Link masthead title and subtitle to app or exhibit home

app/assets/stylesheets/modules/layout.scss

@@ -47,6 +47,10 @@
 }
 
 .masthead {
+  .masthead-title a {
+    --bs-link-hover-decoration: none;
+  }
+
   .masthead-navigation {
     li {
       --sul-link-font-weight: 700;

app/components/masthead_title_component.html.erb

@@ -0,0 +1,4 @@
+<div class="masthead-title">
+  <%= title %>
+  <%= subtitle %>
+</div>

app/components/masthead_title_component.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+# Draws the title in the masthead
+class MastheadTitleComponent < ViewComponent::Base
+  def initialize(title:, subtitle:)
+    @title = title
+    @subtitle = subtitle
+    super
+  end
+
+  def title
+    tag.h1 link(@title), class: 'site-title h2'
+  end
+
+  def subtitle
+    return unless @subtitle
+
+    tag.small link(@subtitle), class: 'py-2 fs-4'
+  end
+
+  private
+
+  def link(link_text)
+    return link_to link_text, helpers.spotlight.exhibit_path(helpers.current_exhibit) if helpers.current_exhibit
+
+    link_to link_text, helpers.spotlight.exhibits_path
+  end
+end

app/views/shared/_masthead.html.erb

@@ -6,20 +6,8 @@
 
 <div class="masthead bg-light fog-light mb-0 pb-2">
   <div class="container d-flex flex-wrap flex-md-row flex-column justify-content-between align-items-md-center align-items-start">
-    <div class="">
-      <h1 class="site-title h2">
-        <% if content_for? :masthead %>
-            <%= content_for :masthead %>
-        <% else %>
-            <%= masthead_heading_content %>
-        <% end %>
-      </h1>
-
-      <% if masthead_subheading_content %>
-        <small class="py-2 fs-4"><%= masthead_subheading_content %></small>
-      <% end %>
-    </div>
-
+    <%= render MastheadTitleComponent.new(title: content_for(:masthead) || masthead_heading_content, subtitle: masthead_subheading_content) %>
+
     <div class="align-self-md-end align-self-start">
       <div class="collapse d-md-flex me-md-2"
         aria-label="browse" id="user-util-collapse">

spec/components/masthead_title_component_spec.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe MastheadTitleComponent, type: :component do
+  subject(:rendered) do
+    Capybara::Node::Simple.new(render_inline(described_class.new(title: 'Exhibit Title',
+                                                                 subtitle: 'Exhibit Subtitle')).to_s)
+  end
+
+  context 'when there is no current exhibit' do
+    it { expect(rendered).to have_link('Exhibit Title', href: '/') }
+    it { expect(rendered).to have_link('Exhibit Subtitle', href: '/') }
+  end
+
+  context 'when there is a current exhibit' do
+    before do
+      allow(vc_test_controller).to receive(:current_exhibit)
+        .and_return(create(:exhibit, slug: 'exhibit-slug'))
+    end
+
+    it { expect(rendered).to have_link('Exhibit Title', href: '/exhibit-slug') }
+    it { expect(rendered).to have_link('Exhibit Subtitle', href: '/exhibit-slug') }
+  end
+end