JSON keys in our style specification don't have a defined order. This change sorts them alphabetically so that we can rely on the order remaining them same across code generation runs.
`LayerManager` is now responsible for `RenderLayer` instances creation,
so that there is a single entry point for creating of objects, which
correspond to a certain layer type.
The `LayerType type` field is dropped from `Layer::Impl`.
The `LayerTypeInfo` contains static meta data about certain layer type.
Each layer module should have a single immutable `LayerTypeInfo` instance
for the represented layer type. Both `LayerImpl` and `LayerFactory` from the
module always refer to the same `LayerTypeInfo` instance, so address of this
instance can be used as a layer module Id during the process life time.
This patch introduces the initial implementation of
- A `LayerFactory` abstract class that creates `style::Layer` instances of
a certain layer type (line, hillshade, round, ..)
- A singleton `LayerManager` class, which is responsible for initializing
the `LayerFactory` instances and forwarding the `create()` calls to the
corresponding factory.
The `style::Layer` class now exposes all the properties contained at `style::LayerImpl`.
This allowed to drop `style::Layer::accept()` method usage, avoid the repeated generated code
and thus save some binary size.
This patch is a part of the layers modularization effort.
* [ios, macos] new struct MGLTransition
* [ios] MGLTransition struct moved to MGLTypes.h
* [ios] MGLTransition implemented for style layer properties
* [ios, macos] added support for getting property transitions
* [ios, macos] updated to MGLDurationFromTimeInterval and MGLTimeIntervalFromDuration
* [ios, macos] added transition properties test
* [ios, macos] modified key strings imp
* [ios, macos] The impl for transition properties were changed to public methods
* [ios, macos] Changelog update
* [ios] Fixed layer space formatting
* [core] The name space was fixed for getters that returned TransitionOptions
* [ios, macos] Added rawLayer transition property tests
* [ios] Added a factory method for MGLTransition and transition-related methods to NSValue(MGLAdditions)
* [ios, macos] Copyedited changelog blurbs about transition properties
This converts the style property classes (CirclePaintProperties and so on) to the same tuple-based approach as gl::Attribute and gl::Uniform. The approach is outlined in https://github.com/mapbox/cpp/blob/master/C%2B%2B%20Structural%20Metaprogramming.md.
The main advantage of this approach is it allows writing algorithms that work on sets of style properties, without resorting to code generation or manually repetitive code. This lets us iterate on approaches to data-driven properties more easily.
Another advantage is that the cascading, unevaluated, and evaluated states of a set of properties exist as independent structures, instead of individual properties holding their own state. This is a more functional approach that makes data flow clearer and reduces state.
This paves the way for updates to filter and layout properties to trigger a source reload, without each SDK having to participate in the implementation.
