Events

lui has a typed DOM-style event system in lui-events, with dispatch in lui-tree.

Event Hierarchy

pub struct HtmlEvent {
    pub event_type: HtmlEventType,
    pub phase: EventPhase,
    pub target_path: Vec<usize>,
    pub current_target_path: Vec<usize>,
    pub bubbles: bool,
    pub cancelable: bool,
    pub default_prevented: bool,
    pub time_origin: Instant,
}

Event Types

Category	Event Types
Mouse	Click, DblClick, AuxClick, MouseDown, MouseUp, MouseMove, MouseEnter, MouseLeave, ContextMenu
Keyboard	KeyDown, KeyUp
Focus	Focus, Blur, FocusIn, FocusOut
Input	Input, BeforeInput, Change
Scroll	Scroll, Wheel
Form	Submit, Reset
Clipboard	Copy, Cut, Paste
Drag	DragStart, DragEnd, Drag, DragEnter, DragLeave, DragOver, Drop
Selection	Select, SelectionChange
Touch	TouchStart, TouchMove, TouchEnd, TouchCancel
Media	Load, Error, Abort, CanPlay

Event Phases

pub enum EventPhase {
    None,
    Capturing,  // root → target (not yet dispatched)
    AtTarget,   // on the target element
    Bubbling,   // target → root (dispatched on ancestors)
}

Bubbling

Mouse events (mousedown, mouseup, click, dblclick, contextmenu, auxclick), keyboard events, focus events, and most input events bubble up the tree. mouseenter and mouseleave do NOT bubble.

Click synthesis: mousedown + mouseup on the same element produces a click event via deepest-common-ancestor resolution. Drag-to-select suppresses click.

Callbacks

Per-node callbacks (on Node)

// Typed event callback — catches all event types
node.on_event.push(Arc::new(|e: &HtmlEvent| {
    match &e.event_type {
        HtmlEventType::Click(mouse_event) => { /* ... */ }
        _ => {}
    }
}));

// Legacy per-event-type callbacks
node.on_click.push(Arc::new(|e: &MouseEvent| { /* ... */ }));
node.on_keydown.push(Arc::new(|e: &HtmlEvent| { /* ... */ }));

Available per-type callback slots: on_click, on_mouse_down, on_mouse_up, on_mouse_move, on_mouse_enter, on_mouse_leave, on_dblclick, on_contextmenu, on_auxclick, on_dragstart, on_dragend, on_drop, on_drag, on_dragover, on_dragenter, on_dragleave, on_keydown, on_keyup, on_focus, on_blur, on_focusin, on_focusout, on_input, on_beforeinput, on_change, on_wheel, on_copy, on_cut, on_paste, on_scroll, on_select.

Tree hooks (global interception)

pub trait TreeHook {
    fn on_event(&mut self, tree: &mut Tree, event: &mut HtmlEvent) -> TreeHookResponse;
    fn on_keyboard_event(&mut self, tree: &mut Tree, event: &mut KeyboardEvent) -> TreeHookResponse;
    fn on_focus_event(&mut self, tree: &mut Tree, event: &mut FocusEvent) -> TreeHookResponse;
    // ... and more
}

Hooks can return TreeHookResponse::Continue or TreeHookResponse::Stop to control propagation.

Layout-Free Dispatch

When you have a hit-test path but not a LayoutBox, use the lui_tree::dispatch functions:

use lui_tree::dispatch;

dispatch_pointer_move(&mut tree, target_path, pos, Some(cursor));
dispatch_mouse_down(&mut tree, target_path, pos, button, Some(cursor));
dispatch_mouse_up(&mut tree, target_path, pos, button, Some(cursor));