Do not set focus on cursor target following diff scroll

The diff cursor suspends the underlying cursor's scroll behavior while
the diff is rendering if the user scrolls the page before the render is
complete. However, when focus-on-move is enabled, the underlying cursor
also sets focus and this causes a scroll anyway. With this change the
cursor manager suspends the focus-on-move in the same way that it
suspends the scroll behavior to prevent this unwanted scroll/focus.

Bug: Issue 7390
Change-Id: I2bc7a06e940475b6b3c94995494f4207902acb40

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

@@ -23,7 +23,7 @@ limitations under the License.
         id="cursorManager"
         scroll-behavior="[[_scrollBehavior]]"
         cursor-target-class="target-row"
-        focus-on-move
+        focus-on-move="[[_focusOnMove]]"
         target="{{diffRow}}"></gr-cursor-manager>
   </template>
   <script src="gr-diff-cursor.js"></script>

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

@@ -80,6 +80,11 @@
         value: ScrollBehavior.KEEP_VISIBLE,
       },
 
+      _focusOnMove: {
+        type: Boolean,
+        value: true,
+      },
+
       _listeningForScroll: Boolean,
     },
 
@@ -207,6 +212,7 @@
     _handleWindowScroll() {
       if (this._listeningForScroll) {
         this._scrollBehavior = ScrollBehavior.NEVER;
+        this._focusOnMove = false;
         this._listeningForScroll = false;
       }
     },
@@ -218,6 +224,7 @@
         this.reInitCursor();
       }
       this._scrollBehavior = ScrollBehavior.KEEP_VISIBLE;
+      this._focusOnMove = true;
       this._listeningForScroll = false;
     },
 

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

@@ -102,12 +102,15 @@ limitations under the License.
     test('cursor scroll behavior', () => {
       cursorElement._handleDiffRenderStart();
       assert.equal(cursorElement._scrollBehavior, 'keep-visible');
+      assert.isTrue(cursorElement._focusOnMove);
 
       cursorElement._handleWindowScroll();
       assert.equal(cursorElement._scrollBehavior, 'never');
+      assert.isFalse(cursorElement._focusOnMove);
 
       cursorElement.handleDiffUpdate();
       assert.equal(cursorElement._scrollBehavior, 'keep-visible');
+      assert.isTrue(cursorElement._focusOnMove);
     });
 
     suite('unified diff', () => {