Scroll the body element if last activated node is not visible.

1 files changed, 44 insertions, 0 deletions

diff --git a/lib/utils.js b/lib/utils.js
index ef961833..0c86970e 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -30,4 +30,48 @@ var utils = {
     }
     return document.evaluate(xpath, document.documentElement, namespaceResolver, resultType, null);
   },
+
+  /**
+   * Returns the first visible clientRect of an element if it exists. Otherwise it returns null.
+   */
+  getVisibleClientRect: function(element) {
+    // Note: this call will be expensive if we modify the DOM in between calls.
+    var clientRects = element.getClientRects();
+    var clientRectsLength = clientRects.length;
+
+    for (var i = 0; i < clientRectsLength; i++) {
+      if (clientRects[i].top < 0 || clientRects[i].top >= window.innerHeight - 4 ||
+          clientRects[i].left < 0 || clientRects[i].left  >= window.innerWidth - 4)
+        continue;
+
+      if (clientRects[i].width < 3 || clientRects[i].height < 3)
+        continue;
+
+      // eliminate invisible elements (see test_harnesses/visibility_test.html)
+      var computedStyle = window.getComputedStyle(element, null);
+      if (computedStyle.getPropertyValue('visibility') != 'visible' ||
+          computedStyle.getPropertyValue('display') == 'none')
+        continue;
+
+      return clientRects[i];
+    }
+
+    for (var i = 0; i < clientRectsLength; i++) {
+      // If the link has zero dimensions, it may be wrapping visible
+      // but floated elements. Check for this.
+      if (clientRects[i].width == 0 || clientRects[i].height == 0) {
+        for (var j = 0, childrenCount = element.children.length; j < childrenCount; j++) {
+          var computedStyle = window.getComputedStyle(element.children[j], null);
+          // Ignore child elements which are not floated and not absolutely positioned for parent elements with zero width/height
+          if (computedStyle.getPropertyValue('float') == 'none' && computedStyle.getPropertyValue('position') != 'absolute')
+            continue;
+          var childClientRect = this.getVisibleClientRect(element.children[j]);
+          if (childClientRect === null)
+            continue;
+          return childClientRect;
+        }
+      }
+    };
+    return null;
+  },
 };