From 75d93600072ebd3129ba76a0b3b6014641813e5c Mon Sep 17 00:00:00 2001
From: Alexander Baranov <baranovas@vtb.ru>
Date: Wed, 3 Jun 2026 21:20:23 +0300
Subject: [PATCH] =?UTF-8?q?=D0=9F=D1=80=D0=BE=D0=B5=D0=BA=D1=82=D0=BD?=
 =?UTF-8?q?=D0=B0=D1=8F=20=D1=80=D0=B0=D0=B1=D0=BE=D1=82=D0=B0=20-=20WIP?=
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---
 snake-game/examples/time.rs | 121 ++++++++++++++++++++++++++++++++++++
 snake-game/src/domain.rs    |  10 +--
 snake-game/src/gameplay.rs  |  15 ++++-
 snake-game/src/lib.rs       |   2 +-
 snake-game/src/main.rs      |   8 +--
 snake-game/src/observers.rs |  10 +--
 snake-game/src/startup.rs   |  16 +----
 7 files changed, 151 insertions(+), 31 deletions(-)
 create mode 100644 snake-game/examples/time.rs

diff --git a/snake-game/examples/time.rs b/snake-game/examples/time.rs
new file mode 100644
index 0000000..c9f21d9
--- /dev/null
+++ b/snake-game/examples/time.rs
@@ -0,0 +1,121 @@
+//! An example that illustrates how Time is handled in ECS.
+
+use bevy::{app::AppExit, prelude::*};
+
+use std::{
+    io::{self, BufRead},
+    time::Duration,
+};
+
+fn banner() {
+    println!("This example is meant to intuitively demonstrate how Time works in Bevy.");
+    println!();
+    println!("Time will be printed in three different schedules in the app:");
+    println!("- PreUpdate: real time is printed");
+    println!("- FixedUpdate: fixed time step time is printed, may be run zero or multiple times");
+    println!("- Update: virtual game time is printed");
+    println!();
+    println!("Max delta time is set to 5 seconds. Fixed timestep is set to 1 second.");
+    println!();
+}
+
+fn help() {
+    println!("The app reads commands line-by-line from standard input.");
+    println!();
+    println!("Commands:");
+    println!("  empty line: Run app.update() once on the Bevy App");
+    println!("  q: Quit the app.");
+    println!("  f: Set speed to fast, 2x");
+    println!("  n: Set speed to normal, 1x");
+    println!("  s: Set speed to slow, 0.5x");
+    println!("  p: Pause");
+    println!("  u: Unpause");
+}
+
+fn runner(mut app: App) -> AppExit {
+    banner();
+    help();
+    let stdin = io::stdin();
+    for line in stdin.lock().lines() {
+        if let Err(err) = line {
+            println!("read err: {err:#}");
+            break;
+        }
+        match line.unwrap().as_str() {
+            "" => {
+                app.update();
+            }
+            "f" => {
+                println!("FAST: setting relative speed to 2x");
+                app.world_mut()
+                    .resource_mut::<Time<Virtual>>()
+                    .set_relative_speed(2.0);
+            }
+            "n" => {
+                println!("NORMAL: setting relative speed to 1x");
+                app.world_mut()
+                    .resource_mut::<Time<Virtual>>()
+                    .set_relative_speed(1.0);
+            }
+            "s" => {
+                println!("SLOW: setting relative speed to 0.5x");
+                app.world_mut()
+                    .resource_mut::<Time<Virtual>>()
+                    .set_relative_speed(0.5);
+            }
+            "p" => {
+                println!("PAUSE: pausing virtual clock");
+                app.world_mut().resource_mut::<Time<Virtual>>().pause();
+            }
+            "u" => {
+                println!("UNPAUSE: resuming virtual clock");
+                app.world_mut().resource_mut::<Time<Virtual>>().unpause();
+            }
+            "q" => {
+                println!("QUITTING!");
+                break;
+            }
+            _ => {
+                help();
+            }
+        }
+    }
+
+    AppExit::Success
+}
+
+fn print_real_time(time: Res<Time<Real>>) {
+    println!(
+        "PreUpdate: this is real time clock, delta is {:?} and elapsed is {:?}",
+        time.delta(),
+        time.elapsed()
+    );
+}
+
+fn print_fixed_time(time: Res<Time>) {
+    println!(
+        "FixedUpdate: this is generic time clock inside fixed, delta is {:?} and elapsed is {:?}",
+        time.delta(),
+        time.elapsed()
+    );
+}
+
+fn print_time(time: Res<Time>) {
+    println!(
+        "Update: this is generic time clock, delta is {:?} and elapsed is {:?}",
+        time.delta(),
+        time.elapsed()
+    );
+}
+
+fn main() {
+    App::new()
+        .add_plugins(MinimalPlugins)
+        .insert_resource(Time::<Virtual>::from_max_delta(Duration::from_secs(5)))
+        .insert_resource(Time::<Fixed>::from_duration(Duration::from_secs(1)))
+        .add_systems(PreUpdate, print_real_time)
+        .add_systems(FixedUpdate, print_fixed_time)
+        .add_systems(Update, print_time)
+        .set_runner(runner)
+        .run();
+}
diff --git a/snake-game/src/domain.rs b/snake-game/src/domain.rs
index 3a18128..3f8da36 100644
--- a/snake-game/src/domain.rs
+++ b/snake-game/src/domain.rs
@@ -2,7 +2,6 @@ use std::collections::HashMap;
 
 use bevy::prelude::*;
 
-pub const FRAMES_PER_SECOND: u8 = 24;
 pub const GRID_SIZE: u8 = 48;
 pub const HEAD_SIZE: u8 = (GRID_SIZE as f32 * 1.1) as u8;
 pub const SNAKE_VELOCITY: u8 = (GRID_SIZE as f32 / 1.0) as u8;
@@ -104,14 +103,15 @@ impl SnakePath {
         )
     }
 
-    pub fn push(&mut self, transform: &Transform, direction: Direction) {
+    pub fn push(&mut self, transform: &Transform, direction: Direction) -> (i16, i16, Direction) {
         let key = SnakePath::to_key(transform);
         self.0.insert(key, direction.clone());
+        (key.0, key.1, direction.clone())
     }
 
-    pub fn pick(&self, transform: &Transform) -> Option<Direction> {
+    pub fn pick(&self, transform: &Transform) -> Option<(i16, i16, Direction)> {
         let key = SnakePath::to_key(transform);
-        self.0.get(&key).cloned()
+        self.0.get(&key).cloned().map(|d| (key.0, key.1, d))
     }
 
     pub fn drop(&mut self, transform: &Transform) -> Option<(i16, i16, Direction)> {
@@ -132,7 +132,7 @@ mod test {
         snake_path.push(&Transform::default(), Direction::default());
         assert_eq!(snake_path.0.len(), 1);
 
-        assert!(snake_path.pick(&Transform::default()) == Some(Direction::default()));
+        assert!(snake_path.pick(&Transform::default()) == Some((0, 0, Direction::default())));
         assert_eq!(snake_path.0.len(), 1);
 
         assert!(snake_path.drop(&Transform::default()) == Some((0, 0, Direction::default())));
diff --git a/snake-game/src/gameplay.rs b/snake-game/src/gameplay.rs
index 3be1a1e..efd27e7 100644
--- a/snake-game/src/gameplay.rs
+++ b/snake-game/src/gameplay.rs
@@ -32,9 +32,9 @@ pub fn head_rotation(
     }
 }
 
-/// Системе движения для всех движущихся сущностей
+/// Система движения для всех движущихся сущностей
 pub fn moving(
-    time: Res<Time>,
+    time: Res<Time<Fixed>>,
     query: Query<(&mut Transform, &mut Inert, &Direction, &Velocity, Entity)>,
     mut commands: Commands,
 ) {
@@ -43,7 +43,7 @@ pub fn moving(
         let src = inert.0.get_coord(&transform);
         let sign = inert.0.get_change_sign();
         let dst = src + sign * delta;
-        let mut splited = split_by_grid(src, dst, GRID_SIZE as f32).into_iter();
+        let mut splited = _split_by_grid_tracing(src, dst, GRID_SIZE as f32).into_iter();
         let first = splited.next().unwrap_or((0.0, 0.0));
         inert.0.set_coord(&mut transform, first.0);
         if let Some(second) = splited.next() {
@@ -57,3 +57,12 @@ pub fn moving(
         }
     }
 }
+
+fn _split_by_grid_tracing(src: f32, dst: f32, grid: f32) -> Vec<(f32, f32)> {
+    let result = split_by_grid(src, dst, grid);
+    trace!(
+        "\tsplit_by_grid({:?}, {:?}, {:?}) -> {:?}",
+        src, dst, grid, result
+    );
+    result
+}
diff --git a/snake-game/src/lib.rs b/snake-game/src/lib.rs
index ed2bc21..3603f77 100644
--- a/snake-game/src/lib.rs
+++ b/snake-game/src/lib.rs
@@ -6,5 +6,5 @@ mod startup;
 mod tools;
 
 pub use gameplay::{head_rotation, moving};
-pub use startup::{setup_frame_rate, startup};
+pub use startup::startup;
 pub use tools::define_log_layer;
diff --git a/snake-game/src/main.rs b/snake-game/src/main.rs
index 617587d..48f39e9 100644
--- a/snake-game/src/main.rs
+++ b/snake-game/src/main.rs
@@ -1,5 +1,5 @@
 use bevy::prelude::*;
-use snake_game::{head_rotation, moving, setup_frame_rate, startup};
+use snake_game::{head_rotation, moving, startup};
 
 fn main() {
     App::new()
@@ -16,11 +16,11 @@ fn main() {
                     task_pool_options: TaskPoolOptions::with_num_threads(1),
                 }),
         )
-        .insert_resource(bevy::winit::WinitSettings::desktop_app())
         .insert_resource(ClearColor(Color::srgb(0.3, 0.6, 0.8)))
-        .add_systems(Startup, (startup, setup_frame_rate))
+        .add_systems(Startup, (startup,))
         // .add_systems(PostStartup, snake_game::debug::print_all_entities)
-        .add_systems(Update, (head_rotation, moving))
+        .add_systems(Update, (head_rotation,))
+        .add_systems(FixedUpdate, (moving,))
         // .add_systems(
         //     PostUpdate,
         //     snake_game::debug::print_all_entities_by_press_enter,
diff --git a/snake-game/src/observers.rs b/snake-game/src/observers.rs
index 21f75bf..d6b7a8a 100644
--- a/snake-game/src/observers.rs
+++ b/snake-game/src/observers.rs
@@ -9,13 +9,13 @@ pub fn tail_observer(
     mut query: Query<(&mut Direction, &Transform)>,
     snake_path: Res<SnakePath>,
 ) {
-    trace!("...changing direction: triggered");
     if event.observer() == event.0 {
-        trace!("...changing direction: observer == event.0");
         if let Ok((mut direction, transform)) = query.get_mut(event.0) {
-            trace!("...changing direction: query success");
-            if let Some(new_direction) = snake_path.pick(transform) {
-                trace!("change direction for {:?} to {:?}", event.0, new_direction);
+            if let Some((x, y, new_direction)) = snake_path.pick(transform) {
+                trace!(
+                    "change direction for {:?} in ({:?}, {:?}) to {:?}",
+                    event.0, x, y, new_direction
+                );
                 *direction = new_direction;
             }
         }
diff --git a/snake-game/src/startup.rs b/snake-game/src/startup.rs
index 95fea64..2600c73 100644
--- a/snake-game/src/startup.rs
+++ b/snake-game/src/startup.rs
@@ -1,23 +1,13 @@
-use bevy::{prelude::*, winit::WinitSettings};
-use std::time::Duration;
+use bevy::prelude::*;
 
 use crate::{
     domain::{End, SnakePath, Tail},
     observers::{cleanup_snake_path, schedule_set_velocity, tail_observer},
 };
 
-/// Настройка частоты кадров
-pub fn setup_frame_rate(mut winit: ResMut<WinitSettings>) {
-    use crate::domain::FRAMES_PER_SECOND;
-
-    winit.focused_mode =
-        bevy::winit::UpdateMode::reactive(Duration::from_secs_f32(1. / FRAMES_PER_SECOND as f32));
-    winit.unfocused_mode =
-        bevy::winit::UpdateMode::reactive(Duration::from_secs_f32(1. / FRAMES_PER_SECOND as f32));
-}
-
 /// Инициализация игрового мира
-pub fn startup(mut commands: Commands) {
+pub fn startup(mut commands: Commands, mut timer: ResMut<Time<Fixed>>) {
+    timer.set_timestep_hz(32.0);
     spawn_snake(&mut commands);
     crate::debug::spawn_grid(&mut commands);
     commands.spawn(Camera2d);