updateResize method
Updates the brush during a resize.
Implementation
void updateResize(double position, double minBound, double maxBound) {
if (gestureStartExtent == null) return;
final clampedPosition = position.clamp(minBound, maxBound);
if (brushState == BrushState.resizingStart) {
extent = BrushExtent(clampedPosition, gestureStartExtent!.end);
} else {
extent = BrushExtent(gestureStartExtent!.start, clampedPosition);
}
widget.onBrush?.call(extent!);
setState(() {});
}