Include descriptive text with the specified parameter value
in error, and always check that sources were loaded to avoid
raw Python exceptions when they are not
and add new QgsGeometry::fromPolyline which uses QgsPoint
We want to encourage people not to use the QgsPointXY method, as it drops
Z/M values. So it's moved across to a different name to make way
for a new QgsGeometry::fromPolyline which uses a QgsPoint list
instead of QgsPointXY, thus keeping Z/M values intact.
Similarly, QgsPolyline now is a list of QgsPoint (keeping z/m values)
and the old 2d QgsPolyline type was renamed to QgsPolylineXY.
Making the QgsPoint method the "preferred" method and making linestrings
just as easy to create from z/m dimensioned points as 2d points is
important to push people to write code which does not discard
these important dimensions.
As a bonus, the QgsPoint methods are more efficient anyway, since
they don't require creation of a temporary list.
initAlgorithm() method
This allows 2 benefits:
- algorithms can be subclassed and have subclasses add additional
parameters/outputs to the algorithm. With the previous approach
of declaring parameters/outputs in the constructor, it's not
possible to call virtual methods to add additional parameters/
outputs (since you can't call virtual methods from a constructor).
- initAlgorithm takes a variant map argument, allowing the algorithm
to dynamically adjust its declared parameters and outputs according
to this configuration map. This potentially allows model algorithms which
can be configured to have variable numbers of parameters and
outputs at run time. E.g. a "router" algorithm which directs
features to one of any number of output sinks depending on some
user configured criteria.
Algorithms and other processing code should use this method
(instead of dataobjects.getLayerFromString) to
retrieve layers from a string, as it considers the processing
context and allows resolving strings to temporarily stored layers.
This permits processing models to function correctly when
intermediate results are stored as memory layers. Subsequent
model algorithms can then access these temporary layers as inputs.
All temporary layers will be removed when the context object
is destroyed after the model algorithm is run.
Also
- simplify and add tests
- remove large memory leak (persistant store of all non-project layers)
- remove broken support for direct loading postgres/virtual layers
by string (Python version was very broken and would never match
a postgres/virtual layer)
Because
- OTF reprojection is mature and stable
- Should be no cost when not required - transforms are shortcut
when not required
- Reduces code complexity
- Canvas OTF support was being incorrectly used as a flag for
whether measurements should be made in ellipsoidal mode. Instead
the project's ellipsoid setting should be checked for this.
- Should simplify behavior for new users
