collapseLeading method

void collapseLeading()

Collapse the leading pane.

Implementation

void collapseLeading() {
  if (_isLeadingCollapsed) return;
  _savedRatio = _ratio ?? 0.5;
  _isLeadingCollapsed = true;
  _isTrailingCollapsed = false;
  _ratio = 0.0;
  _leadingExtent = 0.0;
  notifyListeners();
}