flatten

Returns a sequence that does a depth-first preorder traversal of the entire widget tree whose roots are this list. This is the same order elements occur in code.

For example, given the following structure:

Column {
  Toolbar {
    Icon(...)
    Title(...)
  }
  Row {
    Text(...)
    Button(...)
  }
}

The flattened elements are returned in this order:

Column,
Toolbar,
Icon,
Title,
Row,
Text,
Button