HistoryFilter

Predicate to check if either we're searching for a term or if we're in history-browsing mode and some predicate is true.

Very often we want to capture keystrokes in search-mode more aggressively than in history-mode, e.g. search-mode drops you out more aggressively than history-mode does, and its up/down keys cycle through history more aggressively on every keystroke while history-mode only cycles when you reach the top/bottom line of the multi-line input.

Kicks the HistoryFilter from passive-mode into search-history mode

the .toString of this object, except by making it separate we force the implementer to provide something and stop them from accidentally leaving it as the meaningless default.

Returns a string representation of the object.

The default representation is platform dependent.

-1 means we haven't started looking at history, n >= 0 means we're currently at history command n

Records the last buffer that the filter has observed while it's in search/history mode. If the new buffer differs from this, assume that some other filter modified the buffer and drop out of search/history

The term we're searching for, if any.

• None means we're not searching for anything, e.g. we're just browsing history

• Some(term) where term is not empty is what it normally looks like when we're searching for something

• Some(term) where term is empty only really happens when you start searching and delete things, or if you Ctrl-R on an empty prompt