From b590eaa2f64ead3384eadc6fe58f6358aa1a0478 Mon Sep 17 00:00:00 2001
From: Wojtek Kosior <koszko@koszko.org>
Date: Wed, 22 Dec 2021 16:39:34 +0100
Subject: reworked build system; added missing license notices

---
 common/observables.js | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 common/observables.js

(limited to 'common/observables.js')

diff --git a/common/observables.js b/common/observables.js
new file mode 100644
index 0000000..f1db88c
--- /dev/null
+++ b/common/observables.js
@@ -0,0 +1,61 @@
+/**
+ * This file is part of Haketilo.
+ *
+ * Function: Facilitate listening to (internal, self-generated) events.
+ *
+ * Copyright (C) 2021 Wojtek Kosior
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * As additional permission under GNU GPL version 3 section 7, you
+ * may distribute forms of that code without the copy of the GNU
+ * GPL normally required by section 4, provided you include this
+ * license notice and, in case of non-source distribution, a URL
+ * through which recipients can access the Corresponding Source.
+ * If you modify file(s) with this exception, you may extend this
+ * exception to your version of the file(s), but you are not
+ * obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ *
+ * As a special exception to the GPL, any HTML file which merely
+ * makes function calls to this code, and for that purpose
+ * includes it by reference shall be deemed a separate work for
+ * copyright law purposes. If you modify this code, you may extend
+ * this exception to your version of the code, but you are not
+ * obligated to do so. If you do not wish to do so, delete this
+ * exception statement from your version.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ * I, Wojtek Kosior, thereby promise not to sue for violation of this file's
+ * license. Although I request that you do not make use this code in a
+ * proprietary program, I am not going to enforce this in court.
+ */
+
+#EXPORT  (value=undefined) => ({value, listeners: new Set()})  AS make
+#EXPORT  (observable, cb) => observable.listeners.add(cb)      AS subscribe
+#EXPORT  (observable, cb) => observable.listeners.delete(cb)   AS unsubscribe
+
+const silent_set = (observable, value) => observable.value = value;
+#EXPORT silent_set
+
+const broadcast = (observable, ...values) =>
+      observable.listeners.forEach(cb => cb(...values));
+#EXPORT broadcast
+
+function set(observable, value)
+{
+    const old_value = observable.value;
+    silent_set(observable, value);
+    broadcast(observable, value, old_value);
+}
+#EXPORT set
-- 
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