X11workbench
X11 developer's 'workbench' and lightweight toolkit API
...The primary goal of the workbench is to provide an editor on X11 platforms that integrates development, provides rapid development 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