From 516dd41c49565521bf0511bcc9c886076d4f40c8 Mon Sep 17 00:00:00 2001
From: Dan Robertson <dan@dlrobertson.com>
Date: Wed, 3 Jan 2024 19:12:22 +0000
Subject: [PATCH] Bug 1858984 - Fix ComputeNeedToScroll with large line sizes.
 r=emilio,devtools-reviewers,ochameau

When the line scroll amount is larger than that of the rectangle to
scroll into view, do not use the line size to determine if we should
scroll.

Depends on D192869

Differential Revision: https://phabricator.services.mozilla.com/D192870
---
 devtools/client/inspector/markup/test/head.js              | 1 +
 layout/base/PresShell.cpp                                  | 7 +++++++
 ...cus-large-element-in-overflow-hidden-container.html.ini | 2 --
 ...s-visible-element-in-overflow-hidden-container.html.ini | 2 --
 4 files changed, 8 insertions(+), 4 deletions(-)
 delete mode 100644 testing/web-platform/meta/focus/focus-large-element-in-overflow-hidden-container.html.ini
 delete mode 100644 testing/web-platform/meta/focus/focus-visible-element-in-overflow-hidden-container.html.ini

diff --git a/devtools/client/inspector/markup/test/head.js b/devtools/client/inspector/markup/test/head.js
index fb2153d5dc80..ddd04516082a 100644
--- a/devtools/client/inspector/markup/test/head.js
+++ b/devtools/client/inspector/markup/test/head.js
@@ -478,6 +478,7 @@ async function simulateNodeDrag(
     typeof selector === "string"
       ? await getContainerForSelector(selector, inspector)
       : selector;
+  container.elt.scrollIntoView(true);
   const rect = container.tagLine.getBoundingClientRect();
   const scrollX = inspector.markup.doc.documentElement.scrollLeft;
   const scrollY = inspector.markup.doc.documentElement.scrollTop;
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
index 18c7d7c422e5..a39c0b88ff3a 100644
--- a/layout/base/PresShell.cpp
+++ b/layout/base/PresShell.cpp
@@ -3326,6 +3326,13 @@ static bool ComputeNeedToScroll(WhenToScroll aWhenToScroll, nscoord aLineSize,
       // The caller wants the frame as visible as possible
       return true;
     case WhenToScroll::IfNotVisible:
+      if (aLineSize > (aRectMax - aRectMin)) {
+        // If the line size is greater than the size of the rect
+        // to scroll into view, do not use the line size to determine
+        // if we need to scroll.
+        aLineSize = 0;
+      }
+
       // Scroll only if no part of the frame is visible in this view.
       return aRectMax - aLineSize <= aViewMin ||
              aRectMin + aLineSize >= aViewMax;
diff --git a/testing/web-platform/meta/focus/focus-large-element-in-overflow-hidden-container.html.ini b/testing/web-platform/meta/focus/focus-large-element-in-overflow-hidden-container.html.ini
deleted file mode 100644
index 703dfe13847c..000000000000
--- a/testing/web-platform/meta/focus/focus-large-element-in-overflow-hidden-container.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[focus-large-element-in-overflow-hidden-container.html]
-  expected: FAIL
diff --git a/testing/web-platform/meta/focus/focus-visible-element-in-overflow-hidden-container.html.ini b/testing/web-platform/meta/focus/focus-visible-element-in-overflow-hidden-container.html.ini
deleted file mode 100644
index e3e234c8f16f..000000000000
--- a/testing/web-platform/meta/focus/focus-visible-element-in-overflow-hidden-container.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[focus-visible-element-in-overflow-hidden-container.html]
-  expected: FAIL