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Commands and subscriptions, and gui-update

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gui-update is a plain function, so it cannot wait. It returns the work to do
as values. A command is an (Event %m), synced in a fiber of its own, whose
answer is the next message. A subscription is a source of messages that the
model asks for: after each update the app starts the new ones and cancels the
ones that are gone, by key. every sends a message on a timer, and
subscription takes a source of one's own.

The fibers belong to the app's scope and post their messages to the UI
thread, so gui-update and view only run there. Closing the window cancels
them. The prelude's path macros already use the name update, hence
gui-update.

🤖 Generated with [ECA](https://eca.dev) (anthropic/claude-opus-4-8)

Co-Authored-By: eca-agent <git@eca.dev>
This commit is contained in:
Linus Björnstam 2026-10-25 17:02:02 +01:00
parent 2f4c99ba62
commit 4f48282314
6 changed files with 460 additions and 67 deletions
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21
tests/app.bjo
View file

@ -8,7 +8,7 @@
;;
;; No window is opened. The test raises the events a user would cause on the
;; Avalonia controls, and reads back what the controls hold, so it goes
;; through the handlers, update, view and patch as a program does.
;; through the handlers, gui-update, view and patch as a program does.
(import (std prelude))
(import (std simpletest))
@ -60,14 +60,15 @@
(type (: Msg (Union Inc Dec (: Typed string) (: Shout bool) Reset)))
(type (: Model (Record (: count int) (: name string) (: loud bool))))
(: update (-> Msg Model Model))
(defun (update msg m)
(match msg
(Inc (record-set m (count (+ (.count m) 1))))
(Dec (record-set m (count (- (.count m) 1))))
((Typed s) (record-set m (name s)))
((Shout b) (record-set m (loud b)))
(Reset (Model (count 0) (name "") (loud #f)))))
(: gui-update (-> Msg Model (Tuple Model (List (Event Msg)))))
(defun (gui-update msg m)
(next
(match msg
(Inc (record-set m (count (+ (.count m) 1))))
(Dec (record-set m (count (- (.count m) 1))))
((Typed s) (record-set m (name s)))
((Shout b) (record-set m (loud b)))
(Reset (Model (count 0) (name "") (loud #f))))))
(: greeting (-> Model string))
(defun (greeting m)
@ -92,7 +93,7 @@
(defun (main)
(def/mutable roots 0)
(def app (start-app (Model (count 0) (name "") (loud #f)) update view
(def app (start-app (Model (count 0) (name "") (loud #f)) gui-update view
(fun (c) (set! roots (+ roots 1)))))
(defun (at path) (app-control-at app path))