I created a split-screen Markdown editor for the iPad before iOS introduced Split View.

The app was released in July 2015 (a few weeks after Apple announced Split View for iPad). It didn’t sell well, and was discontinued in November 2016.

The app consists of three panes: a Web browser, a Markdown editor and a Markdown preview pane. We can swipe between the panes and can switch between split-screen and full-screen modes.


The browser had a unified search/address bar, tabs and custom context menus.

Tabs out of view are offloaded to disk when under memory pressure. To maintain tab history of offloaded tabs, Bisect maintains a back-forward navigation list separate from WKWebView’s internal list.

Markdown editor

The editor provides accurate Markdown syntax highlighting by using a Markdown parser run to generate the highlighting ranges. The same run of the Markdown parser generates the Markdown preview.

While editing, the keyboard accessory view features context-specific Markdown actions. Some of the things that can be accomplished using these context-specific actions are:

  • Open a URL in the browser pane
  • Fill a link’s URL from the browser pane
  • Fill in link references using references defined in the document
  • Increase or decrease the heading level

Markdown preview

To generate a fast preview as the user edits the text, Bisect diffs the current HTML output with the previous HTML and applies the diff onto the WKWebView using JavaScript. To make the diffing fast, Bisect creates a DOM-like tree of the output HTML when parsing the Markdown text.

App website:
App preview video: