Render Layers (#15)

* feat: add render layers support

* fix: hide cached NodeBundle when not in used

* chore: add comments

src/renderer.rs

@@ -1,7 +1,7 @@
 use std::marker::PhantomData;
 
 use crate::{prelude::*, typst_element::prelude::*};
-use bevy::{prelude::*, utils::HashMap};
+use bevy::{prelude::*, render::view::RenderLayers, utils::HashMap};
 use bevy_vello::prelude::*;
 use typst_vello::TypstScene;
 
@@ -149,6 +149,7 @@ fn render_velyst_scene<F: TypstFunc>(
     mut commands: Commands,
     mut q_scenes: Query<(&mut VelloScene, &mut Style)>,
     mut scene: ResMut<VelystScene<F>>,
+    func: Res<F>,
 ) {
     let scene = scene.bypass_change_detection();
 
@@ -166,7 +167,7 @@ fn render_velyst_scene<F: TypstFunc>(
                     coordinate_space: CoordinateSpace::ScreenSpace,
                     ..default()
                 })
-                .insert(NodeBundle::default())
+                .insert((NodeBundle::default(), func.render_layers()))
                 .id(),
         );
     }
@@ -175,7 +176,7 @@ fn render_velyst_scene<F: TypstFunc>(
 /// Construct the interaction tree using bevy ui nodes.
 fn construct_interaction_tree<F: TypstFunc>(
     mut commands: Commands,
-    mut q_nodes: Query<(&mut Style, &mut Transform, &mut ZIndex)>,
+    mut q_nodes: Query<(&mut Style, &mut Transform, &mut ZIndex, &mut Visibility)>,
     mut scene: ResMut<VelystScene<F>>,
 ) {
     let scene = scene.bypass_change_detection();
@@ -214,7 +215,8 @@ fn construct_interaction_tree<F: TypstFunc>(
         let height = Val::Px(group.size().y as f32);
         let scale = Vec3::new(coeffs[0] as f32, coeffs[3] as f32, 0.0);
 
-        if let Some((mut style, mut transform, mut z_index)) = scene
+        // Reuse cached nodes when available, otherwise, spawn a new one.
+        if let Some((mut style, mut transform, mut z_index, mut viz)) = scene
             .cached_entities
             .get_mut(&label)
             .and_then(|entities| entities.iter_mut().find(|(_, used)| *used == false))
@@ -232,6 +234,8 @@ fn construct_interaction_tree<F: TypstFunc>(
             transform.scale = scale;
             // ZIndex
             *z_index = ZIndex::Local(i as i32);
+            // Visibility
+            *viz = Visibility::Inherited;
         } else {
             let new_entity = commands
                 .spawn((
@@ -266,6 +270,18 @@ fn construct_interaction_tree<F: TypstFunc>(
             }
         }
     }
+
+    // Hide unused cached nodes
+    for entities in scene.cached_entities.values() {
+        for (entity, used) in entities {
+            match *used {
+                true => continue,
+                false => {
+                    commands.entity(*entity).insert(Visibility::Hidden);
+                }
+            }
+        }
+    }
 }
 
 #[derive(Resource, Deref, DerefMut)]
@@ -359,6 +375,11 @@ pub struct TypstLabel(TypLabel);
 pub trait TypstFunc: Resource {
     fn func_name(&self) -> &str;
 
+    // TODO: Create macro to automatically generate the render layers function.
+    fn render_layers(&self) -> RenderLayers {
+        RenderLayers::layer(0)
+    }
+
     // TODO: Create macro to automatically generate the content function.
     fn content(&self, func: foundations::Func) -> Content;