[processing][feature] Add "Force polygons clockwise" (native:forcecw) and "Force polygons counter-clockwise" (native:forceccw) algorithms (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#64668
Author: @agiudiceandrea
QGIS version: 4.0

[processing][feature] Add "Force polygons clockwise" (native:forcecw) and "Force polygons counter-clockwise" (native:forceccw) algorithms

PR Description:

Description

This PR adds the "Force polygons clockwise" (native:forcecw) and the "Force polygons counter-clockwise" (native:forceccw) processing algorithms.

"Force polygons clockwise" (native:forcecw), which is based on QgsGeometry::forcePolygonClockwise(), forces polygon geometries to respect the convention where the exterior ring is oriented in a clockwise direction and the interior rings in a counter-clockwise direction.
It has the same behaviour of the already existing "Force right-hand-rule" (native:forcerhr) which is based on QgsGeometry::forceRHR() which in turn is based on QgsGeometry::forcePolygonClockwise() too.

"Force polygons counter-clockwise" (native:forceccw), which is based on QgsGeometry::forcePolygonCounterClockwise(), forces polygon geometries to respect the convention where the exterior ring is oriented in a counter-clockwise direction and the interior rings in a clockwise direction.

Following the approach used in qgis/QGIS#45718, this PR also adds a note in the "Force right-hand-rule" algorithm short help recommending to use the new "Force polygons clockwise" algorithm instead.

Some tests have been added.

Fixes qgis/QGIS#45723.

Commits tagged with [need-docs] or [FEATURE]