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Make Light & Dark Visuals Customizable When Following The System Theme (#4744)

* Closes <https://github.com/emilk/egui/issues/4490>
* [x] I have followed the instructions in the PR template

---

Unfortunately, this PR contains a bunch of breaking changes because
`Context` no longer has one style, but two. I could try to add some of
the methods back if that's desired.

The most subtle change is probably that `style_mut` mutates both the
dark and the light style (which from the usage in egui itself felt like
the right choice but might be surprising to users).

I decided to deviate a bit from the data structure suggested in the
linked issue.
Instead of this:
```rust
pub theme: Theme, // Dark or Light
pub follow_system_theme: bool, // Change [`Self::theme`] based on `RawInput::system_theme`?
```

I decided to add a `ThemePreference` enum and track the current system
theme separately.
This has a couple of benefits:
* The user's theme choice is not magically overwritten on the next
frame.
* A widget for changing the theme preference only needs to know the
`ThemePreference` and not two values.
* Persisting the `theme_preference` is fine (as opposed to persisting
the `theme` field which may actually be the system theme).

The `small_toggle_button` currently only toggles between dark and light
(so you can never get back to following the system). I think it's easy
to improve on this in a follow-up PR :)
I made the function `pub(crate)` for now because it should eventually be
a method on `ThemePreference`, not `Theme`.

To showcase the new capabilities I added a new example that uses
different "accent" colors in dark and light mode:

<img
src="https://github.com/user-attachments/assets/0bf728c6-2720-47b0-a908-18bd250d15a6"
width="250" alt="A screenshot of egui's widget gallery demo in dark mode
using a purple accent color instead of the default blue accent">

<img
src="https://github.com/user-attachments/assets/e816b380-3e59-4f11-b841-8c20285988d6"
width="250" alt="A screenshot of egui's widget gallery demo in light
mode using a green accent color instead of the default blue accent">

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
This commit is contained in:
Tau Gärtli
2024-09-11 17:52:53 +02:00
committed by GitHub
parent f4697bc007
commit b5627c7d40
22 changed files with 382 additions and 123 deletions

View File

@@ -3,6 +3,7 @@
use eframe::egui;
use egui::{FontFamily, FontId, RichText, TextStyle};
use std::collections::BTreeMap;
fn main() -> eframe::Result {
env_logger::init(); // Log to stderr (if you run with `RUST_LOG=debug`).
@@ -28,8 +29,7 @@ fn heading3() -> TextStyle {
fn configure_text_styles(ctx: &egui::Context) {
use FontFamily::{Monospace, Proportional};
let mut style = (*ctx.style()).clone();
style.text_styles = [
let text_styles: BTreeMap<TextStyle, FontId> = [
(TextStyle::Heading, FontId::new(25.0, Proportional)),
(heading2(), FontId::new(22.0, Proportional)),
(heading3(), FontId::new(19.0, Proportional)),
@@ -39,7 +39,7 @@ fn configure_text_styles(ctx: &egui::Context) {
(TextStyle::Small, FontId::new(8.0, Proportional)),
]
.into();
ctx.set_style(style);
ctx.all_styles_mut(move |style| style.text_styles = text_styles.clone());
}
fn content(ui: &mut egui::Ui) {