropertyChange dispatch a manual slider edit uses — so from ShaderModule's point of view a fed value is indistinguishable from one a slider set.

The control server

Control/ControlServer.cs is a plain System.Net.HttpListener (deliberately not Kestrel/ASP.NET Core — HttpListener is already in the BCL, trims cleanly under PublishAot, and doesn't grow the single-file AppImage) serving one self-contained HTML/JS page (inline CSS/JS, no CDN, no build step) with a small hand-written-JSON API over Control/PropertyStore.cs. Every registered property — fft.attack/fft.decay/fft.gain (the same knobs --fft-attack/-decay/-gain set at startup) plus whatever the active module declared via #request property — shows up there as a slider automatically; no per-property UI code to write as new properties get added. PropertyStore.TrySet (called from the HTTP handler thread) only validates and queues a change; PropertyStore.DrainPending (called once per frame from AppWindow.Run, the only thread with the GL context current) is what actually applies it, via IFft.SetAttack/SetDecay/SetGain or ShaderModule.SetProperty. System.Text.Json's reflection-based serializer would trip the csproj's IL2026/IL3050 warnings-as-errors without a source-generated JsonSerializerContext — not worth the ceremony for a payload this small, so the JSON is hand-written instead.

  • Binds 127.0.0.1:8642 by default (--control-port); --control-bind 0.0.0.0 opts into LAN access (e.g. a phone/tablet on the same network) — there's no authentication, so only widen this on a network you trust. --no-control disables it entirely, --no-hot-reload disables the file watcher.
  • A bind failure (most commonly: another GlavaSharp instance already holds the port) is non-fatal — logged as a warning, the app keeps running without a control channel.
  • Independent of --desktop/pinned-embedded mode by construction — the control server is a background thread that doesn't know or care which windowing mode is active.

See Status & Roadmap for the live verification of each of these pieces.