Historically the configuration used to be stored in layer's custom properties, but that does not scale
beyond simple rendering and so rule-based labeling introduced storage of configuration natively in XML elements.
That left us with two different ways of reading/writing labeling configurations. This work makes all configuration
to use native XML elements.
To keep compatibility of 2.x projects, reading of configuration from custom properties is preserved.
This commit also adds Python APIs for direct manipulation of labeling configuration through vector layer's
setLabeling() and labeling() calls.
Avoids unpredictable behavior when transforms are being
conducted in background threads, such as map renders.
Refs #11441
This commit:
1. Uses thread_local storage for projCtx objects, to ensure
that every thread correctly has its own projCtx context.
2. Refactors QgsCoordinateTransformPrivate so that the
projPJ source and destination objects are instead stored
in a map (by projCtx). This allows transforms to be
transparently performed using the correct projPJ objects
for the particular thread in which the transform is being
conducted. This approach avoids expensive detachment
of QgsCoordinateTransformPrivate, and allows a single
QgsCoordinateTransformPrivate to be safely utilised
by QgsCoordinateTransform objects in different threads.
This allows gui widgets to utilise native platform interfaces.
Additionally attaching the instance to QgsGui allows QgsNative
to become a QObject in future if required and for use
of signals/slots in the native interfaces.
A QgsNative base class is added, that offers default implementations for
a platform interface. These methods can be overridded for the current
platform at compile time to allow specialized handling for integration
with the current system.
* Change browser context menu item text for adding layer to 'Add selected layer(s) to canvas'
* Use title case for Add Selected Layer(s) to Canvas browser context menu text
