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# Objective Mostly covers the first point in https://github.com/bevyengine/bevy/issues/13713#issuecomment-2364786694 The idea here is that a lot of people want to load their own texture atlases, and many of them do this by deserializing some custom version of `TextureAtlasLayout`. This makes that a little easier by providing `serde` impls for them. ## Solution In order to make `TextureAtlasLayout` serializable, the custom texture mappings that are added by `TextureAtlasBuilder` were separated into their own type, `TextureAtlasSources`. The inner fields are made public so people can create their own version of this type, although because it embeds asset IDs, it's not as easily serializable. In particular, atlases that are loaded directly (e.g. sprite sheets) will not have a copy of this map, and so, don't need to construct it at all. As an aside, since this is the very first thing in `bevy_sprite` with `serde` impls, I've added a `serialize` feature to the crate and made sure it gets activated when the `serialize` feature is enabled on the parent `bevy` crate. ## Testing I was kind of shocked that there isn't anywhere in the code besides a single example that actually used this functionality, so, it was relatively straightforward to do. In #13713, among other places, folks have mentioned adding custom serialization into their pipelines. It would be nice to hear from people whether this change matches what they're doing in their code, and if it's relatively seamless to adapt to. I suspect that the answer is yes, but, that's mainly the only other kind of testing that can be added. ## Migration Guide `TextureAtlasBuilder` no longer stores a mapping back to the original images in `TextureAtlasLayout`; that functionality has been added to a new struct, `TextureAtlasSources`, instead. This also means that the signature for `TextureAtlasBuilder::finish` has changed, meaning that calls of the form: ```rust let (atlas_layout, image) = builder.build()?; ``` Will now change to the form: ```rust let (atlas_layout, atlas_sources, image) = builder.build()?; ``` And instead of performing a reverse-lookup from the layout, like so: ```rust let atlas_layout_handle = texture_atlases.add(atlas_layout.clone()); let index = atlas_layout.get_texture_index(&my_handle); let handle = TextureAtlas { layout: atlas_layout_handle, index, }; ``` You can perform the lookup from the sources instead: ```rust let atlas_layout = texture_atlases.add(atlas_layout); let index = atlas_sources.get_texture_index(&my_handle); let handle = TextureAtlas { layout: atlas_layout, index, }; ``` Additionally, `TextureAtlasSources` also has a convenience method, `handle`, which directly combines the index and an existing `TextureAtlasLayout` handle into a new `TextureAtlas`: ```rust let atlas_layout = texture_atlases.add(atlas_layout); let handle = atlas_sources.handle(atlas_layout, &my_handle); ``` ## Extra notes In the future, it might make sense to combine the three types returned by `TextureAtlasBuilder` into their own struct, just so that people don't need to assign variable names to all three parts. In particular, when creating a version that can be loaded directly (like #11873), we could probably use this new type. |
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Bevy Internal
