> The structure and function of your UI is naturally expressed in the code of the functions that draw it, instead of in ephemeral and opaque object trees that o

> The structure and function of your UI is naturally expressed in the code of the functions that draw it, instead of in ephemeral and opaque object trees that only exist in RAM after they're constructed at runtime This is probably it (although perhaps it is not quite the best explanation, but the example in the article helps to explain it); there are many possible implementations of an idea such as this. However, depending on the program and on other stuff, it is not always best for all kind of programs and all kind of UI. (In some cases, a kind of hybrid might do.) And, as they say about the example, there are things to criticize about it. Still, it can show an example of its use, even though it is a simple example. I had made my own variant of IMGUI. It uses a "win_form" block, which can be nested and which supports "break", and various other commands inside of the win_form block such as "win_command", "win_numeric", "win_boolean", etc; these commands do not have to be directly but can also be inside of a "if", "for", "switch", etc. These are implemented by C99 macros. The amount of state is small, not more than twenty bytes per active form (regardless of the number of widgets), and it is stored in the stack (but there is no need to explicitly add commands to declare or allocate this state; the "win_form" macro does this automatically). The git repository https://github.com/zzo38/superzz0 https://github.com/zzo38/superzz0 is for a program that contains this UI implementation. The file called "common.h" contains the macros and function declarations, and "window.c" contains the implementation. You can see many uses of it in "edit.c" (search for "win_form" to find many of the uses). As they say in the article, immediate mode does not necessarily mean that the library doesn't retain data (mine retains a single pointer, which is used to restore state when leaving a nested win_form block), that it needs a GPU to render, etc.