Asset Editing

Under certain conditions, it is possible to edit assets that are not stored in the currently open file. This happens through special asset system managed files (as opposed to normal user managed files), and the BKE_asset_edit.hh API. Every such editable asset is saved in a single such file, together with its dependencies (and external files packed).

Only brush assets support this currently.

Asset System Files (.asset.blend Files)

These files are indicated by a dedicated flag (G_FILE_ASSET_EDIT_FILE) stored in the file's "global" data section, and use the .asset.blend file extension. Both the flag and the extension need to be used for a file to be considered an asset system file. That means users may still use the .asset.blend extension for normal files. It's just a useful indicator for them, but also so Blender can tell if a file may be an asset file without having to open it it.

The design is to let the asset system regenerate these files when user's save changes to the assets. This way we keep the updating simple, and avoid many possible issues coming from loading and saving assets in normal, user managed .blend files. If users could open and overwrite these special .asset.blend files, user created data would be stored in them that would be lost the next time the asset system regenerates the files. That's why these files need to be special. Users can open, but not save these files (but use "Save As" to create a new, normal file). Warnings are displayed in the UI to notify the user about this.