This commit sets the framework for allowing expression functions to
use named parameters. Ie, instead of:
clamp(1,2,3)
you can use:
clamp( min:=1, value:=2, max:=3)
This also allows arguments to be switched, eg:
clamp( value:=2, max:=3, min:=1)
Additionally, it allows for a more structured definition of function
parameters to handle optional arguments and default values for
parameters. These are currently being done using a hacky infinite
argument list.
I've utilised the postgres ':=' syntax for specifying named arguments
to avoid potential collisions which may arise with the equality test
if we re-used just the '=' operator alone.
Sponsored by North Road
- add accessors: geometry_n, interior_ring_n
- add num_geometries, num_rings, num_interior_rings
- add nodes_to_points for converting every node in a geometry
to a multipoint geometry
- add segments_to_lines for converting every segment in a geometry
to a multiline geometry
nodes_to_points and segments_to_lines are intended for use with
geometry generator symbology, eg to allow use of m and z values
for nodes/lines with data defined symbology.
- New expression functions for area(geom), perimeter(geom),
point_n(geom), start_point(geom), end_point(geom), make_point(x,y)
- Add new variant to length() function which takes a geometry object,
allows for length(geom) evaluation.
- Rename x_at, y_at to $x_at, $y_at (alias old names) to reflect that
these only work on current feature geometry
- Add x(geom), y(geom) functions which return x and y coordinate
for point geometries or centroid x/y for non-point geometries
(fix#11008)
A new script then parses these json help files into the html help
contents, in a standardised manner. Previously, the function help
was a bunch of different formats and structures.
Now, a custom stylesheet can be applied (and later tweaked!) to
format these help. Eg, this commit colors variables and function
names in the syntax section for greater readability.
function
layer_property takes a layer name/id and a property (eg 'crs')
and returns the matching value. This approach is more flexible than
having all these values as variables, since it allows retrieval
of properties of a layer from contexts which aren't layer-aware
(eg a composer label showing the metadata of a layer).
A new QgsStringUtils class has been added containing some
common fuzzy matching algorithms, including Levenshtein edit
distance and Soundex. These can be used for finding "similar"
strings in a table.
Expression functions for these algorithms have also been
added to a new "Fuzzy Matching" group.
The usage examples for the 'LIKE' operator are not really pertinent. The proposed change adds an example that actually illustrates the usual usage of the 'LIKE' operator.
This change allows for some cleanups to the built in expression
functions, by making it possible to differentiate variables
(eg $feature) from functions which don't require parameters
(eg uuid(), now()... ). Also adds aliases for uuid(), now(), and
pi().
