One or more progression handlers. Alternatively, this
functions accepts also a single vector of progression handlers as input.
If this vector is empty, then an empty set of progression handlers will
be set.
append
(logical) If FALSE, the specified progression handlers
replace the current ones, otherwise appended to them.
on_missing
(character) If "error", an error is thrown if one of
the progression handlers does not exists. If "warning", a warning
is produces and the missing handlers is ignored. If "ignore", the
missing handlers is ignored.
default
The default progression calling handler to use if none
are set.
Value
(invisibly) the previous list of progression handlers set.
If no arguments are specified, then the current set of progression
handlers is returned.
Details
This function provides a convenient alternative for getting and setting
option progressr.handlers.
IMPORTANT: Setting progression handlers is a privilege that should be
left to the end user. It should not be used by R packages, which only task
is to signal progress updates, not to decide if, when, and how progress
should be reported.