7989cb2650
# Objective - Make `Time` API more consistent. - Support time accel/decel/pause. ## Solution This is just the `Time` half of #3002. I was told that part isn't controversial. - Give the "delta time" and "total elapsed time" methods `f32`, `f64`, and `Duration` variants with consistent naming. - Implement accelerating / decelerating the passage of time. - Implement stopping time. --- ## Changelog - Changed `time_since_startup` to `elapsed` because `time.time_*` is just silly. - Added `relative_speed` and `set_relative_speed` methods. - Added `is_paused`, `pause`, `unpause` , and methods. (I'd prefer `resume`, but `unpause` matches `Timer` API.) - Added `raw_*` variants of the "delta time" and "total elapsed time" methods. - Added `first_update` method because there's a non-zero duration between startup and the first update. ## Migration Guide - `time.time_since_startup()` -> `time.elapsed()` - `time.seconds_since_startup()` -> `time.elapsed_seconds_f64()` - `time.seconds_since_startup_wrapped_f32()` -> `time.elapsed_seconds_wrapped()` If you aren't sure which to use, most systems should continue to use "scaled" time (e.g. `time.delta_seconds()`). The realtime "unscaled" time measurements (e.g. `time.raw_delta_seconds()`) are mostly for debugging and profiling.
53 lines
1.4 KiB
Rust
53 lines
1.4 KiB
Rust
//! This example illustrates how to react to component change.
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use bevy::prelude::*;
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use rand::Rng;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(change_component)
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.add_system(change_detection)
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.add_system(tracker_monitoring)
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.run();
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}
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#[derive(Component, Debug)]
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struct MyComponent(f32);
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fn setup(mut commands: Commands) {
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commands.spawn(MyComponent(0.));
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commands.spawn(Transform::IDENTITY);
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}
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fn change_component(time: Res<Time>, mut query: Query<(Entity, &mut MyComponent)>) {
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for (entity, mut component) in &mut query {
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if rand::thread_rng().gen_bool(0.1) {
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info!("changing component {:?}", entity);
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component.0 = time.elapsed_seconds();
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}
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}
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}
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// There are query filters for `Changed<T>` and `Added<T>`
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// Only entities matching the filters will be in the query
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fn change_detection(query: Query<(Entity, &MyComponent), Changed<MyComponent>>) {
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for (entity, component) in &query {
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info!("{:?} changed: {:?}", entity, component,);
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}
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}
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// By looking at trackers, the query is not filtered but the information is available
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fn tracker_monitoring(
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query: Query<(
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Entity,
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Option<&MyComponent>,
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Option<ChangeTrackers<MyComponent>>,
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)>,
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) {
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for (entity, component, trackers) in &query {
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info!("{:?}: {:?} -> {:?}", entity, component, trackers);
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}
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}
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