viewport-lib 0.16.0

//! Runtime plugin trait and phase ordering.

use crate::interaction::selection::NodeId;
use super::context::RuntimeStepContext;

/// Named priority band constants for runtime plugins.
///
/// Each constant is the base priority for a logical execution phase. Plugins
/// can use values between bands (e.g. `phase::ANIMATE + 50`) to run at a
/// specific point within a range.
pub mod phase {
    /// First phase each frame. Update time-dependent state before any queries.
    pub const PREPARE:    i32 = 100;
    /// Ray-cast and object picking.
    pub const PICK:       i32 = 200;
    /// Selection state updates driven by pick results.
    pub const SELECT:     i32 = 300;
    /// Transform manipulation from gizmo drag or keyboard input.
    pub const MANIPULATE: i32 = 400;
    /// Procedural or keyframe animation.
    pub const ANIMATE:    i32 = 500;
    /// Physics or simulation. With a fixed timestep this runs once per
    /// accumulated step.
    pub const SIMULATE:   i32 = 600;
    /// Runs after all Simulate iterations, before Writeback.
    pub const POST_SIM:   i32 = 700;
    /// Flush accumulated transform ops to the scene.
    pub const WRITEBACK:  i32 = 800;
}

/// Named execution phase for a runtime plugin.
///
/// This enum is a convenience alias for the numeric priority bands in the
/// [`phase`] module. Use [`to_priority`](RuntimePhase::to_priority) to convert
/// to an `i32` priority value.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub enum RuntimePhase {
    /// Runs first. Update time-dependent state before any queries.
    Prepare,
    /// Ray-cast and object picking.
    Pick,
    /// Selection state updates driven by pick results.
    Select,
    /// Transform manipulation from gizmo drag or keyboard input.
    Manipulate,
    /// Procedural or keyframe animation.
    Animate,
    /// Physics or simulation. With a fixed timestep this runs once per
    /// accumulated step, so it may execute multiple times per rendered frame.
    Simulate,
    /// Runs after all Simulate iterations, before Writeback.
    PostSimulate,
    /// Flush accumulated transform ops to the scene. Runs once per frame after
    /// all other phases, including after all `Simulate` iterations.
    Writeback,
}

impl RuntimePhase {
    /// Convert this phase to its numeric priority value.
    pub fn to_priority(&self) -> i32 {
        match self {
            RuntimePhase::Prepare      => phase::PREPARE,
            RuntimePhase::Pick         => phase::PICK,
            RuntimePhase::Select       => phase::SELECT,
            RuntimePhase::Manipulate   => phase::MANIPULATE,
            RuntimePhase::Animate      => phase::ANIMATE,
            RuntimePhase::Simulate     => phase::SIMULATE,
            RuntimePhase::PostSimulate => phase::POST_SIM,
            RuntimePhase::Writeback    => phase::WRITEBACK,
        }
    }
}

/// An event emitted by the runtime when the scene node set changes.
#[derive(Debug, Clone)]
pub enum RuntimeEvent {
    /// A node was added to the scene since the last frame.
    NodeAdded(NodeId),
    /// A node was removed from the scene since the last frame.
    NodeRemoved(NodeId),
}

/// A plugin that executes during the scene step.
///
/// Register plugins with [`super::ViewportRuntime::with_plugin`]. Each frame
/// the runtime calls `submit`, then `step` (once or more for simulate phases),
/// then `collect`.
///
/// # Example
///
/// ```rust,ignore
/// use viewport_lib::runtime::{RuntimePlugin, RuntimeStepContext};
/// use viewport_lib::runtime::plugin::phase;
///
/// struct GravityPlugin {
///     gravity: glam::Vec3,
/// }
///
/// impl RuntimePlugin for GravityPlugin {
///     fn priority(&self) -> i32 {
///         phase::SIMULATE
///     }
///
///     fn step(&mut self, ctx: &mut RuntimeStepContext) {
///         // Apply gravity to tracked bodies via ctx.writeback.set(id, new_transform).
///     }
/// }
/// ```
pub trait RuntimePlugin: Send + 'static {
    /// Numeric execution priority. Lower values run first. Use the constants
    /// in [`phase`] as base values and offset within a band if needed.
    fn priority(&self) -> i32;

    /// Called once per frame before the step loop, in priority order.
    ///
    /// Use this to kick off background work (e.g. async physics) that will
    /// be read in `collect` on the next frame.
    fn submit(&mut self, _ctx: &RuntimeStepContext<'_>) {}

    /// Called once per frame after the step loop, in priority order.
    ///
    /// Use this to read results from background work started in `submit`.
    fn collect(&mut self, _ctx: &mut RuntimeStepContext<'_>) {}

    /// Called for each lifecycle event before the step loop.
    fn on_event(&mut self, _event: &RuntimeEvent, _ctx: &mut RuntimeStepContext<'_>) {}

    /// Called once per phase execution.
    ///
    /// For plugins in the `[SIMULATE, POST_SIM)` range with a fixed timestep,
    /// `ctx.dt` is the fixed step size and this is called once per step. For
    /// all other priorities, `ctx.dt` is the wall-clock frame delta and this
    /// is called once per frame.
    fn step(&mut self, ctx: &mut RuntimeStepContext<'_>);
}