We recently started to use Dear ImGUI in our custom game engine. Before we used Unity which has its own immediate mode gui solution. And I have hard time to switch. I don't know if I don't understand how Dear ImGui work yet in comparison to Unity's one but it feels so limited.

So main difference is that Unity is multipass (it calls your gui drawing code multiple times per frame) and because of it it supports horizontal layout, vertical layout, custom layout modifiers, styles and it is easy to use

in Dear ImGUI I am struggling to write stuff like:

layout 3 controls horizontally, allocate fixed size for first and last one and use all left space for middle one

or

layout next N controls vertically of unknown height and use this background color for them, then layout another set of controls and use different background style for them

I am not the person who was actively working on integration it into our engine, so maybe it's the problem of not having documentation on our wrapper...or me not understanding very basics of it