viewport-lib 0.15.0

3D viewport rendering library
Documentation 
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//! Per-frame and per-step context types for runtime plugins.

use crate::camera::camera::Camera;
use crate::interaction::input::ActionFrame;
use crate::scene::scene::Scene;

use super::output::{RuntimeOutput, TransformWriteback};
use super::resources::RuntimeResources;

/// Per-frame inputs to [`super::ViewportRuntime::step`].
#[derive(Default)]
#[non_exhaustive]
pub struct RuntimeFrameContext {
    /// Wall-clock delta time in seconds since the last frame.
    pub dt: f32,
    /// Current camera state.
    pub camera: Camera,
    /// Viewport dimensions in logical pixels.
    pub viewport_size: glam::Vec2,
    /// Resolved input actions for this frame.
    pub input: ActionFrame,
    /// Pick result under the cursor for this frame. Supply from CPU or GPU picking.
    /// None if no picking was done or nothing was hit.
    pub pick_hit: Option<crate::interaction::picking::PickHit>,
    /// True on the frame the primary pointer button was clicked (pressed and released without drag).
    pub clicked: bool,
    /// True on the frame a primary drag began.
    pub drag_started: bool,
    /// True while a primary drag is ongoing.
    pub dragging: bool,
    /// Pointer movement in viewport pixels since last frame.
    pub pointer_delta: glam::Vec2,
    /// Cursor position in viewport-local pixels. None when outside the viewport.
    pub cursor_viewport: Option<glam::Vec2>,
    /// True when the shift modifier is held (for shift-click multi-select).
    pub shift_held: bool,
}

/// Context passed to each plugin during its execution step.
///
/// Provides read-only scene access and write access to the transform writeback
/// buffer, output accumulator, and shared resource registry. To write transforms,
/// call [`TransformWriteback::set`] on `self.writeback`. To share state between
/// plugins, use `self.resources`.
pub struct RuntimeStepContext<'a> {
    /// The numeric priority of the plugin executing in this context.
    pub priority: i32,
    /// Delta time for this step. For plugins in the simulate range with a fixed
    /// timestep this is the fixed step size, not the wall dt.
    pub dt: f32,
    /// Read-only scene access. To write transforms, use `writeback`.
    pub scene: &'a Scene,
    /// Accumulate transform writes here. The runtime flushes them to the scene
    /// after the writeback phase.
    pub writeback: &'a mut TransformWriteback,
    /// Accumulate selection changes and contact events here.
    pub output: &'a mut RuntimeOutput,
    /// Forwarded from RuntimeFrameContext for plugins that need the current pick result.
    pub pick_hit: Option<crate::interaction::picking::PickHit>,
    /// Shared typed resource registry. Plugins use this to coordinate through
    /// engine-owned state without custom wiring in the application.
    ///
    /// In `submit` (called with `&RuntimeStepContext`), only `get` and `contains`
    /// are accessible through the shared reference. In `step`, `collect`, and
    /// `on_event` (called with `&mut RuntimeStepContext`), full insert/get_mut/remove
    /// access is available.
    pub resources: &'a mut RuntimeResources,
}

impl<'a> RuntimeStepContext<'a> {
    /// Construct a [`SimulationStepContext`] from this context.
    ///
    /// Pass the step count from [`super::ViewportRuntime::step_index`] so the
    /// simulation context reflects the current runtime step. The runtime does not
    /// thread the step index into `RuntimeStepContext` automatically -- you must
    /// supply it.
    ///
    /// ```rust,ignore
    /// fn step(&mut self, ctx: &mut RuntimeStepContext) {
    ///     let sim = ctx.as_simulation(runtime.step_index());
    ///     // use sim.step_index for deterministic seeding or replay
    /// }
    /// ```
    ///
    /// Note: within a fixed-timestep frame that runs N simulate steps,
    /// `runtime.step_index()` returns the count at the start of that frame.
    /// If you need a per-sub-step index (0..N) within a single frame, maintain
    /// a local counter in your plugin.
    ///
    /// Passing an incorrect value does not cause undefined behavior, but
    /// physics code that uses `step_index` for deterministic seeding or replay
    /// will produce wrong results.
    pub fn as_simulation(&mut self, step_index: u64) -> SimulationStepContext<'_> {
        SimulationStepContext {
            dt: self.dt,
            step_index,
            scene: self.scene,
            writeback: self.writeback,
        }
    }
}

/// Narrower context for simulation plugins that need a per-step index.
///
/// Constructed via [`RuntimeStepContext::as_simulation`] inside a simulate-range
/// plugin to get the current simulation step count alongside scene and writeback access.
pub struct SimulationStepContext<'a> {
    /// Fixed step size in seconds.
    pub dt: f32,
    /// Monotonically increasing step counter (wraps on overflow).
    pub step_index: u64,
    /// Read-only scene access.
    pub scene: &'a Scene,
    /// Write transforms to this buffer.
    pub writeback: &'a mut TransformWriteback,
}