Integrated hint alerts in the main frame
diff --git a/dev/js/src/hint/alert.js b/dev/js/src/hint/alert.js
new file mode 100644
index 0000000..a5b43de
--- /dev/null
+++ b/dev/js/src/hint/alert.js
@@ -0,0 +1,35 @@
+/**
+ * Hint menu alert
+ */
+define(function () {
+  "use strict";
+  return {
+    create : function (msg) {
+      return Object.create(this)._init(msg);
+    },
+    _init : function (msg) {
+      this.active = false;
+      this._element = document.createElement('div');
+      this._element.style.opacity = 0;
+      this._element.classList.add('alert', 'hint');
+      return this;
+    },
+    show : function (msg) {
+      this._element.textContent = msg;
+      this.active = true;
+      this._element.style.opacity = 1;
+    },
+
+    unshow : function () {
+      if (!this.active)
+	return false;
+      this._element.style.opacity = 0;
+      this.active = false;
+      return true;
+    },
+
+    element : function () {
+      return this._element;
+    }
+  }
+});