Immediate mode Node editors

This note simply gathers some info and thoughts on building Node Editor, especially in an
immediate mode setting.

Q: How does imgui render rounded rects?
Check imgui AddRectFilled
Imgui drawing api is closer to nanoVG
 - Path is kept
 - Contents are modified based on path
 

RESOURCES
==========================
Node editor code examples:

https://github.com/CedricGuillemet/Imogen
This is quite full fledged editor, supports things like deletion, copy and undo.
Interestingly, the undo redo is done with lambdas.
However it does seem a bit complex.


https://github.com/Nelarius/imnodes 
Decent rendering. Does not support copying. Does not support zooming
Can select multiple nodes
Q: How they perform panning? 

https://github.com/rokups/ImNodes
Eh, no building script... Would need a working imgui app.
Example seems to have std::vector of connections, so already bad.
Codewise I like the idea of
if( createNewConnection( node_idx, prop_idx, mouse_pos ) { create_link() } // Or maybe not. Seems like some thin retained state would be better
This one is similar to mine in a sense that it has a bit of state

Imguis:
https://github.com/rxi/microui\
+ dear imgui  / nuklear obviously

Blog posts:
http://carlivan.com/engine-tools/visual-scripting/
http://carlivan.com/engine-tools/blueprints/
http://sol.gfxile.net/imgui/index.html