Debug toggling (#9)

#8 introduced some additional debug information to the view, which was already
rendering some information and visualizations which were not necessary relevant
to the end-user experience. This PR adds an input action (bound to Ctrl + `) to
toggle the display of those visualizations, and disables them by default.

studio/src/debug.rs

@@ -0,0 +1,83 @@
+use bevy::{prelude::*, window::PrimaryWindow};
+use bevy_inspector_egui::quick::WorldInspectorPlugin;
+use bevy_mod_picking::debug::DebugPickingMode;
+
+use crate::{
+    camera_controller::{CameraController, CameraMotionSystem},
+    input::{Action, InputAction, Lifecycle},
+};
+
+#[derive(Resource, Deref, DerefMut)]
+pub struct DebugMode(bool);
+
+pub struct DebugPlugin;
+impl Plugin for DebugPlugin {
+    fn build(&self, app: &mut App) {
+        app.insert_resource(DebugMode(false))
+            .add_plugins(WorldInspectorPlugin::new().run_if(is_debug_mode))
+            .insert_resource(State::new(DebugPickingMode::Disabled))
+            .insert_resource(GizmoConfig {
+                enabled: true,
+                depth_bias: -0.1,
+                line_perspective: false,
+                line_width: 2.,
+                ..default()
+            })
+            .add_systems(
+                Update,
+                (
+                    toggle_debug_mode,
+                    update_debug_picking_mode.run_if(resource_changed::<DebugMode>()),
+                    update_gizmo_line_thickness,
+                    draw_world_axes
+                        .after(CameraMotionSystem)
+                        .run_if(is_debug_mode),
+                ),
+            );
+    }
+}
+
+fn toggle_debug_mode(mut input: EventReader<InputAction>, mut r_debug: ResMut<DebugMode>) {
+    if input
+        .iter()
+        .any(|action| matches!(action, InputAction(Lifecycle::Stop, Action::ToggleDebug)))
+    {
+        **r_debug = !**r_debug;
+    }
+}
+
+fn update_debug_picking_mode(
+    r_debug: Res<DebugMode>,
+    mut s_debug_picking: ResMut<NextState<DebugPickingMode>>,
+) {
+    s_debug_picking.set(match **r_debug {
+        true => DebugPickingMode::Normal,
+        false => DebugPickingMode::Disabled,
+    });
+}
+
+pub fn is_debug_mode(r_debug: Res<DebugMode>) -> bool {
+    **r_debug
+}
+
+fn update_gizmo_line_thickness(
+    mut config: ResMut<GizmoConfig>,
+    q_window: Query<&Window, (Changed<Window>, With<PrimaryWindow>)>,
+) {
+    if let Ok(scale_factor) = q_window.get_single().map(|win| win.scale_factor() as f32) {
+        config.line_width = 2. * scale_factor;
+    }
+}
+
+fn draw_world_axes(mut gizmos: Gizmos, q: Query<&CameraController>) {
+    let &CameraController { focus, radius, .. } = q.single();
+
+    let mut draw_axis = |direction: Vec3, color: Color| {
+        let end = focus + direction * radius / 15.;
+        gizmos.line(focus, end, color);
+    };
+
+    draw_axis(Vec3::X, Color::RED);
+    draw_axis(Vec3::Y, Color::GREEN);
+    draw_axis(Vec3::Z, Color::BLUE);
+}