a304fd9a99
# Objective - Hierarchy tools are not just used for `Transform`: they are also used for scenes. - In the future there's interest in using them for other features, such as visiibility inheritance. - The fact that these tools are found in `bevy_transform` causes a great deal of user and developer confusion - Fixes #2758. ## Solution - Split `bevy_transform` into two! - Make everything work again. Note that this is a very tightly scoped PR: I *know* there are code quality and docs issues that existed in bevy_transform that I've just moved around. We should fix those in a seperate PR and try to merge this ASAP to reduce the bitrot involved in splitting an entire crate. ## Frustrations The API around `GlobalTransform` is a mess: we have massive code and docs duplication, no link between the two types and no clear way to extend this to other forms of inheritance. In the medium-term, I feel pretty strongly that `GlobalTransform` should be replaced by something like `Inherited<Transform>`, which lives in `bevy_hierarchy`: - avoids code duplication - makes the inheritance pattern extensible - links the types at the type-level - allows us to remove all references to inheritance from `bevy_transform`, making it more useful as a standalone crate and cleaning up its docs ## Additional context - double-blessed by @cart in https://github.com/bevyengine/bevy/issues/4141#issuecomment-1063592414 and https://github.com/bevyengine/bevy/issues/2758#issuecomment-913810963 - preparation for more advanced / cleaner hierarchy tools: go read https://github.com/bevyengine/rfcs/pull/53 ! - originally attempted by @finegeometer in #2789. It was a great idea, just needed more discussion! Co-authored-by: Carter Anderson <mcanders1@gmail.com>
73 lines
2.9 KiB
Rust
73 lines
2.9 KiB
Rust
use crate::components::*;
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use bevy_ecs::{
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entity::Entity,
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prelude::Changed,
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query::Without,
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system::{Commands, Query},
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};
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use bevy_utils::HashMap;
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use smallvec::SmallVec;
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/// Updates parents when the hierarchy is changed
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pub fn parent_update_system(
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mut commands: Commands,
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removed_parent_query: Query<(Entity, &PreviousParent), Without<Parent>>,
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mut parent_query: Query<(Entity, &Parent, Option<&mut PreviousParent>), Changed<Parent>>,
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mut children_query: Query<&mut Children>,
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) {
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// Entities with a missing `Parent` (ie. ones that have a `PreviousParent`), remove
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// them from the `Children` of the `PreviousParent`.
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for (entity, previous_parent) in removed_parent_query.iter() {
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if let Ok(mut previous_parent_children) = children_query.get_mut(previous_parent.0) {
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previous_parent_children.0.retain(|e| *e != entity);
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commands.entity(entity).remove::<PreviousParent>();
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}
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}
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// Tracks all newly created `Children` Components this frame.
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let mut children_additions = HashMap::<Entity, SmallVec<[Entity; 8]>>::default();
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// Entities with a changed Parent (that also have a PreviousParent, even if None)
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for (entity, parent, possible_previous_parent) in parent_query.iter_mut() {
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if let Some(mut previous_parent) = possible_previous_parent {
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// New and previous point to the same Entity, carry on, nothing to see here.
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if previous_parent.0 == parent.0 {
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continue;
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}
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// Remove from `PreviousParent.Children`.
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if let Ok(mut previous_parent_children) = children_query.get_mut(previous_parent.0) {
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(*previous_parent_children).0.retain(|e| *e != entity);
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}
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// Set `PreviousParent = Parent`.
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*previous_parent = PreviousParent(parent.0);
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} else {
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commands.entity(entity).insert(PreviousParent(parent.0));
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};
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// Add to the parent's `Children` (either the real component, or
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// `children_additions`).
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if let Ok(mut new_parent_children) = children_query.get_mut(parent.0) {
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// This is the parent
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// PERF: Ideally we shouldn't need to check for duplicates
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if !(*new_parent_children).0.contains(&entity) {
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(*new_parent_children).0.push(entity);
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}
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} else {
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// The parent doesn't have a children entity, lets add it
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children_additions
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.entry(parent.0)
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.or_insert_with(Default::default)
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.push(entity);
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}
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}
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// Flush the `children_additions` to the command buffer. It is stored separate to
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// collect multiple new children that point to the same parent into the same
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// SmallVec, and to prevent redundant add+remove operations.
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children_additions.iter().for_each(|(e, v)| {
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commands.entity(*e).insert(Children::with(v));
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});
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}
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