Commitf8cd8e66Recorded20 Jul 2026Repositorylantern

lantern-app: add services: hook for background goroutines

Message

Apps can declare services: — one-arg procedures (lambda (ctx) ...) run as goroutines INSIDE the loop's async scope, so they may freely go/await (unlike on-event 'ready, which fires before run-loop establishes the scheduler). Each service gets a ctx carrying wv:/window:/registry:/app:/emit:/emit-bulk, so a resident host service (a control socket, a file watcher, a timer) can both reach the page and emit events. First consumer: the slate-client control socket.

Framework tests unchanged (39 pass).

Changed
 lantern/src/lantern/app.sgl | 43 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 35 insertions(+), 8 deletions(-)
Diff
lantern/src/lantern/app.sglmodified
@@ -56,11 +56,22 @@
56
;; can prompt (e.g. save unsaved work) and then call `app.quit` itself. Default
57
;; #f keeps the plain close-is-exit behavior. (Requires a backend that can veto
58
;; its window close; degrades to the default on backends that cannot.)
+59
;; `services:` are background goroutines the app runs FOR ITS WHOLE LIFETIME,
+60
;; started INSIDE the loop's async scope (unlike `on-event 'ready`, which fires
+61
;; before run-loop establishes the scheduler, so a service may freely `go` /
+62
;; `await-*`). Each service is a one-arg procedure `(lambda (ctx) ...)` where
+63
;; ctx carries wv:/window:/registry:/app: + emit:/emit-bulk: (same shape a
+64
;; command handler gets), so a service can both reach the page (webview-eval-js
+65
;; wv window …) and emit events. This is the seam a resident host service — a
+66
;; control socket, a file watcher, a timer — plugs into. A service thunk that
+67
;; returns simply ends that goroutine; one that loops runs until the window
+68
;; quits (the quit-watcher exits the process out from under it).
69
(define (lantern-app (keys: (name "lantern-app")
70
(assets "./dist")
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(modules (list))
72
(commands (list))
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(plugins (list))
+74
(services (list))
75
(on-event #f)
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(intercept-close #f)))
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(dict lantern/app: #t
@@ -69,6 +80,7 @@
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modules: modules
81
commands: commands
82
plugins: plugins
+83
services: services
84
on-event: on-event
85
intercept-close: intercept-close))
86
@@ -225,6 +237,19 @@
237
(let ((on-event (dict-ref app on-event: #f)))
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(when (procedure? on-event) (on-event 'ready (dict wv: wv window: win))))
239
+240
;; App services (§ lantern-app services:) run as goroutines inside the
+241
;; loop's async scope, each handed a ctx like a command handler's (wv/
+242
;; window for page access, emit/emit-bulk for events). Bound here so they
+243
;; start alongside the bridge dispatcher under run-loop's with-async.
+244
(let* ((make-service-thunk
+245
(lambda (svc)
+246
(lambda ()
+247
(svc (dict wv: wv window: win registry: registry app: app
+248
emit: (lambda (event payload) (bridge-emit bridge event payload))
+249
emit-bulk: (lambda (event meta b64) (bridge-emit-bulk bridge event meta b64)))))))
+250
(service-thunks
+251
(map make-service-thunk (dict-ref app services: (list)))))
+252
253
;; Hand the thread to the Option A loop; the bridge dispatcher drains
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;; the queue and runs each command in its own goroutine (may await).
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;;
@@ -239,11 +264,13 @@
264
;; a window app's close IS its exit (kernel cleanup closes pty
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;; masters, so child shells get SIGHUP). Teardown-on-exit quirks are
266
;; cosmetic (see the framework note); a live headless zombie is not.
−242
(run-loop wv
−243
(bridge-dispatcher bridge)
−244
(lambda ()
−245
(let watch ()
−246
(sleep 0.05)
−247
(if (webview-should-quit? wv)
−248
(begin (bridge-stop! bridge) (exit 0))
−249
(watch))))))))))
+267
(apply run-loop wv
+268
(append
+269
(list (bridge-dispatcher bridge))
+270
service-thunks
+271
(list (lambda ()
+272
(let watch ()
+273
(sleep 0.05)
+274
(if (webview-should-quit? wv)
+275
(begin (bridge-stop! bridge) (exit 0))
+276
(watch)))))))))))))