  Screencasts, where computer screen is broadcast to a large audience on the
web, are becoming popular as an online educational tool. Among various types of
screencast content, popular are the contents that involve text editing,
including computer programming. There are emerging platforms that support such
text-based screencasts by recording every character insertion/deletion from the
creator and reconstructing its playback on the viewer's screen. However, these
platforms lack rich support for creating and editing the screencast itself,
mainly due to the difficulty of manipulating recorded text changes; the changes
are tightly coupled in sequence, thus modifying arbitrary part of the sequence
is not trivial. We present a non-linear editing tool for text-based
screencasts. With the proposed selective history rewrite process, our editor
allows users to substitute an arbitrary part of a text-based screencast while
preserving overall consistency of the rest of the text-based screencast.
