From 2df4f38a97ba9c2f2fabc4934d2b2d44ce0b4cf6 Mon Sep 17 00:00:00 2001
From: Kelv <kelv@discourse.org>
Date: Tue, 14 May 2024 00:12:38 +0800
Subject: [PATCH] FIX: restore docked body document from glimmer site header
 (#27003)

---
 .../discourse/app/components/glimmer-site-header.gjs |  2 +-
 spec/system/header_spec.rb                           | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/app/assets/javascripts/discourse/app/components/glimmer-site-header.gjs b/app/assets/javascripts/discourse/app/components/glimmer-site-header.gjs
index e6bccbc3c41..c7d81ad1894 100644
--- a/app/assets/javascripts/discourse/app/components/glimmer-site-header.gjs
+++ b/app/assets/javascripts/discourse/app/components/glimmer-site-header.gjs
@@ -243,7 +243,7 @@ export default class GlimmerSiteHeader extends Component {
 
   @bind
   dockCheck() {
-    if (this._docAt === null) {
+    if (this._docAt === undefined || this._docAt === null) {
       if (!this.headerElement) {
         return;
       }
diff --git a/spec/system/header_spec.rb b/spec/system/header_spec.rb
index 3bf987da3ae..c0d00a53d4b 100644
--- a/spec/system/header_spec.rb
+++ b/spec/system/header_spec.rb
@@ -89,6 +89,18 @@ RSpec.describe "Glimmer Header", type: :system do
     expect(header.get_computed_style_value(".d-header", "--header-offset")).to eq("60px")
   end
 
+  it "body document is permanently docked regardless of scroll positioning" do
+    Fabricate.times(20, :topic)
+    sign_in(current_user)
+    visit "/"
+
+    expect(page).to have_selector("body.docked")
+    page.execute_script("window.scrollBy(0, 1000)")
+    expect(page).to have_selector("body.docked")
+    page.execute_script("window.scrollTo(0, 0)")
+    expect(page).to have_selector("body.docked")
+  end
+
   it "moves focus between tabs using arrow keys" do
     sign_in(current_user)
     visit "/"