18243240671

Committed 04 Oct 2025 10:36AM UTC coverage: 66.58% (+0.1%) from 66.455%

Build # 18243240671

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push

github

Committed by

web-flow

Commit Message

Split extraction and render into unit systems (#499)

Reorganize most of the extraction and render systems into smaller,
unit-like systems with limited (ideally, a single) responsibility. Split
most of the data into separate, smaller components too. This not only
enable better multithreading, but also greatly simplify maintenance by
clarifying the logic and responsibility of each system and component.

As part of this change, add a "ready state" to the effect, which is read
back from the render world and informs the main world about whether an
effect is ready for simulation and rendering. This includes:

- All GPU resources being allocated, and in particular the PSOs
  (pipelines) which in Bevy are compiled asynchronously and can be very
  slow (many frames of delay).
- The ready state of all descendant effects, recursively. This ensures a
  child is ready to _e.g._ receive GPU spawn events before its parent,
  which emits those events, starts simulating.

This new ready state is accessed via
`CompiledParticleEffect::is_ready()`. Note that the state is updated
during the extract phase with the information collected from the
previous render frame, so by the time `is_ready()` returns `true`,
already one frame of simulation and rendering generally occurred.

Remove the outdated `copyless` dependency.

Run Details

594 of 896 new or added lines in 12 files covered. (66.29%)

21 existing lines in 3 files now uncovered.

5116 of 7684 relevant lines covered (66.58%)

416.91 hits per line

Source File
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78.83

/src/render/effect_cache.rs

use std::{
    cmp::Ordering,
    num::{NonZeroU32, NonZeroU64},
    ops::Range,
};

use bevy::{
    asset::Handle,
    ecs::{component::Component, resource::Resource},
    log::{trace, warn},
    platform::collections::HashMap,
    render::{mesh::allocator::MeshBufferSlice, render_resource::*, renderer::RenderDevice},
    utils::default,
};
use bytemuck::cast_slice_mut;

use super::{buffer_table::BufferTableId, BufferBindingSource};
use crate::{
    asset::EffectAsset,
    render::{
        calc_hash, event::GpuChildInfo, GpuDrawIndexedIndirectArgs, GpuDrawIndirectArgs,
        GpuEffectMetadata, GpuSpawnerParams, StorageType as _, INDIRECT_INDEX_SIZE,
    },
    ParticleLayout,
};

/// Describes all particle slices of particles in the particle buffer
/// for a single effect.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct EffectSlice {
    /// Slice into the underlying [`BufferVec`].
    ///
    /// This is measured in items, not bytes.
    pub slice: Range<u32>,
    /// ID of the particle slab in the [`EffectCache`].
    pub slab_id: SlabId,
    /// Particle layout of the effect.
    pub particle_layout: ParticleLayout,
}

impl Ord for EffectSlice {
    fn cmp(&self, other: &Self) -> Ordering {
        match self.slab_id.cmp(&other.slab_id) {
            Ordering::Equal => self.slice.start.cmp(&other.slice.start),
            ord => ord,
        }
    }
}

impl PartialOrd for EffectSlice {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

/// A reference to a slice allocated inside an [`ParticleSlab`].
#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct SlabSliceRef {
    /// Range into an [`ParticleSlab`], in item count.
    range: Range<u32>,
    pub(crate) particle_layout: ParticleLayout,
}

impl SlabSliceRef {
    /// The length of the slice, in number of items.
    #[allow(dead_code)]
    pub fn len(&self) -> u32 {
        self.range.end - self.range.start
    }

    /// The size in bytes of the slice.
    #[allow(dead_code)]
    pub fn byte_size(&self) -> usize {
        (self.len() as usize) * (self.particle_layout.min_binding_size().get() as usize)
    }

    pub fn range(&self) -> Range<u32> {
        self.range.clone()
    }
}

#[derive(Debug, Default, Clone, Copy, PartialEq, Eq)]
struct SimBindGroupKey {
    buffer: Option<BufferId>,
    offset: u32,
    size: u32,
}

impl SimBindGroupKey {
    /// Invalid key, often used as placeholder.
    pub const INVALID: Self = Self {
        buffer: None,
        offset: u32::MAX,
        size: 0,
    };
}

impl From<&BufferBindingSource> for SimBindGroupKey {
    fn from(value: &BufferBindingSource) -> Self {
        Self {
            buffer: Some(value.buffer.id()),
            offset: value.offset,
            size: value.size.get(),
        }
    }
}

impl From<Option<&BufferBindingSource>> for SimBindGroupKey {
    fn from(value: Option<&BufferBindingSource>) -> Self {
        if let Some(bbs) = value {
            Self {
                buffer: Some(bbs.buffer.id()),
                offset: bbs.offset,
                size: bbs.size.get(),
            }
        } else {
            Self::INVALID
        }
    }
}

/// State of a [`ParticleSlab`] after an insertion or removal operation.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SlabState {
    /// The slab is in use, with allocated resources.
    Used,
    /// Like `Used`, but the slab was resized, so any bind group is
    /// nonetheless invalid.
    Resized,
    /// The slab is free (its resources were deallocated).
    Free,
}

/// ID of a [`ParticleSlab`] inside an [`EffectCache`].
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct SlabId(u32);

impl SlabId {
    /// An invalid value, often used as placeholder.
    pub const INVALID: SlabId = SlabId(u32::MAX);

    /// Create a new slab ID from its underlying index.
    pub const fn new(index: u32) -> Self {
        assert!(index != u32::MAX);
        Self(index)
    }

    /// Check if the current ID is valid, that is, is different from
    /// [`INVALID`].
    ///
    /// [`INVALID`]: Self::INVALID
    #[inline]
    pub const fn is_valid(&self) -> bool {
        self.0 != Self::INVALID.0
    }

    /// Get the raw underlying index.
    ///
    /// This is mostly used for debugging / logging.
    #[inline]
    pub const fn index(&self) -> u32 {
        self.0
    }
}

impl Default for SlabId {
    fn default() -> Self {
        Self::INVALID
    }
}

/// Storage for the per-particle data of effects sharing compatible layouts.
///
/// Currently only accepts a single unique particle layout, fixed at creation.
/// If an effect has a different particle layout, it needs to be stored in a
/// different slab.
///
/// Also currently only accepts instances of a unique effect asset, although
/// this restriction is purely for convenience and may be relaxed in the future
/// to improve batching.
#[derive(Debug)]
pub struct ParticleSlab {
    /// GPU buffer storing all particles for the entire slab of effects.
    ///
    /// Each particle is a collection of attributes arranged according to
    /// [`Self::particle_layout`]. The buffer contains storage for exactly
    /// [`Self::capacity`] particles.
    particle_buffer: Buffer,
    /// GPU buffer storing the indirection indices for the entire slab of
    /// effects.
    ///
    /// Each indirection item contains 3 values:
    /// - the ping-pong alive particles and render indirect indices at offsets 0
    ///   and 1
    /// - the dead particle indices at offset 2
    ///
    /// The buffer contains storage for exactly [`Self::capacity`] items.
    indirect_index_buffer: Buffer,
    /// Layout of particles.
    particle_layout: ParticleLayout,
    /// Total slab capacity, in number of particles.
    capacity: u32,
    /// Used slab size, in number of particles, either from allocated slices
    /// or from slices in the free list.
    used_size: u32,
    /// Array of free slices for new allocations, sorted in increasing order
    /// inside the slab buffers.
    free_slices: Vec<Range<u32>>,

    /// Handle of all effects common in this slab. TODO - replace with
    /// compatible layout.
    asset: Handle<EffectAsset>,
    /// Layout of the particle@1 bind group for the render pass.
    // TODO - move; this only depends on the particle and spawner layouts, can be shared across
    // slabs
    render_particles_buffer_layout: BindGroupLayout,
    /// Bind group particle@1 of the simulation passes (init and udpate).
    sim_bind_group: Option<BindGroup>,
    /// Key the `sim_bind_group` was created from.
    sim_bind_group_key: SimBindGroupKey,
}

impl ParticleSlab {
    /// Minimum buffer capacity to allocate, in number of particles.
    // FIXME - Batching is broken due to binding a single GpuSpawnerParam instead of
    // N, and inability for a particle index to tell which Spawner it should
    // use. Setting this to 1 effectively ensures that all new buffers just fit
    // the effect, so batching never occurs.
    pub const MIN_CAPACITY: u32 = 1; // 65536; // at least 64k particles

    /// Create a new slab and the GPU resources to back it up.
    ///
    /// The slab cannot contain less than [`MIN_CAPACITY`] particles. If the
    /// input `capacity` is smaller, it's rounded up to [`MIN_CAPACITY`].
    ///
    /// [`MIN_CAPACITY`]: Self::MIN_CAPACITY
    pub fn new(
        slab_id: SlabId,
        asset: Handle<EffectAsset>,
        capacity: u32,
        particle_layout: ParticleLayout,
        render_device: &RenderDevice,
    ) -> Self {
        trace!(
            "ParticleSlab::new(slab_id={}, capacity={}, particle_layout={:?}, item_size={}B)",
            slab_id.0,
            capacity,
            particle_layout,
            particle_layout.min_binding_size().get(),
        );

        // Calculate the clamped capacity of the group, in number of particles.
        let capacity = capacity.max(Self::MIN_CAPACITY);
        debug_assert!(
            capacity > 0,
            "Attempted to create a zero-sized effect buffer."
        );

        // Allocate the particle buffer itself, containing the attributes of each
        // particle.
        let particle_capacity_bytes: BufferAddress =
            capacity as u64 * particle_layout.min_binding_size().get();
        let particle_label = format!("hanabi:buffer:slab{}:particle", slab_id.0);
        let particle_buffer = render_device.create_buffer(&BufferDescriptor {
            label: Some(&particle_label),
            size: particle_capacity_bytes,
            usage: BufferUsages::COPY_DST | BufferUsages::STORAGE,
            mapped_at_creation: false,
        });

        // Each indirect buffer stores 3 arrays of u32, of length the number of
        // particles.
        let capacity_bytes: BufferAddress = capacity as u64 * 4 * 3;

        let indirect_label = format!("hanabi:buffer:slab{}:indirect", slab_id.0);
        let indirect_index_buffer = render_device.create_buffer(&BufferDescriptor {
            label: Some(&indirect_label),
            size: capacity_bytes,
            usage: BufferUsages::COPY_DST | BufferUsages::STORAGE,
            mapped_at_creation: true,
        });
        // Set content
        {
            // Scope get_mapped_range_mut() to force a drop before unmap()
            {
                let slice: &mut [u8] = &mut indirect_index_buffer
                    .slice(..capacity_bytes)
                    .get_mapped_range_mut();
                let slice: &mut [u32] = cast_slice_mut(slice);
                for index in 0..capacity {
                    slice[3 * index as usize + 2] = capacity - 1 - index;
                }
            }
            indirect_index_buffer.unmap();
        }

        // Create the render layout.
        // TODO - move; this only depends on the particle and spawner layouts, can be
        // shared across slabs
        let spawner_params_size = GpuSpawnerParams::aligned_size(
            render_device.limits().min_storage_buffer_offset_alignment,
        );
        let entries = [
            // @group(1) @binding(0) var<storage, read> particle_buffer : ParticleBuffer;
            BindGroupLayoutEntry {
                binding: 0,
                visibility: ShaderStages::VERTEX_FRAGMENT,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Storage { read_only: true },
                    has_dynamic_offset: false,
                    min_binding_size: Some(particle_layout.min_binding_size()),
                },
                count: None,
            },
            // @group(1) @binding(1) var<storage, read> indirect_buffer : IndirectBuffer;
            BindGroupLayoutEntry {
                binding: 1,
                visibility: ShaderStages::VERTEX,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Storage { read_only: true },
                    has_dynamic_offset: false,
                    min_binding_size: Some(NonZeroU64::new(INDIRECT_INDEX_SIZE as u64).unwrap()),
                },
                count: None,
            },
            // @group(1) @binding(2) var<storage, read> spawner : Spawner;
            BindGroupLayoutEntry {
                binding: 2,
                visibility: ShaderStages::VERTEX,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Storage { read_only: true },
                    has_dynamic_offset: true,
                    min_binding_size: Some(spawner_params_size),
                },
                count: None,
            },
        ];
        let label = format!(
            "hanabi:bind_group_layout:render:particles@1:vfx{}",
            slab_id.0
        );
        trace!(
            "Creating render layout '{}' with {} entries",
            label,
            entries.len(),
        );
        let render_particles_buffer_layout =
            render_device.create_bind_group_layout(&label[..], &entries[..]);

        Self {
            particle_buffer,
            indirect_index_buffer,
            particle_layout,
            render_particles_buffer_layout,
            capacity,
            used_size: 0,
            free_slices: vec![],
            asset,
            sim_bind_group: None,
            sim_bind_group_key: SimBindGroupKey::INVALID,
        }
    }

    // TODO - move; this only depends on the particle and spawner layouts, can be
    // shared across slabs
    pub fn render_particles_buffer_layout(&self) -> &BindGroupLayout {
        &self.render_particles_buffer_layout
    }

    #[inline]
    pub fn particle_buffer(&self) -> &Buffer {
        &self.particle_buffer
    }

    #[inline]
    pub fn indirect_index_buffer(&self) -> &Buffer {
        &self.indirect_index_buffer
    }

    #[inline]
    pub fn particle_offset(&self, row: u32) -> u32 {
        self.particle_layout.min_binding_size().get() as u32 * row
    }

    #[inline]
    pub fn indirect_index_offset(&self, row: u32) -> u32 {
        row * 12
    }

    /// Return a binding for the entire particle buffer.
    pub fn as_entire_binding_particle(&self) -> BindingResource<'_> {
        let capacity_bytes = self.capacity as u64 * self.particle_layout.min_binding_size().get();
        BindingResource::Buffer(BufferBinding {
            buffer: &self.particle_buffer,
            offset: 0,
            size: Some(NonZeroU64::new(capacity_bytes).unwrap()),
        })
        //self.particle_buffer.as_entire_binding()
    }

    /// Return a binding source for the entire particle buffer.
    pub fn max_binding_source(&self) -> BufferBindingSource {
        let capacity_bytes = self.capacity * self.particle_layout.min_binding_size32().get();
        BufferBindingSource {
            buffer: self.particle_buffer.clone(),
            offset: 0,
            size: NonZeroU32::new(capacity_bytes).unwrap(),
        }
    }

    /// Return a binding for the entire indirect buffer associated with the
    /// current effect buffer.
    pub fn as_entire_binding_indirect(&self) -> BindingResource<'_> {
        let capacity_bytes = self.capacity as u64 * 12;
        BindingResource::Buffer(BufferBinding {
            buffer: &self.indirect_index_buffer,
            offset: 0,
            size: Some(NonZeroU64::new(capacity_bytes).unwrap()),
        })
        //self.indirect_index_buffer.as_entire_binding()
    }

    /// Create the "particle" bind group @1 for the init and update passes if
    /// needed.
    ///
    /// The `slab_id` must be the ID of the current [`ParticleSlab`] inside the
    /// [`EffectCache`].
    pub fn create_particle_sim_bind_group(
        &mut self,
        layout: &BindGroupLayout,
        slab_id: &SlabId,
        render_device: &RenderDevice,
        parent_binding_source: Option<&BufferBindingSource>,
    ) {
        let key: SimBindGroupKey = parent_binding_source.into();
        if self.sim_bind_group.is_some() && self.sim_bind_group_key == key {
            return;
        }

        let label = format!("hanabi:bind_group:sim:particle@1:vfx{}", slab_id.index());
        let entries: &[BindGroupEntry] = if let Some(parent_binding) =
            parent_binding_source.as_ref().map(|bbs| bbs.as_binding())
        {
            &[
                BindGroupEntry {
                    binding: 0,
                    resource: self.as_entire_binding_particle(),
                },
                BindGroupEntry {
                    binding: 1,
                    resource: self.as_entire_binding_indirect(),
                },
                BindGroupEntry {
                    binding: 2,
                    resource: parent_binding,
                },
            ]
        } else {
            &[
                BindGroupEntry {
                    binding: 0,
                    resource: self.as_entire_binding_particle(),
                },
                BindGroupEntry {
                    binding: 1,
                    resource: self.as_entire_binding_indirect(),
                },
            ]
        };

        trace!(
            "Create particle simulation bind group '{}' with {} entries (has_parent:{})",
            label,
            entries.len(),
            parent_binding_source.is_some(),
        );
        let bind_group = render_device.create_bind_group(Some(&label[..]), layout, entries);
        self.sim_bind_group = Some(bind_group);
        self.sim_bind_group_key = key;
    }

    /// Invalidate any existing simulate bind group.
    ///
    /// Invalidate any existing bind group previously created by
    /// [`create_particle_sim_bind_group()`], generally because a buffer was
    /// re-allocated. This forces a re-creation of the bind group
    /// next time [`create_particle_sim_bind_group()`] is called.
    ///
    /// [`create_particle_sim_bind_group()`]: self::ParticleSlab::create_particle_sim_bind_group
    #[allow(dead_code)] // FIXME - review this...
    fn invalidate_particle_sim_bind_group(&mut self) {
        self.sim_bind_group = None;
        self.sim_bind_group_key = SimBindGroupKey::INVALID;
    }

    /// Return the cached particle@1 bind group for the simulation (init and
    /// update) passes.
    ///
    /// This is the per-buffer bind group at binding @1 which binds all
    /// per-buffer resources shared by all effect instances batched in a single
    /// buffer. The bind group is created by
    /// [`create_particle_sim_bind_group()`], and cached until a call to
    /// [`invalidate_particle_sim_bind_groups()`] clears the
    /// cached reference.
    ///
    /// [`create_particle_sim_bind_group()`]: self::ParticleSlab::create_particle_sim_bind_group
    /// [`invalidate_particle_sim_bind_groups()`]: self::ParticleSlab::invalidate_particle_sim_bind_groups
    pub fn particle_sim_bind_group(&self) -> Option<&BindGroup> {
        self.sim_bind_group.as_ref()
    }

    /// Try to recycle a free slice to store `size` items.
    fn pop_free_slice(&mut self, size: u32) -> Option<Range<u32>> {
        if self.free_slices.is_empty() {
            return None;
        }

        struct BestRange {
            range: Range<u32>,
            capacity: u32,
            index: usize,
        }

        let mut result = BestRange {
            range: 0..0, // marker for "invalid"
            capacity: u32::MAX,
            index: usize::MAX,
        };
        for (index, slice) in self.free_slices.iter().enumerate() {
            let capacity = slice.end - slice.start;
            if size > capacity {
                continue;
            }
            if capacity < result.capacity {
                result = BestRange {
                    range: slice.clone(),
                    capacity,
                    index,
                };
            }
        }
        if !result.range.is_empty() {
            if result.capacity > size {
                // split
                let start = result.range.start;
                let used_end = start + size;
                let free_end = result.range.end;
                let range = start..used_end;
                self.free_slices[result.index] = used_end..free_end;
                Some(range)
            } else {
                // recycle entirely
                self.free_slices.remove(result.index);
                Some(result.range)
            }
        } else {
            None
        }
    }

    /// Allocate a new entry in the slab to store the particles of a single
    /// effect.
    pub fn allocate(&mut self, capacity: u32) -> Option<SlabSliceRef> {
        trace!("ParticleSlab::allocate(capacity={})", capacity);

        if capacity > self.capacity {
            return None;
        }

        let range = if let Some(range) = self.pop_free_slice(capacity) {
            range
        } else {
            let new_size = self.used_size.checked_add(capacity).unwrap();
            if new_size <= self.capacity {
                let range = self.used_size..new_size;
                self.used_size = new_size;
                range
            } else {
                if self.used_size == 0 {
                    warn!(
                        "Cannot allocate slice of size {} in particle slab of capacity {}.",
                        capacity, self.capacity
                    );
                }
                return None;
            }
        };

        trace!("-> allocated slice {:?}", range);
        Some(SlabSliceRef {
            range,
            particle_layout: self.particle_layout.clone(),
        })
    }

    /// Free an allocated slice, and if this was the last allocated slice also
    /// free the buffer.
    pub fn free_slice(&mut self, slice: SlabSliceRef) -> SlabState {
        // If slice is at the end of the buffer, reduce total used size
        if slice.range.end == self.used_size {
            self.used_size = slice.range.start;
            // Check other free slices to further reduce used size and drain the free slice
            // list
            while let Some(free_slice) = self.free_slices.last() {
                if free_slice.end == self.used_size {
                    self.used_size = free_slice.start;
                    self.free_slices.pop();
                } else {
                    break;
                }
            }
            if self.used_size == 0 {
                assert!(self.free_slices.is_empty());
                // The buffer is not used anymore, free it too
                SlabState::Free
            } else {
                // There are still some slices used, the last one of which ends at
                // self.used_size
                SlabState::Used
            }
        } else {
            // Free slice is not at end; insert it in free list
            let range = slice.range;
            match self.free_slices.binary_search_by(|s| {
                if s.end <= range.start {
                    Ordering::Less
                } else if s.start >= range.end {
                    Ordering::Greater
                } else {
                    Ordering::Equal
                }
            }) {
                Ok(_) => warn!("Range {:?} already present in free list!", range),
                Err(index) => self.free_slices.insert(index, range),
            }
            SlabState::Used
        }
    }

    /// Check whether this slab is compatible with the given asset.
    ///
    /// This allows determining whether an instance of the effect can be stored
    /// inside this slab.
    pub fn is_compatible(
        &self,
        handle: &Handle<EffectAsset>,
        _particle_layout: &ParticleLayout,
    ) -> bool {
        // TODO - replace with check particle layout is compatible to allow tighter
        // packing in less buffers, and update in the less dispatch calls
        *handle == self.asset
    }
}

/// A single cached effect in the [`EffectCache`].
#[derive(Debug, Component)]
pub(crate) struct CachedEffect {
    /// ID of the slab of the slab storing the particles for this effect in the
    /// [`EffectCache`].
    pub slab_id: SlabId,
    /// The allocated effect slice within that slab.
    pub slice: SlabSliceRef,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum AnyDrawIndirectArgs {
    /// Args of a non-indexed draw call.
    NonIndexed(GpuDrawIndirectArgs),
    /// Args of an indexed draw call.
    Indexed(GpuDrawIndexedIndirectArgs),
}

impl AnyDrawIndirectArgs {
    /// Create from a vertex buffer slice and an optional index buffer one.
    pub fn from_slices(
        vertex_slice: &MeshBufferSlice<'_>,
        index_slice: Option<&MeshBufferSlice<'_>>,
    ) -> Self {
        if let Some(index_slice) = index_slice {
            Self::Indexed(GpuDrawIndexedIndirectArgs {
                index_count: index_slice.range.len() as u32,
                instance_count: 0,
                first_index: index_slice.range.start,
                base_vertex: vertex_slice.range.start as i32,
                first_instance: 0,
            })
        } else {
            Self::NonIndexed(GpuDrawIndirectArgs {
                vertex_count: vertex_slice.range.len() as u32,
                instance_count: 0,
                first_vertex: vertex_slice.range.start,
                first_instance: 0,
            })
        }
    }

    /// Check if this args are for an indexed draw call.
    #[inline(always)]
    pub fn is_indexed(&self) -> bool {
        matches!(*self, Self::Indexed(..))
    }

    /// Bit-cast the args to the row entry of the GPU buffer.
    ///
    /// If non-indexed, this returns an indexed struct bit-cast from the actual
    /// non-indexed one, ready for GPU upload.
    pub fn bitcast_to_row_entry(&self) -> GpuDrawIndexedIndirectArgs {
        match self {
            AnyDrawIndirectArgs::NonIndexed(args) => GpuDrawIndexedIndirectArgs {
                index_count: args.vertex_count,
                instance_count: args.instance_count,
                first_index: args.first_vertex,
                base_vertex: args.first_instance as i32,
                first_instance: 0,
            },
            AnyDrawIndirectArgs::Indexed(args) => *args,
        }
    }
}

impl From<GpuDrawIndirectArgs> for AnyDrawIndirectArgs {
    fn from(args: GpuDrawIndirectArgs) -> Self {
        Self::NonIndexed(args)
    }
}

impl From<GpuDrawIndexedIndirectArgs> for AnyDrawIndirectArgs {
    fn from(args: GpuDrawIndexedIndirectArgs) -> Self {
        Self::Indexed(args)
    }
}

/// Index of a row (entry) into the [`BufferTable`] storing the indirect draw
/// args of a single draw call.
#[derive(Debug, Clone, Copy, Component)]
pub(crate) struct CachedDrawIndirectArgs {
    pub row: BufferTableId,
    pub args: AnyDrawIndirectArgs,
}

impl Default for CachedDrawIndirectArgs {
    fn default() -> Self {
        Self {
            row: BufferTableId::INVALID,
            args: AnyDrawIndirectArgs::NonIndexed(default()),
        }
    }
}

impl CachedDrawIndirectArgs {
    /// Check if the index is valid.
    ///
    /// An invalid index doesn't correspond to any allocated args entry. A valid
    /// one may, but note that the args entry in the buffer may have been freed
    /// already with this index. There's no mechanism to detect reuse either.
    #[inline(always)]
    pub fn is_valid(&self) -> bool {
        self.get_row_raw().is_valid()
    }

    /// Check if this row index refers to an indexed draw args entry.
    #[inline(always)]
    pub fn is_indexed(&self) -> bool {
        self.args.is_indexed()
    }

    /// Get the raw index value.
    ///
    /// Retrieve the raw index value, losing the discriminant between indexed
    /// and non-indexed draw. This is useful when storing the index value into a
    /// GPU buffer. The rest of the time, prefer retaining the typed enum for
    /// safety.
    ///
    /// # Panics
    ///
    /// Panics if the index is invalid, whether indexed or non-indexed.
    pub fn get_row(&self) -> BufferTableId {
        let idx = self.get_row_raw();
        assert!(idx.is_valid());
        idx
    }

    #[inline(always)]
    fn get_row_raw(&self) -> BufferTableId {
        self.row
    }
}

/// The indices in the indirect dispatch buffers for a single effect, as well as
/// that of the metadata buffer.
#[derive(Debug, Default, Clone, Copy, Component)]
pub(crate) struct DispatchBufferIndices {
    /// The index of the [`GpuDispatchIndirect`] row in the GPU buffer
    /// [`EffectsMeta::update_dispatch_indirect_buffer`].
    ///
    /// [`GpuDispatchIndirect`]: super::GpuDispatchIndirect
    /// [`EffectsMeta::update_dispatch_indirect_buffer`]: super::EffectsMeta::dispatch_indirect_buffer
    pub(crate) update_dispatch_indirect_buffer_row_index: u32,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
struct ParticleBindGroupLayoutKey {
    pub min_binding_size: NonZeroU32,
    pub parent_min_binding_size: Option<NonZeroU32>,
}

/// Cache for effect instances sharing common GPU data structures.
#[derive(Resource)]
pub struct EffectCache {
    /// Render device the GPU resources (buffers) are allocated from.
    render_device: RenderDevice,
    /// Collection of particle slabs managed by this cache. Some slabs might be
    /// `None` if the entry is not used. Since the slabs are referenced
    /// by index, we cannot move them once they're allocated.
    particle_slabs: Vec<Option<ParticleSlab>>,
    /// Cache of bind group layouts for the particle@1 bind groups of the
    /// simulation passes (init and update). Since all bindings depend only
    /// on buffers managed by the [`EffectCache`], we also cache the layouts
    /// here for convenience.
    particle_bind_group_layouts: HashMap<ParticleBindGroupLayoutKey, BindGroupLayout>,
    /// Cache of bind group layouts for the metadata@3 bind group of the init
    /// pass.
    metadata_init_bind_group_layout: [Option<BindGroupLayout>; 2],
    /// Cache of bind group layouts for the metadata@3 bind group of the
    /// updatepass.
    metadata_update_bind_group_layouts: HashMap<u32, BindGroupLayout>,
}

impl EffectCache {
    /// Create a new empty cache.
    pub fn new(device: RenderDevice) -> Self {
        Self {
            render_device: device,
            particle_slabs: vec![],
            particle_bind_group_layouts: default(),
            metadata_init_bind_group_layout: [None, None],
            metadata_update_bind_group_layouts: default(),
        }
    }

    /// Get all the particle slab slots. Unallocated slots are `None`. This can
    /// be indexed by the slab index.
    #[allow(dead_code)]
    #[inline]
    pub fn slabs(&self) -> &[Option<ParticleSlab>] {
        &self.particle_slabs
    }

    /// Get all the particle slab slots. Unallocated slots are `None`. This can
    /// be indexed by the slab ID.
    #[allow(dead_code)]
    #[inline]
    pub fn slabs_mut(&mut self) -> &mut [Option<ParticleSlab>] {
        &mut self.particle_slabs
    }

    /// Fetch a specific slab by ID.
    #[inline]
    pub fn get_slab(&self, slab_id: &SlabId) -> Option<&ParticleSlab> {
        self.particle_slabs.get(slab_id.0 as usize)?.as_ref()
    }

    /// Fetch a specific buffer by ID.
    #[allow(dead_code)]
    #[inline]
    pub fn get_slab_mut(&mut self, slab_id: &SlabId) -> Option<&mut ParticleSlab> {
        self.particle_slabs.get_mut(slab_id.0 as usize)?.as_mut()
    }

    /// Invalidate all the particle@1 bind group for all buffers.
    ///
    /// This iterates over all valid buffers and calls
    /// [`ParticleSlab::invalidate_particle_sim_bind_group()`] on each one.
    #[allow(dead_code)] // FIXME - review this...
    pub fn invalidate_particle_sim_bind_groups(&mut self) {
        for buffer in self.particle_slabs.iter_mut().flatten() {
            buffer.invalidate_particle_sim_bind_group();
        }
    }

    /// Insert a new effect instance in the cache.
    pub fn insert(
        &mut self,
        asset: Handle<EffectAsset>,
        capacity: u32,
        particle_layout: &ParticleLayout,
    ) -> CachedEffect {
        trace!("Inserting new effect into cache: capacity={capacity}");
        let (slab_id, slice) = self
            .particle_slabs
            .iter_mut()
            .enumerate()
            .find_map(|(slab_index, maybe_slab)| {
                // Ignore empty (non-allocated) entries as we're trying to fit the new allocation inside an existing slab.
                let Some(slab) = maybe_slab else { return None; };

                // The slab must be compatible with the effect's layout, otherwise ignore it.
                if !slab.is_compatible(&asset, particle_layout) {
                    return None;
                }

                // Try to allocate a slice into the slab
                slab
                    .allocate(capacity)
                    .map(|slice| (SlabId::new(slab_index as u32), slice))
            })
            .unwrap_or_else(|| {
                // Cannot find any suitable slab; allocate a new one
                let index = self.particle_slabs.iter().position(|buf| buf.is_none()).unwrap_or(self.particle_slabs.len());
                let byte_size = capacity.checked_mul(particle_layout.min_binding_size().get() as u32).unwrap_or_else(|| panic!(
                    "Effect size overflow: capacity={:?} particle_layout={:?} item_size={}",
                    capacity, particle_layout, particle_layout.min_binding_size().get()
                ));
                trace!(
                    "Creating new particle slab #{} for effect {:?} (capacity={:?}, particle_layout={:?} item_size={}, byte_size={})",
                    index,
                    asset,
                    capacity,
                    particle_layout,
                    particle_layout.min_binding_size().get(),
                    byte_size
                );
                let slab_id = SlabId::new(index as u32);
                let mut slab = ParticleSlab::new(
                    slab_id,
                    asset,
                    capacity,
                    particle_layout.clone(),
                    &self.render_device,
                );
                let slice_ref = slab.allocate(capacity).unwrap();
                if index >= self.particle_slabs.len() {
                    self.particle_slabs.push(Some(slab));
                } else {
                    debug_assert!(self.particle_slabs[index].is_none());
                    self.particle_slabs[index] = Some(slab);
                }
                (slab_id, slice_ref)
            });

        let slice = SlabSliceRef {
            range: slice.range.clone(),
            particle_layout: slice.particle_layout,
        };

        trace!(
            "Insert effect slab_id={} slice={}B particle_layout={:?}",
            slab_id.0,
            slice.particle_layout.min_binding_size().get(),
            slice.particle_layout,
        );
        CachedEffect { slab_id, slice }
    }

    /// Remove an effect from the cache. If this was the last effect, drop the
    /// underlying buffer and return the index of the dropped buffer.
    pub fn remove(&mut self, cached_effect: &CachedEffect) -> Result<SlabState, ()> {
        // Resolve the buffer by index
        let Some(maybe_buffer) = self
            .particle_slabs
            .get_mut(cached_effect.slab_id.0 as usize)
        else {
            return Err(());
        };
        let Some(buffer) = maybe_buffer.as_mut() else {
            return Err(());
        };

        // Free the slice inside the resolved buffer
        if buffer.free_slice(cached_effect.slice.clone()) == SlabState::Free {
            *maybe_buffer = None;
            return Ok(SlabState::Free);
        }

        Ok(SlabState::Used)
    }

    //
    // Bind group layouts
    //

    /// Ensure a bind group layout exists for the bind group @1 ("particles")
    /// for use with the given min binding sizes.
    pub fn ensure_particle_bind_group_layout(
        &mut self,
        min_binding_size: NonZeroU32,
        parent_min_binding_size: Option<NonZeroU32>,
    ) -> &BindGroupLayout {
        // FIXME - This "ensure" pattern means we never de-allocate entries. This is
        // probably fine, because there's a limited number of realistic combinations,
        // but could cause wastes if e.g. loading widely different scenes.
        let key = ParticleBindGroupLayoutKey {
            min_binding_size,
            parent_min_binding_size,
        };
        self.particle_bind_group_layouts
            .entry(key)
            .or_insert_with(|| {
                trace!("Creating new particle sim bind group @1 for min_binding_size={} parent_min_binding_size={:?}", min_binding_size, parent_min_binding_size);
                create_particle_sim_bind_group_layout(
                    &self.render_device,
                    min_binding_size,
                    parent_min_binding_size,
                )
            })
    }

    /// Get the bind group layout for the bind group @1 ("particles") for use
    /// with the given min binding sizes.
    pub fn particle_bind_group_layout(
        &self,
        min_binding_size: NonZeroU32,
        parent_min_binding_size: Option<NonZeroU32>,
    ) -> Option<&BindGroupLayout> {
        let key = ParticleBindGroupLayoutKey {
            min_binding_size,
            parent_min_binding_size,
        };
        self.particle_bind_group_layouts.get(&key)
    }

    /// Ensure a bind group layout exists for the metadata@3 bind group of
    /// the init pass.
    pub fn ensure_metadata_init_bind_group_layout(&mut self, consume_gpu_spawn_events: bool) {
        let layout = &mut self.metadata_init_bind_group_layout[consume_gpu_spawn_events as usize];
        if layout.is_none() {
            *layout = Some(create_metadata_init_bind_group_layout(
                &self.render_device,
                consume_gpu_spawn_events,
            ));
        }
    }

    /// Get the bind group layout for the metadata@3 bind group of the init
    /// pass.
    pub fn metadata_init_bind_group_layout(
        &self,
        consume_gpu_spawn_events: bool,
    ) -> Option<&BindGroupLayout> {
        self.metadata_init_bind_group_layout[consume_gpu_spawn_events as usize].as_ref()
    }

    /// Ensure a bind group layout exists for the metadata@3 bind group of
    /// the update pass.
    pub fn ensure_metadata_update_bind_group_layout(&mut self, num_event_buffers: u32) {
        self.metadata_update_bind_group_layouts
            .entry(num_event_buffers)
            .or_insert_with(|| {
                create_metadata_update_bind_group_layout(&self.render_device, num_event_buffers)
            });
    }

    /// Get the bind group layout for the metadata@3 bind group of the
    /// update pass.
    pub fn metadata_update_bind_group_layout(
        &self,
        num_event_buffers: u32,
    ) -> Option<&BindGroupLayout> {
        self.metadata_update_bind_group_layouts
            .get(&num_event_buffers)
    }

    //
    // Bind groups
    //

    /// Get the "particle" bind group for the simulation (init and update)
    /// passes a cached effect stored in a given GPU particle buffer.
    pub fn particle_sim_bind_group(&self, slab_id: &SlabId) -> Option<&BindGroup> {
        self.get_slab(slab_id)
            .and_then(|slab| slab.particle_sim_bind_group())
    }

    pub fn create_particle_sim_bind_group(
        &mut self,
        slab_id: &SlabId,
        render_device: &RenderDevice,
        min_binding_size: NonZeroU32,
        parent_min_binding_size: Option<NonZeroU32>,
        parent_binding_source: Option<&BufferBindingSource>,
    ) -> Result<(), ()> {
        // Create the bind group
        let layout = self
            .ensure_particle_bind_group_layout(min_binding_size, parent_min_binding_size)
            .clone();
        let slot = self
            .particle_slabs
            .get_mut(slab_id.index() as usize)
            .ok_or(())?;
        let effect_buffer = slot.as_mut().ok_or(())?;
        effect_buffer.create_particle_sim_bind_group(
            &layout,
            slab_id,
            render_device,
            parent_binding_source,
        );
        Ok(())
    }
}

/// Create the bind group layout for the "particle" group (@1) of the init and
/// update passes.
fn create_particle_sim_bind_group_layout(
    render_device: &RenderDevice,
    particle_layout_min_binding_size: NonZeroU32,
    parent_particle_layout_min_binding_size: Option<NonZeroU32>,
) -> BindGroupLayout {
    let mut entries = Vec::with_capacity(3);

    // @group(1) @binding(0) var<storage, read_write> particle_buffer :
    // ParticleBuffer
    entries.push(BindGroupLayoutEntry {
        binding: 0,
        visibility: ShaderStages::COMPUTE,
        ty: BindingType::Buffer {
            ty: BufferBindingType::Storage { read_only: false },
            has_dynamic_offset: false,
            min_binding_size: Some(particle_layout_min_binding_size.into()),
        },
        count: None,
    });

    // @group(1) @binding(1) var<storage, read_write> indirect_buffer :
    // IndirectBuffer
    entries.push(BindGroupLayoutEntry {
        binding: 1,
        visibility: ShaderStages::COMPUTE,
        ty: BindingType::Buffer {
            ty: BufferBindingType::Storage { read_only: false },
            has_dynamic_offset: false,
            min_binding_size: Some(NonZeroU64::new(INDIRECT_INDEX_SIZE as _).unwrap()),
        },
        count: None,
    });

    // @group(1) @binding(2) var<storage, read> parent_particle_buffer :
    // ParentParticleBuffer;
    if let Some(min_binding_size) = parent_particle_layout_min_binding_size {
        entries.push(BindGroupLayoutEntry {
            binding: 2,
            visibility: ShaderStages::COMPUTE,
            ty: BindingType::Buffer {
                ty: BufferBindingType::Storage { read_only: true },
                has_dynamic_offset: false,
                min_binding_size: Some(min_binding_size.into()),
            },
            count: None,
        });
    }

    let hash = calc_hash(&entries);
    let label = format!("hanabi:bind_group_layout:sim:particles_{:016X}", hash);
    trace!(
        "Creating particle bind group layout '{}' for init pass with {} entries. (parent_buffer:{})",
        label,
        entries.len(),
        parent_particle_layout_min_binding_size.is_some(),
    );
    render_device.create_bind_group_layout(&label[..], &entries)
}

/// Create the bind group layout for the metadata@3 bind group of the init pass.
fn create_metadata_init_bind_group_layout(
    render_device: &RenderDevice,
    consume_gpu_spawn_events: bool,
) -> BindGroupLayout {
    let storage_alignment = render_device.limits().min_storage_buffer_offset_alignment;
    let effect_metadata_size = GpuEffectMetadata::aligned_size(storage_alignment);

    let mut entries = Vec::with_capacity(3);

    // @group(3) @binding(0) var<storage, read_write> effect_metadata :
    // EffectMetadata;
    entries.push(BindGroupLayoutEntry {
        binding: 0,
        visibility: ShaderStages::COMPUTE,
        ty: BindingType::Buffer {
            ty: BufferBindingType::Storage { read_only: false },
            has_dynamic_offset: false,
            // This WGSL struct is manually padded, so the Rust type GpuEffectMetadata doesn't
            // reflect its true min size.
            min_binding_size: Some(effect_metadata_size),
        },
        count: None,
    });

    if consume_gpu_spawn_events {
        // @group(3) @binding(1) var<storage, read> child_info_buffer : ChildInfoBuffer;
        entries.push(BindGroupLayoutEntry {
            binding: 1,
            visibility: ShaderStages::COMPUTE,
            ty: BindingType::Buffer {
                ty: BufferBindingType::Storage { read_only: true },
                has_dynamic_offset: false,
                min_binding_size: Some(GpuChildInfo::min_size()),
            },
            count: None,
        });

        // @group(3) @binding(2) var<storage, read> event_buffer : EventBuffer;
        entries.push(BindGroupLayoutEntry {
            binding: 2,
            visibility: ShaderStages::COMPUTE,
            ty: BindingType::Buffer {
                ty: BufferBindingType::Storage { read_only: true },
                has_dynamic_offset: false,
                min_binding_size: Some(NonZeroU64::new(4).unwrap()),
            },
            count: None,
        });
    }

    let hash = calc_hash(&entries);
    let label = format!(
        "hanabi:bind_group_layout:init:metadata@3_{}{:016X}",
        if consume_gpu_spawn_events {
            "events"
        } else {
            "noevent"
        },
        hash
    );
    trace!(
        "Creating metadata@3 bind group layout '{}' for init pass with {} entries. (consume_gpu_spawn_events:{})",
        label,
        entries.len(),
        consume_gpu_spawn_events,
    );
    render_device.create_bind_group_layout(&label[..], &entries)
}

/// Create the bind group layout for the metadata@3 bind group of the update
/// pass.
fn create_metadata_update_bind_group_layout(
    render_device: &RenderDevice,
    num_event_buffers: u32,
) -> BindGroupLayout {
    let storage_alignment = render_device.limits().min_storage_buffer_offset_alignment;
    let effect_metadata_size = GpuEffectMetadata::aligned_size(storage_alignment);

    let mut entries = Vec::with_capacity(num_event_buffers as usize + 2);

    // @group(3) @binding(0) var<storage, read_write> effect_metadata :
    // EffectMetadata;
    entries.push(BindGroupLayoutEntry {
        binding: 0,
        visibility: ShaderStages::COMPUTE,
        ty: BindingType::Buffer {
            ty: BufferBindingType::Storage { read_only: false },
            has_dynamic_offset: false,
            // This WGSL struct is manually padded, so the Rust type GpuEffectMetadata doesn't
            // reflect its true min size.
            min_binding_size: Some(effect_metadata_size),
        },
        count: None,
    });

    if num_event_buffers > 0 {
        // @group(3) @binding(1) var<storage, read_write> child_infos : array<ChildInfo,
        // N>;
        entries.push(BindGroupLayoutEntry {
            binding: 1,
            visibility: ShaderStages::COMPUTE,
            ty: BindingType::Buffer {
                ty: BufferBindingType::Storage { read_only: false },
                has_dynamic_offset: false,
                min_binding_size: Some(GpuChildInfo::min_size()),
            },
            count: None,
        });

        for i in 0..num_event_buffers {
            // @group(3) @binding(2+i) var<storage, read_write> event_buffer_#i :
            // EventBuffer;
            entries.push(BindGroupLayoutEntry {
                binding: 2 + i,
                visibility: ShaderStages::COMPUTE,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Storage { read_only: false },
                    has_dynamic_offset: false,
                    min_binding_size: Some(NonZeroU64::new(4).unwrap()),
                },
                count: None,
            });
        }
    }

    let hash = calc_hash(&entries);
    let label = format!("hanabi:bind_group_layout:update:metadata_{:016X}", hash);
    trace!(
        "Creating particle bind group layout '{}' for init update with {} entries. (num_event_buffers:{})",
        label,
        entries.len(),
        num_event_buffers,
    );
    render_device.create_bind_group_layout(&label[..], &entries)
}

#[cfg(all(test, feature = "gpu_tests"))]
mod gpu_tests {
    use std::borrow::Cow;

    use bevy::math::Vec4;

    use super::*;
    use crate::{
        graph::{Value, VectorValue},
        test_utils::MockRenderer,
        Attribute, AttributeInner,
    };

    #[test]
    fn effect_slice_ord() {
        let particle_layout = ParticleLayout::new().append(Attribute::POSITION).build();
        let slice1 = EffectSlice {
            slice: 0..32,
            slab_id: SlabId::new(1),
            particle_layout: particle_layout.clone(),
        };
        let slice2 = EffectSlice {
            slice: 32..64,
            slab_id: SlabId::new(1),
            particle_layout: particle_layout.clone(),
        };
        assert!(slice1 < slice2);
        assert!(slice1 <= slice2);
        assert!(slice2 > slice1);
        assert!(slice2 >= slice1);

        let slice3 = EffectSlice {
            slice: 0..32,
            slab_id: SlabId::new(0),
            particle_layout,
        };
        assert!(slice3 < slice1);
        assert!(slice3 < slice2);
        assert!(slice1 > slice3);
        assert!(slice2 > slice3);
    }

    const F4A_INNER: &AttributeInner = &AttributeInner::new(
        Cow::Borrowed("F4A"),
        Value::Vector(VectorValue::new_vec4(Vec4::ONE)),
    );
    const F4B_INNER: &AttributeInner = &AttributeInner::new(
        Cow::Borrowed("F4B"),
        Value::Vector(VectorValue::new_vec4(Vec4::ONE)),
    );
    const F4C_INNER: &AttributeInner = &AttributeInner::new(
        Cow::Borrowed("F4C"),
        Value::Vector(VectorValue::new_vec4(Vec4::ONE)),
    );
    const F4D_INNER: &AttributeInner = &AttributeInner::new(
        Cow::Borrowed("F4D"),
        Value::Vector(VectorValue::new_vec4(Vec4::ONE)),
    );

    const F4A: Attribute = Attribute(F4A_INNER);
    const F4B: Attribute = Attribute(F4B_INNER);
    const F4C: Attribute = Attribute(F4C_INNER);
    const F4D: Attribute = Attribute(F4D_INNER);

    #[test]
    fn slice_ref() {
        let l16 = ParticleLayout::new().append(F4A).build();
        assert_eq!(16, l16.size());
        let l32 = ParticleLayout::new().append(F4A).append(F4B).build();
        assert_eq!(32, l32.size());
        let l48 = ParticleLayout::new()
            .append(F4A)
            .append(F4B)
            .append(F4C)
            .build();
        assert_eq!(48, l48.size());
        for (range, particle_layout, len, byte_size) in [
            (0..0, &l16, 0, 0),
            (0..16, &l16, 16, 16 * 16),
            (0..16, &l32, 16, 16 * 32),
            (240..256, &l48, 16, 16 * 48),
        ] {
            let sr = SlabSliceRef {
                range,
                particle_layout: particle_layout.clone(),
            };
            assert_eq!(sr.len(), len);
            assert_eq!(sr.byte_size(), byte_size);
        }
    }

    #[test]
    fn effect_buffer() {
        let renderer = MockRenderer::new();
        let render_device = renderer.device();

        let l64 = ParticleLayout::new()
            .append(F4A)
            .append(F4B)
            .append(F4C)
            .append(F4D)
            .build();
        assert_eq!(64, l64.size());

        let asset = Handle::<EffectAsset>::default();
        let capacity = 4096;
        let mut buffer = ParticleSlab::new(
            SlabId::new(42),
            asset,
            capacity,
            l64.clone(),
            &render_device,
        );

        assert_eq!(buffer.capacity, capacity.max(ParticleSlab::MIN_CAPACITY));
        assert_eq!(64, buffer.particle_layout.size());
        assert_eq!(64, buffer.particle_layout.min_binding_size().get());
        assert_eq!(0, buffer.used_size);
        assert!(buffer.free_slices.is_empty());

        assert_eq!(None, buffer.allocate(buffer.capacity + 1));

        let mut offset = 0;
        let mut slices = vec![];
        for size in [32, 128, 55, 148, 1, 2048, 42] {
            let slice = buffer.allocate(size);
            assert!(slice.is_some());
            let slice = slice.unwrap();
            assert_eq!(64, slice.particle_layout.size());
            assert_eq!(64, buffer.particle_layout.min_binding_size().get());
            assert_eq!(offset..offset + size, slice.range);
            slices.push(slice);
            offset += size;
        }
        assert_eq!(offset, buffer.used_size);

        assert_eq!(SlabState::Used, buffer.free_slice(slices[2].clone()));
        assert_eq!(1, buffer.free_slices.len());
        let free_slice = &buffer.free_slices[0];
        assert_eq!(160..215, *free_slice);
        assert_eq!(offset, buffer.used_size); // didn't move

        assert_eq!(SlabState::Used, buffer.free_slice(slices[3].clone()));
        assert_eq!(SlabState::Used, buffer.free_slice(slices[4].clone()));
        assert_eq!(SlabState::Used, buffer.free_slice(slices[5].clone()));
        assert_eq!(4, buffer.free_slices.len());
        assert_eq!(offset, buffer.used_size); // didn't move

        // this will collapse all the way to slices[1], the highest allocated
        assert_eq!(SlabState::Used, buffer.free_slice(slices[6].clone()));
        assert_eq!(0, buffer.free_slices.len()); // collapsed
        assert_eq!(160, buffer.used_size); // collapsed

        assert_eq!(SlabState::Used, buffer.free_slice(slices[0].clone()));
        assert_eq!(1, buffer.free_slices.len());
        assert_eq!(160, buffer.used_size); // didn't move

        // collapse all, and free buffer
        assert_eq!(SlabState::Free, buffer.free_slice(slices[1].clone()));
        assert_eq!(0, buffer.free_slices.len());
        assert_eq!(0, buffer.used_size); // collapsed and empty
    }

    #[test]
    fn pop_free_slice() {
        let renderer = MockRenderer::new();
        let render_device = renderer.device();

        let l64 = ParticleLayout::new()
            .append(F4A)
            .append(F4B)
            .append(F4C)
            .append(F4D)
            .build();
        assert_eq!(64, l64.size());

        let asset = Handle::<EffectAsset>::default();
        let capacity = 2048; // ParticleSlab::MIN_CAPACITY;
        assert!(capacity >= 2048); // otherwise the logic below breaks
        let mut buffer = ParticleSlab::new(
            SlabId::new(42),
            asset,
            capacity,
            l64.clone(),
            &render_device,
        );

        let slice0 = buffer.allocate(32);
        assert!(slice0.is_some());
        let slice0 = slice0.unwrap();
        assert_eq!(slice0.range, 0..32);
        assert!(buffer.free_slices.is_empty());

        let slice1 = buffer.allocate(1024);
        assert!(slice1.is_some());
        let slice1 = slice1.unwrap();
        assert_eq!(slice1.range, 32..1056);
        assert!(buffer.free_slices.is_empty());

        let state = buffer.free_slice(slice0);
        assert_eq!(state, SlabState::Used);
        assert_eq!(buffer.free_slices.len(), 1);
        assert_eq!(buffer.free_slices[0], 0..32);

        // Try to allocate a slice larger than slice0, such that slice0 cannot be
        // recycled, and instead the new slice has to be appended after all
        // existing ones.
        let slice2 = buffer.allocate(64);
        assert!(slice2.is_some());
        let slice2 = slice2.unwrap();
        assert_eq!(slice2.range.start, slice1.range.end); // after slice1
        assert_eq!(slice2.range, 1056..1120);
        assert_eq!(buffer.free_slices.len(), 1);

        // Now allocate a small slice that fits, to recycle (part of) slice0.
        let slice3 = buffer.allocate(16);
        assert!(slice3.is_some());
        let slice3 = slice3.unwrap();
        assert_eq!(slice3.range, 0..16);
        assert_eq!(buffer.free_slices.len(), 1); // split
        assert_eq!(buffer.free_slices[0], 16..32);

        // Allocate a second small slice that fits exactly the left space, completely
        // recycling
        let slice4 = buffer.allocate(16);
        assert!(slice4.is_some());
        let slice4 = slice4.unwrap();
        assert_eq!(slice4.range, 16..32);
        assert!(buffer.free_slices.is_empty()); // recycled
    }

    #[test]
    fn effect_cache() {
        let renderer = MockRenderer::new();
        let render_device = renderer.device();

        let l32 = ParticleLayout::new().append(F4A).append(F4B).build();
        assert_eq!(32, l32.size());

        let mut effect_cache = EffectCache::new(render_device);
        assert_eq!(effect_cache.slabs().len(), 0);

        let asset = Handle::<EffectAsset>::default();
        let capacity = ParticleSlab::MIN_CAPACITY;
        let item_size = l32.size();

        // Insert an effect
        let effect1 = effect_cache.insert(asset.clone(), capacity, &l32);
        //assert!(effect1.is_valid());
        let slice1 = &effect1.slice;
        assert_eq!(slice1.len(), capacity);
        assert_eq!(
            slice1.particle_layout.min_binding_size().get() as u32,
            item_size
        );
        assert_eq!(slice1.range, 0..capacity);
        assert_eq!(effect_cache.slabs().len(), 1);

        // Insert a second copy of the same effect
        let effect2 = effect_cache.insert(asset.clone(), capacity, &l32);
        //assert!(effect2.is_valid());
        let slice2 = &effect2.slice;
        assert_eq!(slice2.len(), capacity);
        assert_eq!(
            slice2.particle_layout.min_binding_size().get() as u32,
            item_size
        );
        assert_eq!(slice2.range, 0..capacity);
        assert_eq!(effect_cache.slabs().len(), 2);

        // Remove the first effect instance
        let buffer_state = effect_cache.remove(&effect1).unwrap();
        // Note: currently batching is disabled, so each instance has its own buffer,
        // which becomes unused once the instance is destroyed.
        assert_eq!(buffer_state, SlabState::Free);
        assert_eq!(effect_cache.slabs().len(), 2);
        {
            let slabs = effect_cache.slabs();
            assert!(slabs[0].is_none());
            assert!(slabs[1].is_some()); // id2
        }

        // Regression #60
        let effect3 = effect_cache.insert(asset, capacity, &l32);
        //assert!(effect3.is_valid());
        let slice3 = &effect3.slice;
        assert_eq!(slice3.len(), capacity);
        assert_eq!(
            slice3.particle_layout.min_binding_size().get() as u32,
            item_size
        );
        assert_eq!(slice3.range, 0..capacity);
        // Note: currently batching is disabled, so each instance has its own buffer.
        assert_eq!(effect_cache.slabs().len(), 2);
        {
            let slabs = effect_cache.slabs();
            assert!(slabs[0].is_some()); // id3
            assert!(slabs[1].is_some()); // id2
        }
    }
}

djeedai / bevy_hanabi / 18243240671

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