From a079e8682025fa4e6850f8e69c74ce54f62c87b4 Mon Sep 17 00:00:00 2001
From: Cameron McCormack <cam@mcc.id.au>
Date: Sat, 3 Dec 2016 14:53:31 +0800
Subject: [PATCH] stylo: Add FFI function to check if a node is dirty.

---
 ports/geckolib/glue.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/ports/geckolib/glue.rs b/ports/geckolib/glue.rs
index 3043f879e648..02d54692b19f 100644
--- a/ports/geckolib/glue.rs
+++ b/ports/geckolib/glue.rs
@@ -202,6 +202,23 @@ pub extern "C" fn Servo_Element_ClearData(element: RawGeckoElementBorrowed) -> (
     GeckoElement(element).clear_data();
 }
 
+#[no_mangle]
+pub extern "C" fn Servo_Element_ShouldTraverse(element: RawGeckoElementBorrowed) -> bool {
+    let element = GeckoElement(element);
+    if let Some(data) = element.get_data() {
+        debug_assert!(!element.has_dirty_descendants(),
+                      "only call Servo_Element_ShouldTraverse if you know the element \
+                       does not have dirty descendants");
+        match *data.borrow() {
+            ElementData::Initial(None) |
+            ElementData::Restyle(..) => true,
+            _ => false,
+        }
+    } else {
+        false
+    }
+}
+
 #[no_mangle]
 pub extern "C" fn Servo_StyleSheet_Empty(mode: SheetParsingMode) -> RawServoStyleSheetStrong {
     let url = ServoUrl::parse("about:blank").unwrap();