This implements an improved version of vector.createVectorWriter
in QgsProcessingUtils. The improved version relies on the
core class QgsVectorLayerImport to create empty layers,
which:
- reduces duplicate code and reuses the mature QgsVectorLayerImport
routines
- avoids manual conversion of field types to destination provider
field types
- potentially allows any writable provider to be used as a feature
sink for algorithms (e.g. output direct to MSSQL/Oracle/db2). This
should work now - it just needs exposing via UI.
The geometry cache was only used for few geometry editing operations anyway. In earlier versions
of QGIS the geometry cache was also used by old snapping classes which have been replaced
by QgsPointLocator that also keeps a spatial index of geometries and it is not rebuilt on every re-render.
Reasons for removal:
- geometry cache was repopulated on every redraw of layers in editing mode, slowing down rendering
- data structure for the cache was a simple map with features accessed by their ID (no spatial index)
- the cache was only getting refreshed for the current view of the main map canvas (not a generic cache)
- not used for snapping anymore where caching was important to avoid roundtrips to data provider
- provider() was renamed to createProvider()
- selectWidget() was renamed to createSelectionWidget()
- providerLibrary() was renamed to createProviderLibrary()
of new memory layers from QgsFields/QgsCoordinateReferenceSystem/etc
Since memory provider cannot use QgsVectorLayerImport we need
another centeralized function for creating new memory layers
without the need to manually create the uri string.
This commit introduces basic support for non-library based
data providers, and moves the memory provider from a library
based provider to a core provider.
The memory provider is used so frequently throughout QGIS that
it has become integral to QGIS functionality and must be
available wherever the QGIS core library is used.
The changes here (while not exposed yet to Python) could potentially
be built on to allow creation of pure Python data providers.
there was an issue in libdxf which includes qgslogger in debug mode
and qgsdebug.h includes qgis.h include qgswkbtypes.h (which geometry directory was not listed in libdxrw included paths)
