add settings.js

apps/metronome/settings.js

@@ -0,0 +1,48 @@
+// This file should contain exactly one function, which shows the app's settings
+/**
+ * @param {function} back Use back() to return to settings menu
+ */
+(function(back) {
+  const SETTINGS_FILE = 'metronome.settings.json';
+
+  // initialize with default settings...
+  let s = {
+    'beatsperbar': 4,
+    'buzzintens': 0.75,
+  };
+  // ...and overwrite them with any saved values
+  // This way saved values are preserved if a new version adds more settings
+  const storage = require('Storage');
+  const saved = storage.readJSON(SETTINGS_FILE, 1) || {};
+  for (const key in saved) {
+    s[key] = saved[key];
+  }
+
+  // creates a function to safe a specific setting, e.g.  save('color')(1)
+  function save(key) {
+    return function(value) {
+      s[key] = value;
+      storage.write(SETTINGS_FILE, s);
+    };
+  }
+
+  const menu = {
+    '': { 'title': 'Metronome' },
+    '< Back': back,
+    'beats per bar': {
+      value: s.beatsperbar,
+      min: 1,
+      max: 8,
+      step: 1,
+      onchange: save('beatsperbar'),
+    },
+    'buzz intensity': {
+      value: s.buzzintens,
+      min: 0.0,
+      max: 1.0,
+      step: 0.25,
+      onchange: save('buzzintens'),
+    },
+  };
+  E.showMenu(menu);
+});