StringFieldHandle

Description#

Only the operations a field's type actually supports are declared, so pane::active.starts_with(...) is a compile error rather than a runtime surprise.

A handle also reads a row, so the same name serves as a ranges projection — and a flag handle as a predicate — rather than a lambda that spells the accessor a second time. sort(panes, {}, pane::index) then orders by the number tmux rendered, where projecting the text puts %10 before %9.