Implements a method in QgsGeometry and a processing algorithm to
calculate the pole of inaccessibility for a surface, which is the
most distant internal point from the boundary of the surface. This function
uses the 'polylabel' algorithm (Vladimir Agafonkin, 2016), which is an iterative
approach guaranteed to find the true pole of inaccessibility within a specified
tolerance. More precise tolerances require more iterations and will take longer
to calculate.
default value SQL clauses
QgsVectorDataProvider now has two methods:
- defaultValueClause: returns SQL fragment which must be evaluated
by the provider to obtain the default value, eg sequence values
- defaultValue: returns the literal constant default value
for a field
Warnings are shown, but features can be committed. Fields which
fail an unenforced constraint are now shaded in yellow to differentiate
from the red failure for enforced constraints.
Non-enforced constraints just show a warning to the user, but
do not prevent committing the feature. Enforced constraints
block users from comitting non compliant features.
Any constraints detected by the provider are always
enforced.
and not any constraints enforced by the provider
Because:
1. we want to keep browsing features nice and responsive. It's nice to give
feedback as to whether the value checks out, but not if it's too slow to
do so. Some constraints (eg unique) can be expensive to test. A user can
freely remove a layer-based constraint if it proves to be too slow to
test, but they are unlikely to have any control over provider-side
constraints
2. the provider has already accepted the value, so presumably it doesn't
violate the constraint and there's no point rechecking!
Contains static helper methods for working with vector layers.
Initially only contains a method to test whether a value
exists within a layer's attributes.
To make the implementation saner, the legend node that may be embedded within parent
layer node is kept separately from activeNodes.
(cherry picked from commit b385ebd9ba9272516eed61e5825a603fcee969e9)
Made sure that both closestVertex() and closestSegment() return negative
distance on error (e.g. with null or emtpy geometry).
Also fixes snapping when dealing with layers with null/invalid geometries
(cherry picked from commit c093d5188fad685c4a596ff23c27aad7d151dac2)
This makes it possible to access attributes and geometry from the parent
feature when in the filter of the "aggregate" expression function.
With this in place aggregates can be calculated per feature.
E.g. max "measurement" for each point_station per polygon_research_area.
Or a default attribute value when digitizing features:
aggregate(layer:='countries', aggregate:='max', expression:=\"code\",
filter:=intersects( $geometry, geometry(@parent) ) )
Make nCoordinates virtual, and provide shortcuts for some
geometry types. The base method which calls coordinateSequence()
is quite slow in certain circumstances.
Speeds up rendering point layers by ~25%, also likely to
speed up lots of geometry heavy operations throughout QGIS
Refs #15752
