Merge "Fire event when gr-diff-cursor is attached to DOM"

polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor.js

@@ -35,9 +35,9 @@
   const LEFT_SIDE_CLASS = 'target-side-left';
   const RIGHT_SIDE_CLASS = 'target-side-right';
 
-  class GrDiffCursor extends Polymer.GestureEventListeners(
-      Polymer.LegacyElementMixin(
-          Polymer.Element)) {
+  class GrDiffCursor extends Polymer.mixinBehaviors([Gerrit.FireBehavior],
+      Polymer.GestureEventListeners(
+          Polymer.LegacyElementMixin(Polymer.Element))) {
     static get is() { return 'gr-diff-cursor'; }
 
     static get properties() {
@@ -105,6 +105,23 @@
       ];
     }
 
+    ready() {
+      super.ready();
+      Polymer.RenderStatus.afterNextRender(this, () => {
+        /*
+        This represents the diff cursor is ready for interaction coming from
+        client components. It is more then Polymer "ready" lifecycle, as no
+        "ready" events are automatically fired by Polymer, it means
+        the cursor is completely interactable - in this case attached and
+        painted on the page. We name it "ready" instead of "rendered" as the
+        long-term goal is to make gr-diff-cursor a javascript class - not a DOM
+        element with an actual lifecycle. This will be triggered only once
+        per element.
+        */
+        this.fire('ready', null, {bubbles: false});
+      });
+    }
+
     attached() {
       super.attached();
       // Catch when users are scrolling as the view loads.

polygerrit-ui/app/elements/diff/gr-diff-cursor/gr-diff-cursor_test.html

@@ -42,6 +42,12 @@ limitations under the License.
   </template>
 </test-fixture>
 
+<test-fixture id="empty">
+  <template>
+    <div></div>
+  </template>
+</test-fixture>
+
 <script>
   suite('gr-diff-cursor tests', () => {
     let sandbox;
@@ -370,4 +376,24 @@ limitations under the License.
       });
     });
   });
+
+  suite('gr-diff-cursor event tests', () => {
+    let sandbox;
+    let someEmptyDiv;
+
+    setup(() => {
+      sandbox = sinon.sandbox.create();
+      someEmptyDiv = fixture('empty');
+    });
+
+    teardown(() => sandbox.restore());
+
+    test('ready is fired after component is rendered', done => {
+      const cursorElement = document.createElement('gr-diff-cursor');
+      cursorElement.addEventListener('ready', () => {
+        done();
+      });
+      someEmptyDiv.appendChild(cursorElement);
+    });
+  });
 </script>