tor-browser

commit 7bfb0e0a3a9794ba601e16630eac7d42c3521a18
parent 692649f52101262f67a2f1a36399cc6d4639158e
Author: DJ <dj@walker.dev>
Date:   Fri, 24 Oct 2025 14:13:41 +0000

Bug 1987784 - Prevent tabstrip from changing scroll position when expanding a tab group. r=sthompson,tabbrowser-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D264327

Diffstat:
M
browser/components/tabbrowser/content/tabs.js
 | 
17
++++++++++++++---
M
browser/components/tabbrowser/test/browser/tabs/browser_tab_groups.js
 | 
48
++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 62 insertions(+), 3 deletions(-)
diff --git a/browser/components/tabbrowser/content/tabs.js b/browser/components/tabbrowser/content/tabs.js
@@ -19,6 +19,7 @@
 
     #mustUpdateTabMinHeight = false;
     #tabMinHeight = 36;
+    #animatingGroups = new Set();
 
     constructor() {
       super();
@@ -34,6 +35,7 @@
       this.addEventListener("TabGroupLabelHoverEnd", this);
       this.addEventListener("TabGroupExpand", this);
       this.addEventListener("TabGroupCollapse", this);
+      this.addEventListener("TabGroupAnimationComplete", this);
       this.addEventListener("TabGroupCreate", this);
       this.addEventListener("TabGroupRemoved", this);
       this.addEventListener("transitionend", this);
@@ -371,13 +373,19 @@
       this.previewPanel?.deactivate(event.target.group);
     }
 
-    on_TabGroupExpand() {
+    on_TabGroupExpand(event) {
       this._invalidateCachedVisibleTabs();
+      this.#animatingGroups.add(event.target.id);
     }
 
-    on_TabGroupCollapse() {
+    on_TabGroupCollapse(event) {
       this._invalidateCachedVisibleTabs();
       this._unlockTabSizing();
+      this.#animatingGroups.add(event.target.id);
+    }
+
+    on_TabGroupAnimationComplete(event) {
+      this.#animatingGroups.delete(event.target.id);
     }
 
     on_TabGroupCreate() {
@@ -737,7 +745,10 @@
 
       this.toggleAttribute("overflow", true);
       this._updateCloseButtons();
-      this._handleTabSelect(true);
+
+      if (!this.#animatingGroups.size) {
+        this._handleTabSelect(true);
+      }
 
       document
         .getElementById("tab-preview-panel")
diff --git a/browser/components/tabbrowser/test/browser/tabs/browser_tab_groups.js b/browser/components/tabbrowser/test/browser/tabs/browser_tab_groups.js
@@ -239,6 +239,54 @@ add_task(async function test_tabGroupCollapseWhileSelected() {
   await removeTabGroup(group);
 });
 
+add_task(async function test_tabGroupPreventScrollOnUncollapse() {
+  let win = await BrowserTestUtils.openNewBrowserWindow();
+
+  // create a tab group that overflows the tabstrip
+  await BrowserTestUtils.overflowTabs(null, win);
+  let bigGroup = win.gBrowser.addTabGroup(win.gBrowser.tabs);
+
+  // create some more tabs after the group
+  createManyTabs(4, win);
+
+  await BrowserTestUtils.waitForCondition(() => {
+    return Array.from(win.gBrowser.tabs).every(tab => tab._fullyOpen);
+  });
+
+  info("selecting the last tab");
+  let tabSelected = BrowserTestUtils.waitForEvent(win, "TabSelect");
+  win.gBrowser.selectedTab = win.gBrowser.tabs[win.gBrowser.tabs.length - 1];
+  await tabSelected;
+
+  info("scrolling to beginning of tabstrip");
+  let arrowScrollbox = win.gBrowser.tabContainer.arrowScrollbox;
+  let scrolledToStart = BrowserTestUtils.waitForCondition(() =>
+    arrowScrollbox.hasAttribute("scrolledtostart")
+  );
+
+  bigGroup.labelElement.scrollIntoView(true);
+  await scrolledToStart;
+  Assert.ok(!bigGroup.collapsed, "Group is expanded");
+  Assert.ok(
+    arrowScrollbox.hasAttribute("scrolledtostart"),
+    "arrowscrollbox is scrolled to start"
+  );
+
+  info("Collapsing and expanding the big group");
+  await TabGroupTestUtils.toggleCollapsed(bigGroup, true);
+  Assert.ok(bigGroup.collapsed, "Group is collapsed");
+  await TabGroupTestUtils.toggleCollapsed(bigGroup, false);
+  Assert.ok(!bigGroup.collapsed, "Group is expanded");
+
+  Assert.ok(
+    arrowScrollbox.hasAttribute("scrolledtostart"),
+    "arrowscrollbox is still scrolled to start"
+  );
+
+  await TabGroupTestUtils.removeTabGroup(bigGroup);
+  BrowserTestUtils.closeWindow(win);
+});
+
 /**
  * Bug 1979067 - The collapsed tab group's overflow counter should be included in the bounds
  * calculations that determine whether the tabstrip scroll button is enabled.