widbatwarn: create Battery Warning

apps.json

@@ -456,6 +456,23 @@
       {"name":"widbatpc.json"}
     ]
   },
+  { "id": "widbatwarn",
+    "name": "Battery Warning",
+    "shortName": "Battery Warning",
+    "icon": "widget.png",
+    "version":"0.01",
+    "description": "Show a warning when the battery runs low.",
+    "tags": "tool,battery",
+    "type":"widget",
+    "dependencies": { "notify":"type" },
+    "storage": [
+      {"name":"widbatwarn.wid.js","url":"widget.js"},
+      {"name":"widbatwarn.settings.js","url":"settings.js"}
+    ],
+    "data": [
+      {"name":"widbatwarn.json"}
+    ]
+  },
   { "id": "widbt",
     "name": "Bluetooth Widget",
     "icon": "widget.png",

apps/widbatwarn/ChangeLog

@@ -0,0 +1 @@
+0.01: New Battery Warning!

apps/widbatwarn/icons.txt

@@ -0,0 +1,2 @@
+widget.png: https://icons8.com/icon/vga9edYpuB7a/warning-battery
+battery-low.png: https://icons8.com/icon/96282/low-battery (recolored)

apps/widbatwarn/settings.js

@@ -0,0 +1,47 @@
+/**
+ * @param {function} back Use back() to return to settings menu
+ */
+(function(back) {
+  const SETTINGS_FILE = "widbatwarn.json",
+    storage = require("Storage"),
+    translate = require("locale").translate;
+
+  // initialize with default settings...
+  let s = {
+    buzz: true,
+    percentage: 10,
+  };
+  // ...and overwrite them with any saved values
+  // This way saved values are preserved if a new version adds more settings
+  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('buzz')(true)
+  function save(key) {
+    return function(value) {
+      s[key] = value;
+      storage.write(SETTINGS_FILE, s);
+      WIDGETS["batwarn"].reload();
+    };
+  }
+
+  const menu = {
+    "": {"title": "Battery Warning"},
+    "< Back": back,
+    "Percentage": {
+      value: s.percentage,
+      min: 5,
+      max: 100,
+      step: 5,
+      onchange: save("percentage"),
+    },
+    "Buzz": {
+      value: s.buzz,
+      format: b => translate(b?"Yes":"No"),
+      onchange: save("buzz"),
+    },
+  };
+  E.showMenu(menu);
+});

apps/widbatwarn/widget.js

@@ -0,0 +1,59 @@
+(function() {
+  const SETTINGS_FILE = "widbatwarn.json";
+  let settings;
+
+  function loadSettings() {
+    settings = require("Storage").readJSON(SETTINGS_FILE, 1) || {};
+    const DEFAULTS = {
+      buzz: true,
+      percentage: 10,
+    };
+    Object.keys(DEFAULTS).forEach(k => {
+      if (settings[k]===undefined) settings[k] = DEFAULTS[k];
+    });
+  }
+
+  function setting(key) {
+    if (!settings) { loadSettings(); }
+    return settings[key];
+  }
+
+  let warning = false; // did we show the warning already?
+  function check() {
+    if (Bangle.isCharging()
+      || E.getBattery()>setting("percentage")) {
+      require("notify").hide({id: "widbatwarn"});
+      warning = false;
+      return;
+    }
+    if (warning) return; // already warned
+    warning = true; // only show once (until we recharge)
+    require("notify").show({
+      size: 56, id: "widbatwarn",
+      // battery-low.png
+      icon: require("heatshrink").decompress(atob("jEYwgfchnM5nABaQJCBoQLSAhAL/Bf6bHAAYLpACgA==")),
+      title: "Low Battery",
+      render: a => {
+        g.setFont("6x8", 2).setFontAlign(-1, 0)
+          .setColor(-1).drawString("Battery: ", a.x+8, a.y+a.h/2)
+          .setColor(0xF800).drawString(`${E.getBattery()}%`, a.x+8+100, a.y+a.h/2);
+      },
+    });
+    if (setting("buzz")) Bangle.buzz();
+  }
+
+  Bangle.on("charging", check);
+
+  function reload() {
+    loadSettings();
+    // check right away, so user sees it work when fiddling with settings
+    check();
+  }
+
+  // we never draw anything, but 'area' and 'draw' are required
+  WIDGETS["batwarn"] = {width: 0, reload: reload, area: "tl", draw: () => {}};
+
+  // check every minute
+  // deliberately not right away, to prevent instant notifications in settings
+  setTimeout(check, 60000);
+})();