[Info-vax] DCL "READ/TIME_OUT=n" from terminal; timer resets if message written to screen

[Simon Clubley]

On 2021-05-22, Volker Halle <volker_halle at hotmail.com> wrote:
> Scott,
>
> this is expected and documented behaviour. It has nothing to do with DCL.
>
> https://vmssoftware.com/docs/VSI_IO_REF.pdf 
>
> Table 5.6. Read QIO Function Modifiers for the Terminal Driver
>
> IO$M_TIMED ... 
> If a read operation is interrupted by either a broadcast write or a synchronous write request, the timer operation is restarted.
>
> Volker.

What could the point of that behaviour possibly be ???

This sounds to me like someone added timeout support to the terminal driver,
found a bug where the timer gets reset on terminal writes, could not find
a way to easily fix it, so they ended up documenting the bug as expected
behaviour. :-)

If that wasn't the case, and this was actually intended behaviour, then
what could the reasoning for this behaviour possibly be ?

And before everyone jumps on me, just remember that we talking about
a driver that is apparently so convoluted internally that adding code
to allow editing of lines longer than the terminal width is apparently
not viable to do (even though you can do this just fine on other operating
systems).

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.