From e4106f7b64c3540508c8306b272184282968a65a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emilio=20Cobos=20=C3=81lvarez?= <emilio@crisal.io>
Date: Sat, 22 Feb 2020 20:08:22 +0000
Subject: [PATCH] Bug 1615955 - Suppress scroll anchoring when scroll offset is
 zero. r=dholbert

As per https://github.com/w3c/csswg-drafts/pull/4679.

Differential Revision: https://phabricator.services.mozilla.com/D63761

--HG--
extra : moz-landing-system : lando
---
 layout/generic/ScrollAnchorContainer.cpp         |  7 +++++--
 .../zero-scroll-offset.html.ini                  | 16 ----------------
 2 files changed, 5 insertions(+), 18 deletions(-)
 delete mode 100644 testing/web-platform/meta/css/css-scroll-anchoring/zero-scroll-offset.html.ini

diff --git a/layout/generic/ScrollAnchorContainer.cpp b/layout/generic/ScrollAnchorContainer.cpp
index a2863b7da5a8..70834fc639f8 100644
--- a/layout/generic/ScrollAnchorContainer.cpp
+++ b/layout/generic/ScrollAnchorContainer.cpp
@@ -382,16 +382,19 @@ void ScrollAnchorContainer::ApplyAdjustments() {
       mScrollFrame->HasPendingScrollRestoration() ||
       mScrollFrame->IsProcessingScrollEvent() ||
       mScrollFrame->IsProcessingAsyncScroll() ||
-      mScrollFrame->mApzSmoothScrollDestination.isSome()) {
+      mScrollFrame->mApzSmoothScrollDestination.isSome() ||
+      mScrollFrame->GetScrollPosition() == nsPoint()) {
     ANCHOR_LOG(
         "Ignoring post-reflow (anchor=%p, dirty=%d, disabled=%d, "
         "pendingRestoration=%d, scrollevent=%d, asyncScroll=%d, "
-        "apzSmoothDestination=%d, pendingSuppression=%d, container=%p).\n",
+        "apzSmoothDestination=%d, zeroScrollPos=%d pendingSuppression=%d, "
+        "container=%p).\n",
         mAnchorNode, mAnchorNodeIsDirty, mDisabled,
         mScrollFrame->HasPendingScrollRestoration(),
         mScrollFrame->IsProcessingScrollEvent(),
         mScrollFrame->IsProcessingAsyncScroll(),
         mScrollFrame->mApzSmoothScrollDestination.isSome(),
+        mScrollFrame->GetScrollPosition() == nsPoint(),
         mSuppressAnchorAdjustment, this);
     if (mSuppressAnchorAdjustment) {
       mSuppressAnchorAdjustment = false;
diff --git a/testing/web-platform/meta/css/css-scroll-anchoring/zero-scroll-offset.html.ini b/testing/web-platform/meta/css/css-scroll-anchoring/zero-scroll-offset.html.ini
deleted file mode 100644
index 59b09d005c99..000000000000
--- a/testing/web-platform/meta/css/css-scroll-anchoring/zero-scroll-offset.html.ini
+++ /dev/null
@@ -1,16 +0,0 @@
-[zero-scroll-offset.html]
-  [Scroll anchoring suppressed when scroll offset is zero.]
-    expected:
-      if (os == "win") and debug and not webrender and not fission and (processor == "x86"): ["PASS", "FAIL"]
-      if (os == "linux") and not fission and (processor == "x86_64") and debug and not webrender: ["PASS", "FAIL"]
-      if (os == "linux") and not fission and (processor == "x86_64") and debug and webrender: ["PASS", "FAIL"]
-      if (os == "linux") and not fission and (processor == "x86_64") and not debug and webrender: ["PASS", "FAIL"]
-      if (os == "linux") and not fission and (processor == "x86_64") and not debug and not webrender: ["PASS", "FAIL"]
-      if (os == "win") and debug and webrender and fission: ["PASS", "FAIL"]
-      if (os == "win") and not debug and not fission and webrender: FAIL
-      if (os == "linux") and fission and not debug and not webrender: ["PASS", "FAIL"]
-      if (os == "linux") and fission and debug and webrender: ["PASS", "FAIL"]
-      if (os == "linux") and fission and debug and not webrender: ["PASS", "FAIL"]
-      if (os == "win") and not debug and fission: FAIL
-      [FAIL, PASS]
-