Delay in terminfo parameterized strings

Question

In the manpage of terminfo, it is mentioned that $<> in the encoding for specifying delay in ms , and within it's angular brackets is the a number with at most one decimal place of precision.

And with the following python script I confirmed that $< is only used for specifying delay ie there wasn't a parameterized string where $< had been used for not specifying delay.

#!/usr/bin/env python3
# './test/data/stressTestTerms.txt' contains contains terminal names
# and directory './test/data/mirror' contains terminal databases of 2718 terminals

import subprocess
import re


def check_dollar_angular(caps):
    string_caps = [cap for cap in caps.split(',') if '=' in cap]

    # search for $<..> type delays in string caps
    delay = r"\$<(\d+(\.(\d)+)?\*?/?|(\.(\d)+)?\*?/?)>"

    caps_with_dollar = 0
    delay_matches = 0

    for cap in string_caps:
        matches = list(re.finditer(delay, cap))
        dollar_idx = cap.find('$<')

        if dollar_idx != -1:
            caps_with_dollar += 1
            if any([True if match.start() == dollar_idx else False for match in matches]):
                delay_matches += 1

    if caps_with_dollar == delay_matches:
        return True
    else:
        return False


if __name__ == "__main__":

    with open('./test/data/stressTestTerms.txt') as terminal_names:
        res = []

        for each_terminal in terminal_names:
            output = subprocess.run(
                ['infocmp', '-0', '-A', './test/data/mirror', each_terminal.strip()], stdout=subprocess.PIPE)

            try:
                output.check_returncode()
                caps = output.stdout.decode('utf-8')

                res.append(check_dollar_angular(caps))

            except subprocess.CalledProcessError as e:
                print(e)

        if (not all(res)):
            print(
                "We have a terminal where in one of it's caps there is a dollar-angular but it doesn't signify delay")
        else:
            print(
                "Success! no terminal found where '$<' is used for anything else other than specifying delay")

So my question is, Whether $< be part of text/sequence and not represent a delay? Eg. can there be a case(now or in the future terminals) like: $<%p1%d or $<A , where there is no ending angular bracket and delay isn't meant to be specified using $< and still be valid terminfo sequence?

Answer 1

The manual page is pretty explicit about syntax:

   A  delay  in  milliseconds  may appear anywhere in a string capability,
   enclosed in $<..> brackets, as in el=\EK$<5>,  and  padding  characters
   are supplied by tputs(3x) to provide this delay.

   o   The delay must be a number with at most one decimal place of preci-
       sion; it may be followed by suffixes "*" or "/" or both.

   o   A "*" indicates that the padding required is  proportional  to  the
       number  of lines affected by the operation, and the amount given is
       the per-affected-unit padding required.  (In  the  case  of  insert
       character, the factor is still the number of lines affected.)

       Normally, padding is advisory if the device has the xon capability;
       it is used for cost computation but does not trigger delays.

   o   A "/" suffix indicates that the padding is mandatory and  forces  a
       delay of the given number of milliseconds even on devices for which
       xon is present to indicate flow control.

If there's no ending < , and the enclosed text is not a valid number (with possible * and/or / ), then tputs should not treat it as a delay.

There's no example with $< not followed by a digit or "." in ncurses's terminal database, but that does not mean it would be invalid , since the terminal database should be able to describe most strings (aside from the special case where \\200 (octal) is treated the same as \\0 to accommodate the C language's NUL-terminated strings.