Add spawn entity button

examples/demo.rs

@@ -2,7 +2,7 @@ use bevy::{
     app::{App, Startup},
     core::{DebugName, Name},
     core_pipeline::core_2d::Camera2dBundle,
-    ecs::{entity::Entity, query::Without, system::Commands},
+    ecs::{entity::Entity, query::Without, system::Commands, world::World},
     ui::{node_bundles::NodeBundle, Node},
     DefaultPlugins,
 };
@@ -47,6 +47,10 @@ fn SceneTree<'a>(cx: Scope, selected_entity: &'a UseState<Option<Entity>>) -> El
     let mut entities = entities.into_iter().collect::<Vec<_>>();
     entities.sort_by_key(|(entity, _)| *entity);
 
+    let spawn_entity = use_system(cx, |world: &mut World| {
+        world.spawn_empty();
+    });
+
     render! {
         div {
             onclick: move |_| selected_entity.set(None),
@@ -68,6 +72,12 @@ fn SceneTree<'a>(cx: Scope, selected_entity: &'a UseState<Option<Entity>>) -> El
                     }
                 }
             }
+            div {
+                onclick: move |_| spawn_entity(),
+                padding: "8",
+                background_color: NEUTRAL_800,
+                "Spawn Entity"
+            }
         }
     }
 }

src/apply_mutations.rs

@@ -44,7 +44,14 @@ pub fn apply_mutations(
                     parent.add_child(child);
                 }
             }
-            Mutation::AssignId { path, id } => todo!(),
+            Mutation::AssignId { path, id } => {
+                let mut entity = *stack.last().unwrap();
+                for index in path {
+                    entity = world.entity(entity).get::<Children>().unwrap()[*index as usize];
+                }
+                element_id_to_bevy_ui_entity.insert(id, entity);
+                bevy_ui_entity_to_element_id.insert(entity, id);
+            }
             Mutation::CreatePlaceholder { id } => {
                 let entity = world.spawn(NodeBundle::default()).id();
                 element_id_to_bevy_ui_entity.insert(id, entity);
@@ -102,7 +109,20 @@ pub fn apply_mutations(
                     element_id_to_bevy_ui_entity.remove(&existing_element_id);
                 }
             }
-            Mutation::InsertAfter { id, m } => todo!(),
+            Mutation::InsertAfter { id, m } => {
+                let entity = element_id_to_bevy_ui_entity[&id];
+                let parent = world.entity(entity).get::<Parent>().unwrap().get();
+                let mut parent = world.entity_mut(parent);
+
+                let index = parent
+                    .get::<Children>()
+                    .unwrap()
+                    .iter()
+                    .position(|child| *child == entity)
+                    .unwrap();
+                let new = stack.drain((stack.len() - m)..).collect::<Vec<Entity>>();
+                parent.insert_children(index + 1, &new);
+            }
             Mutation::InsertBefore { id, m } => todo!(),
             Mutation::SetAttribute {
                 name,