From 4dfde193e0c7f7d1dbb002a33c92128fa6ad54c1 Mon Sep 17 00:00:00 2001
From: Philip Walton <philip@philipwalton.com>
Date: Mon, 3 May 2021 16:44:31 -0700
Subject: [PATCH] Add workaround for Safari FCP bug

---
 src/getFCP.ts | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/getFCP.ts b/src/getFCP.ts
index d848735d..d068eac9 100644
--- a/src/getFCP.ts
+++ b/src/getFCP.ts
@@ -44,10 +44,18 @@ export const getFCP = (onReport: ReportHandler, reportAllChanges?: boolean) => {
     }
   };
 
-  const po = observe('paint', entryHandler);
-  if (po) {
+  // TODO(philipwalton): remove the use of `fcpEntry` once this bug is fixed.
+  // https://bugs.webkit.org/show_bug.cgi?id=225305
+  const fcpEntry = performance.getEntriesByName('first-contentful-paint')[0];
+  const po = fcpEntry ? null : observe('paint', entryHandler);
+
+  if (fcpEntry || po) {
     report = bindReporter(onReport, metric, reportAllChanges);
 
+    if (fcpEntry) {
+      entryHandler(fcpEntry);
+    }
+
     onBFCacheRestore((event) => {
       metric = initMetric('FCP');
       report = bindReporter(onReport, metric, reportAllChanges);