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Add Scalar action kind for UI sliders

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Adds a fourth ActionKind, Scalar, carrying an f32 from a slider's
ValueChange<f32>. It is edge-triggered like Instant but value-carrying
like Axis, completing the edge/level split (Instant/Scalar vs Toggle/Axis).

- ActionValue::Scalar(f32) + as_scalar(); ActionState scalar()/set_scalar().
- active() is now kind-dispatched: edge kinds report "this frame", level
  kinds report current state.
- slider_to_action observer stores live value on every change but only
  triggers on is_final, so gated consumers run once per settled change.
- scalar_value(a) typed provider pipes a bare f32 into In<f32>.
- #[action_kind(scalar)] added to the derive macro.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
main
Elijah Voigt 6 days ago
parent d8e00525ec
commit 40b3f2adfc
2 changed files with 173 additions and 53 deletions
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7
engine/macros/src/lib.rs
Unescape Escape View File

@ -10,8 +10,8 @@ use syn::{spanned::Spanned, Data, DeriveInput, Fields, Ident};
/// Derives `engine::GameAction` for a fieldless enum.
///
/// Each variant must be annotated with `#[action_kind(instant)]`,
/// `#[action_kind(toggle)]`, or `#[action_kind(axis)]`:
/// Each variant must be annotated with `#[action_kind(...)]` — one of `instant`,
/// `toggle`, `axis`, or `scalar`:
///
/// ```ignore
/// #[derive(Copy, Clone, Eq, PartialEq, Hash, GameAction)]
@ -100,11 +100,12 @@ fn parse_kind(
"instant" => quote!(#engine::ActionKind::Instant),
"toggle" => quote!(#engine::ActionKind::Toggle),
"axis" => quote!(#engine::ActionKind::Axis),
"scalar" => quote!(#engine::ActionKind::Scalar),
other => {
return Err(syn::Error::new(
variant_name.span(),
format!(
"unknown action kind `{other}`, expected `instant`, `toggle`, or `axis`"
"unknown action kind `{other}`, expected `instant`, `toggle`, `axis`, or `scalar`"
),
))
}

215
engine/src/actions.rs
Unescape Escape View File

@ -17,6 +17,8 @@
//! Grid,
//! #[action_kind(axis)] // carries a Vec2
//! Move,
//! #[action_kind(scalar)] // carries an f32, from a slider
//! Volume,
//! }
//!
//! App::new()
@ -34,7 +36,10 @@
//! // `run_if(on_action(a))` gates a system; `action_value(a).pipe(sys)` feeds it.
//! .add_systems(Update, jump.run_if(on_action(Action::Jump)))
//! .add_systems(Update, draw_grid.run_if(on_action(Action::Grid)))
//! .add_systems(Update, action_value(Action::Move).pipe(move_player));
//! .add_systems(Update, action_value(Action::Move).pipe(move_player))
//! // Typed pipe: deliver the slider's f32, only on the frame it changes.
//! .add_systems(Update,
//! scalar_value(Action::Volume).pipe(set_volume).run_if(on_action(Action::Volume)));
//!
//! // Piped consumer: receives an `ActionValue` and never touches `ActionState`.
//! fn move_player(In(value): In<ActionValue>, mut q: Query<&mut Transform, With<Player>>) {
@ -44,18 +49,28 @@
//! }
//! }
//!
//! fn set_volume(In(v): In<f32>, mut audio: ResMut<AudioSettings>) { audio.volume = v; }
//!
//! // 2. UI feeds the same actions: tag a widget with the action it drives.
//! // commands.spawn((button(..), ActionSource(Action::Jump))); // Activate -> Instant
//! // commands.spawn((checkbox(..), ActionSource(Action::Grid))); // ValueChange -> Toggle
//! // commands.spawn((checkbox(..), ActionSource(Action::Grid))); // ValueChange<bool> -> Toggle
//! // commands.spawn((slider(..), ActionSource(Action::Volume))); // ValueChange<f32> -> Scalar
//! ```
//!
//! ## How it works
//!
//! All input sources fan in to a single [`ActionState<T>`] resource. Instant
//! actions live in a momentary set cleared every frame; toggles live in a
//! persistent set; axes hold a per-frame [`Vec2`]. [`ActionState::value`] reads
//! whichever bucket the action's kind selects and returns a unified
//! [`ActionValue`], so every downstream read is kind-agnostic.
//! persistent set; axes hold a per-frame [`Vec2`]; scalars (sliders) hold a
//! persistent [`f32`]. [`ActionState::value`] reads whichever bucket the action's
//! kind selects and returns a unified [`ActionValue`], so every downstream read is
//! kind-agnostic.
//!
//! Kinds split by *trigger style*: [`Instant`](ActionKind::Instant) and
//! [`Scalar`](ActionKind::Scalar) are **edge-triggered** (they fire on the frame
//! they happen — a press, a slider change), while [`Toggle`](ActionKind::Toggle)
//! and [`Axis`](ActionKind::Axis) are **level-triggered** (they report a state
//! that is currently true). [`on_action`] reflects that per kind.
//!
//! ## Two symmetrical entry points
//!
@ -63,16 +78,17 @@
//! differs only in *how the system gets involved*, not in which actions it accepts:
//!
//! * **`sys.run_if(on_action(a))`** — gate a system on the action. A run condition
//! can only return `bool`, so this reports [`ActionValue::is_active`]: `true` for
//! a fired instant, an on toggle, **or a deflected axis**. Reach for it when the
//! fact that the action is active is all the system needs — including "run every
//! frame the stick is being moved".
//! can only return `bool`, so this reports [`ActionState::active`]: an instant
//! fired / a slider changed **this frame** (edge), or a toggle is on / an axis is
//! deflected (level). Reach for it when the fact that the action is active is all
//! the system needs — "run while the stick is moved", "run when the slider moves".
//! * **`action_value(a).pipe(sys)`** — deliver the action's [`ActionValue`] into a
//! system that takes `In<ActionValue>`. Reach for it when the system needs the
//! **payload** (the axis [`Vec2`], or a toggle's bool to store). The consumer
//! pulls its type out with [`ActionValue::as_axis`] / [`ActionValue::as_bool`],
//! or use the typed [`axis_value`] / [`toggle_value`] helpers to pipe a bare
//! `Vec2` / `bool`.
//! **payload** (the axis [`Vec2`], the slider [`f32`], a toggle's bool). The
//! consumer pulls its type out with [`ActionValue::as_axis`] /
//! [`ActionValue::as_scalar`] / [`ActionValue::as_bool`], or use the typed
//! [`axis_value`] / [`scalar_value`] / [`toggle_value`] helpers to pipe a bare
//! `Vec2` / `f32` / `bool`.
//!
//! They compose — `action_value(a).pipe(sys).run_if(on_action(a))` delivers the
//! payload *and* skips the system when the action is inactive — and neither is
@ -88,17 +104,28 @@ use bevy::{
ui_widgets::{Activate, Checkbox, SetChecked, ValueChange},
};
/// How an action behaves: momentary, a persistent on/off toggle, or an analog
/// 2D axis (e.g. a gamepad stick).
/// How an action behaves.
///
/// The kinds split two ways by *trigger style*: [`Instant`](Self::Instant) and
/// [`Scalar`](Self::Scalar) are **edge-triggered** (they fire on the frame
/// something happens), while [`Toggle`](Self::Toggle) and [`Axis`](Self::Axis) are
/// **level-triggered** (they report a state that is currently true). This is what
/// [`on_action`] reflects per kind.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum ActionKind {
/// Fires for a single frame each time it is triggered (jump, shoot, confirm).
/// Edge-triggered.
Instant,
/// Holds an on/off state until toggled again (show grid, mute, pause).
/// Level-triggered.
Toggle,
/// Carries a [`Vec2`] direction + magnitude, refreshed every frame (movement,
/// aiming). Read the value with [`ActionState::axis`].
/// aiming). Level-triggered. Read the value with [`ActionState::axis`].
Axis,
/// Carries an `f32`, emitted when a slider changes. Edge-triggered like
/// [`Instant`](Self::Instant) but value-carrying like [`Axis`](Self::Axis).
/// Read the value with [`ActionState::scalar`].
Scalar,
}
/// The current value of an action, unified across kinds so one provider
@ -106,45 +133,62 @@ pub enum ActionKind {
///
/// Digital kinds ([`Instant`](ActionKind::Instant)/[`Toggle`](ActionKind::Toggle))
/// produce [`Bool`](Self::Bool); [`Axis`](ActionKind::Axis) produces
/// [`Axis`](Self::Axis). A consumer that knows the kind it wants pulls the payload
/// out with [`as_bool`](Self::as_bool) or [`as_axis`](Self::as_axis).
/// [`Axis`](Self::Axis); [`Scalar`](ActionKind::Scalar) produces
/// [`Scalar`](Self::Scalar). A consumer that knows the kind it wants pulls the
/// payload out with [`as_bool`](Self::as_bool), [`as_axis`](Self::as_axis), or
/// [`as_scalar`](Self::as_scalar).
#[derive(Copy, Clone, Debug, PartialEq)]
pub enum ActionValue {
/// A digital value: an instant action fired this frame, or a toggle is on.
Bool(bool),
/// An analog 2D value.
Axis(Vec2),
/// An analog 1D value (e.g. a slider position).
Scalar(f32),
}
impl ActionValue {
/// Whether the action is "active": a `true` bool, or a non-zero axis. This is
/// what [`on_action`] gates on, so a system can run "while the stick is moved"
/// exactly as it runs "while the toggle is on".
/// Whether the value is "non-zero": a `true` bool, a non-zero axis, or a
/// non-zero scalar. Note this is a property of the *value* — for the
/// edge-triggered kinds ([`Instant`](ActionKind::Instant)/[`Scalar`](ActionKind::Scalar)),
/// [`on_action`] instead reports "happened this frame" via
/// [`ActionState::active`].
pub fn is_active(self) -> bool {
match self {
ActionValue::Bool(b) => b,
ActionValue::Axis(v) => v != Vec2::ZERO,
ActionValue::Scalar(v) => v != 0.0,
}
}
/// The digital payload. An axis collapses to whether it is deflected, so a
/// bool consumer can read an axis action too.
/// The digital payload. Analog values collapse to whether they are non-zero,
/// so a bool consumer can read an axis or scalar action too.
pub fn as_bool(self) -> bool {
self.is_active()
}
/// The analog payload. A digital value maps to [`Vec2::ZERO`] when off; a
/// `true` bool has no direction and also yields [`Vec2::ZERO`].
/// The 2D analog payload. Non-axis values yield [`Vec2::ZERO`] (a `true` bool
/// or a scalar has no direction).
pub fn as_axis(self) -> Vec2 {
match self {
ActionValue::Axis(v) => v,
ActionValue::Bool(_) => Vec2::ZERO,
ActionValue::Bool(_) | ActionValue::Scalar(_) => Vec2::ZERO,
}
}
/// The 1D analog payload. A scalar yields its value; an axis yields its `x`;
/// a bool yields `0.0`.
pub fn as_scalar(self) -> f32 {
match self {
ActionValue::Scalar(v) => v,
ActionValue::Axis(v) => v.x,
ActionValue::Bool(_) => 0.0,
}
}
}
/// Derive macro for [`GameAction`]: annotate each variant with
/// `#[action_kind(instant)]` or `#[action_kind(toggle)]`.
/// `#[action_kind(...)]` — `instant`, `toggle`, `axis`, or `scalar`.
///
/// ```rust,ignore
/// #[derive(Copy, Clone, Eq, PartialEq, Hash, GameAction)]
@ -165,7 +209,8 @@ pub use engine_macros::GameAction;
/// identifiers. `kind` is the only thing the engine needs from the game.
pub trait GameAction: Copy + Eq + Hash + Send + Sync + 'static {
/// Returns whether this action is [`Instant`](ActionKind::Instant),
/// [`Toggle`](ActionKind::Toggle), or [`Axis`](ActionKind::Axis).
/// [`Toggle`](ActionKind::Toggle), [`Axis`](ActionKind::Axis), or
/// [`Scalar`](ActionKind::Scalar).
fn kind(self) -> ActionKind;
}
@ -248,16 +293,20 @@ impl<T: GameAction> InputMap<T> {
/// Populated by the engine each frame from the [`InputMap`] and UI widgets.
/// Read it kind-agnostically via [`value`](Self::value) (behind [`on_action`] and
/// [`action_value`]), or reach for a specific bucket with [`axis`](Self::axis) /
/// [`enabled`](Self::enabled). Games may also drive actions programmatically with
/// [`press`](Self::press), [`set`](Self::set), and [`toggle`](Self::toggle).
/// [`scalar`](Self::scalar) / [`enabled`](Self::enabled). Games may also drive
/// actions programmatically with [`press`](Self::press), [`set`](Self::set),
/// [`toggle`](Self::toggle), and [`set_scalar`](Self::set_scalar).
#[derive(Resource)]
pub struct ActionState<T> {
/// Instant actions active this frame; cleared at the start of every frame.
/// Instant/Scalar actions that fired or changed this frame; cleared every frame.
momentary: HashSet<T>,
/// Toggle actions currently switched on; persists across frames.
enabled: HashSet<T>,
/// Axis actions and their current value; refreshed every frame.
axes: HashMap<T, Vec2>,
/// Scalar (slider) actions and their latest value; persists across frames so
/// the current value is readable between changes.
scalars: HashMap<T, f32>,
}
impl<T> Default for ActionState<T> {
@ -266,6 +315,7 @@ impl<T> Default for ActionState<T> {
momentary: HashSet::default(),
enabled: HashSet::default(),
axes: HashMap::default(),
scalars: HashMap::default(),
}
}
}
@ -273,7 +323,8 @@ impl<T> Default for ActionState<T> {
impl<T: GameAction> ActionState<T> {
/// The current [`ActionValue`] of `action`, dispatched by its
/// [`ActionKind`]: [`Bool`](ActionValue::Bool) for instant/toggle,
/// [`Axis`](ActionValue::Axis) for axes.
/// [`Axis`](ActionValue::Axis) for axes, [`Scalar`](ActionValue::Scalar) for
/// scalars.
///
/// This is the single accessor every other read is built on, so one provider
/// ([`action_value`]) and one run condition ([`on_action`]) serve all kinds.
@ -282,16 +333,27 @@ impl<T: GameAction> ActionState<T> {
ActionKind::Instant => ActionValue::Bool(self.momentary.contains(&action)),
ActionKind::Toggle => ActionValue::Bool(self.enabled.contains(&action)),
ActionKind::Axis => ActionValue::Axis(self.axis(action)),
ActionKind::Scalar => ActionValue::Scalar(self.scalar(action)),
}
}
/// Whether `action` is currently active: an [`Instant`](ActionKind::Instant)
/// action fired this frame, a [`Toggle`](ActionKind::Toggle) that is on, or an
/// [`Axis`](ActionKind::Axis) that is deflected (non-zero).
/// Whether `action` is currently active — what [`on_action`] gates on.
///
/// Dispatched by trigger style (see [`ActionKind`]):
/// * **edge** — [`Instant`](ActionKind::Instant) fired / [`Scalar`](ActionKind::Scalar)
/// changed **this frame**;
/// * **level** — [`Toggle`](ActionKind::Toggle) is on / [`Axis`](ActionKind::Axis)
/// is deflected (non-zero).
///
/// Shorthand for `self.value(action).is_active()`; what [`on_action`] gates on.
/// For edge kinds this differs from [`value`](Self::value)`(a).is_active()`
/// (which is a value property): a slider resting at `3.0` is *active only on the
/// frame it moves*, not every frame its value is non-zero.
pub fn active(&self, action: T) -> bool {
self.value(action).is_active()
match action.kind() {
ActionKind::Instant | ActionKind::Scalar => self.momentary.contains(&action),
ActionKind::Toggle => self.enabled.contains(&action),
ActionKind::Axis => self.axis(action) != Vec2::ZERO,
}
}
/// Whether a toggle `action` is currently switched on.
@ -305,6 +367,13 @@ impl<T: GameAction> ActionState<T> {
self.axes.get(&action).copied().unwrap_or(Vec2::ZERO)
}
/// The latest value of a scalar (slider) `action`, or `0.0` if it has never
/// been set. Persists between changes, so it is readable on any frame — pair
/// with [`on_action`] to react only when it changes.
pub fn scalar(&self, action: T) -> f32 {
self.scalars.get(&action).copied().unwrap_or(0.0)
}
/// Fires an instant `action` for this frame.
pub fn press(&mut self, action: T) {
self.momentary.insert(action);
@ -330,15 +399,23 @@ impl<T: GameAction> ActionState<T> {
pub fn set_axis(&mut self, action: T, value: Vec2) {
self.axes.insert(action, value);
}
/// Sets a scalar (slider) `action`'s latest value, and marks it as changed
/// this frame (so [`active`](Self::active)/[`on_action`] fire this frame).
pub fn set_scalar(&mut self, action: T, value: f32) {
self.scalars.insert(action, value);
self.momentary.insert(action);
}
}
/// Marker component linking a UI widget to the action it drives.
///
/// Put it on a `Button` ([`Instant`](ActionKind::Instant)) or `Checkbox`
/// ([`Toggle`](ActionKind::Toggle)) — the engine wires the widget's events into
/// [`ActionState`] and keeps checkboxes visually in sync.
#[derive(Component, Copy, Clone, Debug)]
pub struct ActionSource<T: GameAction>(pub T);
/// Put it on a `Button` ([`Instant`](ActionKind::Instant)), `Checkbox`
/// ([`Toggle`](ActionKind::Toggle)), or `Slider` ([`Scalar`](ActionKind::Scalar)) —
/// the engine wires the widget's events into [`ActionState`] and keeps checkboxes
/// visually in sync.
#[derive(Component, Copy, Clone, Debug, Default)]
pub struct ActionSource<T: GameAction + Default>(pub T);
/// The two symmetrical entry points below let any system consume any action:
///
@ -348,14 +425,17 @@ pub struct ActionSource<T: GameAction>(pub T);
/// Both accept an action of any [`ActionKind`]; the value type is unified by
/// [`ActionValue`].
/// Run condition that is active while `action` is active, for **any** kind: a
/// `true` bool (instant fired / toggle on) or a non-zero axis (stick deflected).
/// Run condition on `action`, for **any** kind — see [`ActionState::active`] for
/// the per-kind meaning: an instant fired / a slider changed this frame (edge), or
/// a toggle is on / an axis is deflected (level).
///
/// So the same call gates "run while paused" and "run while the stick is moved".
/// So the same call gates "run while paused", "run while the stick is moved", and
/// "run when the slider changes".
///
/// ```rust,ignore
/// app.add_systems(Update, jump.run_if(on_action(Action::Jump)));
/// app.add_systems(Update, camera_follow.run_if(on_action(Action::Move))); // stick moved
/// app.add_systems(Update, save_volume.run_if(on_action(Action::Volume))); // slider changed
/// ```
pub fn on_action<T: GameAction>(action: T) -> impl FnMut(Res<ActionState<T>>) -> bool + Clone {
move |state: Res<ActionState<T>>| state.active(action)
@ -402,6 +482,15 @@ pub fn toggle_value<T: GameAction>(action: T) -> impl FnMut(Res<ActionState<T>>)
move |state: Res<ActionState<T>>| state.enabled(action)
}
/// Typed convenience over [`action_value`] for scalar (slider) actions: pipes a
/// bare `f32`, so the consumer takes `In<f32>`.
///
/// Pair with [`on_action`] to run — and deliver the value — only when the slider
/// changes: `scalar_value(a).pipe(sys).run_if(on_action(a))`.
pub fn scalar_value<T: GameAction>(action: T) -> impl FnMut(Res<ActionState<T>>) -> f32 + Clone {
move |state: Res<ActionState<T>>| state.scalar(action)
}
// --- fan-in systems -------------------------------------------------------
/// Clears momentary state at the start of each frame so instant actions have
@ -463,6 +552,8 @@ fn hardware_to_actions<T: GameAction>(
}
}
}
// Scalar actions come only from UI sliders, never from a binding.
ActionKind::Scalar => {}
}
}
}
@ -479,7 +570,7 @@ fn button_to_action<T: GameAction>(
// A button bound to a toggle acts as a "flip" control (menu item).
ActionKind::Toggle => state.toggle(*action),
// A button can't produce an analog value; nothing to do.
ActionKind::Axis => {}
ActionKind::Axis | ActionKind::Scalar => {}
}
}
}
@ -497,6 +588,30 @@ fn checkbox_to_action<T: GameAction>(
}
}
/// UI fan-in: a `Slider`'s [`ValueChange<f32>`](ValueChange) feeds a scalar action.
///
/// The latest value is stored on every change so [`ActionState::scalar`] tracks
/// the slider live (including mid-drag), while the edge trigger — what
/// [`on_action`] fires on — only marks the interaction's *final* value, so
/// gated consumers run once per settled change rather than every drag frame.
fn slider_to_action<T: GameAction>(
change: On<ValueChange<f32>>,
sources: Query<&ActionSource<T>>,
mut state: ResMut<ActionState<T>>,
) {
if let Ok(ActionSource(action)) = sources.get(change.source) {
if let ActionKind::Scalar = action.kind() {
if change.is_final {
// Store value + mark changed this frame (edge trigger).
state.set_scalar(*action, change.value);
} else {
// Mid-drag: keep the live value readable, but don't trigger.
state.scalars.insert(*action, change.value);
}
}
}
}
/// State -> UI sync: pushes toggle state back onto checkboxes so a keyboard or
/// gamepad toggle also moves the checkmark. Runs only when state changed.
fn sync_checkboxes<T: GameAction>(
@ -511,7 +626,10 @@ fn sync_checkboxes<T: GameAction>(
if let ActionKind::Toggle = action.kind() {
let want = state.enabled(*action);
if want != is_checked {
commands.trigger(SetChecked { entity, checked: want });
commands.trigger(SetChecked {
entity,
checked: want,
});
}
}
}
@ -558,6 +676,7 @@ impl<T: GameAction> Plugin for ActionsPlugin<T> {
.add_systems(PreUpdate, hardware_to_actions::<T>)
.add_systems(Update, sync_checkboxes::<T>)
.add_observer(button_to_action::<T>)
.add_observer(checkbox_to_action::<T>);
.add_observer(checkbox_to_action::<T>)
.add_observer(slider_to_action::<T>);
}
}

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