Do not use columns for long articles

If long articles use columns, it forces the user to scroll up and down
repeatedly.

This was originally introduced in a7f2490 but
later reverted for reasons unknown in 42e0ed4.

Let’s re-add the condition and also centre the body for nicer experience.

NEWS.md

@@ -3,6 +3,7 @@
 ### New features
 - Thumbnails can be disabled ([#897](https://github.com/SSilence/selfoss/pull/897))
 - Reddit spout replaced fragile imgur heuristics with previews provided by the JSON API ([#1033](https://github.com/SSilence/selfoss/pull/1033))
+- Long articles will no longer be arranged into columns, allowing for smoother reading experience ([#1081](https://github.com/SSilence/selfoss/pull/1081))
 
 ### Bug fixes
 - Reddit spout allows wider range of URLs, including absolute URLs and searches ([#1033](https://github.com/SSilence/selfoss/pull/1033))

public/css/style.css

@@ -550,6 +550,7 @@ body * {
             -webkit-column-count: 1;
             column-count: 1;
             max-width: 750px;
+            margin: auto;
         }
 
         .entry-content pre, .entry-content table {

public/js/selfoss-events-entries.js

@@ -110,6 +110,11 @@ selfoss.events.entries = function() {
                 if ($('#config').data('scroll_to_article_header') == '1') {
                     parent.get(0).scrollIntoView();
                 }
+
+                // turn of column view if entry is too long
+                if (entryContent.height() > $(window).height()) {
+                    entryContent.addClass('entry-content-nocolumns');
+                }
             }
 
             // load images not on mobile devices