* Part of https://github.com/emilk/egui/issues/5113
* Part of https://github.com/emilk/egui/issues/3524
## What
This deprecates `eframe::App::update` and replaces it with two new
functions:
```rs
pub trait App {
/// Called just before `ui`, and in the future this will
/// also be called for background apps when needed.
fn logic(&mut self, ctx: &egui::Context, frame: &mut Frame) { }
/// Show your user interface to the user.
fn ui(&mut self, ui: &mut egui::Ui, frame: &mut Frame);
…
}
```
Similarly, `Context::run` is deprecated in favor of `Context::run_ui`.
`Plugin`s are now handed a `Ui` instead of just a `Context` in
`on_begin/end_frame`.
## TODO
…either in this PR or a later one
* [x] Deprecate `App::update`
* [x] Deprecate `Context::run`
* [x] Change plugins to get a `Ui`
* [x] Update kittest
* [x] Change viewports to get UI:s (`show_viewport_immediate` etc)
- https://github.com/emilk/egui/pull/7779
## Later PRs
* [ ] Deprecate `Panel::show`
* [ ] Deprecate `CentralPanel::show`
* [ ] Deprecate `CentralPanel` ?
The closure passed to `eframe::run_native` now returns a `Result`,
allowing you to return an error during app creation, which will be
returned to the caller of `run_native`.
This means you need to wrap your `Box::new(MyApp::new(…))` in an
`Ok(…)`.
* Closes https://github.com/emilk/egui/issues/4474
