[cups-devel] low level operation with PCL?

[Helge Blischke]

AFAIK, there is no PCL command to incrementally advance the paper, so your problem
seems to be unsolvable.

> Am 21.03.2015 um 15:45 schrieb Toomas Rosin <toomas at rosin.ee>:
> 
> Hello!
> 
> I know that PCL is a page description (not low-level) language, and so
> it is perhaps no surprise that I cannot do what I would like to.  But
> after an extensive search in the Internet and the PCL documentation, I
> have not yet found a definite negative answer either.  Here is my
> problem:
> 
> I cannot figure out how to make my printer (HP DeskJet 1280 on USB)
> show me everything I have sent to it so far, *without ejecting the
> page*.  I am sending only plain raster graphics and cursor positioning
> commands --- no vector graphics, no text.
> 
> It seems that the printer has an internal buffer to store the data,
> and that it flushes (i.e., prints out) that buffer after it has grown
> above some level.  And there seems to be no way to tell it to flush it
> immediately, without doing anything else.  Even "\033*rC" (End Raster
> Graphics) has no immediate effect.
> 
> I use CUPS' USB backend to communicate with the printer, and have
> verified (with usbmon) that the backend really sends all my data to
> the printer as soon as I give them to it, so it cannot be the issue of
> data getting stuck in software.
> 
> Commands that print out partial pages include "\033E" (Printer Reset),
> "\033%%-12345X" (Universal Exit Language), "\033&r1F" (Flush All Pages
> (including partial pages)) --- but all of them have the side-effect of
> ejecting the page.
> 
> What I would like to achieve is this: 1) After I have sent some raster
> data to the printer (with Transfer Raster Data ("\033*b%dW")), be able
> to make it print it out right away and stop, without ejecting the
> page.  2) After I send a vertical cursor positioning command (e.g.,
> Vertical Cursor Positioning (Decipoints) ("\033&a%+dV")), be able to
> make the printer advance the paper to the new position right away, and
> stop there.
> 
> Can somebody confirm my impression that what I want is an absolute
> impossibility, or perhaps suggest a clever way to do it?
> 
> Thanks in advance,
> T.
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