Ticket #48902: 48902.diff

src/js/_enqueues/wp/customize/controls.js

@@ -5277 +5277 @@
                  */
                 ready: function() {
                         var control = this;
+
+                        /*
+                         * If the section is ready but the control isn't active yet, refresh the
+                         * CodeMirror instance when the control does become active so it restyles
+                         * itself according to the element's new dimensions. See #48902.
+                         */
+                        if ( ! control.active() ) {
+                                control.active.bind( _.once( function () {
+                                        control.deferred.codemirror.done( function () {
+                                                control.editor.codemirror.refresh();
+                                        } )
+                                } ) );
+                        }
+
                         if ( ! control.section() ) {
                                 control.initEditor();
                                 return;