[Merged by Bors] - 0.8 Migration guide

content/learn/book/migration-guides/0.7-0.8/_index.md

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++++
+title = "0.7 to 0.8"
+weight = 4
+sort_by = "weight"
+template = "book-section.html"
+page_template = "book-section.html"
+insert_anchor_links = "right"
+[extra]
+long_title = "Migration Guide: 0.7 to 0.8"
++++
+
+<!-- Github filter used to find the relevant PRs "is:pr label:C-Breaking-Change closed:>2022-04-15 [Merged by Bors]" -->
+
+### [Make ScalingMode more flexible](https://github.com/bevyengine/bevy/pull/3253)
+
+Adds ability to specify scaling factor for `WindowSize`, size of the fixed axis for `FixedVertical` and `FixedHorizontal` and a new `ScalingMode` that is a mix of `FixedVertical` and `FixedHorizontal`
+
+### [Allow closing windows at runtime](https://github.com/bevyengine/bevy/pull/3575)
+
+`bevy::input::system::exit_on_esc_system` has been removed. Use `bevy::window::close_on_esc` instead.
+`CloseWindow` has been removed. Use `Window::close` instead.
+The Close variant has been added to `WindowCommand`. Handle this by closing the relevant window.
+
+### [Make RunOnce a non-manual System impl](https://github.com/bevyengine/bevy/pull/3922)
+
+The run criterion `RunOnce`, which would make the controlled systems run only once, has been replaced with a new run criterion function ShouldRun::once. Replace all instances of RunOnce with `ShouldRun::once`.
+
+### [Move system_param fetch struct into anonymous scope to avoid name collisions](https://github.com/bevyengine/bevy/pull/4100)
+
+For code that was using a system param's fetch struct, such as EventReader's EventReaderState, the fetch struct can now be identified via the SystemParam trait associated type Fetch, e.g. for `EventReader<T>` it can be identified as `<EventReader<'static, 'static, T>` as SystemParam>::Fetch
+
+### [Task doesn't impl Component](https://github.com/bevyengine/bevy/pull/4113)
+
+If you need a `Task` to be a `Component` you should use a wrapper type.
+
+```rs
+// 0.7
+fn system(mut commands: Commands) {
+    let task = thread_pool.spawn(async move {
+        let start_time = Instant::now();
+        while Instant::now() - start_time < Duration::from_secs_f32(5.0) {
+            // Spinning for 'duration', simulating doing hard
+        }
+        Vec2::ZERO
+    });
+    commands.spawn().insert(task);
+}
+
+// 0.8
+#[derive(Component)]
+struct ComputeVec2(Task<Vec2>);
+
+fn system(mut commands: Commands) {
+    let task = thread_pool.spawn(async move {
+        let start_time = Instant::now();
+        while Instant::now() - start_time < Duration::from_secs_f32(5.0) {
+            // Spinning for 'duration', simulating doing hard
+        }
+        Vec2::ZERO
+    });
+    commands.spawn().insert(ComputeVec2(task))
+}
+```
+
+### [Split time functionality into bevy_time](https://github.com/bevyengine/bevy/pull/4187)
+
+* Time related types (e.g. `Time`, `Timer`, `Stopwatch`, `FixedTimestep`, etc.) should be imported from `bevy::time::*` rather than `bevy::core::*`.
+* If you were adding `CorePlugin` manually, you'll also want to add `TimePlugin` from `bevy::time`.
+* The `bevy::core::CorePlugin::Time` system label is replaced with `bevy::time::TimeSystem`.
+
+### [Move float_ord from bevy_core to bevy_utils](https://github.com/bevyengine/bevy/pull/4189)
+
+Replace imports of `bevy::core::FloatOrd` with `bevy::utils::FloatOrd`.
+
+### [Move Rect to bevy_ui and rename it to UiRect](https://github.com/bevyengine/bevy/pull/4276)
+
+The `Rect` type got renamed to `UiRect`. To migrate you just have to change every occurrence of `Rect` to `UiRect`.
+
+### [Rename ElementState to ButtonState](https://github.com/bevyengine/bevy/pull/4314)
+
+The `ElementState` type received a rename and is now called `ButtonState`. To migrate you just have to change every occurrence of `ElementState` to `ButtonState`.
+
+### [Improve docs and naming for RawWindowHandle functionality](https://github.com/bevyengine/bevy/pull/4335)
+
+rename `HasRawWindowHandleWrapper` to `ThreadLockedRawWindowHandleWrapper`
+
+### [Migrate to encase from crevice](https://github.com/bevyengine/bevy/pull/4339)
+
+#### StorageBuffer
+
+* removed set_body(), values(), values_mut(), clear(), push(), append()
+* added set(), get(), get_mut()
+
+#### UniformVec -> UniformBuffer
+
+* renamed uniform_buffer() to buffer()
+* removed len(), is_empty(), capacity(), push(), reserve(), clear(), values()
+* added set(), get()
+
+#### DynamicUniformVec -> DynamicUniformBuffer
+
+* renamed uniform_buffer() to buffer()
+* removed capacity(), reserve()
+
+### [Make paused timers update just_finished on tick](https://github.com/bevyengine/bevy/pull/4445)
+
+`Timer::times_finished has` been renamed to `Timer::times_finished_this_tick` for clarity.
+
+### [Change default Image FilterMode to Linear](https://github.com/bevyengine/bevy/pull/4465)
+
+```rs
+// 0.7
+
+//TODO
+
+// 0.8
+
+// TODO
+```
+
+### [Remove .system()](https://github.com/bevyengine/bevy/pull/4499)
+
+You can no longer use `.system()`. It was deprecated in 0.7.0. You can just remove the method call.
+
+If you needed this for tests purposes, you can use `bevy_ecs::system::assert_is_system` instead.
+
+### [Change gamepad.rs tuples to normal structs](https://github.com/bevyengine/bevy/pull/4519)
+
+The `Gamepad`, `GamepadButton`, `GamepadAxis`, `GamepadEvent` and `GamepadEventRaw` types are now normal structs instead of tuple structs and have a new() function. To migrate change every instantiation to use the `new()` function instead and use the appropriate field names instead of .0 and .1.
+
+### [Remove EntityMut::get_unchecked](https://github.com/bevyengine/bevy/pull/4547)
+
+Replace calls to `EntityMut::get_unchecked` with calls to `EntityMut::get`.
+
+### [Replace ReadOnlyFetch with ReadOnlyWorldQuery](https://github.com/bevyengine/bevy/pull/4626)
+
+The trait ReadOnlyFetch has been replaced with ReadOnlyWorldQuery along with the WorldQueryGats::ReadOnlyFetch assoc type which has been replaced with <WorldQuery::ReadOnly as WorldQueryGats>::Fetch
+
+The trait `ReadOnlyFetch` has been replaced with `ReadOnlyWorldQuery` along with the `WorldQueryGats::ReadOnlyFetch` assoc type which has been replaced with `<WorldQuery::ReadOnly as WorldQueryGats>::Fetch`
+
+* Any where clauses such as `QueryFetch<Q>: ReadOnlyFetch` should be replaced with `Q: ReadOnlyWorldQuery`.
+* Any custom world query impls should implement `ReadOnlyWorldQuery` insead of `ReadOnlyFetch`
+
+Functions `update_component_access` and `update_archetype_component_access` have been moved from the `FetchState` trait to `WorldQuery`
+
+* Any callers should now call `Q::update_component_access(state` instead of `state.update_component_access` (and `update_archetype_component_access` respectively)
+* Any custom world query impls should move the functions from the `FetchState` impl to `WorldQuery` impl
+
+`WorldQuery` has been made an `unsafe trait`, `FetchState` has been made a safe `trait`. (I think this is how it should have always been, but regardless this is _definitely_ necessary now that the two functions have been moved to `WorldQuery`)
+
+* If you have a custom `FetchState` impl make it a normal `impl` instead of `unsafe impl`
+* If you have a custom `WorldQuery` impl make it an `unsafe impl`, if your code was sound before it is going to still be sound
+
+### [Fix unsoundness with Or/AnyOf/Option component access'](https://github.com/bevyengine/bevy/pull/4659)
+
+<!-- TODO make this a bit friendlier -->
+
+If you are now getting query conflicts from `Or`/`AnyOf`/`Option` rip to you and ur welcome for it now being caught.
+
+### [Remove task_pool parameter from par_for_each(_mut)](https://github.com/bevyengine/bevy/pull/4705)
+
+The `task_pool` parameter for `Query(State)::par_for_each(_mut)` has been removed. Remove these parameters from all calls to these functions.
+
+Before:
+
+```rust
+fn parallel_system(
+   task_pool: Res<ComputeTaskPool>,
+   query: Query<&MyComponent>,
+) {
+   query.par_for_each(&task_pool, 32, |comp| {
+        ...
+   });
+}
+```
+
+After:
+
+```rust
+fn parallel_system(query: Query<&MyComponent>) {
+   query.par_for_each(32, |comp| {
+        ...
+   });
+}
+```
+
+If using `Query(State)` outside of a system run by the scheduler, you may need to manually configure and initialize a `ComputeTaskPool` as a resource in the `World`.
+
+### [Fail to compile on 16-bit platforms](https://github.com/bevyengine/bevy/pull/4736)
+
+`bevy_ecs` will now explicitly fail to compile on 16-bit platforms. If this is required, there is currently no alternative. Please file an issue (<https://github.com/bevyengine/bevy/issues>) to help detail your use case.
+
+### [Camera Driven Rendering](https://github.com/bevyengine/bevy/pull/4745)
+
+<!-- TODO pls cart add a migration guide section :( -->
+
+This is a very complicated change and it is recommended to read the linked PRs for more details
+
+```rust
+// old 3d perspective camera
+commands.spawn_bundle(PerspectiveCameraBundle::default())
+
+// new 3d perspective camera
+commands.spawn_bundle(Camera3dBundle::default())
+```
+
+```rust
+// old 2d orthographic camera
+commands.spawn_bundle(OrthographicCameraBundle::new_2d())
+
+// new 2d orthographic camera
+commands.spawn_bundle(Camera2dBundle::default())
+```
+
+```rust
+// old 3d orthographic camera
+commands.spawn_bundle(OrthographicCameraBundle::new_3d())
+
+// new 3d orthographic camera
+commands.spawn_bundle(Camera3dBundle {
+    projection: OrthographicProjection {
+        scale: 3.0,
+        scaling_mode: ScalingMode::FixedVertical,
+        ..default()
+    }.into(),
+    ..default()
+})
+```
+
+UI no longer requires a dedicated camera. `UiCameraBundle` has been removed. `Camera2dBundle` and `Camera3dBundle` now both default to rendering UI as part of their own render graphs. To disable UI rendering for a camera, disable it using the CameraUi component:
+
+```rust
+commands
+    .spawn_bundle(Camera3dBundle::default())
+    .insert(CameraUi {
+        is_enabled: false,
+        ..default()
+    })
+```
+
+### [Enforce type safe usage of Handle::get](https://github.com/bevyengine/bevy/pull/4794)
+
+`Assets::<T>::get` and `Assets::<T>::get_mut` now require that the passed handles are `Handle<T>`, improving the type safety of handles. If you were previously passing in:
+
+* a `HandleId`, use `&Handle::weak(id)` instead, to create a weak handle. You may have been able to store a type safe `Handle` instead.
+* a `HandleUntyped`, use `&handle_untyped.typed_weak()` to create a weak handle of the specified type. This is most likely to be the useful when using [load_folder](https://docs.rs/bevy_asset/latest/bevy_asset/struct.AssetServer.html#method.load_folder)
+* a `Handle<U>` of  of a different type, consider whether this is the correct handle type to store. If it is (i.e. the same handle id is used for multiple different Asset types) use `Handle::weak(handle.id)` to cast to a different type.
+
+### [Allow higher order systems](https://github.com/bevyengine/bevy/pull/4833)
+
+<!-- TODO marked as breaking change, but need to figure out what actually is breaking -->
+
+### [Added offset parameter to TextureAtlas::from_grid_with_padding](https://github.com/bevyengine/bevy/pull/4836)
+
+Calls to `TextureAtlas::from_grid_with_padding` should be modified to include a new parameter, which can be set to `Vec2::ZERO` to retain old behaviour.
+
+```rust
+from_grid_with_padding(texture, tile_size, columns, rows, padding)
+                                  |
+                                  V
+from_grid_with_padding(texture, tile_size, columns, rows, padding, Vec2::ZERO)
+```
+
+### [Split mesh shader files](https://github.com/bevyengine/bevy/pull/4867)
+
+* In shaders for 3D meshes:
+  * `#import bevy_pbr::mesh_view_bind_group` -> `#import bevy_pbr::mesh_view_bindings`
+  * `#import bevy_pbr::mesh_struct` -> `#import bevy_pbr::mesh_types`
+    * NOTE: If you are using the mesh bind group at bind group index 2, you can remove those binding statements in your shader and just use `#import bevy_pbr::mesh_bindings` which itself imports the mesh types needed for the bindings.
+* In shaders for 2D meshes:
+  * `#import bevy_sprite::mesh2d_view_bind_group` -> `#import bevy_sprite::mesh2d_view_bindings`
+  * `#import bevy_sprite::mesh2d_struct` -> `#import bevy_sprite::mesh2d_types`
+    * NOTE: If you are using the mesh2d bind group at bind group index 2, you can remove those binding statements in your shader and just use `#import bevy_sprite::mesh2d_bindings` which itself imports the mesh2d types needed for the bindings.
+
+### [Camera Driven Viewports](https://github.com/bevyengine/bevy/pull/4898)
+
+`Camera::projection_matrix` is no longer a public field. Use the new `Camera::projection_matrix()` method instead:
+
+```rust
+
+// 0.7
+let projection = camera.projection_matrix;
+
+// 0.8
+let projection = camera.projection_matrix();
+```
+
+### [diagnostics: meaningful error when graph node has wrong number of inputs](https://github.com/bevyengine/bevy/pull/4924)
+
+Exhaustive matches on `RenderGraphRunnerError` will need to add a branch to handle the new `MismatchedInputCount` variant.
+
+### [Make Reflect safe to implement](https://github.com/bevyengine/bevy/pull/5010)
+
+* Reflect derives should not have to change anything
+* Manual reflect impls will need to remove the `unsafe` keyword, add `any()` implementations, and rename the old `any` and `any_mut` to `as_any` and `as_mut_any`.
+* Calls to `any`/`any_mut` must be changed to `as_any`/`as_mut_any`
+
+### [Mark mutable APIs under ECS storage as pub(crate)](https://github.com/bevyengine/bevy/pull/5065)
+
+<!-- Dear God, I hope not. -->
+
+If you experienced any problems caused by this change, please [create an issue](https://github.com/bevyengine/bevy/issues) explaining _in detail_ what you were doing with those apis.