Add context menu item for toggle comments (#472)

* Add context menu item for toggle comments

* Remove redundant code

* Rename variable to make clearer

* Update label

src/Services/CommentToggler.vala

@@ -64,6 +64,15 @@ public class Scratch.CommentToggler {
         return CommentType.NONE;
     }
 
+    public static bool language_has_comments (Gtk.SourceLanguage? lang) {
+        if (lang == null) {
+            return false;
+        }
+
+        var type = get_comment_tags_for_lang (lang, CommentType.LINE, null, null);
+        return type != CommentType.NONE;
+    }
+
     // Returns whether or not all lines within a region are already commented.
     // This is to detect whether to toggle comments on or off. If all lines are commented, then we want to remove
     // those comments. If only some are commented, then the user likely selected a chunk of code that already contained

src/Widgets/SourceView.vala

@@ -329,8 +329,19 @@ namespace Scratch.Widgets {
             var sort_item = new Gtk.MenuItem.with_label (_("Sort Selected Lines"));
             sort_item.sensitive = get_selected_line_count () > 1;
             sort_item.activate.connect (sort_selected_lines);
-
             menu.add (sort_item);
+
+            if (buffer is Gtk.SourceBuffer) {
+                var can_comment = CommentToggler.language_has_comments ((buffer as Gtk.SourceBuffer).get_language ());
+                var comment_item = new Gtk.MenuItem.with_label (_("Toggle Comment"));
+                comment_item.sensitive = get_selected_line_count () > 0 && can_comment;
+                comment_item.activate.connect (() => {
+                    CommentToggler.toggle_comment (buffer as Gtk.SourceBuffer);
+                });
+
+                menu.add (comment_item);
+            }
+
             menu.show_all ();
         }