Centralise display name normalisation

conference.js

     dominantSpeakerChanged,
     getAvatarURLByParticipantId,
     getLocalParticipant,
+    getNormalizedDisplayName,
     getParticipantById,
     localParticipantConnectionStatusChanged,
     localParticipantRoleChanged,
-    MAX_DISPLAY_NAME_LENGTH,
     participantConnectionStatusChanged,
     participantPresenceChanged,
     participantRoleChanged,
             JitsiConferenceEvents.DISPLAY_NAME_CHANGED,
             (id, displayName) => {
                 const formattedDisplayName
-                    = displayName.substr(0, MAX_DISPLAY_NAME_LENGTH);
+                    = getNormalizedDisplayName(displayName);
 
                 APP.store.dispatch(participantUpdated({
                     conference: room,
      * @param nickname {string} the new display name
      */
     changeLocalDisplayName(nickname = '') {
-        const formattedNickname
-            = nickname.trim().substr(0, MAX_DISPLAY_NAME_LENGTH);
+        const formattedNickname = getNormalizedDisplayName(nickname);
         const { id, name } = getLocalParticipant(APP.store.getState());
 
         if (formattedNickname === name) {

react/features/base/conference/actions.js

 import { JitsiConferenceEvents } from '../lib-jitsi-meet';
 import { setAudioMuted, setVideoMuted } from '../media';
 import {
-    MAX_DISPLAY_NAME_LENGTH,
     dominantSpeakerChanged,
+    getNormalizedDisplayName,
     participantConnectionStatusChanged,
     participantPresenceChanged,
     participantRoleChanged,
         (id, displayName) => dispatch(participantUpdated({
             conference,
             id,
-            name: displayName.substr(0, MAX_DISPLAY_NAME_LENGTH)
+            name: getNormalizedDisplayName(displayName)
         })));
 
     conference.on(

react/features/base/participants/actions.js

     PARTICIPANT_UPDATED,
     PIN_PARTICIPANT
 } from './actionTypes';
-import { MAX_DISPLAY_NAME_LENGTH } from './constants';
-import { getLocalParticipant } from './functions';
+import { getLocalParticipant, getNormalizedDisplayName } from './functions';
 
 /**
  * Create an action for when dominant speaker changes.
  * }}
  */
 export function participantUpdated(participant = {}) {
+    const participantToUpdate = {
+        ...participant
+    };
+
     if (participant.name) {
-        participant.name = participant.name.substr(0, MAX_DISPLAY_NAME_LENGTH);
+        participantToUpdate.name = getNormalizedDisplayName(participant.name);
     }
 
     return {
         type: PARTICIPANT_UPDATED,
-        participant
+        participant: participantToUpdate
     };
 }
 

react/features/base/participants/functions.js

 import {
     DEFAULT_AVATAR_RELATIVE_PATH,
     LOCAL_PARTICIPANT_DEFAULT_ID,
+    MAX_DISPLAY_NAME_LENGTH,
     PARTICIPANT_ROLE
 } from './constants';
 
     return participants.find(p => p.local);
 }
 
+/**
+ * Normalizes a display name so then no invalid values (padding, length...etc)
+ * can be set.
+ *
+ * @param {string} name - The display name to set.
+ * @returns {string}
+ */
+export function getNormalizedDisplayName(name: string) {
+    if (!name || !name.trim()) {
+        return undefined;
+    }
+
+    return name.trim().substring(0, MAX_DISPLAY_NAME_LENGTH);
+}
+
 /**
  * Returns participant by ID from Redux state.
  *