Dear ImGui users: I've finally reworked BeginChild() api to switch that annoying 'bool border = false' param to becomes flags (miraculously not API breaking!), and added various new features to child windows in the process, including manual resize, auto-resize etc. BeginChild("name", .., ImGuiChildFlags_ResizeX);

Double-click to auto-fit on single axis (also works on regular windows). Saved in settings.

Also see: using auto-resize on Y axis + a constraint so it grows up to a maximum number of lines, convenient idiom.

There are various ways to achieve similar things but this one is quite accessible now.

It wasn't lots of code, but it is difficult to state how many iterations and subtle yak-shaving I had to go through to get this right, without badly breaking api, without being misleading (hopefully), etc as everything tends to have an effect on many other things.
@ocornut Just as I thought I needed that, awesome :)