OpenPrinting Summit - Print Dialog and Colour Management

John Layt johnlayt at
Sun Mar 20 19:59:18 GMT 2011


Some very good points, some definately belong in the dialog, others belong in 
CUPS itself, but I'll take them all with me as everyone will be at the summit.

> - My biggest wish for a printing dialog is that the preview exactly matches
> the output. All current print dialogs that I know on linux have the problem
> that the output is not really predictible if one goes away from the
> default: printing A4 portrait to an A4 portrait printer.

This is actually a very hard thing to do, basically it would involve asking 
the print system (in our case CUPS) to process the print job right up to the 
point of sending it to the printer, then to give us back the processed job to 
use for the preview which would be close, but there's always a conversion 
process from the job format (was ps, soon to be pdf) into the printer format 
(e.g. PCL) as there's very few printers that speak ps or pdf natively.  So 
there's always a chance something will still not look right.  All this back-
and-forth of course adds overhead and slows the process down.  I know there's 
a wish for this in the CUPS bugzilla.

At the moment the CPD uses poppler to render the pdf print file as the 
preview, and then does manipulations on that pdf to simulate what CUPS would 
do.  I assume the filters it applies to the preview pdf are the same ones used 
in CUPS so it should be fairly close.

> - The choice of the output paper size and tray should be more prominent. I
> have one printer where I can find the paper size only in the General tab at
> the last position of 50 options.

The design of the CPD is that all the options will appear in the one area, no 
more tabs or separate Properties dialog.  To control what options appear at 
any one time there will be a number of filters you can apply and even a search  
box.  You'll also be able to save groups of presets.  The default should be 
the most commonly used options.  It's the polish on this stuff that the dialog 
is currently lacking and is planned for this years GSoC.

It will be interesting to see if this works as well in practice as the 
usability engineers designed it to.

> - There should be visual feedback how the document applies to the paper.
> What happens if I print an A4 document and select an A5 paper? How can I
> specify that the document has to be shrunk to fit?

> - For duplex printing I would like to see a left and right page or top and
> down page side by side in the preview.

> - The preview should optionally show the media borders, the printable area
> borders and the document borders on the media.

These should all be part of the dialog preview, I'll see if it's in the design 
or not, it could be one of the unimplemented things.

> - Is it possible let the dialog shrink the document by a given percentage
> and to align the document on the paper to have more empty space on the
> left for a hole-puncher

This is usually best achieved using a word processor and setting different 
margins for odd/even pages, but not every app can do that, so it sounds like a 
good idea for CUPS to implement.  CUPS can certainly apply the shrink, and it 
can apply the paper margins, but I don't think it can currently vary the 
margins based on page being odd/even.

> - Is it possible to print an A5 document on A4 paper centered with optional
> with crop marks at the border?

I've think I've seen Adobe Acrobat do that on Windows?  It would be a nice 
CUPS option, but something the dialog could generate too with a filter.

> - Will the applications be able to change the document and send a new
> preview as soon as the options change?

Yes, that's part of the protocol, as soon as any option that affects the 
document layout changes (as opposed to affecting the printed page layout), 
then the dialog tells the app and requests a new preview.  It will be 
interesting to see what performance lag there is as a result.

> - If one prints more than one document page on a paper sheet it should be
> possible to specify the horizontal and vertical gaps.

That's definately a new CUPS setting, as it's CUPS that processes the n-up 

> - One advanced option I would like to see: I do not know of any duplex
> printer that is able to print the front and back page such that for example
> crop marks exactly match. Often there is an offset one has to apply. It
> would be nice if one could do this independently for the front and back
> page in the dialog.

Oooo, tricky.  Again probably a CUPS thing?  I'll ask anyway.

It's good to know we have some advanced printer users about, I have very 
limited needs and resources myself so there's stuff I just won'think of.



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