PuTTY semi-bug withdraw-decedm

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summary: Withdraw (wrong) implementation of DECEDM terminal escape sequence
class: semi-bug: This might or might not be a bug, depending on your precise definition of what a bug is.
difficulty: fun: Just needs tuits, and not many of them.
present-in: 7a79df8fe6285542ae2fdc0e3031929c30d7706f 0.52 0.53 0.53b 0.54 0.55 0.56 0.57 0.58 0.59 0.60 0.61 0.62 0.63 0.64 0.65 0.66 0.67 0.68 0.69 0.70 0.71
fixed-in: e3a14e1ad6844b8dd4d4e9bb179080d10d00e451 (0.72)

For a long time, PuTTY has interpreted the DECEDM mode of the SM/RM terminal escape sequences (ESC [ ?10 h/l) to affect whether the local line editing mode was in use.

As far as we can tell, that's not the original intended use of this sequence. It was specific to DEC terminals supporting "block mode", such as the VT132, and doesn't make a lot of sense without the rest of block mode. (The VT132 user guide p72 describes DECEDM, but isn't that informative; descriptions of "edit mode" elsewhere give some idea what effect it had.)

Also, no other terminal emulator we've come across implements this sequence.

Hence, support for DECEDM has been withdrawn from PuTTY.

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Audit trail for this semi-bug.
(last revision of this bug record was at 2020-12-02 19:15:26 +0000)