X11workbench
X11 developer's 'workbench' and lightweight toolkit API
... tools (like 'wizards' and safe X11 debugging), and allows you to move the cursor past the end of a line without creating 'end of line' whitespace or 'bouncing' the cursor horizontally while scrolling vertically.
Source snapshots and archive tarballs are kept on SourceForge with repository at:
http://github.com/bombasticbob/X11workbenchProject/
Documentation is here:
http://bombasticbob.github.io/X11workbench/
'splash' video
http://bombasticbob.github.io/X11workbench.startup.mp4