Yeah, that's peanuts to be honest.

We wrote a layout manager and it's under 400 lines with very liberal vertical spacing. There's really not much to it - just hook the container window and reshuffle the contents in response to WM_SIZING, WM_SIZE. Handle WM_GETMINMAXINFO too if needed.

Custom controls aren't that much harder, but they do require some work indeed. TreeView and ListView are _really_ well designed in terms of customization support. The documentation is a bit heavy, granted, but once you get a gist of NMCUSTOMDRAW phases it's all pretty trivial from there.