Index: gc_lang/fr/webext/content_scripts/message_box.js
==================================================================
--- gc_lang/fr/webext/content_scripts/message_box.js
+++ gc_lang/fr/webext/content_scripts/message_box.js
@@ -1,15 +1,30 @@
 // JavaScript
 // Panel creator
 
+/* jshint esversion:6, -W097 */
+/* jslint esversion:6 */
+/* global oGrammalecte, xGrammalectePort, showError, window, document, console */
+
 "use strict";
 
 
 class GrammalecteMessageBox {
 
-    constructor (sId, sTitle) {
+    constructor (sUrl, sId, sTitle) {
         this.sId = sId;
+        this.sUrl = sUrl;
+
+        this.bShadow = document.body.createShadowRoot || document.body.attachShadow;
+        if (this.bShadow){
+            this.oShadowPanel = oGrammalecte.createNode("div", {id: this.sId+"_shadow", style: "width:0;height:0;"});
+            this.oShadow = this.oShadowPanel.attachShadow({mode: "open"});
+            this.oParent = this.oShadow;
+        } else {
+            this.oParent = document;
+        }
+
         this.xMessageBoxBar = oGrammalecte.createNode("div", {className: "grammalecte_message_box_bar"});
         this.xMessageBoxContent = oGrammalecte.createNode("div", {className: "grammalecte_message_box_content"});
         this.xMessageBox = this._createPanel(sTitle);
     }
 
@@ -48,11 +63,22 @@
         xButton.onclick = function () { this.hide(); }.bind(this);  // better than writing “let that = this;” before the function?
         return xButton;
     }
 
     insertIntoPage () {
-        document.body.appendChild(this.xMessageBox);
+        if (this.bShadow){
+            this.oShadow.appendChild(
+                oGrammalecte.createNode("link", {rel: "stylesheet", type: "text/css", media: "all", href: this.sUrl+"content_scripts/panel.css"})
+            );
+            this.oShadow.appendChild(
+                oGrammalecte.createNode("link", {rel: "stylesheet", type: "text/css", media: "all", href: this.sUrl+"content_scripts/message_box.css"})
+            );
+            this.oShadow.appendChild(this.xMessageBox);
+            document.body.appendChild(this.oShadowPanel);
+        } else {
+            document.body.appendChild(this.xMessageBox);
+        }
     }
 
     show () {
         this.xMessageBox.style.display = "block";
     }