* 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>
You can now set custom tags on the `UiStack`. This allows you to write
code that is situationally aware at runtime. For instance, you could
decide wether or not a label should truncate its text depending on what
part of your ui it is in, without having to pass that info down via the
callstack.
* Closes#4534
This PR:
- Introduces `Ui::stack()`, which returns the `UiStack` structure
providing information on the current `Ui` hierarchy.
- **BREAKING**: `Ui::new()` now takes a `UiStackInfo` argument, which is
used to populate some of this `Ui`'s `UiStack`'s fields.
- **BREAKING**: `Ui::child_ui()` and `Ui::child_ui_with_id_source()` now
take an `Option<UiStackInfo>` argument, which is used to populate some
of the children `Ui`'s `UiStack`'s fields.
- New `Area::kind()` builder function, to set the `UiStackKind` value of
the `Area`'s `Ui`.
- Adds a (minimalistic) demo to egui demo (in the "Misc Demos" window).
- Adds a more thorough `test_ui_stack` test/playground demo.
TODO:
- [x] benchmarks
- [x] add example to demo
Future work:
- Add `UiStackKind` and related support for more container (e.g.
`CollapsingHeader`, etc.)
- Add a tag/property system that would allow adding arbitrary data to a
stack node. This data could then be queried by nested `Ui`s. Probably
needed for #3284.
- Add support to track columnar layouts.
---------
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Tau Gärtli
Nicolas
rustbasic
Emil Ernerfeldt
Antoine Beyeler