[QGIS-Developer] Proj 7 auto grid download

Nyall Dawson nyall.dawson at gmail.com
Thu Mar 19 17:13:06 PDT 2020

On Thu, 19 Mar 2020 at 22:04, Martin Dobias <wonder.sk at gmail.com> wrote:
> Hi Nyall
> On Thu, Mar 19, 2020 at 7:53 AM Nyall Dawson <nyall.dawson at gmail.com> wrote:
> >
> > On Thu, 19 Mar 2020 at 16:49, J├╝rgen E. Fischer <jef at norbit.de> wrote:
> > >
> > > Yes. proj-dev-data is to huge for NSIS.  Best install via OSGeo4W until grids
> > > are downloadable via proj.
> >
> > There's no plans to use proj 7's built in auto grid download. This
> > isn't designed for GUI applications like QGIS -- if we did, we'd get
> > UI hangs all over the place while QGIS is trying to transform
> > coordinates, and proj blocks and waits for the download to occur.
> Do you have some thoughts on how we are going to handle this in QGIS?
> (Apart from that plan to download all grids on the first start :-))
> My assumption was that QGIS would be shipped with no grids (simply too
> much data to ship in installers), and if there would be a
> transformation available with a missing grid, QGIS would show a
> warning and let user download such a grid file with one click? Or did
> you have something else in mind?

That's basically what we have now. When a grid is desirable (and not
installed) you get a warning in the message bar, which you can click
to open a dialog which explains the situation and provides a download
link, and a button to "install" (copy to the right place) the
downloaded file.

The only extra steps we could do to improve this would be:
- Avoid the "click to download in your browser" link, and instead have
a button which downloads in the background of QGIS itself and
auto-installs after download
- Take it another step further, and just immediately trigger the
download task when we first show that warning
- Avoid all these issues and download EVERYTHING for EVERYWHERE at
first startup ;)


> Cheers
> Martin

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