From 88cbe89247a4ebdf9498d77eb0f7e675b7a4c785 Mon Sep 17 00:00:00 2001
From: Stanley Shyiko
Date: Mon, 28 Oct 2013 22:13:37 +0200
Subject: Fixed detection of links which are only partially inside the viewport

---
 lib/dom_utils.coffee                  | 16 +++++++++++++---
 tests/dom_tests/dom_utils_test.coffee |  8 ++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/lib/dom_utils.coffee b/lib/dom_utils.coffee
index 38b23202..70e52a6c 100644
--- a/lib/dom_utils.coffee
+++ b/lib/dom_utils.coffee
@@ -46,11 +46,21 @@ DomUtils =
   #
   getVisibleClientRect: (element) ->
     # Note: this call will be expensive if we modify the DOM in between calls.
-    clientRects = element.getClientRects()
+    clientRects = ({
+      top: clientRect.top, right: clientRect.right, bottom: clientRect.bottom, left: clientRect.left,
+      width: clientRect.width, height: clientRect.height
+    } for clientRect in element.getClientRects())
 
     for clientRect in clientRects
-      if (clientRect.top < -2 || clientRect.top >= window.innerHeight - 4 ||
-          clientRect.left < -2 || clientRect.left  >= window.innerWidth - 4)
+      if (clientRect.top < 0)
+        clientRect.height += clientRect.top
+        clientRect.top = 0
+
+      if (clientRect.left < 0)
+        clientRect.width += clientRect.left
+        clientRect.left = 0
+
+      if (clientRect.top >= window.innerHeight - 4 || clientRect.left  >= window.innerWidth - 4)
         continue
 
       if (clientRect.width < 3 || clientRect.height < 3)
diff --git a/tests/dom_tests/dom_utils_test.coffee b/tests/dom_tests/dom_utils_test.coffee
index d0f881ba..130a3014 100644
--- a/tests/dom_tests/dom_utils_test.coffee
+++ b/tests/dom_tests/dom_utils_test.coffee
@@ -42,6 +42,14 @@ context "Check visibility",
     assert.equal null, DomUtils.getVisibleClientRect document.getElementById 'foo'
     assert.equal null, DomUtils.getVisibleClientRect document.getElementById 'bar'
 
+  should "detect links only partially outside viewport as visible", ->
+    document.getElementById("test-div").innerHTML = """
+    <a id='foo' style='position:absolute;top:-10px'>test</a>
+    <a id='bar' style='position:absolute;left:-10px'>test</a>
+    """
+    assert.isTrue (DomUtils.getVisibleClientRect document.getElementById 'foo') != null
+    assert.isTrue (DomUtils.getVisibleClientRect document.getElementById 'bar') != null
+
   should "detect opacity:0 links as hidden", ->
     document.getElementById("test-div").innerHTML = """
     <a id='foo' style='opacity:0'>test</a>
-- 
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