[FIX] mass_mailing: prevent selection change into zone outside snippets

When starting with an empty mailing, it was possible to click in the
document and start typing, while this should not be allowed since that
zone is not really editable. We want to only allow writing into
snippets.

task-2778412

closes odoo/odoo#85328

X-original-commit: c9ebe6996f61c24c2a67212beba5dcc95e9a7ed9
Signed-off-by: David Monjoie (dmo) <dmo@odoo.com>

addons/mass_mailing/static/src/js/wysiwyg.js

@@ -5,6 +5,25 @@ var Wysiwyg = require('web_editor.wysiwyg');
 var MassMailingSnippetsMenu = require('mass_mailing.snippets.editor');
 
 const MassMailingWysiwyg = Wysiwyg.extend({
+    //--------------------------------------------------------------------------
+    // Public
+    //--------------------------------------------------------------------------
+
+    start: async function () {
+        const res = await this._super(...arguments);
+        // Prevent selection change outside of snippets.
+        this.$editable.on('mousedown', e => {
+            if ($(e.target).is('.o_editable:empty') || e.target.querySelector('.o_editable')) {
+                e.preventDefault();
+            }
+        });
+        return res;
+    },
+
+    //--------------------------------------------------------------------------
+    // Private
+    //--------------------------------------------------------------------------
+
     /**
      * @override
      */