Identify Unhandled ANSI Control Sequences

Description

Will return position and types of unhandled Control Sequences in a character vector. Unhandled sequences may cause fansi to interpret strings in a way different to your display. See fansi for details.

Usage

unhandled_ctl(x)

Arguments

Details

This is a debugging function that is not optimized for speed.

The return value is a data frame with five columns:

• index: integer the index in x with the unhandled sequence

• start: integer the start position of the sequence (in characters)

• stop: integer the end of the sequence (in characters), but note that if there are multiple ESC sequences abutting each other they will all be treated as one, even if some of those sequences are valid.

• error: the reason why the sequence was not handled:

  • exceed-term-cap: contains color codes not supported by the terminal (see term_cap_test).

  • special: SGR substring contains uncommon characters in ":<=>".

  • unknown: SGR substring with a value that does not correspond to a known SGR code.

  • non-SGR: a non-SGR CSI sequence.

  • non-CSI: a non-CSI escape sequence, i.e. one where the ESC is followed by something other than "[". Since we assume all non-CSI sequences are only 2 characters long include the ESC, this type of sequence is the most likely to cause problems as many are not actually two characters long.

  • malformed-CSI: a malformed CSI sequence.

  • malformed-ESC: a malformed ESC sequence (i.e. one not ending in 0x40-0x7e).

  • C0: a "C0" control character (e.g. tab, bell, etc.).

• translated: whether the string was translated to UTF-8, might be helpful in odd cases were character offsets change depending on encoding. You should only worry about this if you cannot tie out the start/stop values to the escape sequence shown.

• esc: character the unhandled escape sequence

Value

data frame with as many rows as there are unhandled escape sequences and columns containing useful information for debugging the problem. See details.

Note

Non-ASCII strings are converted to UTF-8 encoding.

See Also

fansi for details on how Control Sequences are interpreted, particularly if you are getting unexpected results.

Examples

string <- c(
  "\033[41mhello world\033[m", "foo\033[22>m", "\033[999mbar",
  "baz \033[31#3m", "a\033[31k", "hello\033m world"
)
unhandled_ctl(string)