Bug#982925: libgtk: print dialog lists autodetected printer twice

[Simon McVittie]

Here is hopefully a better solution for GTK 3 in bullseye:

    https://people.debian.org/~smcv/bullseye-gtk-printing/mr6.1/

or if the release team will not accept that, then this:

    https://people.debian.org/~smcv/bullseye-gtk-printing/mr9.1/

Please try those (in preference to mr6, mr9) and see what happens with
your particular printers.

As before, the _binary.changes and .dsc files are signed with my key in
the Debian keyring, and can be verified with the dscverify tool from the
devscripts package (this requires devscripts and debian-archive-keyring
installed).

Test results below.

    smcv

> * Which versions of cups-daemon and cups-filters-core-drivers are installed?

cups-daemon	2.3.3op2-3+deb11u1
cups-filters-core-drivers	1.28.7-1

> * How many printers are physically present on your network?

One HP Color LaserJet MFP M277dw.

> * Is cups-browsed installed? If yes, which version?

I tested both with and without cups-browsed 1.28.7-1.

Test methodology for each of the 8 attempts listed here (I'm using an
expendable test machine, do not do these steps unless you are willing
to lose manual CUPS configuration):

sudo apt purge cups-browsed cups-daemon
sudo rm -fr /etc/cups
sudo apt install cups cups-core-drivers cups-daemon cups-browsed-
(optionally) Configure printer: gnome-control-center, Printers, Unlock,
             Add..., wait, click on the single printer that appears, Add
(optionally) sudo apt install cups-browsed
gedit
Try to print

GTK 3.24.24-4 (status quo in bullseye)
======================================

Repeating my previous test results for reference:

                                    | cups-browsed installed |
                                    |    no      | yes       |
    --------------------------------|------------|-----------|
    printer manually configured   no|unavailable | works     |
                                 yes| works      |duplicated |
    --------------------------------|------------|-----------|

GTK based on merge request 6 (full backport from 3.24.29)
=========================================================

                                    | cups-browsed installed |
                                    |    no      | yes       |
    --------------------------------|------------|-----------|
    printer manually configured   no| works      | works     |
                                 yes| works      | works     |
    --------------------------------|------------|-----------|

With no configuration and no cups-browsed: One printer appears in the
GTK dialog, labelled HP_Color_LaserJet_MFP_M277dw_xxxxxx_. It is not
listed in /etc/cups/printers.conf. Printing is successful.

With cups-browsed only: One printer appears, labelled
HP_Color_LaserJet_MFP_M277dw_xxxxxx_.
It is listed in /etc/cups/printers.conf, labelled as having come from
cups-browsed. It prints successfully.

With manual configuration only: One printer, HP-Color-LaserJet-MFP-M277dw.
It appears in /etc/cups/printers.conf. Printing is successful.
(This is actually better than the Qt app featherpad, which displays two
printers in this situation.)

With both: Same as with manual configuration only.

GTK based on merge request 9 (Daniel's minimal backport)
========================================================

                                    | cups-browsed installed          |
                                    |    no      | yes                |
    --------------------------------|------------|--------------------|
    printer manually configured   no| works      | works              |
                                 yes| works      | duplicated         |
    --------------------------------|------------|--------------------|

With no configuration and no cups-browsed: One printer appears in the
GTK dialog, labelled HP_Color_LaserJet_MFP_M277dw_xxxxxx_. It is not
listed in /etc/cups/printers.conf. Printing is successful.

With cups-browsed only: One printer, HP_Color_LaserJet_MFP_M277dw_xxxxxx_,
where xxxxxx is a unique ID taken from its MAC address. It is in
/etc/cups/printers.conf. Printing is successful.

With manual configuration only: One printer, HP-Color-LaserJet-MFP-M277dw.
It appears in /etc/cups/printers.conf. Printing is successful.

With both: both of the printers mentioned above appear in the GTK dialog
and in /etc/cups/printers.conf. Only the first one printed successfully:
the second logged "NO_DEST_FOUND".