Add wheel circumference setting

apps.json

@@ -2182,6 +2182,7 @@
     "readme": "README.md",
     "storage": [
       {"name":"cscsensor.app.js","url":"cscsensor.app.js"},
+      {"name":"cscsensor.settings.js","url":"settings.js"}
       {"name":"cscsensor.img","url":"cscsensor-icon.js","evaluate":true}
     ]
   },

apps/cscsensor/settings.js

@@ -0,0 +1,38 @@
+// 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 = 'cscsensor.json'
+  // initialize with default settings...
+  let s = {
+    'wheelcirc': 2230,
+  }
+  // ...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': 'Cycling speed sensor' },
+    '< Back': back,
+    'Wheel diameter (mm)': {
+      value: s.wheelcirc,
+      min: 800,
+      max: 2400,
+      step: 5,
+      onchange: save('wheelcirc'),
+    }
+  }
+  E.showMenu(menu);
+})