Pause at top of descent mod for xp12

Plugins → Pause at ToD → Settings... opens a modern, resizable X-Plane floating window. It's drawn with egui and follows X-Plane's UI scale:

╭─ Pause at ToD ──────────────────────────────────╮
│ ● ARMED                               [ Disarm ] │
│ ╭──────────────────────────────────────────────╮ │
│ │ (●) Top of descent   FMS T/D, 3:1 rule or ... │ │
│ │ Reach [arrival] at [auto] ft MSL              │ │
│ │ Pause [5 nm] before the top of descent        │ │
│ │ T/D in 38.2 nm (to KSEA at 1,933 ft) ...      │ │
│ │ ▓▓▓▓▓▓▓▓▓▓▓▓░░░░░░                            │ │
│ ╰──────────────────────────────────────────────╯ │
│ ╭ (○) Near waypoint ───────────────────────────╮ │
│ ╭ (○) Altitude ────────────────────────────────╮ │
│ ╭ (○) Timer ───────────────────────────────────╮ │
╰─────────────────────────────────────────────────╯

• Switch on the conditions you want and press Arm. The first enabled condition that comes true pauses the sim. The plugin then disarms, and the window pops up with the reason.
• While you edit, the window looks up identifiers as you type, e.g. "KSEA · airport · 142 nm away · cross at 1,933 ft (field 433 + 1,500)".
• While armed, the inputs are locked and each active condition shows a live status line and a progress bar.
• Plugins → Pause at ToD → Armed shows the armed state and toggles it.
• You can bind keys to two commands: pauseattod/toggle_window and pauseattod/toggle_arm.
• Settings are saved in X-Plane/Output/preferences/pauseattod.prf.
• Loading a new flight or aircraft disarms the plugin.

Conditions

Top-of-descent heuristics. All three are evaluated, and none of them run below 1,000 ft AGL:

1. FMS value. If the dataref named by tod_dataref exists and has reported a positive distance, the plugin pauses once that distance is at or below the lead. The default name is X-Plane 12's sim/cockpit2/radios/indicators/fms_distance_to_tod_pilot (float, nm), which the built-in FMS fills once it has a descent planned. If the dataref is missing or never goes positive, this heuristic stays inactive. You can point tod_dataref at an aircraft's own ToD dataref in the prefs file.
2. Geometric 3:1 rule. ToD is (altitude − crossing altitude) / 1000 × 3 nm before the end-of-descent point. The plugin pauses when the distance to go minus that figure is at or below the lead. The point ("Reach X at Y ft MSL") defaults to the arrival airport: the last airport in the pilot's flight plan in X-Plane's built-in FMS. It's read through X-Plane 12.1's flight-plan API when available, otherwise through the legacy FMS calls. Aircraft with their own FMS, such as Zibo or ToLiss, aren't visible this way, so type the arrival airport for those. The crossing altitude defaults to the field elevation + 1,500 ft when the point is an airport. The elevation comes from the nav database, from the airport itself or from the FMS arrival. For other kinds of point it defaults to 1,500 ft MSL. The SDK documents the nav height as feet, but X-Plane returns meters, so the plugin converts it and logs the result (PauseAtToD: KSEA field elevation 433 ft (nav height 132.0 m)). Values outside −1,500 to 15,000 ft are ignored.
3. Descent onset (fallback). The plugin first needs at least 60 s of level flight (|VS| < 300 fpm) above 5,000 ft AGL. After that, a descent of at least 500 fpm sustained for 10 s fires. This covers third-party FMSs (Zibo, ToLiss and others) that don't feed X-Plane's FMS, at the cost of pausing at the descent rather than before it.

Waypoint lookup. Entries in the loaded X-Plane FMS flight plan come first. Otherwise the plugin uses the nav-database airport, VOR, NDB or fix with exactly that ID that's closest to the aircraft. The SDK's fragment search is tried first, and a full exact-match scan runs only if that fails.

Advanced settings exist only in the prefs file: tod_nm_per_kft (default 3), tod_dataref, and descent_vs_fpm (default −500).

Design

crates/core    pauseattod-core: pure Rust, no X-Plane. Settings + file format,
               great-circle math, and the Monitor that evaluates conditions
               against AircraftState samples. All heuristics are unit-tested.
crates/plugin  pauseattod (cdylib → win/lin/mac.xpl)
  ffi.rs       hand-written bindings for the ~40 SDK functions used, checked
               against the official SDK headers and import libraries
  xp.rs        safe wrappers: datarefs, commands, menu, nav/FMS lookups
  gui.rs       egui hosted in an XPLM floating window: input translation,
               keyboard focus, painting with egui_glow
  gl.rs        GL loader, boxel→pixel transform, GL state save/restore
  view.rs      the window's content (plain egui code)
  app.rs       state machine: arm/disarm, sampling, firing, previews, prefs
  lib.rs       XPlugin* entry points and C callbacks
xtask          `cargo xtask dist` packaging/installing, also in Rust

Key decisions:

• No C toolchain or SDK download. On Windows the SDK functions are linked through raw-dylib imports from XPLM_64.dll (and opengl32.dll for the GL loader), so no .lib files or bindgen/libclang are needed. On macOS the build uses -undefined dynamic_lookup. Linux resolves the symbols when X-Plane loads the plugin.
• Sim logic is separate from the sim. core gets plain samples (position, MSL/AGL altitude, VS, sim flight time, optional FMS ToD distance), so you can test every heuristic with cargo test on any machine.
• UI: egui in a modern XPLM window. The window uses X-Plane's own floating-window decoration (title bar, close, resize). Each draw callback runs an egui frame, maps boxels to pixels with the transform X-Plane set up, and paints with egui_glow on X-Plane's GL context. X-Plane 12's Vulkan build still offers that context to plugins. Every piece of GL state egui touches is saved before painting and restored after. Typing reaches the window only while a text field has focus, so sim key bindings keep working.
• Re-entrancy safety. Widget calls can call back into the plugin synchronously. Callbacks never touch the app directly: they post an Event, and one guarded pump (with_app) drains the queue. A re-entrant call queues its event and returns, so a RefCell double borrow can't happen.
• Panics are contained. Every extern "C" callback runs inside catch_unwind. A bug is written to Log.txt and doesn't crash X-Plane.
• Edge detection keeps history. Altitude crossings compare consecutive samples. A jump of more than 2,000 ft between samples is treated as a reposition and ignored. The timer restarts if the sim clock goes backwards (new flight). Conditions are only evaluated while the sim isn't paused, at 10 Hz.
• Pausing uses sim/operation/pause_on, falling back to pause_toggle only if the sim isn't already paused.

Build and install

You need a stable Rust toolchain. Windows needs the MSVC target.

cargo test -p pauseattod-core                     # heuristics
cargo xtask dist                                  # → dist/PauseAtToD/64/win.xpl
cargo xtask dist --install "C:/X-Plane 12"        # also copies to Resources/plugins

For a universal (Intel + Apple Silicon) mac.xpl, run cargo xtask dist --target aarch64-apple-darwin --target x86_64-apple-darwin on a Mac. lin.xpl builds on Linux with plain cargo xtask dist.

GitHub Actions (.github/workflows/build.yml) runs the tests and builds all three platforms on every push. The PauseAtToD artifact holds the complete plugin folder with win.xpl, mac.xpl and lin.xpl. Pushing a v* tag also attaches that bundle to the matching GitHub release. Stable tags (no - in them) also force-push the plugin folder, with its CRC32 whitelist and sizes list, to the orphan skunkcrafts branch. That branch is the SkunkCrafts Updater module named in packaging/skunkcrafts_updater.cfg, which ships in the zip. Log lines go to X-Plane/Log.txt with the prefix PauseAtToD:.

License

MIT, see LICENSE.