Bug 1326163 part 1. The fieldset's border drawing display item shouldn't participate in hit-testing. That's handled by its background item already. r=dbaron

layout/forms/nsFieldSetFrame.cpp

@@ -101,9 +101,6 @@ public:
     MOZ_COUNT_DTOR(nsDisplayFieldSetBorderBackground);
   }
 #endif
-  virtual void HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
-                       HitTestState* aState,
-                       nsTArray<nsIFrame*> *aOutFrames) override;
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      nsRenderingContext* aCtx) override;
   virtual nsDisplayItemGeometry* AllocateGeometry(nsDisplayListBuilder* aBuilder) override;
@@ -114,15 +111,6 @@ public:
   NS_DISPLAY_DECL_NAME("FieldSetBorderBackground", TYPE_FIELDSET_BORDER_BACKGROUND)
 };
 
-void nsDisplayFieldSetBorderBackground::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
-                                                HitTestState* aState, nsTArray<nsIFrame*> *aOutFrames)
-{
-  // aPt is guaranteed to be in this item's bounds. We do the hit test based on the
-  // frame bounds even though our background doesn't cover the whole frame.
-  // It's not clear whether this is correct.
-  aOutFrames->AppendElement(mFrame);
-}
-
 void
 nsDisplayFieldSetBorderBackground::Paint(nsDisplayListBuilder* aBuilder,
                                          nsRenderingContext* aCtx)

testing/web-platform/tests/cssom-view/elementFromPoint.html

@@ -52,6 +52,19 @@
   <area id="rectG" shape="rect" coords="0,0,90,100" href="#" alt="area 1"/>
   <area id="circleO" shape="circle" coords="120,60,30" href="#" alt="area 2"/>
   <area id="polyLE" shape="poly" coords="280,0,310,0,360,30,360,90,280,90" href="#" alt="area 3"/>
+  <!-- Test for fieldsets not doing weird things.  Use a 200x200 div to hold
+       all the bits for this test. Also, place it top/right, so it is not below
+       the bottom edge of the viewport. -->
+  <div style="position: absolute; width: 200px; height: 200px; right: 0; top: 0">
+    <div id="fieldset-div"
+         class="size" style="position: absolute; top: 0; left: 0">
+    </div>
+    <fieldset class="size" style="position: absolute; top: 100px; left: 100px">
+      <!-- Place the child span so the overflow area of the fieldset overlaps
+           the div -->
+      <span style="position: absolute; top: -100px; left: -100px; height: 1px; width: 1px"></span>
+    </fieldset>
+  </div>
   <script>
     setup({explicit_done:true});
     window.onload = function () {
@@ -152,6 +165,15 @@
                         area,
                         "Should have returned the image element");
       }, "Image Maps");
+
+      test(function(){
+          var fieldsetDiv = document.getElementById("fieldset-div");
+          var divRect = fieldsetDiv.getBoundingClientRect();
+          assert_equals(document.elementFromPoint(divRect.left + divRect.width/2,
+                                                  divRect.top + divRect.height/2),
+                        fieldsetDiv,
+                        "The fieldset should not cover up the div it doesn't even overlap");
+      }, "Fieldsets");
       done();
     }
  </script>