Struct FrameWidget 

pub struct FrameWidget { /* private fields */ }

The engine’s entry point for a single rendering context.

Responsibilities

• Owns the Document (DOM tree)
• Owns the Viewport (dimensions, scale factor)
• Owns the EventHandler (input → DOM events)
• Owns the scroll subsystems (ScrollTree, ScrollOffsets)
• Runs the lifecycle pipeline: style → layout → paint

Chrome mapping

Chrome	Kozan
WebFrameWidgetImpl	Platform bridge (input, resize)
LocalFrameView	Lifecycle orchestration
DocumentLifecycle	LifecycleState + DirtyPhases
LayoutView	Document root (layout via DocumentLayoutView)

Usage (from platform)

let mut widget = FrameWidget::new();
widget.resize(1920, 1080);

// User builds DOM
let doc = widget.document_mut();

// Event loop (called from Scheduler::tick render callback)
widget.handle_input(input_event);
widget.update_lifecycle();

// Read paint result
if let Some(dl) = widget.last_display_list() {
    // send to renderer
}

Implementations

impl FrameWidget

pub fn new() -> Self

pub fn document(&self) -> &Document

pub fn document_mut(&mut self) -> &mut Document

pub fn font_system(&self) -> &FontSystem

pub fn viewport(&self) -> &Viewport

pub fn last_fragment(&self) -> Option<&Arc<Fragment>>

pub fn lifecycle(&self) -> LifecycleState

pub fn handle_input(&mut self, event: InputEvent) -> bool

Handle an input event.

Performs hit testing against the last fragment tree, dispatches DOM events, and applies scroll actions via the scroll controller. Returns true if visual state changed (DOM mutation or scroll).

Chrome: WebFrameWidgetImpl::HandleInputEvent().

pub fn apply_compositor_scroll(&mut self, offsets: &ScrollOffsets)

Apply scroll offsets received from the compositor.

Called at the start of each frame on the view thread so the next paint uses the compositor’s authoritative scroll positions.

pub fn update_lifecycle(&mut self)

Run the rendering lifecycle pipeline.

Chrome: LocalFrameView::UpdateLifecyclePhases().

Phases: style recalc → layout → paint. DirtyPhases controls which phases actually run — scroll only invalidates paint, so style+layout are skipped at 60fps during scroll.

pub fn last_display_list(&self) -> Option<Arc<DisplayList>>

The last paint result. The Arc is cloned cheaply — no copy of the list.

pub fn take_layer_tree(&mut self) -> Option<LayerTree>

Take the layer tree for commit to the compositor.

pub fn scroll_state_snapshot(&self) -> (ScrollTree, ScrollOffsets)

Clone scroll state for the compositor. Cheap: typically 1-5 nodes × 40 bytes.

pub fn resize(&mut self, width: u32, height: u32)

Update the viewport dimensions (physical pixels).

pub fn set_scale_factor(&mut self, factor: f64)

pub fn mark_needs_update(&mut self)

Force the lifecycle to re-run on the next update_lifecycle() call.

Called by the platform when the scheduler’s frame callback fires, because set_needs_frame() means something changed that requires a new frame.

pub fn last_timing(&self) -> FrameTiming

pub fn set_focus(&mut self, _focused: bool)

Trait Implementations

impl Default for FrameWidget

fn default() -> Self

Returns the “default value” for a type.