plugin creation documentation

[ghost]

hello, you've got a very good editor, I'm starting to compare its speed of work with vim, but it still can't be compared to vim ...
What interests me is where you can find documentation on writing plugins, otherwise I can't figure it out. Now my goal is to write a plugin that adds a tab close button, but I looked at the core source, but I still couldn't find how to draw a knock and predict an event to it