FIX: Render the correct logo for the active scheme when logo is minimized

javascripts/discourse/connectors/home-logo-contents__after/minimized-hook.gjs

@@ -0,0 +1,29 @@
+import Component from "@glimmer/component";
+import { action } from "@ember/object";
+import didUpdate from "@ember/render-modifiers/modifiers/did-update";
+import { service } from "@ember/service";
+import {
+  changeHomeLogo,
+  COLOR_SCHEME_OVERRIDE_KEY,
+} from "../../lib/color-scheme-override";
+
+export default class MinimizedHook extends Component {
+  @service keyValueStore;
+
+  @action
+  onMinimizedChange() {
+    const storedOverride = this.keyValueStore.getItem(
+      COLOR_SCHEME_OVERRIDE_KEY
+    );
+    if (storedOverride) {
+      changeHomeLogo(storedOverride);
+    }
+  }
+
+  <template>
+    <span
+      class="hidden color-toggler-minimized-hook"
+      {{didUpdate this.onMinimizedChange @outletArgs.minimized}}
+    />
+  </template>
+}

javascripts/discourse/lib/color-scheme-override.js

@@ -10,28 +10,18 @@ export function colorSchemeOverride(type) {
     return;
   }
 
-  const logoDarkSrc = document.querySelector(".title picture source");
-
   switch (type) {
     case "dark":
       lightScheme.origMedia = lightScheme.media;
       lightScheme.media = "none";
       darkScheme.origMedia = darkScheme.media;
       darkScheme.media = "all";
-      if (logoDarkSrc) {
-        logoDarkSrc.origMedia = logoDarkSrc.media;
-        logoDarkSrc.media = "all";
-      }
       break;
     case "light":
       lightScheme.origMedia = lightScheme.media;
       lightScheme.media = "all";
       darkScheme.origMedia = darkScheme.media;
       darkScheme.media = "none";
-      if (logoDarkSrc) {
-        logoDarkSrc.origMedia = logoDarkSrc.media;
-        logoDarkSrc.media = "none";
-      }
       break;
     default:
       if (lightScheme.origMedia) {
@@ -42,7 +32,29 @@ export function colorSchemeOverride(type) {
         darkScheme.media = darkScheme.origMedia;
         darkScheme.removeAttribute("origMedia");
       }
-      if (logoDarkSrc?.origMedia) {
+      break;
+  }
+  changeHomeLogo(type);
+}
+
+export function changeHomeLogo(type) {
+  const logoDarkSrc = document.querySelector(".title picture source");
+
+  if (!logoDarkSrc) {
+    return;
+  }
+
+  switch (type) {
+    case "dark":
+      logoDarkSrc.origMedia = logoDarkSrc.media;
+      logoDarkSrc.media = "all";
+      break;
+    case "light":
+      logoDarkSrc.origMedia = logoDarkSrc.media;
+      logoDarkSrc.media = "none";
+      break;
+    default:
+      if (logoDarkSrc.origMedia) {
         logoDarkSrc.media = logoDarkSrc.origMedia;
       }
       break;

locales/en.yml

@@ -1,2 +1,2 @@
 en:
-  toggle_button_title: Toggle color scheme
+  toggle_button_title: Toggle color palette

spec/system/color_scheme_toggle_spec.rb

@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+RSpec.describe "", system: true do
+  fab!(:topic) { Fabricate(:post).topic }
+  fab!(:user)
+  fab!(:post) { Fabricate(:post, topic:, raw: <<~POST * 20) }
+    Very lengthy post with lots of height for testing logo change when scrolling
+
+    Here's another paragraph to make the post take very large vertical space\n
+  POST
+
+  fab!(:dark_mode_image) { Fabricate(:image_upload, color: "white", width: 400, height: 120) }
+  fab!(:light_mode_image) { Fabricate(:image_upload, color: "black", width: 400, height: 120) }
+
+  fab!(:small_dark_mode_image) { Fabricate(:image_upload, color: "white", width: 120, height: 120) }
+  fab!(:small_light_mode_image) do
+    Fabricate(:image_upload, color: "black", width: 120, height: 120)
+  end
+
+  let!(:theme_component) { upload_theme_component }
+
+  let(:topic_page) { PageObjects::Pages::Topic.new }
+
+  before do
+    SiteSetting.logo = light_mode_image
+    SiteSetting.logo_small = small_light_mode_image
+    SiteSetting.logo_dark = dark_mode_image
+    SiteSetting.logo_small_dark = small_dark_mode_image
+    sign_in(user)
+  end
+
+  it "applies the correct `media` attribute on the source element when the logo is minimized upon scrolling" do
+    topic_page.visit_topic(topic)
+
+    dark_logo_source =
+      find(
+        ".title picture source[media=\"(prefers-color-scheme: dark)\"][srcset*=\"#{dark_mode_image.url}\"]",
+        visible: false,
+      )
+    expect(dark_logo_source).to be_present
+
+    find(".color-scheme-toggler").click
+
+    dark_logo_source =
+      find(
+        ".title picture source[media=\"all\"][srcset*=\"#{dark_mode_image.url}\"]",
+        visible: false,
+      )
+    expect(dark_logo_source).to be_present
+
+    page.scroll_to(find(".topic-footer-main-buttons .create"))
+
+    dark_logo_source =
+      find(
+        ".title picture source[media=\"all\"][srcset*=\"#{small_dark_mode_image.url}\"]",
+        visible: false,
+      )
+    expect(dark_logo_source).to be_present
+  end
+end