Bug#2558: HP-4m handling not robust enough for shared environment

[hpa@zytor.com (H. Peter Anvin)]

>
> The distributed magic filter for the HP-4m laserjet isn't robust
> enough for a shared environment.  It is susceptable to any transient
> configuration from previous print jobs, and it may leave the printer
> in a non-default state for the next print job.  Both of these can
> result in corrupted jobs for someone.
>
> This is particularly noticable when job types are mixed.
>
> The HP-4m defines the sequence ESC % - 1 2 3 4 5 X as the "universal
> exit language" sequence.  This can be used to solve all these problems
> (including situations where the print job switches languages before
> completing).
>
> Here's how I've patched my copy of this filter.  Basically, I've
> bracketted all output with this sequence [it doesn't hurt to send it
> several times in a row].  I haven't tested all the permutations, but
> it works for the obvious cases.
>

This would be better handled by extending magicfilter to include a
prefix/suffix sequence ability.  magicfilter-1.2 (released today) does
not contain such a facility, but I will probably add one in the next
release.

	-hpa

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