Before the algorithm was written to optimise clipping a few
features against thousands of mask features. The revised algorithm
is optimised for clipping thousands of input features against
a few mask features.
Given that this second operation is much more likely, it makes
sense to optimise for this use case.
I've also applied some other optimisations like taking advantage
of spatial indexes on the providers, using prepared geometries
and also only applying an intersection operation if the geometry
isn't wholly contained by the mask geometry.
Benchmarks:
clipping roads layer with 1 million lines against 2 polygons
before: 5 mins 30 seconds
after: 10 seconds
clipping address layer with 5 million points against 2 polygons
before: 50 minutes
after: 30 seconds
This algorithm joins all connected parts of MultiLineString
geometries into single LineString geometries.
If any parts of the input MultiLineString geometries are not
connected, the resultant geometry will be a MultiLineString
containing any lines which could be merged and any non-connected
line parts.
All pointer based methods have been removed.
Now we have only:
void setGeometry( const QgsGeometry& geom )
and
QgsGeometry geometry() const
Benefits include avoiding a whole lot of tricky pointer lifetime
issues, potential memory leaks, and finally closing #777, which
has survived for over 9 years!...
Impacts on PyQGIS code:
- no more need for the messy
g = QgsGeometry( feature.geometry() )
workaround, just use g = feature.geometry() instead
- IMPORTANT: you can no longer test whether a feature has geometry
using `if f.geometry():`, since QgsFeature::geometry() will
*always* return an object. Instead, use
`if not f.geometry().isEmpty():`, or preferably the new method
`if not f.hasGeometry():`
Fix#777
On travis-ci environment, Python version seems to be affected by [this bug](https://bugs.python.org/issue21591).
One way to fix it is to use the old statement instead of exec() function.
This is direct port of abandoned "Rectangles, Ovals and diamonds" plugin.
There are two algorithms: one uses fixed values and second — variable
values from attribute table. Test for fixed distance version included.
