PagePerformance: Delay log of page view/visit to include onload metric

js/piwik.js

@@ -4176,12 +4176,49 @@ 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(){
+                    // Onload event is fired. Wait 15 seconds to assume it has also finished.
+                    setTimeout(logOnce, 15000);
+                });
+                /* Visitor leaves page */
+                addEventListener(windowAlias, 'visibilitychange', function () {
+                    // if not visible
+                    if (documentAlias.visibilityState === 'hidden') {
+                        logOnce();
+                    }
+                }, false);
+            }
+
             /*
              * Construct regular expression of classes
              */