From 52831cd117567299586808d5672ab42347543a42 Mon Sep 17 00:00:00 2001
From: Ayke Halder <rr-it@users.noreply.github.com>
Date: Tue, 16 May 2023 15:57:28 +0200
Subject: [PATCH] PagePerformance: Delay log of page view/visit to include
 `onload` metric

---
 js/piwik.js | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/js/piwik.js b/js/piwik.js
index bbdf165d858..f3584cdd967 100644
--- a/js/piwik.js
+++ b/js/piwik.js
@@ -4274,12 +4274,48 @@ if (typeof window.Matomo !== 'object') {
 
                 // append already available performance metrics if they were not already tracked (or appended)
                 if (configPerformanceTrackingEnabled && !performanceTracked) {
+                    if (!performanceAvailable && supportsSendBeacon()) {
+                        delayLogPageViewWithPerformanceMetrics(request, configTrackerPause, callback);
+                        return;
+                    }
                     request = appendAvailablePerformanceMetrics(request);
                 }
 
                 sendRequest(request, configTrackerPause, callback);
             }
 
+            /*
+             * Delay log of page view / visit
+             * Wait until PerformanceMetrics are available or visitor leaves page.
+             */
+            function delayLogPageViewWithPerformanceMetrics(request, configTrackerPause, callback) {
+                // - Ensure page view is only logged once.
+                // - Matomo context might change in the meantime: Store request in closure to ensure original context.
+                var logOnce = function() {
+                    var store = { request: request, configTrackerPause: configTrackerPause, callback: callback};
+                    var hasRunOnce = false;
+                    return function() {
+                        if (!hasRunOnce) {
+                            hasRunOnce = true;
+                            store.request = appendAvailablePerformanceMetrics(store.request);
+                            sendRequest(store.request, store.configTrackerPause, store.callback);
+                        }
+                    };
+                }();
+
+                /* Performance metrics are available, once onload event has finished */
+                trackCallbackOnLoad(function(){
+                    setTimeout(logOnce, 0);
+                });
+                /* Visitor leaves page */
+                addEventListener(windowAlias, 'visibilitychange', function () {
+                    // if not visible
+                    if (documentAlias.visibilityState === 'hidden') {
+                        logOnce();
+                    }
+                }, false);
+            }
+
             /*
              * Construct regular expression of classes
              */