`ui.label("static string")` is a very common use case,
and currently egui clones the string in these cases.
This PR introduces a new type:
``` rust
pub enum Estring {
Static(&'static str),
Owned(Arc<str>),
}
```
which is used everywhere text is needed, with
`impl Into<Estring>` in the API for e.g. `ui.label`.
This reduces the number of copies drastically and speeds up
the benchmark demo_with_tessellate__realistic by 17%.
This hurts the ergonomics of egui a bit, and this is a breaking change.
For instance, this used to work:
``` rust
fn my_label(ui: &mut egui::Ui, text: &str) {
ui.label(text);
}
```
This must now either be changed to
``` rust
fn my_label(ui: &mut egui::Ui, text: &str) {
ui.label(text.to_string());
}
```
(or the argument must be changed to either
`text: &'static str` or `text: String`)
b3e41e4e9c