new_output_handler: Custom output handlers.

Description

An output_handler handles the results of evaluate, including the values, graphics, conditions. Each type of output is handled by a particular function in the handler object.

Usage

new_output_handler(source = identity, text = identity, graphics = identity, 
    message = identity, warning = identity, error = identity, value = render)

Arguments

source

Function to handle the echoed source code under evaluation.

text

Function to handle any textual console output.

graphics

Function to handle graphics, as returned by recordPlot.

message

Function to handle message output.

warning

Function to handle warning output.

error

Function to handle stop output.

value

Function to handle the values returned from evaluation. If it only has one argument, only visible values are handled; if it has more arguments, the second argument indicates whether the value is visible.

Value

A new output_handler object

Details

The handler functions should accept an output object as their first argument. The return value of the handlers is ignored, except in the case of the value handler, where a visible return value is saved in the output list.

Calling the constructor with no arguments results in the default handler, which mimics the behavior of the console by printing visible values.

Note that recursion is common: for example, if value does any printing, then the text or graphics handlers may be called.