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Add Classes to UiBuilder and some Widgets (#7843)

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* Closes part of <https://github.com/emilk/egui/issues/3284>

Add a class system toward a CSS-like styling. 

Widget and Ui can implement the trait `HasClasses` which can be used
later by theme engines to compute a style based on the set of classes
the component has.

---------

Co-authored-by: adrien <221212@umons.ac.be>
Co-authored-by: Adrien Zianne <adrien@iq002.ipa.iqrypto.com>
Co-authored-by: lucasmerlin <hi@lucasmerlin.me>
This commit is contained in:
YouStones
2026-05-12 13:43:49 +02:00
committed by GitHub
parent e3d7a01a6a
commit 4a8618498e
7 changed files with 201 additions and 19 deletions
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8
crates/egui/src/ui.rs
View File

@@ -4,6 +4,7 @@
use std::{any::Any, hash::Hash, ops::Deref, sync::Arc};
use crate::containers::menu;
use crate::widget_style::{HasClasses as _, ROOT_CLASS};
use crate::{containers::*, ecolor::*, layout::*, placer::Placer, widgets::*, *};
use emath::GuiRounding as _;
// ----------------------------------------------------------------------------
@@ -117,6 +118,7 @@ impl Ui {
style,
sense,
accessibility_parent,
classes,
} = ui_builder;
let layer_id = layer_id.unwrap_or_else(LayerId::background);
@@ -132,6 +134,7 @@ impl Ui {
let disabled = disabled || invisible;
let style = style.unwrap_or_else(|| ctx.global_style());
let sense = sense.unwrap_or_else(Sense::hover);
let classes = classes.with_class(ROOT_CLASS);
let placer = Placer::new(max_rect, layout);
let ui_stack = UiStack {
@@ -141,7 +144,9 @@ impl Ui {
parent: None,
min_rect: placer.min_rect(),
max_rect: placer.max_rect(),
classes,
};
let mut ui = Ui {
id,
unique_id: id,
@@ -214,6 +219,7 @@ impl Ui {
style,
sense,
accessibility_parent,
classes,
} = ui_builder;
let mut painter = self.painter.clone();
@@ -262,7 +268,9 @@ impl Ui {
parent: Some(Arc::clone(&self.stack)),
min_rect: placer.min_rect(),
max_rect: placer.max_rect(),
classes,
};
let mut child_ui = Ui {
id: stable_id,
unique_id,

14
crates/egui/src/ui_builder.rs
View File

@@ -1,8 +1,9 @@
use std::{hash::Hash, sync::Arc};
use crate::ClosableTag;
#[expect(unused_imports)] // Used for doclinks
use crate::Ui;
use crate::widget_style::HasClasses;
use crate::{ClosableTag, widget_style::Classes};
use crate::{Id, LayerId, Layout, Rect, Sense, Style, UiStackInfo};
/// Build a [`Ui`] as the child of another [`Ui`].
@@ -25,6 +26,7 @@ pub struct UiBuilder {
pub style: Option<Arc<Style>>,
pub sense: Option<Sense>,
pub accessibility_parent: Option<Id>,
pub classes: Classes,
}
impl UiBuilder {
@@ -192,3 +194,13 @@ impl UiBuilder {
self
}
}
impl HasClasses for UiBuilder {
fn classes(&self) -> &Classes {
&self.classes
}
fn classes_mut(&mut self) -> &mut Classes {
&mut self.classes
}
}

2
crates/egui/src/ui_stack.rs
View File

@@ -1,6 +1,7 @@
use std::sync::Arc;
use std::{any::Any, iter::FusedIterator};
use crate::widget_style::Classes;
use epaint::Color32;
use crate::{Direction, Frame, Id, Rect};
@@ -212,6 +213,7 @@ pub struct UiStack {
pub min_rect: Rect,
pub max_rect: Rect,
pub parent: Option<Arc<Self>>,
pub classes: Classes,
}
// these methods act on this specific node

139
crates/egui/src/widget_style.rs
View File

@@ -1,8 +1,11 @@
use std::{borrow::Cow, fmt};
use emath::Vec2;
use epaint::{Color32, FontId, Shadow, Stroke, text::TextWrapMode};
use smallvec::SmallVec;
use crate::{
Frame, Response, Style, TextStyle,
Frame, Response, Style, TextBuffer as _, TextStyle,
style::{WidgetVisuals, Widgets},
};
@@ -28,11 +31,13 @@ pub struct WidgetStyle {
pub stroke: Stroke,
}
/// Dedicated button style
pub struct ButtonStyle {
pub frame: Frame,
pub text_style: TextVisuals,
}
/// Dedicated checkbox style
pub struct CheckboxStyle {
/// Frame around
pub frame: Frame,
@@ -53,6 +58,7 @@ pub struct CheckboxStyle {
pub check_stroke: Stroke,
}
/// Dedicated label style
pub struct LabelStyle {
/// Frame around
pub frame: Frame,
@@ -64,6 +70,7 @@ pub struct LabelStyle {
pub wrap_mode: TextWrapMode,
}
/// Dedicated separator style
pub struct SeparatorStyle {
/// How much space is allocated in the layout direction
pub spacing: f32,
@@ -72,6 +79,7 @@ pub struct SeparatorStyle {
pub stroke: Stroke,
}
/// The different state of a widget can be
#[derive(Default, Clone, Copy, Debug, PartialEq, Eq)]
pub enum WidgetState {
Noninteractive,
@@ -82,6 +90,7 @@ pub enum WidgetState {
}
impl Widgets {
/// The widget visuals according to the state
pub fn state(&self, state: WidgetState) -> &WidgetVisuals {
match state {
WidgetState::Noninteractive => &self.noninteractive,
@@ -107,7 +116,8 @@ impl Response {
}
impl Style {
pub fn widget_style(&self, state: WidgetState) -> WidgetStyle {
/// The general widget style. The style is computed according to the classes and state of the widget.
pub fn widget_style(&self, _classes: &Classes, state: WidgetState) -> WidgetStyle {
let visuals = self.visuals.widgets.state(state);
let font_id = self.override_font_id.clone();
WidgetStyle {
@@ -131,11 +141,13 @@ impl Style {
}
}
pub fn button_style(&self, state: WidgetState, selected: bool) -> ButtonStyle {
/// The dedicated button style. The style is computed according to the classes and state of the widget.
/// It depend on the general widget style.
pub fn button_style(&self, classes: &Classes, state: WidgetState) -> ButtonStyle {
let mut visuals = *self.visuals.widgets.state(state);
let mut ws = self.widget_style(state);
let mut ws = self.widget_style(classes, state);
if selected {
if classes.has(SELECTED_CLASS) {
visuals.weak_bg_fill = self.visuals.selection.bg_fill;
visuals.bg_fill = self.visuals.selection.bg_fill;
visuals.fg_stroke = self.visuals.selection.stroke;
@@ -157,9 +169,11 @@ impl Style {
}
}
pub fn checkbox_style(&self, state: WidgetState) -> CheckboxStyle {
/// The dedicated checkbox style. The style is computed according to the classes and state of the widget.
/// It depend on the general widget style.
pub fn checkbox_style(&self, classes: &Classes, state: WidgetState) -> CheckboxStyle {
let visuals = self.visuals.widgets.state(state);
let ws = self.widget_style(state);
let ws = self.widget_style(classes, state);
CheckboxStyle {
frame: Frame::new(),
checkbox_size: self.spacing.icon_width,
@@ -168,8 +182,6 @@ impl Style {
fill: visuals.bg_fill,
corner_radius: visuals.corner_radius,
stroke: visuals.bg_stroke,
// Use the inner_margin for the expansion
inner_margin: visuals.expansion.into(),
..Default::default()
},
text_style: ws.text,
@@ -177,8 +189,10 @@ impl Style {
}
}
pub fn label_style(&self, state: WidgetState) -> LabelStyle {
let ws = self.widget_style(state);
/// The dedicated label style. The style is computed according to the classes and state of the widget.
/// It depend on the general widget style.
pub fn label_style(&self, classes: &Classes, state: WidgetState) -> LabelStyle {
let ws = self.widget_style(classes, state);
LabelStyle {
frame: Frame {
fill: ws.frame.fill,
@@ -193,7 +207,9 @@ impl Style {
}
}
pub fn separator_style(&self, _state: WidgetState) -> SeparatorStyle {
/// The dedicated separator style. The style is computed according to the classes and state of the widget.
/// It depend on the general widget style.
pub fn separator_style(&self, _classes: &Classes, _state: WidgetState) -> SeparatorStyle {
let visuals = self.visuals.noninteractive();
SeparatorStyle {
spacing: 6.0,
@@ -201,3 +217,102 @@ impl Style {
}
}
}
/// The root class is a special class present on every top-level [`crate::Ui`].
pub const ROOT_CLASS: &str = "root";
/// The selected class is a special class present on selected [`crate::Button`].
pub const SELECTED_CLASS: &str = "selected";
/// A class is a static string identifier.
pub type ClassName = Cow<'static, str>;
/// Classes are string identifier that can be set on widget/Ui.
///
/// This can be used by styling engine to compute a different style
/// based on the set of classes present on the widget/Ui.
#[derive(Debug, Default, Clone)]
pub struct Classes {
classes: SmallVec<[ClassName; 5]>,
}
impl Classes {
/// Add a class to the list if the condition is true
#[inline]
fn add_if(&mut self, class: impl Into<ClassName>, condition: bool) {
if condition {
self.classes.push(class.into());
}
}
}
impl HasClasses for Classes {
fn classes(&self) -> &Classes {
self
}
fn classes_mut(&mut self) -> &mut Classes {
self
}
}
impl std::fmt::Display for Classes {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.classes.iter().for_each(|class| {
let _ = f.write_str(class.as_str());
});
f.write_str("")
}
}
/// Any widgets supporting [`Classes`] must implement this trait
pub trait HasClasses {
fn classes(&self) -> &Classes;
fn classes_mut(&mut self) -> &mut Classes;
/// Add the given class by consuming [`self`]
#[inline]
fn with_class(mut self, class: impl Into<ClassName>) -> Self
where
Self: Sized,
{
self.classes_mut().add_if(class.into(), true);
self
}
/// Add the given class by consuming [`self`] if the condition is true
#[inline]
fn with_class_if(mut self, class: impl Into<ClassName>, condition: bool) -> Self
where
Self: Sized,
{
self.classes_mut().add_if(class.into(), condition);
self
}
/// Add the given class in-place
#[inline]
fn add_class(&mut self, class: impl Into<ClassName>) -> &mut Self
where
Self: Sized,
{
self.classes_mut().add_if(class.into(), true);
self
}
/// Add the given class in-place if the condition is true
#[inline]
fn add_class_if(&mut self, class: impl Into<ClassName>, condition: bool) -> &mut Self
where
Self: Sized,
{
self.classes_mut().add_if(class.into(), condition);
self
}
/// True if the class is present
fn has(&self, class: impl Into<ClassName>) -> bool {
self.classes().classes.contains(&class.into())
}
}

19
crates/egui/src/widgets/button.rs
View File

@@ -4,7 +4,7 @@ use crate::{
Atom, AtomExt as _, AtomKind, AtomLayout, AtomLayoutResponse, Color32, CornerRadius, Frame,
Image, IntoAtoms, NumExt as _, Response, Sense, Stroke, TextStyle, TextWrapMode, Ui, Vec2,
Widget, WidgetInfo, WidgetText, WidgetType,
widget_style::{ButtonStyle, WidgetState},
widget_style::{ButtonStyle, Classes, HasClasses, SELECTED_CLASS, WidgetState},
};
/// Clickable button with text.
@@ -38,6 +38,7 @@ pub struct Button<'a> {
selected: bool,
image_tint_follows_text_color: bool,
limit_image_size: bool,
classes: Classes,
}
impl<'a> Button<'a> {
@@ -56,6 +57,7 @@ impl<'a> Button<'a> {
selected: false,
image_tint_follows_text_color: false,
limit_image_size: false,
classes: Classes::default(),
}
}
@@ -286,6 +288,7 @@ impl<'a> Button<'a> {
selected,
image_tint_follows_text_color,
limit_image_size,
mut classes,
} = self;
// Min size height always equal or greater than interact size if not small
@@ -311,7 +314,9 @@ impl<'a> Button<'a> {
let response: Option<Response> = ui.ctx().read_response(id);
let state = response.map(|r| r.widget_state()).unwrap_or_default();
let ButtonStyle { frame, text_style } = ui.style().button_style(state, selected);
classes.add_class_if(SELECTED_CLASS, selected);
let ButtonStyle { frame, text_style } = ui.style().button_style(&classes, state);
let mut button_padding = if has_frame_margin {
frame.inner_margin
@@ -388,3 +393,13 @@ impl Widget for Button<'_> {
self.atom_ui(ui).response
}
}
impl HasClasses for Button<'_> {
fn classes(&self) -> &Classes {
&self.classes
}
fn classes_mut(&mut self) -> &mut Classes {
&mut self.classes
}
}

18
crates/egui/src/widgets/checkbox.rs
View File

@@ -2,7 +2,8 @@ use emath::Rect;
use crate::{
Atom, AtomLayout, Atoms, Id, IntoAtoms, NumExt as _, Response, Sense, Shape, Ui, Vec2, Widget,
WidgetInfo, WidgetType, epaint, pos2, widget_style::CheckboxStyle,
WidgetInfo, WidgetType, epaint, pos2,
widget_style::{CheckboxStyle, Classes, HasClasses},
};
// TODO(emilk): allow checkbox without a text label
@@ -23,6 +24,7 @@ pub struct Checkbox<'a> {
checked: &'a mut bool,
atoms: Atoms<'a>,
indeterminate: bool,
classes: Classes,
}
impl<'a> Checkbox<'a> {
@@ -31,6 +33,7 @@ impl<'a> Checkbox<'a> {
checked,
atoms: atoms.into_atoms(),
indeterminate: false,
classes: Classes::default(),
}
}
@@ -55,6 +58,7 @@ impl Widget for Checkbox<'_> {
checked,
mut atoms,
indeterminate,
classes,
} = self;
// Get the widget style by reading the response from the previous pass
@@ -69,7 +73,7 @@ impl Widget for Checkbox<'_> {
frame,
check_stroke,
text_style,
} = ui.style().checkbox_style(state);
} = ui.style().checkbox_style(&classes, state);
let mut min_size = Vec2::splat(ui.spacing().interact_size.y);
min_size.y = min_size.y.at_least(checkbox_size);
@@ -153,3 +157,13 @@ impl Widget for Checkbox<'_> {
}
}
}
impl HasClasses for Checkbox<'_> {
fn classes(&self) -> &Classes {
&self.classes
}
fn classes_mut(&mut self) -> &mut Classes {
&mut self.classes
}
}

20
crates/egui/src/widgets/separator.rs
View File

@@ -1,4 +1,7 @@
use crate::{Response, Sense, Ui, Vec2, Widget, vec2, widget_style::SeparatorStyle};
use crate::{
Response, Sense, Ui, Vec2, Widget, vec2,
widget_style::{Classes, HasClasses, SeparatorStyle},
};
/// A visual separator. A horizontal or vertical line (depending on [`crate::Layout`]).
///
@@ -16,6 +19,7 @@ pub struct Separator {
spacing: Option<f32>,
grow: f32,
is_horizontal_line: Option<bool>,
classes: Classes,
}
impl Default for Separator {
@@ -24,6 +28,7 @@ impl Default for Separator {
spacing: None,
grow: 0.0,
is_horizontal_line: None,
classes: Classes::default(),
}
}
}
@@ -91,6 +96,7 @@ impl Widget for Separator {
spacing,
grow,
is_horizontal_line,
classes,
} = self;
// Get the widget style by reading the response from the previous pass
@@ -100,7 +106,7 @@ impl Widget for Separator {
let SeparatorStyle {
spacing: spacing_style,
stroke,
} = ui.style().separator_style(state);
} = ui.style().separator_style(&classes, state);
// override the spacing if not set
let spacing = spacing.unwrap_or(spacing_style);
@@ -142,3 +148,13 @@ impl Widget for Separator {
response
}
}
impl HasClasses for Separator {
fn classes(&self) -> &Classes {
&self.classes
}
fn classes_mut(&mut self) -> &mut Classes {
&mut self.classes
}
}