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[TERMINFO BUG?] VT100 reset string ignores scrolling margins and VT52 mo

From: Rob King
Subject: [TERMINFO BUG?] VT100 reset string ignores scrolling margins and VT52 mode
Date: Fri, 10 Mar 2017 17:52:02 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0

The class "vt100|vt100-am" terminfo entry has as its rs2 sequence "rs2=\E>\E[?3l\E[?4l\E[?5l\E[?7h\E[?8h". This resets all of the various DEC private modes to their default values. This is the only reset string currently defined for the VT100.

This sequence does not appear to reset scrolling margins. As the top and bottom margins are settable via escape sequences, it is possible to get the terminal in a state where scrolling is invalid and not fixable via the reset utility.

The reset string likewise does not exit out of VT52 emulation mode, which is also something that is settable via software and therefore a place where a user could get "stuck" and beyond the reach of "reset".

I would recommend, if possible, updating the reset string to something like "\E<\Ec", which would exit VT52 emulation mode (if the terminal is in such a state) and then use the RIS (Reset to Initial State) sequence to completely reset the terminal state.

If this is not desirable due to the side-effects of the RIS sequence (which causes the POST to execute), perhaps the existing reset string could be modified to include "\E<\E[r", to get the terminal in ANSI mode and reset its scrolling margins. The "\E<" would need to be the first component of the reset string, since the following components would not be recognized in VT52 mode.

    Thank you.

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