bevy_diagnostic/
frame_time_diagnostics_plugin.rs

1use crate::{
2    Diagnostic, DiagnosticPath, Diagnostics, FrameCount, RegisterDiagnostic,
3    DEFAULT_MAX_HISTORY_LENGTH,
4};
5use bevy_app::prelude::*;
6use bevy_ecs::prelude::*;
7use bevy_time::{Real, Time};
8
9/// Adds "frame time" diagnostic to an App, specifically "frame time", "fps" and "frame count"
10///
11/// # See also
12///
13/// [`LogDiagnosticsPlugin`](crate::LogDiagnosticsPlugin) to output diagnostics to the console.
14pub struct FrameTimeDiagnosticsPlugin {
15    /// The total number of values to keep for averaging.
16    pub max_history_length: usize,
17    /// The smoothing factor for the exponential moving average. Usually `2.0 / (history_length + 1.0)`.
18    pub smoothing_factor: f64,
19}
20
21impl Default for FrameTimeDiagnosticsPlugin {
22    fn default() -> Self {
23        Self::new(DEFAULT_MAX_HISTORY_LENGTH)
24    }
25}
26
27impl FrameTimeDiagnosticsPlugin {
28    /// Creates a new `FrameTimeDiagnosticsPlugin` with the specified `max_history_length` and a
29    /// reasonable `smoothing_factor`.
30    pub fn new(max_history_length: usize) -> Self {
31        Self {
32            max_history_length,
33            smoothing_factor: 2.0 / (max_history_length as f64 + 1.0),
34        }
35    }
36}
37
38impl Plugin for FrameTimeDiagnosticsPlugin {
39    fn build(&self, app: &mut App) {
40        app.register_diagnostic(
41            Diagnostic::new(Self::FRAME_TIME)
42                .with_suffix("ms")
43                .with_max_history_length(self.max_history_length)
44                .with_smoothing_factor(self.smoothing_factor),
45        )
46        .register_diagnostic(
47            Diagnostic::new(Self::FPS)
48                .with_max_history_length(self.max_history_length)
49                .with_smoothing_factor(self.smoothing_factor),
50        )
51        // An average frame count would be nonsensical, so we set the max history length
52        // to zero and disable smoothing.
53        .register_diagnostic(
54            Diagnostic::new(Self::FRAME_COUNT)
55                .with_smoothing_factor(0.0)
56                .with_max_history_length(0),
57        )
58        .add_systems(Update, Self::diagnostic_system);
59    }
60}
61
62impl FrameTimeDiagnosticsPlugin {
63    /// Frames per second.
64    pub const FPS: DiagnosticPath = DiagnosticPath::const_new("fps");
65
66    /// Total frames since application start.
67    pub const FRAME_COUNT: DiagnosticPath = DiagnosticPath::const_new("frame_count");
68
69    /// Frame time in ms.
70    pub const FRAME_TIME: DiagnosticPath = DiagnosticPath::const_new("frame_time");
71
72    /// Updates frame count, frame time and fps measurements.
73    pub fn diagnostic_system(
74        mut diagnostics: Diagnostics,
75        time: Res<Time<Real>>,
76        frame_count: Res<FrameCount>,
77    ) {
78        diagnostics.add_measurement(&Self::FRAME_COUNT, || frame_count.0 as f64);
79
80        let delta_seconds = time.delta_secs_f64();
81        if delta_seconds == 0.0 {
82            return;
83        }
84
85        diagnostics.add_measurement(&Self::FRAME_TIME, || delta_seconds * 1000.0);
86
87        diagnostics.add_measurement(&Self::FPS, || 1.0 / delta_seconds);
88    }
89}
bevy_diagnostic/frame_time_diagnostics_plugin.rs

bevy_diagnostic/
frame_time_diagnostics_plugin.rs
