FEATURE: prefill topic title, body and category via URL

app/assets/javascripts/discourse/controllers/composer.js.es6

@@ -435,6 +435,21 @@ export default DiscourseController.extend({
     composerModel.set('composeState', Discourse.Composer.OPEN);
     composerModel.set('isWarning', false);
 
+    if (opts.topicTitle && opts.topicTitle.length <= this.get('maxTitleLength')) {
+      this.set('model.title', opts.topicTitle);
+    }
+
+    if (opts.topicCategory) {
+      var category = Discourse.Category.list().findProperty('name', opts.topicCategory);
+      if (category && category.id) {
+        this.set('model.categoryId', category.id);
+      }
+    }
+
+    if (opts.topicBody) {
+      this.set('model.reply', opts.topicBody);
+    }
+
     this.get('controllers.composer-messages').queryFor(composerModel);
   },
 

app/assets/javascripts/discourse/mixins/open_composer.js

@@ -15,7 +15,17 @@ Discourse.OpenComposer = Em.Mixin.create({
       draftKey: controller.get('draft_key'),
       draftSequence: controller.get('draft_sequence')
     });
+  },
+
+  openComposerWithParams: function(controller, title, body, category) {
+    this.controllerFor('composer').open({
+      action: Discourse.Composer.CREATE_TOPIC,
+      topicTitle: title,
+      topicBody: body,
+      topicCategory: category,
+      draftKey: controller.get('draft_key'),
+      draftSequence: controller.get('draft_sequence')
+    });
   }
 
 });
-

app/assets/javascripts/discourse/routes/app-route-map.js.es6

@@ -90,6 +90,8 @@ export default function() {
   this.route('privacy', {path: '/privacy'});
   this.route('guidelines', {path: '/guidelines'});
 
+  this.route('new-topic', {path: '/new-topic'});
+
   this.resource('badges', function() {
     this.route('show', {path: '/:id/:slug'});
   });

app/assets/javascripts/discourse/routes/application.js.es6

@@ -10,7 +10,7 @@ function unlessReadOnly(method) {
   };
 }
 
-const ApplicationRoute = Discourse.Route.extend({
+const ApplicationRoute = Discourse.Route.extend(Discourse.OpenComposer, {
 
   siteTitle: Discourse.computed.setting('title'),
 
@@ -145,6 +145,10 @@ const ApplicationRoute = Discourse.Route.extend({
             factory = this.container.lookupFactory('controller:' + controllerName);
 
       this.render(w, {into: 'modal/topic-bulk-actions', outlet: 'bulkOutlet', controller: factory ? controllerName : 'topic-bulk-actions'});
+    },
+
+    createNewTopicViaParams: function(title, body, category) {
+      this.openComposerWithParams(this.controllerFor('discovery/topics'), title, body, category);
     }
   },
 

app/assets/javascripts/discourse/routes/new-topic.js.es6

@@ -0,0 +1,19 @@
+export default Discourse.Route.extend({
+  beforeModel: function(transition) {
+    const self = this;
+    if (Discourse.User.current()) {
+      // User is logged in
+      self.replaceWith('discovery.latest').then(function(e) {
+        if (self.controllerFor('navigation/default').get('canCreateTopic')) {
+          // User can create topic
+          Ember.run.next(function() {
+            e.send('createNewTopicViaParams', transition.queryParams.title, transition.queryParams.body, transition.queryParams.category);
+          });
+        }
+      });
+    } else {
+      // User is not logged in
+      self.replaceWith('login');
+    }
+  }
+});

config/routes.rb

@@ -411,6 +411,8 @@
   get 'embed/comments' => 'embed#comments'
   get 'embed/count' => 'embed#count'
 
+  get "new-topic" => "list#latest"
+
   # Topic routes
   get "t/id_for/:slug" => "topics#id_for_slug"
   get "t/:slug/:topic_id/wordpress" => "topics#wordpress", constraints: {topic_id: /\d+/}