Fixes #3052 - Ticket follow ups does not always provide "see more" link on new articles.

app/assets/javascripts/app/controllers/ticket_zoom.coffee

@@ -271,6 +271,7 @@ class App.TicketZoom extends App.Controller
     @delay(scrollToDelay, delay, 'scrollToPosition')
 
   pagePosition: (params = {}) =>
+    return if @el.is(':hidden')
 
     # remember for later
     return if params.type is 'init' && !@shown
@@ -288,6 +289,7 @@ class App.TicketZoom extends App.Controller
 
     # scroll to end if new article has been added
     else if !@last_ticket_article_ids || !_.isEqual(_.sortBy(@last_ticket_article_ids), _.sortBy(@ticket_article_ids))
+      App.Event.trigger('ui::ticket::shown', { ticket_id: @ticket_id })
       @scrollToPosition('bottom', 100, article_id)
 
     # trigger shown to article

spec/system/ticket/zoom_spec.rb

@@ -1337,6 +1337,25 @@ RSpec.describe 'Ticket zoom', type: :system do
         end
       end
     end
+
+    context 'when long articles are present' do
+      it 'will properly show the "See more" link if you switch between the ticket and the dashboard on new articles' do
+        ensure_websocket do
+          visit "ticket/zoom/#{ticket.id}"
+          await_empty_ajax_queue
+
+          visit 'dashboard'
+          expect(page).to have_css("a.js-dashboardMenuItem[data-key='Dashboard'].is-active", wait: 10)
+          article_id = create(:'ticket/article', ticket: ticket, body: "#{SecureRandom.uuid} #{"lorem ipsum\n" * 200}")
+          expect(page).to have_css('div.tasks a.is-modified', wait: 10)
+
+          visit "ticket/zoom/#{ticket.id}"
+          within :active_content do
+            expect(find("div#article-content-#{article_id.id}")).to have_text('See more')
+          end
+        end
+      end
+    end
   end
 
   describe 'Macros', authenticated_as: :authenticate do