Main+App+Store: Implement basic setting sync between Electron windows

The app utilizes the Electron IPC to communicate settings' updates
to the other existing windows.

This is still at a fairly rudimentary stage, since some settings are
not syncing at all, while other settings have related side effects that
are not currently being propagated to the remaining windows.

An example of this would be the 'uiScale' setting, in which
the value is properly synced, but the app's actual scaling isn't.

src/main/index.js

@@ -387,6 +387,16 @@ function runApp() {
     createWindow(false, '', false)
   })
 
+  ipcMain.on('syncSetting', (event, setting) => {
+    const otherWindows = openedWindows.filter((window) => {
+      return window.webContents.id !== event.sender.id
+    })
+
+    for (const window of otherWindows) {
+      window.webContents.send('syncSetting', setting)
+    }
+  })
+
   app.on('window-all-closed', () => {
     if (process.platform !== 'darwin') {
       app.quit()

src/renderer/App.js

@@ -80,6 +80,7 @@ export default Vue.extend({
   },
   mounted: function () {
     this.grabUserSettings().then(() => {
+      this.setUpListenerToSyncSettings()
       this.grabAllProfiles(this.$t('Profile.All Channels')).then(async () => {
         this.grabHistory()
         this.grabAllPlaylists()
@@ -404,7 +405,8 @@ export default Vue.extend({
       'grabAllPlaylists',
       'getRegionData',
       'getYoutubeUrlInfo',
-      'getLocale'
+      'getLocale',
+      'setUpListenerToSyncSettings'
     ])
   }
 })

src/renderer/store/modules/settings.js

@@ -121,6 +121,13 @@ for (const settingId of Object.keys(state)) {
       (err, _) => {
         if (!err) {
           commit(mutationId, value)
+          if (getters.getUsingElectron) {
+            const { ipcRenderer } = require('electron')
+            // Propagate setting values to all other existing windows
+            ipcRenderer.send('syncSetting', {
+              _id: settingId, value: value
+            })
+          }
         }
       }
     )
@@ -190,6 +197,18 @@ Object.assign(actions, {
         }
       )
     })
+  },
+
+  setUpListenerToSyncSettings: ({ commit, getters }) => {
+    if (getters.getUsingElectron) {
+      const { ipcRenderer } = require('electron')
+      ipcRenderer.on('syncSetting', (_, setting) => {
+        const capitalizedSettingId =
+          setting._id.replace(/^\w/, (c) => c.toUpperCase())
+
+        commit('set' + capitalizedSettingId, setting.value)
+      })
+    }
   }
 })