Hi, I am excited to be working with Neovim for the following 3 months as a GSoC student for the project mentioned in the title with @bfredl as my mentor. Here is a plan that we decided on for the same:

First Evaluation (Jun 11)

• Split the windows internally into separate grids. Neovim still manages window layout and all window commands (:wincmd ...).
• Add API for the external UI to get/set window grid sizes. This will allow windows with different font size, even if the overall layout remains fixed.
• Implementation of the client side of this API in the screen.lua module of the test suite, and preferably also in a GUI such as the python-gui.

Second Evaluation (Jul 09)

• Finalize the API described in the first step with documentation and examples.
  Design the API for embedders to take control of window commands, and start work on the implementation.
• Externalize cursorline highlighting (ideally, as first example of a general abstraction for highlighting overlays).
• Externalize relativenumber (optional).

Final Evaluation (Aug 06)

• Complete the implementation of an API that give embedders full control of window layout and interpreting window commands. The embedders can subscribe to and receive events for individual windows.
• Complete the working prototype of this API in a GUI.

Any suggestions, improvements and/or comments are welcome and encouraged. Let's have a great summer of code!