everyFrame constant
WidgetUpdatePolicy
const everyFrame
Capture every frame while attached (the default). Captures are throttled to one in flight, and the recording itself reuses the child's retained layers, so the steady-state cost is the rasterize and readback of content that is actually changing.
Per-frame capture is the only trigger that observes every change: repaints inside the child's own repaint boundaries (scrollable items, progress indicators) update their layers in place without notifying ancestors, so a repaint-driven trigger misses them.
Implementation
static const WidgetUpdatePolicy everyFrame = _EveryFrameUpdatePolicy();