HTS Horizontal Tabulation Set

Set a horizontal tab stop at the column the cursor is in. The cursor does not move, and the other tab stops are not affected. The next HT or CHT from left of that column stops there.

HTS is a C1 control. ECMA-48 defines it both as the single byte 88 and as ESC H, and the VT510 manual accepts either. libghostty-vt decodes its input as UTF-8, so it accepts only ESC H: a lone 88 byte is not valid UTF-8 and is printed as U+FFFD, the replacement character, and the code point U+0088 sent as UTF-8 is ignored.

TBC clears tab stops, one or all of them.

Validation

HTS-1: Set a stop

\e[?5W    # reset tab stops: 9 and 17
\e[1;5H
\eH
\e[1;1H
\tX

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HTS-2: The other stops stay

\e[?5W    # reset tab stops: 9 and 17
\e[1;5H
\eH
\e[1;1H
\t\tX     # 5, then 9

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HTS-3: After clearing every stop

\e[3g     # clear every tab stop
\e[1;12H
\eH
\e[1;1H
\tX

|___________X________|

HTS-4: The 8-bit form, sent as UTF-8

\e[3g      # clear every tab stop
\e[1;12H
\u{88}     # U+0088 is HTS in 8 bits; ignored
\e[1;1H
\tX        # no stop was set

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