[Discuss] Double-sided printing with web browsers

[epp at vivaldi.net]

Robert Krawitz wrote:
> On Sun, 12 Aug 2018 11:57:09 -0400, epp at vivaldi.net wrote:
>> On 08/12/2018 10:58 AM, epp at vivaldi.net wrote:
>>> In Chrome, the headers are at 0.33" from the top, the footers are at
>>> .18" from the bottom, when the margins are moved to their placement on
>>> the screen.
>>>
>>> WRT Firefox: I don't know if this information will help, but in the
>>> preferences file (aka about:config), print_print_margin_top and
>>> print_print_margin_bottom both show (as string) 0.5 for the value, but
>>> if this actually means 1/2" from both top and bottom, the headers and
>>> footers print closer than that to the top and bottom of the pages. The
>>> preferences print_print_unwriteable_margin_top and
>>> print_print_unwriteable_margin_bottom both show (as integer) 13 as the
>>> value. I'm not finding a setting anywhere to manually change the
>>> margins in Firefox.
>>
>> Fixed in Firefox.  :-)
>>
>> The "print_print_unwriteable_margin_" entries required changing. Advanced/Power users would know to look in about:config for this, otherwise there is no GUI to change the margins.
> It should be getting that from the PPD file, but apparently the PPD
> file isn't giving correct information for duplex printing (which
> doesn't entirely surprise me; a lot of printers require a wider margin
> for the first side because the printer has to retain enough of the
> paper in the mechanism to pull it back in for the back side).  So it
> really is a driver problem, I think.
>

Most likely.

The mozillazine.org site has a database of (perhaps most of) those 
entries in about:config. For the "print.print_unwriteable_margin" 
entries, it indicates the default setting is -1, which will use the 
system default. I changed all four of the entries to -1 and printed. 
Headers and footers printed on both sides. In looking as to where they 
printed with -1, it seems that 56 for bottom and 25 for top, left and 
right are pretty close to the system default.