✨ Implemented dark theme.

Signed-off-by: Edoardo Odorico <edoubuntu@gmail.com>

public/js/index.js

@@ -1633,6 +1633,10 @@ ui.toolbar.view.click(function () {
 ui.toolbar.both.click(function () {
   changeMode(modeType.both)
 })
+
+ui.toolbar.night.click(function () {
+  toggleNightMode()
+})
 // permission
 // freely
 ui.infobar.permission.freely.click(function () {
@@ -1666,6 +1670,17 @@ $('.ui-delete-modal-confirm').click(function () {
   socket.emit('delete')
 })
 
+function toggleNightMode () {
+  var $body = $('body')
+  var isActive = ui.toolbar.night.hasClass('active')
+  if (isActive) {
+    $body.removeClass('night')
+    appState.nightMode = false
+  } else {
+    $body.addClass('night')
+    appState.nightMode = true
+  }
+}
 function emitPermission (_permission) {
   if (_permission !== permission) {
     socket.emit('permission', _permission)

public/js/lib/appState.js

@@ -2,7 +2,8 @@ import modeType from './modeType'
 
 let state = {
   syncscroll: true,
-  currentMode: modeType.view
+  currentMode: modeType.view,
+  nightMode: false
 }
 
 export default state

public/js/lib/editor/ui-elements.js

@@ -37,6 +37,7 @@ export const getUIElements = () => ({
     edit: $('.ui-edit'),
     view: $('.ui-view'),
     both: $('.ui-both'),
+    night: $('.ui-night'),
     uploadImage: $('.ui-upload-image')
   },
   infobar: {