From c0b7a1247a295e78487fa8112d3ca4ca8d036c15 Mon Sep 17 00:00:00 2001
From: Pu Xingyu <pu.stshine@gmail.com>
Date: Sat, 8 Apr 2017 23:41:53 +0800
Subject: [PATCH] layout: Ensure abs-pos elements establish block formatting
 contexts
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Per CSS 2.1 § 9.4.1, absolutely positioned elements establish new
block formatting contexts for their contents.
---
 components/layout/block.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/components/layout/block.rs b/components/layout/block.rs
index 5504f0fc4121..7707b833475c 100644
--- a/components/layout/block.rs
+++ b/components/layout/block.rs
@@ -1429,6 +1429,9 @@ impl BlockFlow {
     /// Determines the type of formatting context this is. See the definition of
     /// `FormattingContextType`.
     pub fn formatting_context_type(&self) -> FormattingContextType {
+        if self.base.flags.contains(IS_ABSOLUTELY_POSITIONED) {
+            return FormattingContextType::Other
+        }
         let style = self.fragment.style();
         if style.get_box().float != float::T::none {
             return FormattingContextType::Other