--- /dev/null
+{#
+/**
+ * @file
+ * Default theme implementation for a page wrapper.
+ *
+ * For consistent wrapping to {{ page }} render in all themes. The
+ * "data-off-canvas-main-canvas" attribute is required by the off-canvas dialog.
+ * This is used by the settings_tray/drupal.off_canvas library to select the
+ * "main canvas" page element as opposed to the "off canvas" which is the tray
+ * itself. The "main canvas" element must be resized according to the width of
+ * the "off canvas" tray so that no portion of the "main canvas" is obstructed
+ * by the tray. The tray can vary in width when opened and can be resized by the
+ * user. The "data-off-canvas-main-canvas" attribute cannot be removed without
+ * breaking the off-canvas dialog functionality.
+ *
+ * Available variables:
+ * - children: Contains the child elements of the page.
+ *
+ * @ingroup themeable
+ */
+#}
+{% if children %}
+ <div class="dialog-off-canvas__main-canvas" data-off-canvas-main-canvas >
+ {{ children }}
+ </div>
+{% endif %}