Pass in an editor.

src/tooltip/index.ts

@@ -1,10 +1,18 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
+import {
+  Message
+} from 'phosphor/lib/core/messaging';
+
 import {
   Widget
 } from 'phosphor/lib/ui/widget';
 
+import {
+  CodeEditor
+} from '../codeeditor';
+
 
 /**
  * The class name added to each tooltip.
@@ -20,9 +28,39 @@ class TooltipWidget extends Widget {
   /**
    * Instantiate a tooltip.
    */
-  constructor() {
+  constructor(options: TooltipWidget.IOptions) {
     super();
+    this.editor = options.editor;
     this.addClass(TOOLTIP_CLASS);
   }
 
+  /**
+   * The editor referent of the tooltip widget.
+   */
+  readonly editor: CodeEditor.IEditor;
+
+  /**
+   * Handle `'activate-request'` messages.
+   */
+  protected onActivateRequest(msg: Message): void {
+    this.node.tabIndex = -1;
+    this.node.focus();
+  }
+}
+
+/**
+ * A namespace for tooltip widget statics.
+ */
+export
+namespace TooltipWidget {
+  /**
+   * Instantiation options for a tooltip widget.
+   */
+  export
+  interface IOptions {
+    /**
+     * The editor referent of the tooltip widget.
+     */
+    editor: CodeEditor.IEditor;
+  }
 }