[QGIS-Developer] QgsCoordinateTransformContext warnings again

[Nyall Dawson]

On 1 February 2018 at 23:00, Andreas Neumann <a.neumann at carto.net> wrote:
> Hi,
>
> For some reason I did not manage to read the responses to the thread at
> https://lists.osgeo.org/pipermail/qgis-developer/2018-January/051678.html -
> perhaps I accidentally deleted the responses together with some e-mail
> trash. So sorry for not replying directly to this e-mail thread.
>
> Anyway - good to see that I am not alone and that others are also affected
> with this warning.
>
> Is there any chance that the warning could spit out more information - e.g.
> what layer is triggering the issue? I have so many layers in the project
> that it is quite hard for me to find the needle in the haystack.

The debug information should give the full path to the function which
is missing the context.

It's not layer dependent, and instead is caused by bits of QGIS which
are just not upgraded to handle transform contexts and datum
transforms correctly. The warnings are shown for debug builds only
(not release builds - so the final release won't suffer the overhead
of all the debug prints) in order to allow us to identify these code
areas.

The major remaining ones are:

- all raster layers ignore datum transforms (and have since forever)
- some data providers are not transform aware (XYZ layers for instance
trigger a lot of these warnings)

If it comes down to it close to final release, we could hack in some
QgsProject::instance() calls to force the correct transform handling
for these remaining areas. But that causes issues with server, and
will probably turn Martin into a quivering mess hiding in his
cupboard... (or a raging hulk... I don't want to find out which!).

Alternatively if someone has some hidden 3.0 funds available adding
datum handling to rasters would be a good last minute fix...

> I know that the warning is harmless, but because I have other issues in the
> project and need to work with these log messages, they hide all the other
> useful information in the log.

You run your own build, right? You could delete the block in
qgscoordinatetransform.cpp lines 588-591, qgsmapsettings.cpp lines
365-368 and qgsrendercontext.cpp lines 111-114.

Nyall