I agree that this is not a necessary downside to immediate mode GUIs, but we're talking about egui specifically here. AFAIK, egui always redraws at some relatively high rate even when nothing is happening. (I'm having trouble finding documentation about what that rate is though.)
replyThat's not true, it only re-renders if there's an input event or an animation running. This is very easy to see if you just put a `println!` in your UI logic.
replyThis is also mentioned in the gui docs here https://github.com/emilk/egui#why-immediate-mode:
> egui only repaints when there is interaction (e.g. mouse movement) or an animation, so if your app is idle, no CPU is wasted.
Iiuc, a tiny clock in the top right corner of the screen will trigger O(n) work where n is the number of elements on the entire screen. On every change of the clock, e.g. every second. This may be more if there are smooth animations, e.g. 25 times per second if that is the animation frame rate.
replyThere are two modes, reactive and continuous. You can switch between them here in the backend tab:
replyReactive mode is the one you are looking for.
I really wish this were built into imgui as a first-class use case instead of requiring a hodgepodge mix of unofficial hacks.
replyI recall the author posting an imgui update saying this will be an officially supported mode, but AFAIK it's still not the case. Otherwise I would be building all my applications with imgui going forward.
Re-rendering the screen, even if it's fast, incurs a lot of memory bandwidth to draw everything and swap framebuffers etc. Not something you'd like to happen on mobile, in particular. Just because the waste is "small", doesn't mean it's acceptable.
Does ImGui work on mobile? I’ve seen it run in web assembly on mobile but typically none of the keyboard inputs work (the mobile keyboard doesn’t pop up, so effectively it’s not usable, at least in that approach).
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