storyteller-bevy/studio/src/ui/fps.rs

use bevy::{
    diagnostic::{DiagnosticsStore, FrameTimeDiagnosticsPlugin},
    prelude::*,
};

use crate::debug::DebugMode;

pub(super) struct FpsCounterPlugin;

impl Plugin for FpsCounterPlugin {
    fn build(&self, app: &mut App) {
        app.add_plugins(FrameTimeDiagnosticsPlugin)
            .add_systems(Startup, layout)
            .add_systems(Update, update)
            .add_systems(
                Update,
                update_visibility.run_if(resource_exists_and_changed::<DebugMode>()),
            );
    }
}

#[derive(Component)]
struct FramerateCounter;

fn layout(mut cmd: Commands) {
    let mut text_bundle = TextBundle::from_section(
        "0 fps",
        TextStyle {
            color: Color::GREEN,
            font_size: 14.,
            ..default()
        },
    )
    .with_text_alignment(TextAlignment::Right)
    .with_style(Style {
        position_type: PositionType::Absolute,
        right: Val::Px(16.),
        bottom: Val::Px(16.),
        ..default()
    });

    text_bundle.visibility = Visibility::Hidden;

    cmd.spawn((
        FramerateCounter,
        Name::new("Framerate Counter"),
        text_bundle,
    ));
}

fn update(
    time: Res<Time>,
    diag: Res<DiagnosticsStore>,
    mut counter: Query<&mut Text, With<FramerateCounter>>,
) {
    if let Some(fps_diag) = diag.get(FrameTimeDiagnosticsPlugin::FPS) {
        let fps = if let Some(fps_smoothed) = fps_diag.smoothed() {
            fps_smoothed
        } else {
            1. / time.delta_seconds_f64()
        };

        counter.single_mut().sections[0].value = format!("{fps:.2} fps");
    }
}

fn update_visibility(
    r_debug: Res<DebugMode>,
    mut q_visibility: Query<&mut Visibility, With<FramerateCounter>>,
) {
    for mut visibility in q_visibility.iter_mut() {
        *visibility = match **r_debug {
            true => Visibility::Inherited,
            false => Visibility::Hidden,
        }
    }
}