Previously, we had two places where we were passing kwargs that affected
the image generation: the ImageSpec constructor and the generate method.
These were essentially partial applications. With this commit, there's
only one partial application (when the spec is instantiated), and the
generate method is called without arguments. Therefore, specs can now
be treated as generic generators whose constructors just happen to
accept a source_file.
The registry module splits the work that specs.SpecRegistry
used to do into two classes: GeneratorRegistry and
SourceGroupRegistry. These two registries are wrapped in
Register and Unregister utilities for API convenience.
The registry's `get_spec()` was already supporting kwargs as a means to
provide information about the source to the spec constructor/factory
function, but the ``SpecHost`` class wasn't capable of accepting any.
This commit rectifies that. The main goal purpose of this is to allow a
bound field (the file attached by ``ImageSpecFileDescriptor``)--and the
attached model instance--to be taken into account during the spec
instance creation.
Related: #156
This marks a major step towards centralizing some of the "spec" logic
and creating a single access point for them. Because `ImageSpecFields`
are just alternative interfaces for defining and registering specs,
they can be accessed and overridden in the same manner as other specs
(like those used by template tags): via the spec registry.
Somewhere along the line, a change got merged that stopped using the
receivers module. This re-integrates it and moves changes made to the
old receivers (static methods on ImageSpecField) to them.
This new feature gives the user more control over *when* their images
are validated. Image cache backends are now exclusively for controlling
the *how*. This means you won't have to write a lot of code when you
just want to change one or the other.
Signals are now connected without specifying the class and non-IK
models are filtered out in the receivers. This is necessary because of
a bug with how Django handles abstract models.
Closes#126
While this change means users can no longer specify their own filenames,
changing a property of a processor, for example, will now result in a
new image. This solves a lot of the previous invalidation issues.
