Re: Dynamic Paperlength for PS or PDF device

[Deri]

On Thursday, 8 December 2022 17:19:49 GMT G. Branden Robinson wrote:
> Hi Wim,
> 
> At 2022-12-08T15:51:07+0100, Wim Stockman wrote:
> > I am making a simple cash register with a ticket printer.  and I want
> > to figure out how I can detect how long my physical paper should be
> > without cutting some text off. So I can set it for the device. The
> > width is fixed so that is no issue.  Eventually I can run it in some
> > loop and detect when it stops having more than one page.
> 
> I reckon I would have a couple of macros that open and close a
> diversion, then measure against an argument that specifies the limit
> imposed by the hardware (i.e., length of paper roll remaining).
> 
> Here's a conceptual sketch.
> 
> .de StartTicket
> .  br
> .  di Ticket
> ..
> .
> .de EndTicket
> .  di
> ..
> .
> .while 1 \{\
> .  StartTicket
> .\" input for ticket text goes here
> .  EndTicket
> .  if (\n[dn] > \n[ticket-printer-paper-length]) \
> .    ab ticket too long for remaining paper; aborting
> .\}
> 
> Please clarify if I've overlooked a requirement.
> 
> Regards,
> Branden

I'm probably missing something here, but ticket printers are normally 
continuous rolls with a cutter, so isn't this a problem of controlling the 
cutter rather than specifying a media size. There is usually a printer option 
to cut after each print job, so if you make each receipt a separate print job, 
it should do the cutting for you. Just give groff a sufficiently long page 
length for the longest ticket you expect.

I have a Brother thermal printer which I use for labels, but it will take a 
continuous role instead, and I believe it has a proprietary EscP command for 
controlling the cutting, so there may be a solution using something similar.

Cheers 

Deri