Preload sound files for instant playback (#374)

* rm dist at start of build

* renderer style

* preload sound files for instant playback

The first time a sound file is played, the Audio object is cached.

5s after startup, all sound files are automatically preloaded.

renderer/lib/sound.js

@@ -0,0 +1,75 @@
+module.exports = {
+  preload,
+  play
+}
+
+var config = require('../../config')
+var path = require('path')
+
+/* Cache of Audio elements, for instant playback */
+var cache = {}
+
+var sounds = {
+  ADD: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'add.wav'),
+    volume: 0.2
+  },
+  DELETE: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'delete.wav'),
+    volume: 0.1
+  },
+  DISABLE: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'disable.wav'),
+    volume: 0.2
+  },
+  DONE: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'done.wav'),
+    volume: 0.2
+  },
+  ENABLE: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'enable.wav'),
+    volume: 0.2
+  },
+  ERROR: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'error.wav'),
+    volume: 0.2
+  },
+  POP: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'pop.wav'),
+    volume: 0.2
+  },
+  PLAY: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'play.wav'),
+    volume: 0.2
+  },
+  STARTUP: {
+    url: 'file://' + path.join(config.STATIC_PATH, 'sound', 'startup.wav'),
+    volume: 0.4
+  }
+}
+
+function preload () {
+  for (var name in sounds) {
+    if (!cache[name]) {
+      var sound = sounds[name]
+      var audio = cache[name] = new window.Audio()
+      audio.volume = sound.volume
+      audio.src = sound.url
+    }
+  }
+}
+
+function play (name) {
+  var audio = cache[name]
+  if (!audio) {
+    var sound = sounds[name]
+    if (!sound) {
+      throw new Error('Invalid sound name')
+    }
+    audio = cache[name] = new window.Audio()
+    audio.volume = sound.volume
+    audio.src = sound.url
+  }
+  audio.currentTime = 0
+  audio.play()
+}