From bffacaf61caca936ae7b32a9186a55478531d926 Mon Sep 17 00:00:00 2001
From: Brad Werth <bwerth@mozilla.com>
Date: Mon, 28 Nov 2016 13:22:15 -0800
Subject: [PATCH] Bug 1319560 Part 3: Change nsDisplayList::HitTest to exit
 early when HitTestShouldStopAtFirstOpaque() is true. r=mattwoodrow

MozReview-Commit-ID: D8aKGX6z2TV

--HG--
extra : rebase_source : 8a698f3ab58cd571c58d346e8ad2fcc3b0eef4c7
---
 layout/painting/nsDisplayList.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/layout/painting/nsDisplayList.cpp b/layout/painting/nsDisplayList.cpp
index 6a8bb17c90c2..bca5f1228a75 100644
--- a/layout/painting/nsDisplayList.cpp
+++ b/layout/painting/nsDisplayList.cpp
@@ -2218,6 +2218,13 @@ void nsDisplayList::HitTest(nsDisplayListBuilder* aBuilder, const nsRect& aRect,
           writeFrames->AppendElement(f);
         }
       }
+
+      if (aBuilder->HitTestShouldStopAtFirstOpaque() &&
+          item->GetOpaqueRegion(aBuilder, &snap).Contains(aRect)) {
+        // We're exiting early, so pop the remaining items off the buffer.
+        aState->mItemBuffer.SetLength(itemBufferStart);
+        break;
+      }
     }
   }
   // Clear any remaining preserve-3d transforms.