[Qgis-developer] Questions around xyz tile server connections in master 2

[Martin Dobias]

Hi Andreas

On Tue, Oct 4, 2016 at 3:48 PM, Neumann, Andreas <a.neumann at carto.net> wrote:
> Hi,
>
> I have a couple of questions around the new "Tileserver" layer support in
> QGIS desktop to be released with 2.18. I think the main commit is
> https://github.com/qgis/QGIS/commit/f5b657db19eda7e72e6ed34eb7fe333c156acad0
> - right?

Right :-)


> However, I wonder if the usability of the newly added tilserver is already
> good enough? Or at least I think it is not really obvious how to use it.

I agree it could be more user friendly. I was mainly focused on
getting the engine right, so the GUI is very very simple.


> 1. How can add a new connection to a tile server? Is the browser the only
> way? If yes, I hope that an additional entry to Layer --> Add Layer menu
> could be added - all other layer types can be added this way.

Currently yes, only through the browser. If we want to be consistent
with other layer types, a dialog with list of connections could be
added. There are also few more options like min/max zoom level that
are supported by the implementation, but not exposed in the GUI yet.


> 2. What is a correct URL? This is really hard to find out. F.e. I went to
> http://wiki.openstreetmap.org/wiki/Tile_servers and tried to copy some URLs
> and failed about finding the correct syntax. I added the layer to the
> project --> nothing happened. No display, no error message. Maybe because
> the projections do not match? - or would QGIS reproject on the fly?

Basically, the XYZ provider does replacement of {x}, {y}, {z}
placeholders by the tile coordinates. Alternatively, for Bing maps, we
support {q} placeholder that contains XYZ coordinate encoded in a
slightly different way. Generally, the syntax of URLs is the same as
in QuickMapServices plugin...

Reprojection on the fly should just work, CRS of XYZ tile layers is
assumed to be always web mercator.


> 3. Can we add some popular tile map server URLs by default - similar to the
> QuickMapServices plugin?

I we could, but I do not feel easy adding some services by default.
Maybe we could have some predefined services with links to their
license agreements that users would need to confirm beforehand.


> 4. How can one edit an existing tile server connection - e.b. change title
> or URL? Currently, one can only delete and re-add it.

Yeah, that's the only way for now.

Most of the GUI improvements are quite easy to implement, I am sure we
can keep working on them for the next releases (probably too late for
inclusion in 2.18).

Cheers
Martin