feat(editor): add hierarchy_panel with entity tree display and selection

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/voltex_editor/Cargo.toml

@@ -6,5 +6,6 @@ edition = "2021"
 [dependencies]
 bytemuck = { workspace = true }
 voltex_math = { workspace = true }
+voltex_ecs = { workspace = true }
 voltex_renderer = { workspace = true }
 wgpu = { workspace = true }

crates/voltex_editor/src/inspector.rs

@@ -0,0 +1,180 @@
+use crate::ui_context::UiContext;
+use crate::dock::Rect;
+use crate::layout::LayoutState;
+use voltex_ecs::world::World;
+use voltex_ecs::entity::Entity;
+use voltex_ecs::scene::Tag;
+use voltex_ecs::hierarchy::{roots, Children};
+
+const COLOR_SELECTED: [u8; 4] = [0x44, 0x66, 0x88, 0xFF];
+const COLOR_TEXT: [u8; 4] = [0xEE, 0xEE, 0xEE, 0xFF];
+const LINE_HEIGHT: f32 = 16.0;
+const INDENT: f32 = 16.0;
+const PADDING: f32 = 4.0;
+
+/// Count total nodes in subtree (including self).
+pub fn count_entity_nodes(world: &World, entity: Entity) -> usize {
+    let mut count = 1;
+    if let Some(children) = world.get::<Children>(entity) {
+        for &child in &children.0 {
+            count += count_entity_nodes(world, child);
+        }
+    }
+    count
+}
+
+/// Draw a single entity row, then recurse into children.
+fn draw_entity_node(
+    ui: &mut UiContext,
+    world: &World,
+    entity: Entity,
+    depth: usize,
+    selected: &mut Option<Entity>,
+    base_x: f32,
+    row_w: f32,
+) {
+    let y = ui.layout.cursor_y;
+    let x = base_x + PADDING + depth as f32 * INDENT;
+
+    // Highlight selected
+    if *selected == Some(entity) {
+        ui.draw_list.add_rect(base_x, y, row_w, LINE_HEIGHT, COLOR_SELECTED);
+    }
+
+    // Click detection
+    if ui.mouse_clicked && ui.mouse_in_rect(base_x, y, row_w, LINE_HEIGHT) {
+        *selected = Some(entity);
+    }
+
+    // Build label
+    let has_children = world.get::<Children>(entity).map_or(false, |c| !c.0.is_empty());
+    let prefix = if has_children { "> " } else { "  " };
+    let name = if let Some(tag) = world.get::<Tag>(entity) {
+        format!("{}{}", prefix, tag.0)
+    } else {
+        format!("{}Entity({})", prefix, entity.id)
+    };
+
+    // Draw text (inline glyph rendering)
+    let gw = ui.font.glyph_width as f32;
+    let gh = ui.font.glyph_height as f32;
+    let text_y = y + (LINE_HEIGHT - gh) * 0.5;
+    let mut cx = x;
+    for ch in name.chars() {
+        let (u0, v0, u1, v1) = ui.font.glyph_uv(ch);
+        ui.draw_list.add_rect_uv(cx, text_y, gw, gh, u0, v0, u1, v1, COLOR_TEXT);
+        cx += gw;
+    }
+
+    ui.layout.cursor_y += LINE_HEIGHT;
+
+    // Recurse children
+    if let Some(children) = world.get::<Children>(entity) {
+        let child_list: Vec<Entity> = children.0.clone();
+        for child in child_list {
+            draw_entity_node(ui, world, child, depth + 1, selected, base_x, row_w);
+        }
+    }
+}
+
+/// Hierarchy panel: displays entity tree, handles selection.
+pub fn hierarchy_panel(
+    ui: &mut UiContext,
+    world: &World,
+    selected: &mut Option<Entity>,
+    rect: &Rect,
+) {
+    ui.layout = LayoutState::new(rect.x + PADDING, rect.y + PADDING);
+    let root_entities = roots(world);
+    for &entity in &root_entities {
+        draw_entity_node(ui, world, entity, 0, selected, rect.x, rect.w);
+    }
+}
+
+/// Inspector panel stub (implemented in next task).
+pub fn inspector_panel(
+    ui: &mut UiContext,
+    _world: &mut World,
+    _selected: Option<Entity>,
+    rect: &Rect,
+    _tag_buffer: &mut String,
+) {
+    ui.layout = LayoutState::new(rect.x + PADDING, rect.y + PADDING);
+    ui.text("Inspector (TODO)");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use voltex_ecs::transform::Transform;
+    use voltex_math::Vec3;
+
+    fn make_test_world() -> (World, Entity, Entity, Entity) {
+        let mut world = World::new();
+        let e1 = world.spawn();
+        world.add(e1, Transform::from_position(Vec3::new(0.0, 0.0, 0.0)));
+        world.add(e1, Tag("Root".to_string()));
+
+        let e2 = world.spawn();
+        world.add(e2, Transform::from_position(Vec3::new(1.0, 0.0, 0.0)));
+        world.add(e2, Tag("Child1".to_string()));
+
+        let e3 = world.spawn();
+        world.add(e3, Transform::from_position(Vec3::new(2.0, 0.0, 0.0)));
+        world.add(e3, Tag("Child2".to_string()));
+
+        voltex_ecs::hierarchy::add_child(&mut world, e1, e2);
+        voltex_ecs::hierarchy::add_child(&mut world, e1, e3);
+
+        (world, e1, e2, e3)
+    }
+
+    #[test]
+    fn test_count_nodes() {
+        let (world, e1, _, _) = make_test_world();
+        assert_eq!(count_entity_nodes(&world, e1), 3);
+    }
+
+    #[test]
+    fn test_hierarchy_draws_commands() {
+        let (world, _, _, _) = make_test_world();
+        let mut ui = UiContext::new(800.0, 600.0);
+        let mut selected: Option<Entity> = None;
+        let rect = Rect { x: 0.0, y: 0.0, w: 200.0, h: 400.0 };
+
+        ui.begin_frame(0.0, 0.0, false);
+        hierarchy_panel(&mut ui, &world, &mut selected, &rect);
+        ui.end_frame();
+
+        assert!(ui.draw_list.commands.len() > 0);
+    }
+
+    #[test]
+    fn test_hierarchy_click_selects() {
+        let (world, e1, _, _) = make_test_world();
+        let mut ui = UiContext::new(800.0, 600.0);
+        let mut selected: Option<Entity> = None;
+        let rect = Rect { x: 0.0, y: 0.0, w: 200.0, h: 400.0 };
+
+        // Click on first row (y = PADDING + small offset)
+        ui.begin_frame(50.0, PADDING + 2.0, true);
+        hierarchy_panel(&mut ui, &world, &mut selected, &rect);
+        ui.end_frame();
+
+        assert_eq!(selected, Some(e1));
+    }
+
+    #[test]
+    fn test_hierarchy_empty_world() {
+        let world = World::new();
+        let mut ui = UiContext::new(800.0, 600.0);
+        let mut selected: Option<Entity> = None;
+        let rect = Rect { x: 0.0, y: 0.0, w: 200.0, h: 400.0 };
+
+        ui.begin_frame(0.0, 0.0, false);
+        hierarchy_panel(&mut ui, &world, &mut selected, &rect);
+        ui.end_frame();
+
+        assert!(selected.is_none());
+    }
+}

crates/voltex_editor/src/lib.rs

@@ -5,6 +5,7 @@ pub mod renderer;
 pub mod ui_context;
 pub mod widgets;
 pub mod dock;
+pub mod inspector;
 pub mod orbit_camera;
 
 pub use font::FontAtlas;
@@ -13,6 +14,7 @@ pub use layout::LayoutState;
 pub use renderer::UiRenderer;
 pub use ui_context::UiContext;
 pub use dock::{DockTree, DockNode, Axis, Rect, LeafLayout};
+pub use inspector::{hierarchy_panel, inspector_panel};
 pub use orbit_camera::OrbitCamera;
 
 pub mod viewport_texture;