Linus Björnstam
4f48282314
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>
55 lines
2.2 KiB
Text
55 lines
2.2 KiB
Text
;; This Source Code Form is subject to the terms of the Mozilla Public
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;; License, v. 2.0. If a copy of the MPL was not distributed with this
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;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
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;; bjogui/examples/stopwatch.bjo — a subscription and a command.
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;;
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;; bjo run examples/stopwatch.bjo
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;;
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;; The stopwatch ticks while it runs: `subscriptions` asks for a tick only
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;; then, so stopping it stops the fiber. "Lap" saves the time after a pause,
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;; to show a command: the pause runs in a fiber, and the window does not wait
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;; for it.
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(import (std prelude))
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(import (bjogui view))
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(import (bjogui app))
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(type (: Msg (Union Toggle Tick Reset Lap (: Saved int))))
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(type (: Model (Record (: tenths int) (: running bool) (: saving bool) (: laps (List int)))))
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(: gui-update (-> Msg Model (Tuple Model (List (Event Msg)))))
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(defun (gui-update msg m)
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(match msg
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(Toggle (next (record-set m (running (not (.running m))))))
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(Tick (next (record-set m (tenths (+ (.tenths m) 1)))))
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(Reset (next (record-set m (tenths 0) (laps '()))))
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;; The time is taken now, and saved half a second later.
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(Lap (next (record-set m (saving #t))
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(wrap (timeout (milliseconds 500)) (fun (_) (Saved (.tenths m))))))
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((Saved t) (next (record-set m (saving #f) (laps (cons t (.laps m))))))))
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(: subscriptions (-> Model (List (Sub Msg))))
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(defun (subscriptions m)
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(if (.running m) (list (every (milliseconds 100) Tick)) '()))
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(: (-> int string))
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(defun (show tenths)
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#"${(/ tenths 10)}.${(% tenths 10)} s")
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(: view (-> Model (View Msg)))
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(defun (view m)
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(column #:spacing 8.0 #:margin 16.0
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(text (show (.tenths m)) #:size 32.0)
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(row #:spacing 8.0
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(button (if (.running m) "Stop" "Start") Toggle #:width 80.0)
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(button "Lap" Lap #:enabled (not (.saving m)) #:width 80.0)
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(button "Reset" Reset #:width 80.0))
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(apply column (vec->array (vec-map (fun (t) (text #"lap: ${(show t)}"))
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(list->vec (.laps m)))))))
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(defun (main)
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(run-app (Model (tenths 0) (running #f) (saving #f) (laps '()))
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gui-update view
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#:subscriptions subscriptions
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#:title "Stopwatch" #:width 320.0 #:height 300.0))
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