No user visible changes expected.
`AssetIdentifier` holds information to uniquely identify and locate an
asset. More information:
https://wiki.blender.org/wiki/Source/Architecture/Asset_System/Back_End#Asset_Identifier
For the start this is tied quite a bit to file paths, so that external
assets are assumed to be in the file system.
This is needed to support an "All" asset library (see T102879), which
would contain assets from different locations. Currently the location of
an asset is queried via the file browser backend, which however requires
a common root location. It also moves us further away from the file
browser towards the asset system (see T87235) and allows us to remove
some hacks (see following commit).
Move "using" declarations and member variables to the top of the class.
See https://wiki.blender.org/wiki/Style_Guide/C_Cpp#Class_Layout.
Changes access specifiers of some variables from public/protected to
private, there was no point in not having them private.
- Move main comment on class to header comment where it's more visible.
- Improve comment.
- Move stdlib includes first, like we do it usually
- Separate includes my code module
- Remove unnecessary forward declarations
- Move code to manage storage to own class in own file, separates
concerns and different levels of abstraction better.
- Store local ID assets separately in the storage class for more
efficient lookups (e.g. for ID remapping).
- Make API function names and comments more complete.
Adds a new `source/blender/asset_system` directory and moves asset
related files from BKE to it. More asset related code can follow
(e.g. asset indexing, ED_assetlist stuff) but needs further work to
untangle it. I also kept `BKE_asset.h` and `asset.cc` as is, since they
deal with asset DNA data mostly, thus make sense in BKE.
Motivation:
- Makes the asset system design more present (term wasn't even used in
code before).
- An `asset_system` directory is quite descriptive (trivial to identify
core asset system features) and makes it easy to find asset code.
- Asset system is mostly runtime data, with little relation to other
`Main`/BKE/DNA types.
- There's a lot of stuff in BKE already. It shouldn't be just a dump for
all stuff that seems core enough.
- Being its own directly helps us be more mindful about encapsulating
the module well, and avoiding dependencies on other modules.
- We can be more free with splitting files here than in BKE.
- In future there might be an asset system BPY module, which would then
map quite nicely to the `asset_system` directory.
Checked with some other core devs, consensus seems that this makes
sense.
