Blocking buttons (#69)

![image](https://github.com/storytold/storyteller-bevy/assets/10954133/6c963b6c-6551-4379-854e-9f3f57cb173d)

---------

Co-authored-by: Danny McGee <dannymcgee@gmail.com>

studio/src/ui/blocking.rs

@@ -0,0 +1,83 @@
+use std::sync::Arc;
+
+use bevy::prelude::*;
+use bevy_mod_picking::PickableBundle;
+use space_editor::prelude::{
+    space_undo::{AddedEntity, NewChange},
+    *,
+};
+use wasm_bindgen::prelude::*;
+
+use crate::{
+    interaction::Selectable,
+    scene::SceneElement,
+    wasm::{StaticBuffer, WasmMessageBuffer},
+};
+
+pub struct UiBlockingPlugin;
+
+impl Plugin for UiBlockingPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_systems(Update, read_command_system);
+    }
+}
+
+fn read_command_system(mut commands: Commands, mut change_event: EventWriter<NewChange>) {
+    let Some(cmd) = COMMAND.take_message() else {
+        return;
+    };
+
+    let mut new_entity = commands.spawn((
+        SpatialBundle::default(),
+        PrefabMarker,
+        Selectable,
+        SceneElement::Mesh,
+        PickableBundle::default(),
+    ));
+
+    match cmd {
+        BlockingCommand::Cube => {
+            new_entity
+                .insert(MeshPrimitivePrefab::Cube(1.0))
+                .insert(Name::new("Cube"));
+        }
+        BlockingCommand::Sphere => {
+            new_entity
+                .insert(MeshPrimitivePrefab::Sphere(SpherePrefab { r: 1.0 }))
+                .insert(Name::new("Sphere"));
+        }
+        BlockingCommand::Torus => {
+            new_entity
+                .insert(MeshPrimitivePrefab::Torus(TorusPrefab::default()))
+                .insert(Name::new("Torus"));
+        }
+        BlockingCommand::Cylinder => {
+            new_entity
+                .insert(MeshPrimitivePrefab::Cylinder(CylinderPrefab::default()))
+                .insert(Name::new("Cylinder"));
+        }
+    };
+
+    change_event.send(NewChange {
+        change: Arc::new(AddedEntity {
+            entity: new_entity.id(),
+        }),
+    });
+}
+
+#[derive(Clone, Copy, Debug)]
+#[wasm_bindgen]
+pub enum BlockingCommand {
+    Cube,
+    Sphere,
+    Torus,
+    Cylinder,
+}
+
+static COMMAND: WasmMessageBuffer<BlockingCommand> = WasmMessageBuffer::new();
+
+#[wasm_bindgen(js_name = dispatchBlockingCommand)]
+pub fn dispatch_command(command: BlockingCommand) {
+    info!("Dispatching blocking command: {command:?}");
+    COMMAND.write_message(command);
+}