Show public scoreboard QR code for events

app/controllers/contests_controller.rb

@@ -192,6 +192,15 @@ class ContestsController < ApplicationController
         authorize @contest
         render :scoreboard_not_started and return
       end
+      host = Rails.application.config.action_controller.default_url_options[:host]
+      @qrcode = RQRCode::QRCode.new("https://#{host}/public/event/#{@event.friendly_id}?contest_id=#{@contest.id}").as_svg(
+        color: "000",
+        shape_rendering: "crispEdges",
+        module_size: 3,
+        standalone: true,
+        use_path: true,
+        viewbox: true
+      )
     else
       @contest = Contest.find_by(slug: params[:id])
       unless @contest && @contest.public

app/views/layouts/authenticated.html.slim

@@ -48,6 +48,9 @@ html
           - if active_page("/public") == "active" && @is_scoreboard
             - if active_page("/public/event/") == "active"
               = @contest.event.name
+              - if @qrcode
+                .float-end style="width: 80px; height: 80px;"
+                  = @qrcode.html_safe
               = render "event_nav"
             - else
               = @contest.name