Reactivity Module: `src/interpreter/reactive.rs`

Dependency tracking system between variables and VDOM elements. Allows recalculation of only changed elements (Phase 3).

`ElementId(u32)`

Unique element identifier in the VDOM tree. Assigned by ReactiveTracker::alloc_id() during template loading.

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ElementId(pub u32);

Used as:

Key in dirty_set: HashSet<ElementId>
Key in dependencies: HashMap<ElementId, HashSet<String>>
Field in Element::element_id (VDOM → tracker link)
Source for iced::widget::Id (Phase 9.2: format!("ti:{}", id.0))
Source for scrollable_id (el.element_id.0 as u64)

`ReactiveTracker`

Dependency graph: variable → list of elements that reference it.

pub struct ReactiveTracker {
    subscribers: HashMap<String, HashSet<ElementId>>,
    dependencies: HashMap<ElementId, HashSet<String>>,
    dirty_set: HashSet<ElementId>,
    next_id: u32,
}

Fields:

subscribers — for each variable: which ElementIds depend on it
dependencies — for each element: which variables it depends on (reverse mapping)
dirty_set — elements to recalculate in the next frame
next_id — counter for alloc_id()

Methods

Method	Description
`new()`	Empty tracker
`alloc_id() -> ElementId`	Allocate a new ID, increment counter
`add_dependency(element, var_name)`	Register a dependency
`scan_value(element, value)`	Scan a string for `$var` and add dependencies
`on_variable_changed(name)`	Mark all dependent elements as dirty
`take_dirty_set() -> HashSet<ElementId>`	Take dirty_set and clear it
`is_dirty(id) -> bool`	Check if an element is marked dirty
`reset()`	Clear all data

scan_value()

Parses a string for $var_name patterns:

"Hello $name, you are $age years old"
// → add_dependency(element, "name")
// → add_dependency(element, "age")

Used during template loading for each properties string containing $. As a result, each element knows which variables it depends on.

Update cycle

Event → update() → on_variable_changed("var")
  → dirty_set = {element_A, element_B, ...}
  → take_dirty_set() → evaluate_vdom_incr(roots, &dirty_set)
    → for dirty_set elements: recalculate
    → for others: return as-is

Tests

Test	What it checks
`test_basic_dependency_tracking`	Two elements, two variables, correct dirty_set
`test_scan_value`	Parse `$var` from a string
`test_scan_no_vars`	String without `$` creates no dependencies
`test_take_dirty_set`	`take_dirty_set()` clears the internal set
`test_reset`	`reset()` clears everything

2.7 KiB Raw Blame History

Reactivity Module: src/interpreter/reactive.rs

ElementId(u32)

ReactiveTracker