Feature: Adds a button to print a topic

app/assets/javascripts/discourse/models/topic.js.es6

@@ -134,6 +134,10 @@ const Topic = RestModel.extend({
     return this.get('url') + (user ? '?u=' + user.get('username_lower') : '');
   }.property('url'),
 
+  printUrl: function(){
+    return this.get('url') + '/print';
+  }.property('url'),
+
   url: function() {
     let slug = this.get('slug') || '';
     if (slug.trim().length === 0) {

app/assets/javascripts/discourse/views/print-button.js.es6

@@ -0,0 +1,16 @@
+import ButtonView from 'discourse/views/button';
+import { iconHTML } from 'discourse/helpers/fa-icon';
+
+export default ButtonView.extend({
+  classNames: ['print'],
+  textKey: 'topic.print.title',
+  helpKey: 'topic.print.help',
+
+  renderIcon(buffer) {
+    buffer.push(iconHTML("print"));
+  },
+
+  click() {
+    window.open(this.get('controller.model.printUrl'), '', 'menubar=no,toolbar=no,resizable=yes,scrollbars=yes,width=600,height=315');
+  }
+});

app/assets/javascripts/discourse/views/topic-footer-main-buttons.js.es6

@@ -32,6 +32,8 @@ export default ContainerView.extend({
       this.attachViewClass('invite-reply-button');
     }
 
+    this.attachViewClass('print-button');
+
     if (topic.get('isPrivateMessage')) {
       this.attachViewClass('archive-button');
     }

app/controllers/application_controller.rb

@@ -53,7 +53,7 @@ class ApplicationController < ActionController::Base
   end
 
   def use_crawler_layout?
-    @use_crawler_layout ||= (has_escaped_fragment? || CrawlerDetection.crawler?(request.user_agent))
+    @use_crawler_layout ||= (has_escaped_fragment? || CrawlerDetection.crawler?(request.user_agent) || params.key?("print"))
   end
 
   def add_readonly_header

app/controllers/topics_controller.rb

@@ -58,6 +58,7 @@ class TopicsController < ApplicationController
     username_filters = opts[:username_filters]
 
     opts[:slow_platform] = true if slow_platform?
+    opts[:print] = true if params[:print].present?
     opts[:username_filters] = username_filters.split(',') if username_filters.is_a?(String)
 
     # Special case: a slug with a number in front should look by slug first before looking

config/locales/client.en.yml

@@ -1459,6 +1459,10 @@ en:
         title: 'Share'
         help: 'share a link to this topic'
 
+      print:
+        title: 'Print'
+        help: 'Open a printer friendly version of this topic'
+
       flag_topic:
         title: 'Flag'
         help: 'privately flag this topic for attention or send a private notification about it'

config/routes.rb

@@ -554,6 +554,7 @@ Discourse::Application.routes.draw do
 
   # Topic routes
   get "t/id_for/:slug" => "topics#id_for_slug"
+  get "t/:slug/:topic_id/print" => "topics#show", format: :html, print: true, constraints: {topic_id: /\d+/}
   get "t/:slug/:topic_id/wordpress" => "topics#wordpress", constraints: {topic_id: /\d+/}
   get "t/:topic_id/wordpress" => "topics#wordpress", constraints: {topic_id: /\d+/}
   get "t/:slug/:topic_id/moderator-liked" => "topics#moderator_liked", constraints: {topic_id: /\d+/}

lib/topic_view.rb

@@ -12,6 +12,10 @@ class TopicView
     10
   end
 
+  def self.print_chunk_size
+    1000
+  end
+
   def self.chunk_size
     20
   end
@@ -44,7 +48,11 @@ class TopicView
     end
 
     @page = 1 if (!@page || @page.zero?)
-    @chunk_size = options[:slow_platform] ? TopicView.slow_chunk_size : TopicView.chunk_size
+    @chunk_size = case
+                    when options[:slow_platform] then TopicView.slow_chunk_size
+                    when options[:print] then 1000
+                    else TopicView.chunk_size
+                  end
     @limit ||= @chunk_size
 
     setup_filtered_posts