Awesome

Cacao

Pure Swift Cross-platform UIKit (Cocoa Touch) implementation (Supports Linux)

Dependencies

OS X

brew install cairo sdl2 lcms2

Ubuntu

sudo apt-get install libcairo-dev libsdl2-dev liblcms2-dev

Screenshots

Run PaintCode StyleKits in Linux

Hardware-accelered UIView animations

Layout views according to a UIViewContentMode

Create applications that run in the native Window Manager