[QGIS-Developer] Proj 7 auto grid download

[Kristian Evers]

> On 23 Mar 2020, at 01:28, Nyall Dawson <nyall.dawson at gmail.com> wrote:
> 
> Not just QGIS. The auto-download behavior is an opt-in switch for
> applications, it's not the default behavior.
> 
> I can't find any application which use the CDN by default
> -- searching
> github for proj_context_set_enable_network only gets hits in proj
> itself.

PROJ 7 has been out for 23 days. Give everyone a chance to catch up, please.
And honestly, I think many developers look at what you guys are doing, so
expect to be the front-runners on this. 

The PROJ conda-forge package defaults to PROJ_NETWORK=ON unless
the proj-data package is installed [0], so this is out in the wild already. The
QGIS package has PROJ pinned at 6.3.1 it is not available for QGIS but
most other packages requiring PROJ will default to auto-downloading grids
from the CDN.

> And I'd really like consistent behavior here, so that users
> who install QGIS through osgeo4w can get the same transformation
> results regardless if they use QGIS application, GDAL command line, or
> GRASS tools via processing... (which is why I keep coming back to the
> "screw it, this is too complex to solve case-by-case, lets just
> install them ALL for EVERYONE" option).

A point to be made here, is that if everyone uses the auto-downloading
mechanism then consistency will be achieved across the board. Obviously
the various projects using PROJ will have differing timelines with regards
to adopting PROJ 7, so even if everyone is setting PROJ_NETWORK=ON
it will take time to achieve that consistent behaviour, so please don’t let that
be your guiding light on how to proceed with this.

I think a cross-project discussion on this is warranted. It would be nice if
everyone is more or less aligned. I think this is a great topic for the OSGeo
code sprint but given current circumstances I doubt that event will be held
as scheduled. 

Would the choice have been obvious if auto-downloading was turned on
by default?

/Kristian

[0] https://github.com/conda-forge/proj.4-feedstock/blob/master/recipe/scripts/activate.sh