Make tree.hasFocus() more robust

Author: mar10

CHANGELOG.md

@@ -1,4 +1,5 @@
 # 2.33.1-0 / Unreleased
+  * tree.hasFocus() more reliable.
 
 # 2.33.0 / 2019-10-29
   * [Added] event `preInit` (fired before nodes are loaded).

src/jquery.fancytree.js

@@ -3437,7 +3437,21 @@
 		 * @returns {boolean}
 		 */
 		hasFocus: function() {
-			return !!this._hasFocus;
+			var ae = document.activeElement,
+				hasFocus = !!(
+					ae && $(ae).closest(".fancytree-container").length
+				);
+
+			if (hasFocus !== !!this._hasFocus) {
+				this.warn(
+					"hasFocus(): fix inconsistent container state, now: " +
+						hasFocus
+				);
+				this._hasFocus = hasFocus;
+				this.$container.toggleClass("fancytree-treefocus", hasFocus);
+			}
+			return hasFocus;
+			// return !!this._hasFocus;
 		},
 		/** Write to browser console if debugLevel >= 3 (prepending tree name)
 		 * @param {*} msg string or object or array of such