Pointer

lib/ui/examples/explicit_ui_prototype.rs

@@ -68,6 +68,17 @@ fn log_platform_event(event: &PlatformEvent) {
         PlatformEvent::Closed { window_id } => {
             tracing::info!(event = "window_closed", window_id = window_id.raw());
         }
+        PlatformEvent::Pointer { window_id, event } => {
+            tracing::debug!(
+                event = "pointer_event",
+                window_id = window_id.raw(),
+                pointer_id = event.pointer_id,
+                x = event.position.x,
+                y = event.position.y,
+                ?event.kind,
+                "pointer event received"
+            );
+        }
         PlatformEvent::CloseRequested { window_id } => {
             tracing::info!(
                 event = "close_requested",

lib/ui/src/interaction.rs

@@ -0,0 +1,226 @@
+use crate::layout::{HitTarget, InteractionTree};
+use crate::scene::Point;
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum PointerButton {
+    Primary,
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum PointerEventKind {
+    Move,
+    Down { button: PointerButton },
+    Up { button: PointerButton },
+    LeaveWindow,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct PointerEvent {
+    pub pointer_id: u32,
+    pub position: Point,
+    pub kind: PointerEventKind,
+}
+
+impl PointerEvent {
+    pub const fn new(pointer_id: u32, position: Point, kind: PointerEventKind) -> Self {
+        Self {
+            pointer_id,
+            position,
+            kind,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum RoutedPointerEventKind {
+    Enter,
+    Leave,
+    Move,
+    Down { button: PointerButton },
+    Up { button: PointerButton },
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct RoutedPointerEvent {
+    pub kind: RoutedPointerEventKind,
+    pub target: HitTarget,
+    pub pointer_id: u32,
+    pub position: Point,
+}
+
+#[derive(Default)]
+pub struct PointerRouter {
+    hovered: Option<HitTarget>,
+    pressed: Option<HitTarget>,
+}
+
+impl PointerRouter {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn hovered_target(&self) -> Option<&HitTarget> {
+        self.hovered.as_ref()
+    }
+
+    pub fn pressed_target(&self) -> Option<&HitTarget> {
+        self.pressed.as_ref()
+    }
+
+    pub fn route(
+        &mut self,
+        interaction_tree: &InteractionTree,
+        event: PointerEvent,
+    ) -> Vec<RoutedPointerEvent> {
+        let hit_target = match event.kind {
+            PointerEventKind::LeaveWindow => None,
+            _ => interaction_tree.hit_test(event.position),
+        };
+
+        let mut routed = Vec::new();
+        if self.hovered != hit_target {
+            if let Some(previous) = self.hovered.take() {
+                routed.push(RoutedPointerEvent {
+                    kind: RoutedPointerEventKind::Leave,
+                    target: previous,
+                    pointer_id: event.pointer_id,
+                    position: event.position,
+                });
+            }
+            if let Some(target) = hit_target.clone() {
+                routed.push(RoutedPointerEvent {
+                    kind: RoutedPointerEventKind::Enter,
+                    target: target.clone(),
+                    pointer_id: event.pointer_id,
+                    position: event.position,
+                });
+                self.hovered = Some(target);
+            }
+        }
+
+        match event.kind {
+            PointerEventKind::Move => {
+                if let Some(target) = hit_target {
+                    routed.push(RoutedPointerEvent {
+                        kind: RoutedPointerEventKind::Move,
+                        target,
+                        pointer_id: event.pointer_id,
+                        position: event.position,
+                    });
+                }
+            }
+            PointerEventKind::Down { button } => {
+                if let Some(target) = hit_target {
+                    self.pressed = Some(target.clone());
+                    routed.push(RoutedPointerEvent {
+                        kind: RoutedPointerEventKind::Down { button },
+                        target,
+                        pointer_id: event.pointer_id,
+                        position: event.position,
+                    });
+                }
+            }
+            PointerEventKind::Up { button } => {
+                if let Some(target) = self.pressed.take().or(hit_target) {
+                    routed.push(RoutedPointerEvent {
+                        kind: RoutedPointerEventKind::Up { button },
+                        target,
+                        pointer_id: event.pointer_id,
+                        position: event.position,
+                    });
+                }
+            }
+            PointerEventKind::LeaveWindow => {}
+        }
+
+        routed
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        PointerButton, PointerEvent, PointerEventKind, PointerRouter, RoutedPointerEventKind,
+    };
+    use crate::layout::{InteractionTree, LayoutNode, LayoutPath};
+    use crate::scene::{Point, Rect};
+    use crate::tree::ElementId;
+
+    fn interaction_tree() -> InteractionTree {
+        InteractionTree {
+            root: LayoutNode {
+                path: LayoutPath::root(),
+                element_id: None,
+                rect: Rect::new(0.0, 0.0, 200.0, 120.0),
+                pointer_events: false,
+                children: vec![
+                    LayoutNode {
+                        path: LayoutPath::root().child(0),
+                        element_id: Some(ElementId::new(1)),
+                        rect: Rect::new(0.0, 0.0, 120.0, 120.0),
+                        pointer_events: true,
+                        children: Vec::new(),
+                    },
+                    LayoutNode {
+                        path: LayoutPath::root().child(1),
+                        element_id: Some(ElementId::new(2)),
+                        rect: Rect::new(80.0, 0.0, 120.0, 120.0),
+                        pointer_events: true,
+                        children: Vec::new(),
+                    },
+                ],
+            },
+        }
+    }
+
+    #[test]
+    fn router_emits_enter_and_move_for_new_hover_target() {
+        let mut router = PointerRouter::new();
+        let routed = router.route(
+            &interaction_tree(),
+            PointerEvent::new(0, Point::new(20.0, 20.0), PointerEventKind::Move),
+        );
+
+        assert_eq!(routed.len(), 2);
+        assert_eq!(routed[0].kind, RoutedPointerEventKind::Enter);
+        assert_eq!(routed[1].kind, RoutedPointerEventKind::Move);
+        assert_eq!(routed[1].target.element_id, Some(ElementId::new(1)));
+    }
+
+    #[test]
+    fn router_prefers_pressed_target_on_pointer_up() {
+        let mut router = PointerRouter::new();
+        let tree = interaction_tree();
+        let _ = router.route(
+            &tree,
+            PointerEvent::new(
+                0,
+                Point::new(20.0, 20.0),
+                PointerEventKind::Down {
+                    button: PointerButton::Primary,
+                },
+            ),
+        );
+        let routed = router.route(
+            &tree,
+            PointerEvent::new(
+                0,
+                Point::new(160.0, 20.0),
+                PointerEventKind::Up {
+                    button: PointerButton::Primary,
+                },
+            ),
+        );
+
+        assert!(routed.iter().any(|event| matches!(
+            event.kind,
+            RoutedPointerEventKind::Up {
+                button: PointerButton::Primary
+            }
+        )));
+        assert_eq!(
+            routed.last().unwrap().target.element_id,
+            Some(ElementId::new(1))
+        );
+    }
+}

lib/ui/src/layout.rs

@@ -1,6 +1,6 @@
 use crate::scene::{Rect, SceneSnapshot, UiSize};
 use crate::text::TextSystem;
-use crate::tree::{Edges, Element, FlexDirection};
+use crate::tree::{Edges, Element, ElementId, FlexDirection};
 
 pub fn layout_scene(version: u64, logical_size: UiSize, root: &Element) -> SceneSnapshot {
     let mut text_system = TextSystem::new();
@@ -13,8 +13,74 @@ pub fn layout_scene_with_text_system(
     root: &Element,
     text_system: &mut TextSystem,
 ) -> SceneSnapshot {
+    layout_snapshot_with_text_system(version, logical_size, root, text_system).scene
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct LayoutSnapshot {
+    pub scene: SceneSnapshot,
+    pub interaction_tree: InteractionTree,
+}
+
+#[derive(Clone, Debug, Eq, Hash, PartialEq)]
+pub struct LayoutPath(Vec<u32>);
+
+impl LayoutPath {
+    pub fn root() -> Self {
+        Self(Vec::new())
+    }
+
+    pub fn segments(&self) -> &[u32] {
+        &self.0
+    }
+
+    pub(crate) fn child(&self, index: usize) -> Self {
+        let mut segments = self.0.clone();
+        segments.push(index as u32);
+        Self(segments)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct HitTarget {
+    pub path: LayoutPath,
+    pub element_id: Option<ElementId>,
+    pub rect: Rect,
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct LayoutNode {
+    pub path: LayoutPath,
+    pub element_id: Option<ElementId>,
+    pub rect: Rect,
+    pub pointer_events: bool,
+    pub children: Vec<LayoutNode>,
+}
+
+#[derive(Clone, Debug, PartialEq)]
+pub struct InteractionTree {
+    pub root: LayoutNode,
+}
+
+impl InteractionTree {
+    pub fn hit_test(&self, point: crate::scene::Point) -> Option<HitTarget> {
+        hit_test_node(&self.root, point)
+    }
+}
+
+pub fn layout_snapshot(version: u64, logical_size: UiSize, root: &Element) -> LayoutSnapshot {
+    let mut text_system = TextSystem::new();
+    layout_snapshot_with_text_system(version, logical_size, root, &mut text_system)
+}
+
+pub fn layout_snapshot_with_text_system(
+    version: u64,
+    logical_size: UiSize,
+    root: &Element,
+    text_system: &mut TextSystem,
+) -> LayoutSnapshot {
     let mut scene = SceneSnapshot::new(version, logical_size);
-    layout_element(
+    let interaction_root = layout_element(
         root,
         Rect::new(
             0.0,
@@ -22,20 +88,35 @@ pub fn layout_scene_with_text_system(
             logical_size.width.max(0.0),
             logical_size.height.max(0.0),
         ),
+        LayoutPath::root(),
         &mut scene,
         text_system,
     );
-    scene
+    LayoutSnapshot {
+        scene,
+        interaction_tree: InteractionTree {
+            root: interaction_root,
+        },
+    }
 }
 
 fn layout_element(
     element: &Element,
     rect: Rect,
+    path: LayoutPath,
     scene: &mut SceneSnapshot,
     text_system: &mut TextSystem,
-) {
+) -> LayoutNode {
+    let mut interaction = LayoutNode {
+        path,
+        element_id: element.id,
+        rect,
+        pointer_events: element.style.pointer_events,
+        children: Vec::new(),
+    };
+
     if rect.size.width <= 0.0 || rect.size.height <= 0.0 {
-        return;
+        return interaction;
     }
 
     if let Some(color) = element.style.background {
@@ -51,16 +132,16 @@ fn layout_element(
                 text.style.clone().with_bounds(content.size),
             ));
         }
-        return;
+        return interaction;
     }
 
     if element.children.is_empty() {
-        return;
+        return interaction;
     }
 
     let content = inset_rect(rect, element.style.padding);
     if content.size.width <= 0.0 || content.size.height <= 0.0 {
-        return;
+        return interaction;
     }
 
     let gap_count = element.children.len().saturating_sub(1) as f32;
@@ -107,7 +188,7 @@ fn layout_element(
     let remaining_main = (available_main - fixed_total).max(0.0);
     let mut cursor = main_axis_origin(content, element.style.direction);
 
-    for (child, measured) in element.children.iter().zip(measured_children) {
+    for (index, (child, measured)) in element.children.iter().zip(measured_children).enumerate() {
         let child_main = if measured.is_flex {
             if flex_total <= 0.0 {
                 0.0
@@ -124,9 +205,39 @@ fn layout_element(
             child_main.max(0.0),
             measured.cross,
         );
-        layout_element(child, child_rect, scene, text_system);
+        interaction.children.push(layout_element(
+            child,
+            child_rect,
+            interaction.path.child(index),
+            scene,
+            text_system,
+        ));
         cursor += child_main.max(0.0) + element.style.gap;
     }
+
+    interaction
+}
+
+fn hit_test_node(node: &LayoutNode, point: crate::scene::Point) -> Option<HitTarget> {
+    if !node.rect.contains(point) {
+        return None;
+    }
+
+    for child in node.children.iter().rev() {
+        if let Some(hit) = hit_test_node(child, point) {
+            return Some(hit);
+        }
+    }
+
+    if node.pointer_events {
+        return Some(HitTarget {
+            path: node.path.clone(),
+            element_id: node.element_id,
+            rect: node.rect,
+        });
+    }
+
+    None
 }
 
 #[derive(Clone, Copy, Debug)]
@@ -337,10 +448,10 @@ fn child_rect(
 
 #[cfg(test)]
 mod tests {
-    use super::layout_scene;
-    use crate::scene::{Color, DisplayItem, Quad, Rect, UiSize};
+    use super::{layout_scene, layout_snapshot};
+    use crate::scene::{Color, DisplayItem, Point, Quad, Rect, UiSize};
     use crate::text::{TextStyle, TextWrap};
-    use crate::tree::{Edges, Element};
+    use crate::tree::{Edges, Element, ElementId};
 
     #[test]
     fn row_layout_apportions_fixed_and_flex_children() {
@@ -464,4 +575,54 @@ mod tests {
                 .any(|item| matches!(item, DisplayItem::Text(_)))
         );
     }
+
+    #[test]
+    fn interaction_tree_hit_test_returns_deepest_pointer_target() {
+        let root = Element::column()
+            .id(ElementId::new(1))
+            .children([Element::new()
+                .id(ElementId::new(2))
+                .height(80.0)
+                .background(Color::rgb(0x22, 0x33, 0x44))
+                .child(
+                    Element::new()
+                        .id(ElementId::new(3))
+                        .width(120.0)
+                        .height(40.0)
+                        .background(Color::rgb(0x44, 0x55, 0x66)),
+                )]);
+
+        let snapshot = layout_snapshot(1, UiSize::new(320.0, 200.0), &root);
+        let hit = snapshot
+            .interaction_tree
+            .hit_test(Point::new(20.0, 20.0))
+            .expect("point should hit nested child");
+        assert_eq!(hit.element_id, Some(ElementId::new(3)));
+        assert_eq!(hit.path.segments(), &[0, 0]);
+    }
+
+    #[test]
+    fn interaction_tree_skips_pointer_disabled_node_and_falls_back_to_parent() {
+        let root = Element::column().id(ElementId::new(1)).child(
+            Element::new()
+                .id(ElementId::new(2))
+                .height(80.0)
+                .background(Color::rgb(0x22, 0x33, 0x44))
+                .child(
+                    Element::new()
+                        .id(ElementId::new(3))
+                        .width(120.0)
+                        .height(40.0)
+                        .pointer_events(false)
+                        .background(Color::rgb(0x44, 0x55, 0x66)),
+                ),
+        );
+
+        let snapshot = layout_snapshot(1, UiSize::new(320.0, 200.0), &root);
+        let hit = snapshot
+            .interaction_tree
+            .hit_test(Point::new(20.0, 20.0))
+            .expect("point should still hit parent");
+        assert_eq!(hit.element_id, Some(ElementId::new(2)));
+    }
 }

lib/ui/src/lib.rs

@@ -10,6 +10,7 @@ pub(crate) mod trace_targets {
     pub const SCENE: &str = "ruin_ui::scene";
 }
 
+mod interaction;
 mod layout;
 mod platform;
 mod runtime;
@@ -18,6 +19,14 @@ mod text;
 mod tree;
 mod window;
 
+pub use interaction::{
+    PointerButton, PointerEvent, PointerEventKind, PointerRouter, RoutedPointerEvent,
+    RoutedPointerEventKind,
+};
+pub use layout::{
+    HitTarget, InteractionTree, LayoutNode, LayoutPath, LayoutSnapshot, layout_snapshot,
+    layout_snapshot_with_text_system,
+};
 pub use layout::{layout_scene, layout_scene_with_text_system};
 pub use platform::{PlatformClosed, PlatformEvent, PlatformProxy, PlatformRuntime, start_headless};
 pub use runtime::{EventStreamClosed, UiRuntime, WindowController};
@@ -29,7 +38,7 @@ pub use text::{
     TextAlign, TextFontFamily, TextSpan, TextSpanSlant, TextSpanWeight, TextStyle, TextSystem,
     TextWrap,
 };
-pub use tree::{Edges, Element, FlexDirection, Style};
+pub use tree::{Edges, Element, ElementId, FlexDirection, Style};
 pub use window::{
     DecorationMode, WindowConfigured, WindowId, WindowLifecycle, WindowSpec, WindowUpdate,
 };

lib/ui/src/platform.rs

@@ -11,6 +11,7 @@ use ruin_runtime::channel::mpsc;
 use ruin_runtime::{WorkerHandle, queue_future, queue_microtask, spawn_worker};
 use tracing::{debug, info};
 
+use crate::interaction::PointerEvent;
 use crate::scene::{SceneSnapshot, UiSize};
 use crate::trace_targets;
 use crate::window::{WindowConfigured, WindowId, WindowLifecycle, WindowSpec, WindowUpdate};
@@ -53,6 +54,10 @@ pub enum PlatformEvent {
         scene_version: u64,
         item_count: usize,
     },
+    Pointer {
+        window_id: WindowId,
+        event: PointerEvent,
+    },
     CloseRequested {
         window_id: WindowId,
     },

lib/ui/src/scene.rs

@@ -44,6 +44,13 @@ impl Rect {
             size: UiSize::new(width, height),
         }
     }
+
+    pub fn contains(self, point: Point) -> bool {
+        point.x >= self.origin.x
+            && point.y >= self.origin.y
+            && point.x < self.origin.x + self.size.width
+            && point.y < self.origin.y + self.size.height
+    }
 }
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]

lib/ui/src/tree.rs

@@ -1,6 +1,19 @@
 use crate::scene::Color;
 use crate::text::{TextSpan, TextStyle, TextWrap};
 
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+pub struct ElementId(u64);
+
+impl ElementId {
+    pub const fn new(raw: u64) -> Self {
+        Self(raw)
+    }
+
+    pub const fn raw(self) -> u64 {
+        self.0
+    }
+}
+
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 pub enum FlexDirection {
     Row,
@@ -51,6 +64,7 @@ pub struct Style {
     pub gap: f32,
     pub padding: Edges,
     pub background: Option<Color>,
+    pub pointer_events: bool,
 }
 
 impl Default for Style {
@@ -63,6 +77,7 @@ impl Default for Style {
             gap: 0.0,
             padding: Edges::ZERO,
             background: None,
+            pointer_events: true,
         }
     }
 }
@@ -81,6 +96,7 @@ pub(crate) struct TextNode {
 
 #[derive(Clone, Debug, PartialEq)]
 pub struct Element {
+    pub id: Option<ElementId>,
     pub style: Style,
     pub children: Vec<Element>,
     content: ElementContent,
@@ -89,6 +105,7 @@ pub struct Element {
 impl Element {
     pub fn new() -> Self {
         Self {
+            id: None,
             style: Style::default(),
             children: Vec::new(),
             content: ElementContent::Container,
@@ -101,6 +118,7 @@ impl Element {
 
     pub fn spans(spans: impl IntoIterator<Item = TextSpan>, style: TextStyle) -> Self {
         Self {
+            id: None,
             style: Style::default(),
             children: Vec::new(),
             content: ElementContent::Text(TextNode {
@@ -161,6 +179,16 @@ impl Element {
         self
     }
 
+    pub fn id(mut self, id: ElementId) -> Self {
+        self.id = Some(id);
+        self
+    }
+
+    pub fn pointer_events(mut self, pointer_events: bool) -> Self {
+        self.style.pointer_events = pointer_events;
+        self
+    }
+
     pub fn child(mut self, child: Element) -> Self {
         self.assert_container();
         self.children.push(child);