Adds a new interface QgsAbstractValidityCheck which defines
a single "check" which can be performed on a given QgsValidityCheckContext.
A new application-wide QgsValidityCheckRegistry registers
and manages instances of all known checks, and allows running
of all registered checks of a specific type at once.
Initially the framework is focused toward print layout validity
checks, but the interface has been designed to be generic enough
to allow alternative types of validity checks (e.g. project save
validity checks, processing model validity checks, etc.).
The API is designed to be used both by internal validity checks
and also to be extended by custom, organisation-specific
validity checks. E.g., for print layout validity checks we could have:
This new class QgsImageCache is the equivalent of QgsSvgCache
but for raster images.
QgsImageCache stores pre-rendered resampled versions of raster
image files, allowing efficient reuse without incurring the
cost of resampling on every render.
Additionally, it offers the other benefits QgsSvgCache has,
such as thread safety, ability to transparently download remote
images, and support for base64 encoded strings.
