From f6712ec43ae7b5f049311d72372dfd676546e968 Mon Sep 17 00:00:00 2001
From: Dmitry Gozman <dgozman@gmail.com>
Date: Thu, 12 May 2022 18:55:29 +0100
Subject: [PATCH] fix(tracing): workaround chromium scrollTop slowness (#14114)

References #14037.

We used to query and save all non-zero `scrollTop`/`scrollLeft` to restore the page perfectly. However, this became very slow with Chromium v100 regression (see issue).

This change only queries and stores `scrollTop`/`scrollLeft` for elements that are ancestors of the action target. The resulting snapshot does not perfectly recreate the original screen, but should be good enough to inspect the action.
---
 .../trace/recorder/snapshotterInjected.ts     | 27 +++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/packages/playwright-core/src/server/trace/recorder/snapshotterInjected.ts b/packages/playwright-core/src/server/trace/recorder/snapshotterInjected.ts
index 03f9b86543..4b8798171d 100644
--- a/packages/playwright-core/src/server/trace/recorder/snapshotterInjected.ts
+++ b/packages/playwright-core/src/server/trace/recorder/snapshotterInjected.ts
@@ -44,6 +44,7 @@ export function frameSnapshotStreamer(snapshotStreamer: string) {
   const kScrollTopAttribute = '__playwright_scroll_top_';
   const kScrollLeftAttribute = '__playwright_scroll_left_';
   const kStyleSheetAttribute = '__playwright_style_sheet_';
+  const kTargetAttribute = '__playwright_target__';
 
   // Symbols for our own info on Nodes/StyleSheets.
   const kSnapshotFrameId = Symbol('__playwright_snapshot_frameid_');
@@ -273,6 +274,28 @@ export function frameSnapshotStreamer(snapshotStreamer: string) {
       // Ensure we are up to date.
       this._handleMutations(this._observer.takeRecords());
 
+      // Restore scroll positions for all ancestors of action target elements
+      // that will show the highlight/red dot in the trace viewer.
+      // Workaround for chromium regression:
+      // https://bugs.chromium.org/p/chromium/issues/detail?id=1324419
+      // https://github.com/microsoft/playwright/issues/14037
+      // TODO: remove after chromium is fixed?
+      const elementsToRestoreScrollPosition = new Set<Node>();
+      const findElementsToRestoreScrollPositionRecursively = (element: Element) => {
+        let shouldAdd = element.hasAttribute(kTargetAttribute);
+        for (let child = element.firstElementChild; child; child = child.nextElementSibling)
+          shouldAdd = shouldAdd || findElementsToRestoreScrollPositionRecursively(child);
+        if (element.shadowRoot) {
+          for (let child = element.shadowRoot.firstElementChild; child; child = child.nextElementSibling)
+            shouldAdd = shouldAdd || findElementsToRestoreScrollPositionRecursively(child);
+        }
+        if (shouldAdd)
+          elementsToRestoreScrollPosition.add(element);
+        return shouldAdd;
+      };
+      if (document.documentElement)
+        findElementsToRestoreScrollPositionRecursively(document.documentElement);
+
       const visitNode = (node: Node | ShadowRoot): { equals: boolean, n: NodeSnapshot } | undefined => {
         const nodeType = node.nodeType;
         const nodeName = nodeType === Node.DOCUMENT_FRAGMENT_NODE ? 'template' : node.nodeName;
@@ -380,12 +403,12 @@ export function frameSnapshotStreamer(snapshotStreamer: string) {
             expectValue(value);
             attrs[kSelectedAttribute] = value;
           }
-          if (element.scrollTop) {
+          if (elementsToRestoreScrollPosition.has(element) && element.scrollTop) {
             expectValue(kScrollTopAttribute);
             expectValue(element.scrollTop);
             attrs[kScrollTopAttribute] = '' + element.scrollTop;
           }
-          if (element.scrollLeft) {
+          if (elementsToRestoreScrollPosition.has(element) && element.scrollLeft) {
             expectValue(kScrollLeftAttribute);
             expectValue(element.scrollLeft);
             attrs[kScrollLeftAttribute] = '' + element.scrollLeft;