Hi, this is a full rewrite of my iOS diagram sketcher -- it took 4.5 years, 30 features, 400 commits and lots of prayer. It uses Objective-C, Core Animation, UIKit, the works.
The shape recognition is a custom C++ library I call Recog, based on naive Bayesian classifier on geometric statistics.
The automated layout engine is Graphviz, as is the native file format (wrapped in my open-source zip library zipzap).
The help videos are not embedded in code, but are stored in Amazon S3 fronted by CloudFront. That also fronts a small web service written in node.js + sqlite3 for indexing the videos.
