base them on normalized operations
QGIS doesn't need (or want) to care about strictly following
projection definitions here, we ALWAYS want X/Y to be X/Y
Now, proj will search in the current user profile "proj" folder (e.g.
.local/share/QGIS/QGIS3/profiles/default/proj" on linux) for
grid files and other proj helper files.
This allows users (and plugins) to install grid files and make them
available for use in QGIS without requiring administrator access
to the system.
This reworks (on proj 6 builds only!) QgsCoordinateTransformContext
to use proj strings of proj coordinate operations to handle the
users' preferred list of operations when transforming coordinates
between two CRSes.
Previously, the context heavily utilised internal transform ID
numbers, which were QGIS specific and relied on matching entries
from the QGIS srs.db file. This approach was undesirable because
it meant QGIS had to maintain and carry it's own table of
possible transform pathways between CRS pairs (which was difficult
to update, impossible to track, and most likely severely out of
date).
Now we can utilse Proj 6's (wonderful!) logic for determining the
best coordinate operation to utilise between two CRSes. All the
old API has been deprecated and no longer works under proj 6, but
that's unavoidable (and unlikely to be in use by plugins anyway,
it's VERY low level stuff).
A further bonus of this work is that QgsCoordinateTransform no
longer relies on proj strings of the source/dest CRS to build
the transform -- the issue with that approach was that proj
strings are lossy (and not always possible to generate), so
now by default we are generating better pathways between CRS
pairs.
This resolves issues with transforms which rely on pivot datums,
such as GDA94 - GDA2020 conversions.
Sponsored by ICSM
There was a lack of a JSon array around rings of a polygon.
This issue is not present in 3.4
Also fixes an issue with gcc 5.5 of Ubuntu 16.04 that doesn't behave
properly with C++11 brace syntax with code from nlohmann/json.hpp.
The code compiles but the result is invalid: `json foo{ json::array{} }`
is serialized as [[]] instead of []. So use old-style constructor
instead: `json foo( json::array() )`
This PR is on top of https://github.com/qgis/QGIS/pull/30010
Fixes#21986
plus:
- fix multiple string keys with commas in value relation widget
- more robust JSON and array (un)marshalling
- uniform array representation in value relation widgets
- lot of test coverage
- automatic QVariant type conversions in JSON utils
