Struct HoverMap

Resource

pub struct HoverMap(pub HashMap<PointerId, HashMap<Entity, HitData>>);

The source of truth for all hover state. This is used to determine what events to send, and what state components should be in.

Maps pointers to the entities they are hovering over.

“Hovering” refers to the hover state, which is not the same as whether or not a picking backend is reporting hits between a pointer and an entity. A pointer is “hovering” an entity only if the pointer is hitting the entity (as reported by a picking backend) and no entities between it and the pointer block interactions.

For example, if a pointer is hitting a UI button and a 3d mesh, but the button is in front of the mesh, the UI button will be hovered, but the mesh will not. Unless, the Pickable component is present with should_block_lower set to false.

Advanced Users

If you want to completely replace the provided picking events or state produced by this plugin, you can use this resource to do that. All of the event systems for picking are built on top of this authoritative hover state, and you can do the same. You can also use the PreviousHoverMap as a robust way of determining changes in hover state from the previous update.

Tuple Fields

0: HashMap<PointerId, HashMap<Entity, HitData>>

Methods from Deref<Target = HashMap<PointerId, HashMap<Entity, HitData>>>

pub fn hasher(&self) -> &S

Returns a reference to the map’s BuildHasher, or S parameter.

Refer to hasher for further details.

pub fn capacity(&self) -> usize

Returns the number of elements the map can hold without reallocating.

Refer to capacity for further details.

Examples

let map = HashMap::with_capacity(5);

assert!(map.capacity() >= 5);

pub fn keys(&self) -> Keys<'_, K, V>

An iterator visiting all keys in arbitrary order. The iterator element type is &'a K.

Refer to keys for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for key in map.keys() {
    // foo, bar, baz
    // Note that the above order is not guaranteed
}

pub fn values(&self) -> Values<'_, K, V>

An iterator visiting all values in arbitrary order. The iterator element type is &'a V.

Refer to values for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for key in map.values() {
    // 0, 1, 2
    // Note that the above order is not guaranteed
}

Examples found in repository

tests/ecs/ambiguity_detection.rs (line 55)

    fn total(&self) -> usize {
        self.values().sum()
    }

pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>

An iterator visiting all values mutably in arbitrary order. The iterator element type is &'a mut V.

Refer to values for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for key in map.values_mut() {
    // 0, 1, 2
    // Note that the above order is not guaranteed
}

pub fn iter(&self) -> Iter<'_, K, V>

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is (&'a K, &'a V).

Refer to iter for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for (key, value) in map.iter() {
    // ("foo", 0), ("bar", 1), ("baz", 2)
    // Note that the above order is not guaranteed
}

Examples found in repository

examples/testbed/full_ui.rs (line 427)

pub fn update_scroll_position(
    mut mouse_wheel_events: EventReader<MouseWheel>,
    hover_map: Res<HoverMap>,
    mut scrolled_node_query: Query<&mut ScrollPosition>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
) {
    for mouse_wheel_event in mouse_wheel_events.read() {
        let (mut dx, mut dy) = match mouse_wheel_event.unit {
            MouseScrollUnit::Line => (mouse_wheel_event.x * 20., mouse_wheel_event.y * 20.),
            MouseScrollUnit::Pixel => (mouse_wheel_event.x, mouse_wheel_event.y),
        };

        if keyboard_input.pressed(KeyCode::ShiftLeft) || keyboard_input.pressed(KeyCode::ShiftRight)
        {
            std::mem::swap(&mut dx, &mut dy);
        }

        for (_pointer, pointer_map) in hover_map.iter() {
            for (entity, _hit) in pointer_map.iter() {
                if let Ok(mut scroll_position) = scrolled_node_query.get_mut(*entity) {
                    scroll_position.offset_x -= dx;
                    scroll_position.offset_y -= dy;
                }
            }
        }
    }
}

examples/ui/scroll.rs (line 350)

pub fn update_scroll_position(
    mut mouse_wheel_events: EventReader<MouseWheel>,
    hover_map: Res<HoverMap>,
    mut scrolled_node_query: Query<&mut ScrollPosition>,
    keyboard_input: Res<ButtonInput<KeyCode>>,
) {
    for mouse_wheel_event in mouse_wheel_events.read() {
        let (mut dx, mut dy) = match mouse_wheel_event.unit {
            MouseScrollUnit::Line => (
                mouse_wheel_event.x * LINE_HEIGHT,
                mouse_wheel_event.y * LINE_HEIGHT,
            ),
            MouseScrollUnit::Pixel => (mouse_wheel_event.x, mouse_wheel_event.y),
        };

        if keyboard_input.pressed(KeyCode::ControlLeft)
            || keyboard_input.pressed(KeyCode::ControlRight)
        {
            std::mem::swap(&mut dx, &mut dy);
        }

        for (_pointer, pointer_map) in hover_map.iter() {
            for (entity, _hit) in pointer_map.iter() {
                if let Ok(mut scroll_position) = scrolled_node_query.get_mut(*entity) {
                    scroll_position.offset_x -= dx;
                    scroll_position.offset_y -= dy;
                }
            }
        }
    }
}

pub fn iter_mut(&mut self) -> IterMut<'_, K, V>

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is (&'a K, &'a mut V).

Refer to iter_mut for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for (key, value) in map.iter_mut() {
    // ("foo", 0), ("bar", 1), ("baz", 2)
    // Note that the above order is not guaranteed
}

Examples found in repository

examples/3d/tonemapping.rs (line 376)

fn update_color_grading_settings(
    keys: Res<ButtonInput<KeyCode>>,
    time: Res<Time>,
    mut per_method_settings: ResMut<PerMethodSettings>,
    tonemapping: Single<&Tonemapping>,
    current_scene: Res<CurrentScene>,
    mut selected_parameter: ResMut<SelectedParameter>,
) {
    let color_grading = per_method_settings.settings.get_mut(*tonemapping).unwrap();
    let mut dt = time.delta_secs() * 0.25;
    if keys.pressed(KeyCode::ArrowLeft) {
        dt = -dt;
    }

    if keys.just_pressed(KeyCode::ArrowDown) {
        selected_parameter.next();
    }
    if keys.just_pressed(KeyCode::ArrowUp) {
        selected_parameter.prev();
    }
    if keys.pressed(KeyCode::ArrowLeft) || keys.pressed(KeyCode::ArrowRight) {
        match selected_parameter.value {
            0 => {
                color_grading.global.exposure += dt;
            }
            1 => {
                color_grading
                    .all_sections_mut()
                    .for_each(|section| section.gamma += dt);
            }
            2 => {
                color_grading
                    .all_sections_mut()
                    .for_each(|section| section.saturation += dt);
            }
            3 => {
                color_grading.global.post_saturation += dt;
            }
            _ => {}
        }
    }

    if keys.just_pressed(KeyCode::Space) {
        for (_, grading) in per_method_settings.settings.iter_mut() {
            *grading = ColorGrading::default();
        }
    }

    if keys.just_pressed(KeyCode::Enter) && current_scene.0 == 1 {
        for (mapper, grading) in per_method_settings.settings.iter_mut() {
            *grading = PerMethodSettings::basic_scene_recommendation(*mapper);
        }
    }
}

pub fn len(&self) -> usize

Returns the number of elements in the map.

Refer to len for further details.

Examples

let mut map = HashMap::new();

assert_eq!(map.len(), 0);

map.insert("foo", 0);

assert_eq!(map.len(), 1);

Examples found in repository

examples/stress_tests/many_lights.rs (line 178)

fn print_visible_light_count(
    time: Res<Time>,
    mut timer: Local<PrintingTimer>,
    visible: Query<&ExtractedPointLight>,
    global_light_meta: Res<GlobalClusterableObjectMeta>,
) {
    timer.0.tick(time.delta());

    if timer.0.just_finished() {
        info!(
            "Visible Lights: {}, Rendered Lights: {}",
            visible.iter().len(),
            global_light_meta.entity_to_index.len()
        );
    }
}

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Refer to is_empty for further details.

Examples

let mut map = HashMap::new();

assert!(map.is_empty());

map.insert("foo", 0);

assert!(!map.is_empty());

Examples found in repository

examples/2d/mesh2d_manual.rs (line 385)

pub fn queue_colored_mesh2d(
    transparent_draw_functions: Res<DrawFunctions<Transparent2d>>,
    colored_mesh2d_pipeline: Res<ColoredMesh2dPipeline>,
    mut pipelines: ResMut<SpecializedRenderPipelines<ColoredMesh2dPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    render_meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderColoredMesh2dInstances>,
    mut transparent_render_phases: ResMut<ViewSortedRenderPhases<Transparent2d>>,
    views: Query<(&RenderVisibleEntities, &ExtractedView, &Msaa)>,
) {
    if render_mesh_instances.is_empty() {
        return;
    }
    // Iterate each view (a camera is a view)
    for (visible_entities, view, msaa) in &views {
        let Some(transparent_phase) = transparent_render_phases.get_mut(&view.retained_view_entity)
        else {
            continue;
        };

        let draw_colored_mesh2d = transparent_draw_functions.read().id::<DrawColoredMesh2d>();

        let mesh_key = Mesh2dPipelineKey::from_msaa_samples(msaa.samples())
            | Mesh2dPipelineKey::from_hdr(view.hdr);

        // Queue all entities visible to that view
        for (render_entity, visible_entity) in visible_entities.iter::<Mesh2d>() {
            if let Some(mesh_instance) = render_mesh_instances.get(visible_entity) {
                let mesh2d_handle = mesh_instance.mesh_asset_id;
                let mesh2d_transforms = &mesh_instance.transforms;
                // Get our specialized pipeline
                let mut mesh2d_key = mesh_key;
                let Some(mesh) = render_meshes.get(mesh2d_handle) else {
                    continue;
                };
                mesh2d_key |= Mesh2dPipelineKey::from_primitive_topology(mesh.primitive_topology());

                let pipeline_id =
                    pipelines.specialize(&pipeline_cache, &colored_mesh2d_pipeline, mesh2d_key);

                let mesh_z = mesh2d_transforms.world_from_local.translation.z;
                transparent_phase.add(Transparent2d {
                    entity: (*render_entity, *visible_entity),
                    draw_function: draw_colored_mesh2d,
                    pipeline: pipeline_id,
                    // The 2d render items are sorted according to their z value before rendering,
                    // in order to get correct transparency
                    sort_key: FloatOrd(mesh_z),
                    // This material is not batched
                    batch_range: 0..1,
                    extra_index: PhaseItemExtraIndex::None,
                    extracted_index: usize::MAX,
                    indexed: mesh.indexed(),
                });
            }
        }
    }
}

pub fn drain(&mut self) -> Drain<'_, K, V>

Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.

Refer to drain for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

for (key, value) in map.drain() {
    // ("foo", 0), ("bar", 1), ("baz", 2)
    // Note that the above order is not guaranteed
}

assert!(map.is_empty());

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&K, &mut V) -> bool,

Retains only the elements specified by the predicate. Keeps the allocated memory for reuse.

Refer to retain for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

map.retain(|key, value| *value == 2);

assert_eq!(map.len(), 1);

Examples found in repository

examples/shader/custom_render_phase.rs (line 494)

fn extract_camera_phases(
    mut stencil_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
    cameras: Extract<Query<(Entity, &Camera), With<Camera3d>>>,
    mut live_entities: Local<HashSet<RetainedViewEntity>>,
) {
    live_entities.clear();
    for (main_entity, camera) in &cameras {
        if !camera.is_active {
            continue;
        }
        // This is the main camera, so we use the first subview index (0)
        let retained_view_entity = RetainedViewEntity::new(main_entity.into(), None, 0);

        stencil_phases.insert_or_clear(retained_view_entity);
        live_entities.insert(retained_view_entity);
    }

    // Clear out all dead views.
    stencil_phases.retain(|camera_entity, _| live_entities.contains(camera_entity));
}

pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F>

where F: FnMut(&K, &mut V) -> bool,

Drains elements which are true under the given predicate, and returns an iterator over the removed items.

Refer to extract_if for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

let extracted = map
    .extract_if(|key, value| *value == 2)
    .collect::<Vec<_>>();

assert_eq!(map.len(), 2);
assert_eq!(extracted.len(), 1);

pub fn clear(&mut self)

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

Refer to clear for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

map.clear();

assert!(map.is_empty());

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more elements to be inserted in the HashMap. The collection may reserve more space to avoid frequent reallocations.

Refer to reserve for further details.

Examples

let mut map = HashMap::with_capacity(5);

assert!(map.capacity() >= 5);

map.reserve(10);

assert!(map.capacity() - map.len() >= 10);

pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>

Tries to reserve capacity for at least additional more elements to be inserted in the given HashMap<K,V>. The collection may reserve more space to avoid frequent reallocations.

Refer to try_reserve for further details.

Examples

let mut map = HashMap::with_capacity(5);

assert!(map.capacity() >= 5);

map.try_reserve(10).expect("Out of Memory!");

assert!(map.capacity() - map.len() >= 10);

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Refer to shrink_to_fit for further details.

Examples

let mut map = HashMap::with_capacity(5);

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

assert!(map.capacity() >= 5);

map.shrink_to_fit();

assert_eq!(map.capacity(), 3);

pub fn shrink_to(&mut self, min_capacity: usize)

Shrinks the capacity of the map with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Refer to shrink_to for further details.

pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S>

Gets the given key’s corresponding entry in the map for in-place manipulation.

Refer to entry for further details.

Examples

let mut map = HashMap::new();

let value = map.entry("foo").or_insert(0);

Examples found in repository

examples/ecs/observers.rs (line 125)

fn on_add_mine(
    trigger: Trigger<OnAdd, Mine>,
    query: Query<&Mine>,
    mut index: ResMut<SpatialIndex>,
) {
    let mine = query.get(trigger.target()).unwrap();
    let tile = (
        (mine.pos.x / CELL_SIZE).floor() as i32,
        (mine.pos.y / CELL_SIZE).floor() as i32,
    );
    index.map.entry(tile).or_default().insert(trigger.target());
}

// Remove despawned mines from our index
fn on_remove_mine(
    trigger: Trigger<OnRemove, Mine>,
    query: Query<&Mine>,
    mut index: ResMut<SpatialIndex>,
) {
    let mine = query.get(trigger.target()).unwrap();
    let tile = (
        (mine.pos.x / CELL_SIZE).floor() as i32,
        (mine.pos.y / CELL_SIZE).floor() as i32,
    );
    index.map.entry(tile).and_modify(|set| {
        set.remove(&trigger.target());
    });
}

pub fn entry_ref<'a, 'b, Q>( &'a mut self, key: &'b Q, ) -> EntryRef<'a, 'b, K, Q, V, S>

where Q: Hash + Equivalent<K> + ?Sized,

Gets the given key’s corresponding entry by reference in the map for in-place manipulation.

Refer to entry_ref for further details.

Examples

let mut map = HashMap::new();

let value = map.entry_ref("foo").or_insert(0);

pub fn get<Q>(&self, k: &Q) -> Option<&V>

where Q: Hash + Equivalent<K> + ?Sized,

Returns a reference to the value corresponding to the key.

Refer to get for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.get("foo"), Some(&0));

Examples found in repository

examples/ecs/immutable_components.rs (line 70)

    fn get_entity(&self, name: &'static str) -> Option<Entity> {
        self.name_to_entity.get(&Name(name)).copied()
    }

examples/ecs/observers.rs (line 212)

    fn get_nearby(&self, pos: Vec2) -> Vec<Entity> {
        let tile = (
            (pos.x / CELL_SIZE).floor() as i32,
            (pos.y / CELL_SIZE).floor() as i32,
        );
        let mut nearby = Vec::new();
        for x in -1..2 {
            for y in -1..2 {
                if let Some(mines) = self.map.get(&(tile.0 + x, tile.1 + y)) {
                    nearby.extend(mines.iter());
                }
            }
        }
        nearby
    }

examples/3d/tonemapping.rs (line 312)

fn toggle_tonemapping_method(
    keys: Res<ButtonInput<KeyCode>>,
    mut tonemapping: Single<&mut Tonemapping>,
    mut color_grading: Single<&mut ColorGrading>,
    per_method_settings: Res<PerMethodSettings>,
) {
    if keys.just_pressed(KeyCode::Digit1) {
        **tonemapping = Tonemapping::None;
    } else if keys.just_pressed(KeyCode::Digit2) {
        **tonemapping = Tonemapping::Reinhard;
    } else if keys.just_pressed(KeyCode::Digit3) {
        **tonemapping = Tonemapping::ReinhardLuminance;
    } else if keys.just_pressed(KeyCode::Digit4) {
        **tonemapping = Tonemapping::AcesFitted;
    } else if keys.just_pressed(KeyCode::Digit5) {
        **tonemapping = Tonemapping::AgX;
    } else if keys.just_pressed(KeyCode::Digit6) {
        **tonemapping = Tonemapping::SomewhatBoringDisplayTransform;
    } else if keys.just_pressed(KeyCode::Digit7) {
        **tonemapping = Tonemapping::TonyMcMapface;
    } else if keys.just_pressed(KeyCode::Digit8) {
        **tonemapping = Tonemapping::BlenderFilmic;
    }

    **color_grading = (*per_method_settings
        .settings
        .get::<Tonemapping>(&tonemapping)
        .as_ref()
        .unwrap())
    .clone();
}

examples/shader/custom_render_phase.rs (line 358)

    fn get_batch_data(
        (mesh_instances, _render_assets, mesh_allocator): &SystemParamItem<Self::Param>,
        (_entity, main_entity): (Entity, MainEntity),
    ) -> Option<(Self::BufferData, Option<Self::CompareData>)> {
        let RenderMeshInstances::CpuBuilding(ref mesh_instances) = **mesh_instances else {
            error!(
                "`get_batch_data` should never be called in GPU mesh uniform \
                building mode"
            );
            return None;
        };
        let mesh_instance = mesh_instances.get(&main_entity)?;
        let first_vertex_index =
            match mesh_allocator.mesh_vertex_slice(&mesh_instance.mesh_asset_id) {
                Some(mesh_vertex_slice) => mesh_vertex_slice.range.start,
                None => 0,
            };
        let mesh_uniform = {
            let mesh_transforms = &mesh_instance.transforms;
            let (local_from_world_transpose_a, local_from_world_transpose_b) =
                mesh_transforms.world_from_local.inverse_transpose_3x3();
            MeshUniform {
                world_from_local: mesh_transforms.world_from_local.to_transpose(),
                previous_world_from_local: mesh_transforms.previous_world_from_local.to_transpose(),
                lightmap_uv_rect: UVec2::ZERO,
                local_from_world_transpose_a,
                local_from_world_transpose_b,
                flags: mesh_transforms.flags,
                first_vertex_index,
                current_skin_index: u32::MAX,
                material_and_lightmap_bind_group_slot: 0,
                tag: 0,
                pad: 0,
            }
        };
        Some((mesh_uniform, None))
    }
}
impl GetFullBatchData for StencilPipeline {
    type BufferInputData = MeshInputUniform;

    fn get_index_and_compare_data(
        (mesh_instances, _, _): &SystemParamItem<Self::Param>,
        main_entity: MainEntity,
    ) -> Option<(NonMaxU32, Option<Self::CompareData>)> {
        // This should only be called during GPU building.
        let RenderMeshInstances::GpuBuilding(ref mesh_instances) = **mesh_instances else {
            error!(
                "`get_index_and_compare_data` should never be called in CPU mesh uniform building \
                mode"
            );
            return None;
        };
        let mesh_instance = mesh_instances.get(&main_entity)?;
        Some((
            mesh_instance.current_uniform_index,
            mesh_instance
                .should_batch()
                .then_some(mesh_instance.mesh_asset_id),
        ))
    }

    fn get_binned_batch_data(
        (mesh_instances, _render_assets, mesh_allocator): &SystemParamItem<Self::Param>,
        main_entity: MainEntity,
    ) -> Option<Self::BufferData> {
        let RenderMeshInstances::CpuBuilding(ref mesh_instances) = **mesh_instances else {
            error!(
                "`get_binned_batch_data` should never be called in GPU mesh uniform building mode"
            );
            return None;
        };
        let mesh_instance = mesh_instances.get(&main_entity)?;
        let first_vertex_index =
            match mesh_allocator.mesh_vertex_slice(&mesh_instance.mesh_asset_id) {
                Some(mesh_vertex_slice) => mesh_vertex_slice.range.start,
                None => 0,
            };

        Some(MeshUniform::new(
            &mesh_instance.transforms,
            first_vertex_index,
            mesh_instance.material_bindings_index.slot,
            None,
            None,
            None,
        ))
    }

    fn write_batch_indirect_parameters_metadata(
        indexed: bool,
        base_output_index: u32,
        batch_set_index: Option<NonMaxU32>,
        indirect_parameters_buffers: &mut UntypedPhaseIndirectParametersBuffers,
        indirect_parameters_offset: u32,
    ) {
        // Note that `IndirectParameters` covers both of these structures, even
        // though they actually have distinct layouts. See the comment above that
        // type for more information.
        let indirect_parameters = IndirectParametersCpuMetadata {
            base_output_index,
            batch_set_index: match batch_set_index {
                None => !0,
                Some(batch_set_index) => u32::from(batch_set_index),
            },
        };

        if indexed {
            indirect_parameters_buffers
                .indexed
                .set(indirect_parameters_offset, indirect_parameters);
        } else {
            indirect_parameters_buffers
                .non_indexed
                .set(indirect_parameters_offset, indirect_parameters);
        }
    }

    fn get_binned_index(
        _param: &SystemParamItem<Self::Param>,
        _query_item: MainEntity,
    ) -> Option<NonMaxU32> {
        None
    }
}

// When defining a phase, we need to extract it from the main world and add it to a resource
// that will be used by the render world. We need to give that resource all views that will use
// that phase
fn extract_camera_phases(
    mut stencil_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
    cameras: Extract<Query<(Entity, &Camera), With<Camera3d>>>,
    mut live_entities: Local<HashSet<RetainedViewEntity>>,
) {
    live_entities.clear();
    for (main_entity, camera) in &cameras {
        if !camera.is_active {
            continue;
        }
        // This is the main camera, so we use the first subview index (0)
        let retained_view_entity = RetainedViewEntity::new(main_entity.into(), None, 0);

        stencil_phases.insert_or_clear(retained_view_entity);
        live_entities.insert(retained_view_entity);
    }

    // Clear out all dead views.
    stencil_phases.retain(|camera_entity, _| live_entities.contains(camera_entity));
}

// This is a very important step when writing a custom phase.
//
// This system determines which meshes will be added to the phase.
fn queue_custom_meshes(
    custom_draw_functions: Res<DrawFunctions<Stencil3d>>,
    mut pipelines: ResMut<SpecializedMeshPipelines<StencilPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    custom_draw_pipeline: Res<StencilPipeline>,
    render_meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderMeshInstances>,
    mut custom_render_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
    mut views: Query<(&ExtractedView, &RenderVisibleEntities, &Msaa)>,
    has_marker: Query<(), With<DrawStencil>>,
) {
    for (view, visible_entities, msaa) in &mut views {
        let Some(custom_phase) = custom_render_phases.get_mut(&view.retained_view_entity) else {
            continue;
        };
        let draw_custom = custom_draw_functions.read().id::<DrawMesh3dStencil>();

        // Create the key based on the view.
        // In this case we only care about MSAA and HDR
        let view_key = MeshPipelineKey::from_msaa_samples(msaa.samples())
            | MeshPipelineKey::from_hdr(view.hdr);

        let rangefinder = view.rangefinder3d();
        // Since our phase can work on any 3d mesh we can reuse the default mesh 3d filter
        for (render_entity, visible_entity) in visible_entities.iter::<Mesh3d>() {
            // We only want meshes with the marker component to be queued to our phase.
            if has_marker.get(*render_entity).is_err() {
                continue;
            }
            let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(*visible_entity)
            else {
                continue;
            };
            let Some(mesh) = render_meshes.get(mesh_instance.mesh_asset_id) else {
                continue;
            };

            // Specialize the key for the current mesh entity
            // For this example we only specialize based on the mesh topology
            // but you could have more complex keys and that's where you'd need to create those keys
            let mut mesh_key = view_key;
            mesh_key |= MeshPipelineKey::from_primitive_topology(mesh.primitive_topology());

            let pipeline_id = pipelines.specialize(
                &pipeline_cache,
                &custom_draw_pipeline,
                mesh_key,
                &mesh.layout,
            );
            let pipeline_id = match pipeline_id {
                Ok(id) => id,
                Err(err) => {
                    error!("{}", err);
                    continue;
                }
            };
            let distance = rangefinder.distance_translation(&mesh_instance.translation);
            // At this point we have all the data we need to create a phase item and add it to our
            // phase
            custom_phase.add(Stencil3d {
                // Sort the data based on the distance to the view
                sort_key: FloatOrd(distance),
                entity: (*render_entity, *visible_entity),
                pipeline: pipeline_id,
                draw_function: draw_custom,
                // Sorted phase items aren't batched
                batch_range: 0..1,
                extra_index: PhaseItemExtraIndex::None,
                indexed: mesh.indexed(),
            });
        }
    }
}

// Render label used to order our render graph node that will render our phase
#[derive(RenderLabel, Debug, Clone, Hash, PartialEq, Eq)]
struct CustomDrawPassLabel;

#[derive(Default)]
struct CustomDrawNode;
impl ViewNode for CustomDrawNode {
    type ViewQuery = (
        &'static ExtractedCamera,
        &'static ExtractedView,
        &'static ViewTarget,
    );

    fn run<'w>(
        &self,
        graph: &mut RenderGraphContext,
        render_context: &mut RenderContext<'w>,
        (camera, view, target): QueryItem<'w, Self::ViewQuery>,
        world: &'w World,
    ) -> Result<(), NodeRunError> {
        // First, we need to get our phases resource
        let Some(stencil_phases) = world.get_resource::<ViewSortedRenderPhases<Stencil3d>>() else {
            return Ok(());
        };

        // Get the view entity from the graph
        let view_entity = graph.view_entity();

        // Get the phase for the current view running our node
        let Some(stencil_phase) = stencil_phases.get(&view.retained_view_entity) else {
            return Ok(());
        };

        // Render pass setup
        let mut render_pass = render_context.begin_tracked_render_pass(RenderPassDescriptor {
            label: Some("stencil pass"),
            // For the purpose of the example, we will write directly to the view target. A real
            // stencil pass would write to a custom texture and that texture would be used in later
            // passes to render custom effects using it.
            color_attachments: &[Some(target.get_color_attachment())],
            // We don't bind any depth buffer for this pass
            depth_stencil_attachment: None,
            timestamp_writes: None,
            occlusion_query_set: None,
        });

        if let Some(viewport) = camera.viewport.as_ref() {
            render_pass.set_camera_viewport(viewport);
        }

        // Render the phase
        // This will execute each draw functions of each phase items queued in this phase
        if let Err(err) = stencil_phase.render(&mut render_pass, world, view_entity) {
            error!("Error encountered while rendering the stencil phase {err:?}");
        }

        Ok(())
    }

examples/3d/occlusion_culling.rs (line 438)

    fn run<'w>(
        &self,
        _: &mut RenderGraphContext,
        render_context: &mut RenderContext<'w>,
        world: &'w World,
    ) -> Result<(), NodeRunError> {
        // Extract the buffers that hold the GPU indirect draw parameters from
        // the world resources. We're going to read those buffers to determine
        // how many meshes were actually drawn.
        let (Some(indirect_parameters_buffers), Some(indirect_parameters_mapping_buffers)) = (
            world.get_resource::<IndirectParametersBuffers>(),
            world.get_resource::<IndirectParametersStagingBuffers>(),
        ) else {
            return Ok(());
        };

        // Get the indirect parameters buffers corresponding to the opaque 3D
        // phase, since all our meshes are in that phase.
        let Some(phase_indirect_parameters_buffers) =
            indirect_parameters_buffers.get(&TypeId::of::<Opaque3d>())
        else {
            return Ok(());
        };

        // Grab both the buffers we're copying from and the staging buffers
        // we're copying to. Remember that we can't map the indirect parameters
        // buffers directly, so we have to copy their contents to a staging
        // buffer.
        let (
            Some(indexed_data_buffer),
            Some(indexed_batch_sets_buffer),
            Some(indirect_parameters_staging_data_buffer),
            Some(indirect_parameters_staging_batch_sets_buffer),
        ) = (
            phase_indirect_parameters_buffers.indexed.data_buffer(),
            phase_indirect_parameters_buffers
                .indexed
                .batch_sets_buffer(),
            indirect_parameters_mapping_buffers.data.as_ref(),
            indirect_parameters_mapping_buffers.batch_sets.as_ref(),
        )
        else {
            return Ok(());
        };

        // Copy from the indirect parameters buffers to the staging buffers.
        render_context.command_encoder().copy_buffer_to_buffer(
            indexed_data_buffer,
            0,
            indirect_parameters_staging_data_buffer,
            0,
            indexed_data_buffer.size(),
        );
        render_context.command_encoder().copy_buffer_to_buffer(
            indexed_batch_sets_buffer,
            0,
            indirect_parameters_staging_batch_sets_buffer,
            0,
            indexed_batch_sets_buffer.size(),
        );

        Ok(())
    }
}

/// Creates the staging buffers that we use to read back the indirect parameters
/// from the GPU to the CPU.
///
/// We read the indirect parameters from the GPU to the CPU in order to display
/// the number of meshes that were culled each frame.
///
/// We need these staging buffers because `wgpu` doesn't allow us to read the
/// contents of the indirect parameters buffers directly. We must first copy
/// them from the GPU to a staging buffer, and then read the staging buffer.
fn create_indirect_parameters_staging_buffers(
    mut indirect_parameters_staging_buffers: ResMut<IndirectParametersStagingBuffers>,
    indirect_parameters_buffers: Res<IndirectParametersBuffers>,
    render_device: Res<RenderDevice>,
) {
    let Some(phase_indirect_parameters_buffers) =
        indirect_parameters_buffers.get(&TypeId::of::<Opaque3d>())
    else {
        return;
    };

    // Fetch the indirect parameters buffers that we're going to copy from.
    let (Some(indexed_data_buffer), Some(indexed_batch_set_buffer)) = (
        phase_indirect_parameters_buffers.indexed.data_buffer(),
        phase_indirect_parameters_buffers
            .indexed
            .batch_sets_buffer(),
    ) else {
        return;
    };

    // Build the staging buffers. Make sure they have the same sizes as the
    // buffers we're copying from.
    indirect_parameters_staging_buffers.data =
        Some(render_device.create_buffer(&BufferDescriptor {
            label: Some("indexed data staging buffer"),
            size: indexed_data_buffer.size(),
            usage: BufferUsages::MAP_READ | BufferUsages::COPY_DST,
            mapped_at_creation: false,
        }));
    indirect_parameters_staging_buffers.batch_sets =
        Some(render_device.create_buffer(&BufferDescriptor {
            label: Some("indexed batch set staging buffer"),
            size: indexed_batch_set_buffer.size(),
            usage: BufferUsages::MAP_READ | BufferUsages::COPY_DST,
            mapped_at_creation: false,
        }));
}

examples/2d/mesh2d_manual.rs (line 402)

pub fn queue_colored_mesh2d(
    transparent_draw_functions: Res<DrawFunctions<Transparent2d>>,
    colored_mesh2d_pipeline: Res<ColoredMesh2dPipeline>,
    mut pipelines: ResMut<SpecializedRenderPipelines<ColoredMesh2dPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    render_meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderColoredMesh2dInstances>,
    mut transparent_render_phases: ResMut<ViewSortedRenderPhases<Transparent2d>>,
    views: Query<(&RenderVisibleEntities, &ExtractedView, &Msaa)>,
) {
    if render_mesh_instances.is_empty() {
        return;
    }
    // Iterate each view (a camera is a view)
    for (visible_entities, view, msaa) in &views {
        let Some(transparent_phase) = transparent_render_phases.get_mut(&view.retained_view_entity)
        else {
            continue;
        };

        let draw_colored_mesh2d = transparent_draw_functions.read().id::<DrawColoredMesh2d>();

        let mesh_key = Mesh2dPipelineKey::from_msaa_samples(msaa.samples())
            | Mesh2dPipelineKey::from_hdr(view.hdr);

        // Queue all entities visible to that view
        for (render_entity, visible_entity) in visible_entities.iter::<Mesh2d>() {
            if let Some(mesh_instance) = render_mesh_instances.get(visible_entity) {
                let mesh2d_handle = mesh_instance.mesh_asset_id;
                let mesh2d_transforms = &mesh_instance.transforms;
                // Get our specialized pipeline
                let mut mesh2d_key = mesh_key;
                let Some(mesh) = render_meshes.get(mesh2d_handle) else {
                    continue;
                };
                mesh2d_key |= Mesh2dPipelineKey::from_primitive_topology(mesh.primitive_topology());

                let pipeline_id =
                    pipelines.specialize(&pipeline_cache, &colored_mesh2d_pipeline, mesh2d_key);

                let mesh_z = mesh2d_transforms.world_from_local.translation.z;
                transparent_phase.add(Transparent2d {
                    entity: (*render_entity, *visible_entity),
                    draw_function: draw_colored_mesh2d,
                    pipeline: pipeline_id,
                    // The 2d render items are sorted according to their z value before rendering,
                    // in order to get correct transparency
                    sort_key: FloatOrd(mesh_z),
                    // This material is not batched
                    batch_range: 0..1,
                    extra_index: PhaseItemExtraIndex::None,
                    extracted_index: usize::MAX,
                    indexed: mesh.indexed(),
                });
            }
        }
    }
}

Additional examples can be found in:

• examples/ui/directional_navigation.rs

pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>

where Q: Hash + Equivalent<K> + ?Sized,

Returns the key-value pair corresponding to the supplied key.

Refer to get_key_value for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.get_key_value("foo"), Some((&"foo", &0)));

pub fn get_key_value_mut<Q>(&mut self, k: &Q) -> Option<(&K, &mut V)>

where Q: Hash + Equivalent<K> + ?Sized,

Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.

Refer to get_key_value_mut for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.get_key_value_mut("foo"), Some((&"foo", &mut 0)));

pub fn contains_key<Q>(&self, k: &Q) -> bool

where Q: Hash + Equivalent<K> + ?Sized,

Returns true if the map contains a value for the specified key.

Refer to contains_key for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert!(map.contains_key("foo"));

pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>

where Q: Hash + Equivalent<K> + ?Sized,

Returns a mutable reference to the value corresponding to the key.

Refer to get_mut for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.get_mut("foo"), Some(&mut 0));

Examples found in repository

examples/3d/tonemapping.rs (line 341)

fn update_color_grading_settings(
    keys: Res<ButtonInput<KeyCode>>,
    time: Res<Time>,
    mut per_method_settings: ResMut<PerMethodSettings>,
    tonemapping: Single<&Tonemapping>,
    current_scene: Res<CurrentScene>,
    mut selected_parameter: ResMut<SelectedParameter>,
) {
    let color_grading = per_method_settings.settings.get_mut(*tonemapping).unwrap();
    let mut dt = time.delta_secs() * 0.25;
    if keys.pressed(KeyCode::ArrowLeft) {
        dt = -dt;
    }

    if keys.just_pressed(KeyCode::ArrowDown) {
        selected_parameter.next();
    }
    if keys.just_pressed(KeyCode::ArrowUp) {
        selected_parameter.prev();
    }
    if keys.pressed(KeyCode::ArrowLeft) || keys.pressed(KeyCode::ArrowRight) {
        match selected_parameter.value {
            0 => {
                color_grading.global.exposure += dt;
            }
            1 => {
                color_grading
                    .all_sections_mut()
                    .for_each(|section| section.gamma += dt);
            }
            2 => {
                color_grading
                    .all_sections_mut()
                    .for_each(|section| section.saturation += dt);
            }
            3 => {
                color_grading.global.post_saturation += dt;
            }
            _ => {}
        }
    }

    if keys.just_pressed(KeyCode::Space) {
        for (_, grading) in per_method_settings.settings.iter_mut() {
            *grading = ColorGrading::default();
        }
    }

    if keys.just_pressed(KeyCode::Enter) && current_scene.0 == 1 {
        for (mapper, grading) in per_method_settings.settings.iter_mut() {
            *grading = PerMethodSettings::basic_scene_recommendation(*mapper);
        }
    }
}

examples/shader/custom_shader_instancing.rs (line 140)

fn queue_custom(
    transparent_3d_draw_functions: Res<DrawFunctions<Transparent3d>>,
    custom_pipeline: Res<CustomPipeline>,
    mut pipelines: ResMut<SpecializedMeshPipelines<CustomPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderMeshInstances>,
    material_meshes: Query<(Entity, &MainEntity), With<InstanceMaterialData>>,
    mut transparent_render_phases: ResMut<ViewSortedRenderPhases<Transparent3d>>,
    views: Query<(&ExtractedView, &Msaa)>,
) {
    let draw_custom = transparent_3d_draw_functions.read().id::<DrawCustom>();

    for (view, msaa) in &views {
        let Some(transparent_phase) = transparent_render_phases.get_mut(&view.retained_view_entity)
        else {
            continue;
        };

        let msaa_key = MeshPipelineKey::from_msaa_samples(msaa.samples());

        let view_key = msaa_key | MeshPipelineKey::from_hdr(view.hdr);
        let rangefinder = view.rangefinder3d();
        for (entity, main_entity) in &material_meshes {
            let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(*main_entity)
            else {
                continue;
            };
            let Some(mesh) = meshes.get(mesh_instance.mesh_asset_id) else {
                continue;
            };
            let key =
                view_key | MeshPipelineKey::from_primitive_topology(mesh.primitive_topology());
            let pipeline = pipelines
                .specialize(&pipeline_cache, &custom_pipeline, key, &mesh.layout)
                .unwrap();
            transparent_phase.add(Transparent3d {
                entity: (entity, *main_entity),
                pipeline,
                draw_function: draw_custom,
                distance: rangefinder.distance_translation(&mesh_instance.translation),
                batch_range: 0..1,
                extra_index: PhaseItemExtraIndex::None,
                indexed: true,
            });
        }
    }
}

examples/2d/mesh2d_manual.rs (line 390)

pub fn queue_colored_mesh2d(
    transparent_draw_functions: Res<DrawFunctions<Transparent2d>>,
    colored_mesh2d_pipeline: Res<ColoredMesh2dPipeline>,
    mut pipelines: ResMut<SpecializedRenderPipelines<ColoredMesh2dPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    render_meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderColoredMesh2dInstances>,
    mut transparent_render_phases: ResMut<ViewSortedRenderPhases<Transparent2d>>,
    views: Query<(&RenderVisibleEntities, &ExtractedView, &Msaa)>,
) {
    if render_mesh_instances.is_empty() {
        return;
    }
    // Iterate each view (a camera is a view)
    for (visible_entities, view, msaa) in &views {
        let Some(transparent_phase) = transparent_render_phases.get_mut(&view.retained_view_entity)
        else {
            continue;
        };

        let draw_colored_mesh2d = transparent_draw_functions.read().id::<DrawColoredMesh2d>();

        let mesh_key = Mesh2dPipelineKey::from_msaa_samples(msaa.samples())
            | Mesh2dPipelineKey::from_hdr(view.hdr);

        // Queue all entities visible to that view
        for (render_entity, visible_entity) in visible_entities.iter::<Mesh2d>() {
            if let Some(mesh_instance) = render_mesh_instances.get(visible_entity) {
                let mesh2d_handle = mesh_instance.mesh_asset_id;
                let mesh2d_transforms = &mesh_instance.transforms;
                // Get our specialized pipeline
                let mut mesh2d_key = mesh_key;
                let Some(mesh) = render_meshes.get(mesh2d_handle) else {
                    continue;
                };
                mesh2d_key |= Mesh2dPipelineKey::from_primitive_topology(mesh.primitive_topology());

                let pipeline_id =
                    pipelines.specialize(&pipeline_cache, &colored_mesh2d_pipeline, mesh2d_key);

                let mesh_z = mesh2d_transforms.world_from_local.translation.z;
                transparent_phase.add(Transparent2d {
                    entity: (*render_entity, *visible_entity),
                    draw_function: draw_colored_mesh2d,
                    pipeline: pipeline_id,
                    // The 2d render items are sorted according to their z value before rendering,
                    // in order to get correct transparency
                    sort_key: FloatOrd(mesh_z),
                    // This material is not batched
                    batch_range: 0..1,
                    extra_index: PhaseItemExtraIndex::None,
                    extracted_index: usize::MAX,
                    indexed: mesh.indexed(),
                });
            }
        }
    }
}

examples/shader/custom_phase_item.rs (line 239)

fn queue_custom_phase_item(
    pipeline_cache: Res<PipelineCache>,
    custom_phase_pipeline: Res<CustomPhasePipeline>,
    mut opaque_render_phases: ResMut<ViewBinnedRenderPhases<Opaque3d>>,
    opaque_draw_functions: Res<DrawFunctions<Opaque3d>>,
    mut specialized_render_pipelines: ResMut<SpecializedRenderPipelines<CustomPhasePipeline>>,
    views: Query<(&ExtractedView, &RenderVisibleEntities, &Msaa)>,
    mut next_tick: Local<Tick>,
) {
    let draw_custom_phase_item = opaque_draw_functions
        .read()
        .id::<DrawCustomPhaseItemCommands>();

    // Render phases are per-view, so we need to iterate over all views so that
    // the entity appears in them. (In this example, we have only one view, but
    // it's good practice to loop over all views anyway.)
    for (view, view_visible_entities, msaa) in views.iter() {
        let Some(opaque_phase) = opaque_render_phases.get_mut(&view.retained_view_entity) else {
            continue;
        };

        // Find all the custom rendered entities that are visible from this
        // view.
        for &entity in view_visible_entities.get::<CustomRenderedEntity>().iter() {
            // Ordinarily, the [`SpecializedRenderPipeline::Key`] would contain
            // some per-view settings, such as whether the view is HDR, but for
            // simplicity's sake we simply hard-code the view's characteristics,
            // with the exception of number of MSAA samples.
            let pipeline_id = specialized_render_pipelines.specialize(
                &pipeline_cache,
                &custom_phase_pipeline,
                *msaa,
            );

            // Bump the change tick in order to force Bevy to rebuild the bin.
            let this_tick = next_tick.get() + 1;
            next_tick.set(this_tick);

            // Add the custom render item. We use the
            // [`BinnedRenderPhaseType::NonMesh`] type to skip the special
            // handling that Bevy has for meshes (preprocessing, indirect
            // draws, etc.)
            //
            // The asset ID is arbitrary; we simply use [`AssetId::invalid`],
            // but you can use anything you like. Note that the asset ID need
            // not be the ID of a [`Mesh`].
            opaque_phase.add(
                Opaque3dBatchSetKey {
                    draw_function: draw_custom_phase_item,
                    pipeline: pipeline_id,
                    material_bind_group_index: None,
                    lightmap_slab: None,
                    vertex_slab: default(),
                    index_slab: None,
                },
                Opaque3dBinKey {
                    asset_id: AssetId::<Mesh>::invalid().untyped(),
                },
                entity,
                InputUniformIndex::default(),
                BinnedRenderPhaseType::NonMesh,
                *next_tick,
            );
        }
    }
}

examples/shader/custom_render_phase.rs (line 512)

fn queue_custom_meshes(
    custom_draw_functions: Res<DrawFunctions<Stencil3d>>,
    mut pipelines: ResMut<SpecializedMeshPipelines<StencilPipeline>>,
    pipeline_cache: Res<PipelineCache>,
    custom_draw_pipeline: Res<StencilPipeline>,
    render_meshes: Res<RenderAssets<RenderMesh>>,
    render_mesh_instances: Res<RenderMeshInstances>,
    mut custom_render_phases: ResMut<ViewSortedRenderPhases<Stencil3d>>,
    mut views: Query<(&ExtractedView, &RenderVisibleEntities, &Msaa)>,
    has_marker: Query<(), With<DrawStencil>>,
) {
    for (view, visible_entities, msaa) in &mut views {
        let Some(custom_phase) = custom_render_phases.get_mut(&view.retained_view_entity) else {
            continue;
        };
        let draw_custom = custom_draw_functions.read().id::<DrawMesh3dStencil>();

        // Create the key based on the view.
        // In this case we only care about MSAA and HDR
        let view_key = MeshPipelineKey::from_msaa_samples(msaa.samples())
            | MeshPipelineKey::from_hdr(view.hdr);

        let rangefinder = view.rangefinder3d();
        // Since our phase can work on any 3d mesh we can reuse the default mesh 3d filter
        for (render_entity, visible_entity) in visible_entities.iter::<Mesh3d>() {
            // We only want meshes with the marker component to be queued to our phase.
            if has_marker.get(*render_entity).is_err() {
                continue;
            }
            let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(*visible_entity)
            else {
                continue;
            };
            let Some(mesh) = render_meshes.get(mesh_instance.mesh_asset_id) else {
                continue;
            };

            // Specialize the key for the current mesh entity
            // For this example we only specialize based on the mesh topology
            // but you could have more complex keys and that's where you'd need to create those keys
            let mut mesh_key = view_key;
            mesh_key |= MeshPipelineKey::from_primitive_topology(mesh.primitive_topology());

            let pipeline_id = pipelines.specialize(
                &pipeline_cache,
                &custom_draw_pipeline,
                mesh_key,
                &mesh.layout,
            );
            let pipeline_id = match pipeline_id {
                Ok(id) => id,
                Err(err) => {
                    error!("{}", err);
                    continue;
                }
            };
            let distance = rangefinder.distance_translation(&mesh_instance.translation);
            // At this point we have all the data we need to create a phase item and add it to our
            // phase
            custom_phase.add(Stencil3d {
                // Sort the data based on the distance to the view
                sort_key: FloatOrd(distance),
                entity: (*render_entity, *visible_entity),
                pipeline: pipeline_id,
                draw_function: draw_custom,
                // Sorted phase items aren't batched
                batch_range: 0..1,
                extra_index: PhaseItemExtraIndex::None,
                indexed: mesh.indexed(),
            });
        }
    }
}

examples/shader/specialized_mesh_pipeline.rs (line 321)

fn queue_custom_mesh_pipeline(
    pipeline_cache: Res<PipelineCache>,
    custom_mesh_pipeline: Res<CustomMeshPipeline>,
    (mut opaque_render_phases, opaque_draw_functions): (
        ResMut<ViewBinnedRenderPhases<Opaque3d>>,
        Res<DrawFunctions<Opaque3d>>,
    ),
    mut specialized_mesh_pipelines: ResMut<SpecializedMeshPipelines<CustomMeshPipeline>>,
    views: Query<(
        &RenderVisibleEntities,
        &ExtractedView,
        &Msaa,
        Has<NoIndirectDrawing>,
        Has<OcclusionCulling>,
    )>,
    (render_meshes, render_mesh_instances): (
        Res<RenderAssets<RenderMesh>>,
        Res<RenderMeshInstances>,
    ),
    param: StaticSystemParam<<MeshPipeline as GetBatchData>::Param>,
    mut phase_batched_instance_buffers: ResMut<
        PhaseBatchedInstanceBuffers<Opaque3d, <MeshPipeline as GetBatchData>::BufferData>,
    >,
    mut phase_indirect_parameters_buffers: ResMut<PhaseIndirectParametersBuffers<Opaque3d>>,
    mut change_tick: Local<Tick>,
) {
    let system_param_item = param.into_inner();

    let UntypedPhaseBatchedInstanceBuffers {
        ref mut data_buffer,
        ref mut work_item_buffers,
        ref mut late_indexed_indirect_parameters_buffer,
        ref mut late_non_indexed_indirect_parameters_buffer,
        ..
    } = phase_batched_instance_buffers.buffers;

    // Get the id for our custom draw function
    let draw_function_id = opaque_draw_functions
        .read()
        .id::<DrawSpecializedPipelineCommands>();

    // Render phases are per-view, so we need to iterate over all views so that
    // the entity appears in them. (In this example, we have only one view, but
    // it's good practice to loop over all views anyway.)
    for (view_visible_entities, view, msaa, no_indirect_drawing, gpu_occlusion_culling) in
        views.iter()
    {
        let Some(opaque_phase) = opaque_render_phases.get_mut(&view.retained_view_entity) else {
            continue;
        };

        // Create *work item buffers* if necessary. Work item buffers store the
        // indices of meshes that are to be rendered when indirect drawing is
        // enabled.
        let work_item_buffer = gpu_preprocessing::get_or_create_work_item_buffer::<Opaque3d>(
            work_item_buffers,
            view.retained_view_entity,
            no_indirect_drawing,
            gpu_occlusion_culling,
        );

        // Initialize those work item buffers in preparation for this new frame.
        gpu_preprocessing::init_work_item_buffers(
            work_item_buffer,
            late_indexed_indirect_parameters_buffer,
            late_non_indexed_indirect_parameters_buffer,
        );

        // Create the key based on the view. In this case we only care about MSAA and HDR
        let view_key = MeshPipelineKey::from_msaa_samples(msaa.samples())
            | MeshPipelineKey::from_hdr(view.hdr);

        // Set up a slot to hold information about the batch set we're going to
        // create. If there are any of our custom meshes in the scene, we'll
        // need this information in order for Bevy to kick off the rendering.
        let mut mesh_batch_set_info = None;

        // Find all the custom rendered entities that are visible from this
        // view.
        for &(render_entity, visible_entity) in
            view_visible_entities.get::<CustomRenderedEntity>().iter()
        {
            // Get the mesh instance
            let Some(mesh_instance) = render_mesh_instances.render_mesh_queue_data(visible_entity)
            else {
                continue;
            };

            // Get the mesh data
            let Some(mesh) = render_meshes.get(mesh_instance.mesh_asset_id) else {
                continue;
            };

            // Specialize the key for the current mesh entity
            // For this example we only specialize based on the mesh topology
            // but you could have more complex keys and that's where you'd need to create those keys
            let mut mesh_key = view_key;
            mesh_key |= MeshPipelineKey::from_primitive_topology(mesh.primitive_topology());

            // Initialize the batch set information if this was the first custom
            // mesh we saw. We'll need that information later to create the
            // batch set.
            if mesh_batch_set_info.is_none() {
                mesh_batch_set_info = Some(MeshBatchSetInfo {
                    indirect_parameters_index: phase_indirect_parameters_buffers
                        .buffers
                        .allocate(mesh.indexed(), 1),
                    is_indexed: mesh.indexed(),
                });
            }
            let mesh_info = mesh_batch_set_info.unwrap();

            // Allocate some input and output indices. We'll need these to
            // create the *work item* below.
            let Some(input_index) =
                MeshPipeline::get_binned_index(&system_param_item, visible_entity)
            else {
                continue;
            };
            let output_index = data_buffer.add() as u32;

            // Finally, we can specialize the pipeline based on the key
            let pipeline_id = specialized_mesh_pipelines
                .specialize(
                    &pipeline_cache,
                    &custom_mesh_pipeline,
                    mesh_key,
                    &mesh.layout,
                )
                // This should never with this example, but if your pipeline specialization
                // can fail you need to handle the error here
                .expect("Failed to specialize mesh pipeline");

            // Bump the change tick so that Bevy is forced to rebuild the bin.
            let next_change_tick = change_tick.get() + 1;
            change_tick.set(next_change_tick);

            // Add the mesh with our specialized pipeline
            opaque_phase.add(
                Opaque3dBatchSetKey {
                    draw_function: draw_function_id,
                    pipeline: pipeline_id,
                    material_bind_group_index: None,
                    vertex_slab: default(),
                    index_slab: None,
                    lightmap_slab: None,
                },
                // The asset ID is arbitrary; we simply use [`AssetId::invalid`],
                // but you can use anything you like. Note that the asset ID need
                // not be the ID of a [`Mesh`].
                Opaque3dBinKey {
                    asset_id: AssetId::<Mesh>::invalid().untyped(),
                },
                (render_entity, visible_entity),
                mesh_instance.current_uniform_index,
                // This example supports batching, but if your pipeline doesn't
                // support it you can use `BinnedRenderPhaseType::UnbatchableMesh`
                BinnedRenderPhaseType::BatchableMesh,
                *change_tick,
            );

            // Create a *work item*. A work item tells the Bevy renderer to
            // transform the mesh on GPU.
            work_item_buffer.push(
                mesh.indexed(),
                PreprocessWorkItem {
                    input_index: input_index.into(),
                    output_or_indirect_parameters_index: if no_indirect_drawing {
                        output_index
                    } else {
                        mesh_info.indirect_parameters_index
                    },
                },
            );
        }

        // Now if there were any meshes, we need to add a command to the
        // indirect parameters buffer, so that the renderer will end up
        // enqueuing a command to draw the mesh.
        if let Some(mesh_info) = mesh_batch_set_info {
            phase_indirect_parameters_buffers
                .buffers
                .add_batch_set(mesh_info.is_indexed, mesh_info.indirect_parameters_index);
        }
    }
}

pub fn get_many_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once.

Refer to get_many_mut for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

let result = map.get_many_mut(["foo", "bar"]);

assert_eq!(result, [Some(&mut 0), Some(&mut 1)]);

pub fn get_many_key_value_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<(&K, &mut V)>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, with immutable references to the corresponding keys.

Refer to get_many_key_value_mut for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);
map.insert("bar", 1);
map.insert("baz", 2);

let result = map.get_many_key_value_mut(["foo", "bar"]);

assert_eq!(result, [Some((&"foo", &mut 0)), Some((&"bar", &mut 1))]);

pub fn insert(&mut self, k: K, v: V) -> Option<V>

Inserts a key-value pair into the map.

Refer to insert for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.get("foo"), Some(&0));

Examples found in repository

examples/ecs/immutable_components.rs (line 86)

fn on_insert_name(mut world: DeferredWorld<'_>, HookContext { entity, .. }: HookContext) {
    let Some(&name) = world.entity(entity).get::<Name>() else {
        unreachable!("OnInsert hook guarantees `Name` is available on entity")
    };
    let Some(mut index) = world.get_resource_mut::<NameIndex>() else {
        return;
    };

    index.name_to_entity.insert(name, entity);
}

tests/ecs/ambiguity_detection.rs (line 77)

fn count_ambiguities(sub_app: &SubApp) -> AmbiguitiesCount {
    let schedules = sub_app.world().resource::<Schedules>();
    let mut ambiguities = <HashMap<_, _>>::default();
    for (_, schedule) in schedules.iter() {
        let ambiguities_in_schedule = schedule.graph().conflicting_systems().len();
        ambiguities.insert(schedule.label(), ambiguities_in_schedule);
    }
    AmbiguitiesCount(ambiguities)
}

examples/3d/tonemapping.rs (lines 587-590)

    fn default() -> Self {
        let mut settings = <HashMap<_, _>>::default();

        for method in [
            Tonemapping::None,
            Tonemapping::Reinhard,
            Tonemapping::ReinhardLuminance,
            Tonemapping::AcesFitted,
            Tonemapping::AgX,
            Tonemapping::SomewhatBoringDisplayTransform,
            Tonemapping::TonyMcMapface,
            Tonemapping::BlenderFilmic,
        ] {
            settings.insert(
                method,
                PerMethodSettings::basic_scene_recommendation(method),
            );
        }

        Self { settings }
    }

examples/2d/mesh2d_manual.rs (lines 359-368)

pub fn extract_colored_mesh2d(
    mut commands: Commands,
    mut previous_len: Local<usize>,
    // When extracting, you must use `Extract` to mark the `SystemParam`s
    // which should be taken from the main world.
    query: Extract<
        Query<
            (
                Entity,
                RenderEntity,
                &ViewVisibility,
                &GlobalTransform,
                &Mesh2d,
            ),
            With<ColoredMesh2d>,
        >,
    >,
    mut render_mesh_instances: ResMut<RenderColoredMesh2dInstances>,
) {
    let mut values = Vec::with_capacity(*previous_len);
    for (entity, render_entity, view_visibility, transform, handle) in &query {
        if !view_visibility.get() {
            continue;
        }

        let transforms = Mesh2dTransforms {
            world_from_local: (&transform.affine()).into(),
            flags: MeshFlags::empty().bits(),
        };

        values.push((render_entity, ColoredMesh2d));
        render_mesh_instances.insert(
            entity.into(),
            RenderMesh2dInstance {
                mesh_asset_id: handle.0.id(),
                transforms,
                material_bind_group_id: Material2dBindGroupId::default(),
                automatic_batching: false,
                tag: 0,
            },
        );
    }
    *previous_len = values.len();
    commands.try_insert_batch(values);
}

examples/reflection/reflection_types.rs (line 69)

fn setup() {
    let mut z = <HashMap<_, _>>::default();
    z.insert("Hello".to_string(), 1.0);
    let value: Box<dyn Reflect> = Box::new(A {
        x: 1,
        y: vec![1, 2],
        z,
    });

    // There are a number of different "reflect traits", which each expose different operations on
    // the underlying type
    match value.reflect_ref() {
        // `Struct` is a trait automatically implemented for structs that derive Reflect. This trait
        // allows you to interact with fields via their string names or indices
        ReflectRef::Struct(value) => {
            info!(
                "This is a 'struct' type with an 'x' value of {}",
                value.get_field::<usize>("x").unwrap()
            );
        }
        // `TupleStruct` is a trait automatically implemented for tuple structs that derive Reflect.
        // This trait allows you to interact with fields via their indices
        ReflectRef::TupleStruct(_) => {}
        // `Tuple` is a special trait that can be manually implemented (instead of deriving
        // Reflect). This exposes "tuple" operations on your type, allowing you to interact
        // with fields via their indices. Tuple is automatically implemented for tuples of
        // arity 12 or less.
        ReflectRef::Tuple(_) => {}
        // `Enum` is a trait automatically implemented for enums that derive Reflect. This trait allows you
        // to interact with the current variant and its fields (if it has any)
        ReflectRef::Enum(_) => {}
        // `List` is a special trait that can be manually implemented (instead of deriving Reflect).
        // This exposes "list" operations on your type, such as insertion. `List` is automatically
        // implemented for relevant core types like Vec<T>.
        ReflectRef::List(_) => {}
        // `Array` is a special trait that can be manually implemented (instead of deriving Reflect).
        // This exposes "array" operations on your type, such as indexing. `Array`
        // is automatically implemented for relevant core types like [T; N].
        ReflectRef::Array(_) => {}
        // `Map` is a special trait that can be manually implemented (instead of deriving Reflect).
        // This exposes "map" operations on your type, such as getting / inserting by key.
        // Map is automatically implemented for relevant core types like HashMap<K, V>
        ReflectRef::Map(_) => {}
        // `Set` is a special trait that can be manually implemented (instead of deriving Reflect).
        // This exposes "set" operations on your type, such as getting / inserting by value.
        // Set is automatically implemented for relevant core types like HashSet<T>
        ReflectRef::Set(_) => {}
        // `Function` is a special trait that can be manually implemented (instead of deriving Reflect).
        // This exposes "function" operations on your type, such as calling it with arguments.
        // This trait is automatically implemented for types like DynamicFunction.
        // This variant only exists if the `reflect_functions` feature is enabled.
        #[cfg(feature = "reflect_functions")]
        ReflectRef::Function(_) => {}
        // `Opaque` types do not implement any of the other traits above. They are simply a Reflect
        // implementation. Opaque is implemented for opaque types like String and Instant,
        // but also include primitive types like i32, usize, and f32 (despite not technically being opaque).
        ReflectRef::Opaque(_) => {}
        #[expect(
            clippy::allow_attributes,
            reason = "`unreachable_patterns` is not always linted"
        )]
        #[allow(
            unreachable_patterns,
            reason = "This example cannot always detect when `bevy_reflect/functions` is enabled."
        )]
        _ => {}
    }

    let mut dynamic_list = DynamicList::default();
    dynamic_list.push(3u32);
    dynamic_list.push(4u32);
    dynamic_list.push(5u32);

    let mut value: A = value.take::<A>().unwrap();
    value.y.apply(&dynamic_list);
    assert_eq!(value.y, vec![3u32, 4u32, 5u32]);
}

examples/ui/directional_navigation.rs (line 199)

fn setup_ui(
    mut commands: Commands,
    mut directional_nav_map: ResMut<DirectionalNavigationMap>,
    mut input_focus: ResMut<InputFocus>,
) {
    const N_ROWS: u16 = 5;
    const N_COLS: u16 = 3;

    // Rendering UI elements requires a camera
    commands.spawn(Camera2d);

    // Create a full-screen background node
    let root_node = commands
        .spawn(Node {
            width: Val::Percent(100.0),
            height: Val::Percent(100.0),
            ..default()
        })
        .id();

    // Add instruction to the left of the grid
    let instructions = commands
        .spawn((
            Text::new("Use arrow keys or D-pad to navigate. \
            Click the buttons, or press Enter / the South gamepad button to interact with the focused button."),
            Node {
                width: Val::Px(300.0),
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                margin: UiRect::all(Val::Px(12.0)),
                ..default()
            },
        ))
        .id();

    // Set up the root entity to hold the grid
    let grid_root_entity = commands
        .spawn(Node {
            display: Display::Grid,
            // Allow the grid to take up the full height and the rest of the width of the window
            width: Val::Percent(100.),
            height: Val::Percent(100.),
            // Set the number of rows and columns in the grid
            // allowing the grid to automatically size the cells
            grid_template_columns: RepeatedGridTrack::auto(N_COLS),
            grid_template_rows: RepeatedGridTrack::auto(N_ROWS),
            ..default()
        })
        .id();

    // Add the instructions and grid to the root node
    commands
        .entity(root_node)
        .add_children(&[instructions, grid_root_entity]);

    let mut button_entities: HashMap<(u16, u16), Entity> = HashMap::default();
    for row in 0..N_ROWS {
        for col in 0..N_COLS {
            let button_name = format!("Button {}-{}", row, col);

            let button_entity = commands
                .spawn((
                    Button,
                    Node {
                        width: Val::Px(200.0),
                        height: Val::Px(120.0),
                        // Add a border so we can show which element is focused
                        border: UiRect::all(Val::Px(4.0)),
                        // Center the button's text label
                        justify_content: JustifyContent::Center,
                        align_items: AlignItems::Center,
                        // Center the button within the grid cell
                        align_self: AlignSelf::Center,
                        justify_self: JustifySelf::Center,
                        ..default()
                    },
                    ResetTimer::default(),
                    BorderRadius::all(Val::Px(16.0)),
                    BackgroundColor::from(NORMAL_BUTTON),
                    Name::new(button_name.clone()),
                ))
                // Add a text element to the button
                .with_child((
                    Text::new(button_name),
                    // And center the text if it flows onto multiple lines
                    TextLayout {
                        justify: JustifyText::Center,
                        ..default()
                    },
                ))
                .id();

            // Add the button to the grid
            commands.entity(grid_root_entity).add_child(button_entity);

            // Keep track of the button entities so we can set up our navigation graph
            button_entities.insert((row, col), button_entity);
        }
    }

    // Connect all of the buttons in the same row to each other,
    // looping around when the edge is reached.
    for row in 0..N_ROWS {
        let entities_in_row: Vec<Entity> = (0..N_COLS)
            .map(|col| button_entities.get(&(row, col)).unwrap())
            .copied()
            .collect();
        directional_nav_map.add_looping_edges(&entities_in_row, CompassOctant::East);
    }

    // Connect all of the buttons in the same column to each other,
    // but don't loop around when the edge is reached.
    // While looping is a very reasonable choice, we're not doing it here to demonstrate the different options.
    for col in 0..N_COLS {
        let entities_in_column: Vec<Entity> = (0..N_ROWS)
            .map(|row| button_entities.get(&(row, col)).unwrap())
            .copied()
            .collect();

        directional_nav_map.add_edges(&entities_in_column, CompassOctant::South);
    }

    // When changing scenes, remember to set an initial focus!
    let top_left_entity = *button_entities.get(&(0, 0)).unwrap();
    input_focus.set(top_left_entity);
}

pub fn try_insert( &mut self, key: K, value: V, ) -> Result<&mut V, OccupiedError<'_, K, V, S>>

Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.

Refer to try_insert for further details.

Examples

let mut map = HashMap::new();

map.try_insert("foo", 0).unwrap();

assert!(map.try_insert("foo", 1).is_err());

pub fn remove<Q>(&mut self, k: &Q) -> Option<V>

where Q: Hash + Equivalent<K> + ?Sized,

Removes a key from the map, returning the value at the key if the key was previously in the map. Keeps the allocated memory for reuse.

Refer to remove for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.remove("foo"), Some(0));

assert!(map.is_empty());

Examples found in repository

examples/ecs/immutable_components.rs (line 101)

fn on_replace_name(mut world: DeferredWorld<'_>, HookContext { entity, .. }: HookContext) {
    let Some(&name) = world.entity(entity).get::<Name>() else {
        unreachable!("OnReplace hook guarantees `Name` is available on entity")
    };
    let Some(mut index) = world.get_resource_mut::<NameIndex>() else {
        return;
    };

    index.name_to_entity.remove(&name);
}

pub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>

where Q: Hash + Equivalent<K> + ?Sized,

Removes a key from the map, returning the stored key and value if the key was previously in the map. Keeps the allocated memory for reuse.

Refer to remove_entry for further details.

Examples

let mut map = HashMap::new();

map.insert("foo", 0);

assert_eq!(map.remove_entry("foo"), Some(("foo", 0)));

assert!(map.is_empty());

pub fn allocation_size(&self) -> usize

Returns the total amount of memory allocated internally by the hash set, in bytes.

Refer to allocation_size for further details.

Examples

let mut map = HashMap::new();

assert_eq!(map.allocation_size(), 0);

map.insert("foo", 0u32);

assert!(map.allocation_size() >= size_of::<&'static str>() + size_of::<u32>());

pub unsafe fn insert_unique_unchecked( &mut self, key: K, value: V, ) -> (&K, &mut V)

Insert a key-value pair into the map without checking if the key already exists in the map.

Refer to insert_unique_unchecked for further details.

Safety

This operation is safe if a key does not exist in the map.

However, if a key exists in the map already, the behavior is unspecified: this operation may panic, loop forever, or any following operation with the map may panic, loop forever or return arbitrary result.

That said, this operation (and following operations) are guaranteed to not violate memory safety.

However this operation is still unsafe because the resulting HashMap may be passed to unsafe code which does expect the map to behave correctly, and would cause unsoundness as a result.

pub unsafe fn get_many_unchecked_mut<Q, const N: usize>( &mut self, keys: [&Q; N], ) -> [Option<&mut V>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, without validating that the values are unique.

Refer to get_many_unchecked_mut for further details.

Returns an array of length N with the results of each query. None will be used if the key is missing.

For a safe alternative see get_many_mut.

Safety

Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.

pub unsafe fn get_many_key_value_unchecked_mut<Q, const N: usize>( &mut self, keys: [&Q; N], ) -> [Option<(&K, &mut V)>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, with immutable references to the corresponding keys, without validating that the values are unique.

Refer to get_many_key_value_unchecked_mut for further details.

Returns an array of length N with the results of each query. None will be returned if any of the keys are missing.

For a safe alternative see get_many_key_value_mut.

Safety

Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.

Methods from Deref<Target = HashMap<K, V, S>>

pub fn allocator(&self) -> &A

Returns a reference to the underlying allocator.

pub fn hasher(&self) -> &S

Returns a reference to the map’s BuildHasher.

Examples

use hashbrown::HashMap;
use hashbrown::DefaultHashBuilder;

let hasher = DefaultHashBuilder::default();
let map: HashMap<i32, i32> = HashMap::with_hasher(hasher);
let hasher: &DefaultHashBuilder = map.hasher();

pub fn capacity(&self) -> usize

Returns the number of elements the map can hold without reallocating.

This number is a lower bound; the HashMap<K, V> might be able to hold more, but is guaranteed to be able to hold at least this many.

Examples

use hashbrown::HashMap;
let map: HashMap<i32, i32> = HashMap::with_capacity(100);
assert_eq!(map.len(), 0);
assert!(map.capacity() >= 100);

pub fn keys(&self) -> Keys<'_, K, V>

An iterator visiting all keys in arbitrary order. The iterator element type is &'a K.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<&str> = Vec::new();

for key in map.keys() {
    println!("{}", key);
    vec.push(*key);
}

// The `Keys` iterator produces keys in arbitrary order, so the
// keys must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, ["a", "b", "c"]);

assert_eq!(map.len(), 3);

pub fn values(&self) -> Values<'_, K, V>

An iterator visiting all values in arbitrary order. The iterator element type is &'a V.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<i32> = Vec::new();

for val in map.values() {
    println!("{}", val);
    vec.push(*val);
}

// The `Values` iterator produces values in arbitrary order, so the
// values must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [1, 2, 3]);

assert_eq!(map.len(), 3);

pub fn values_mut(&mut self) -> ValuesMut<'_, K, V>

An iterator visiting all values mutably in arbitrary order. The iterator element type is &'a mut V.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();

map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

for val in map.values_mut() {
    *val = *val + 10;
}

assert_eq!(map.len(), 3);
let mut vec: Vec<i32> = Vec::new();

for val in map.values() {
    println!("{}", val);
    vec.push(*val);
}

// The `Values` iterator produces values in arbitrary order, so the
// values must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [11, 12, 13]);

assert_eq!(map.len(), 3);

pub fn iter(&self) -> Iter<'_, K, V>

An iterator visiting all key-value pairs in arbitrary order. The iterator element type is (&'a K, &'a V).

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);
assert_eq!(map.len(), 3);
let mut vec: Vec<(&str, i32)> = Vec::new();

for (key, val) in map.iter() {
    println!("key: {} val: {}", key, val);
    vec.push((*key, *val));
}

// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [("a", 1), ("b", 2), ("c", 3)]);

assert_eq!(map.len(), 3);

pub fn iter_mut(&mut self) -> IterMut<'_, K, V>

An iterator visiting all key-value pairs in arbitrary order, with mutable references to the values. The iterator element type is (&'a K, &'a mut V).

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert("a", 1);
map.insert("b", 2);
map.insert("c", 3);

// Update all values
for (_, val) in map.iter_mut() {
    *val *= 2;
}

assert_eq!(map.len(), 3);
let mut vec: Vec<(&str, i32)> = Vec::new();

for (key, val) in &map {
    println!("key: {} val: {}", key, val);
    vec.push((*key, *val));
}

// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, [("a", 2), ("b", 4), ("c", 6)]);

assert_eq!(map.len(), 3);

pub fn len(&self) -> usize

Returns the number of elements in the map.

Examples

use hashbrown::HashMap;

let mut a = HashMap::new();
assert_eq!(a.len(), 0);
a.insert(1, "a");
assert_eq!(a.len(), 1);

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

Examples

use hashbrown::HashMap;

let mut a = HashMap::new();
assert!(a.is_empty());
a.insert(1, "a");
assert!(!a.is_empty());

pub fn drain(&mut self) -> Drain<'_, K, V, A>

Clears the map, returning all key-value pairs as an iterator. Keeps the allocated memory for reuse.

If the returned iterator is dropped before being fully consumed, it drops the remaining key-value pairs. The returned iterator keeps a mutable borrow on the vector to optimize its implementation.

Examples

use hashbrown::HashMap;

let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");
let capacity_before_drain = a.capacity();

for (k, v) in a.drain().take(1) {
    assert!(k == 1 || k == 2);
    assert!(v == "a" || v == "b");
}

// As we can see, the map is empty and contains no element.
assert!(a.is_empty() && a.len() == 0);
// But map capacity is equal to old one.
assert_eq!(a.capacity(), capacity_before_drain);

let mut a = HashMap::new();
a.insert(1, "a");
a.insert(2, "b");

{   // Iterator is dropped without being consumed.
    let d = a.drain();
}

// But the map is empty even if we do not use Drain iterator.
assert!(a.is_empty());

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&K, &mut V) -> bool,

Retains only the elements specified by the predicate. Keeps the allocated memory for reuse.

In other words, remove all pairs (k, v) such that f(&k, &mut v) returns false. The elements are visited in unsorted (and unspecified) order.

Examples

use hashbrown::HashMap;

let mut map: HashMap<i32, i32> = (0..8).map(|x|(x, x*10)).collect();
assert_eq!(map.len(), 8);

map.retain(|&k, _| k % 2 == 0);

// We can see, that the number of elements inside map is changed.
assert_eq!(map.len(), 4);

let mut vec: Vec<(i32, i32)> = map.iter().map(|(&k, &v)| (k, v)).collect();
vec.sort_unstable();
assert_eq!(vec, [(0, 0), (2, 20), (4, 40), (6, 60)]);

pub fn extract_if<F>(&mut self, f: F) -> ExtractIf<'_, K, V, F, A>

where F: FnMut(&K, &mut V) -> bool,

Drains elements which are true under the given predicate, and returns an iterator over the removed items.

In other words, move all pairs (k, v) such that f(&k, &mut v) returns true out into another iterator.

Note that extract_if lets you mutate every value in the filter closure, regardless of whether you choose to keep or remove it.

If the returned ExtractIf is not exhausted, e.g. because it is dropped without iterating or the iteration short-circuits, then the remaining elements will be retained. Use retain() with a negated predicate if you do not need the returned iterator.

Keeps the allocated memory for reuse.

Examples

use hashbrown::HashMap;

let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();

let drained: HashMap<i32, i32> = map.extract_if(|k, _v| k % 2 == 0).collect();

let mut evens = drained.keys().cloned().collect::<Vec<_>>();
let mut odds = map.keys().cloned().collect::<Vec<_>>();
evens.sort();
odds.sort();

assert_eq!(evens, vec![0, 2, 4, 6]);
assert_eq!(odds, vec![1, 3, 5, 7]);

let mut map: HashMap<i32, i32> = (0..8).map(|x| (x, x)).collect();

{   // Iterator is dropped without being consumed.
    let d = map.extract_if(|k, _v| k % 2 != 0);
}

// ExtractIf was not exhausted, therefore no elements were drained.
assert_eq!(map.len(), 8);

pub fn clear(&mut self)

Clears the map, removing all key-value pairs. Keeps the allocated memory for reuse.

Examples

use hashbrown::HashMap;

let mut a = HashMap::new();
a.insert(1, "a");
let capacity_before_clear = a.capacity();

a.clear();

// Map is empty.
assert!(a.is_empty());
// But map capacity is equal to old one.
assert_eq!(a.capacity(), capacity_before_clear);

pub fn reserve(&mut self, additional: usize)

Reserves capacity for at least additional more elements to be inserted in the HashMap. The collection may reserve more space to avoid frequent reallocations.

Panics

Panics if the new capacity exceeds isize::MAX bytes and abort the program in case of allocation error. Use try_reserve instead if you want to handle memory allocation failure.

Examples

use hashbrown::HashMap;
let mut map: HashMap<&str, i32> = HashMap::new();
// Map is empty and doesn't allocate memory
assert_eq!(map.capacity(), 0);

map.reserve(10);

// And now map can hold at least 10 elements
assert!(map.capacity() >= 10);

pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError>

Tries to reserve capacity for at least additional more elements to be inserted in the given HashMap<K,V>. The collection may reserve more space to avoid frequent reallocations.

Errors

If the capacity overflows, or the allocator reports a failure, then an error is returned.

Examples

use hashbrown::HashMap;

let mut map: HashMap<&str, isize> = HashMap::new();
// Map is empty and doesn't allocate memory
assert_eq!(map.capacity(), 0);

map.try_reserve(10).expect("why is the test harness OOMing on 10 bytes?");

// And now map can hold at least 10 elements
assert!(map.capacity() >= 10);

If the capacity overflows, or the allocator reports a failure, then an error is returned:

use hashbrown::HashMap;
use hashbrown::TryReserveError;
let mut map: HashMap<i32, i32> = HashMap::new();

match map.try_reserve(usize::MAX) {
    Err(error) => match error {
        TryReserveError::CapacityOverflow => {}
        _ => panic!("TryReserveError::AllocError ?"),
    },
    _ => panic!(),
}

pub fn shrink_to_fit(&mut self)

Shrinks the capacity of the map as much as possible. It will drop down as much as possible while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

Examples

use hashbrown::HashMap;

let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to_fit();
assert!(map.capacity() >= 2);

pub fn shrink_to(&mut self, min_capacity: usize)

Shrinks the capacity of the map with a lower limit. It will drop down no lower than the supplied limit while maintaining the internal rules and possibly leaving some space in accordance with the resize policy.

This function does nothing if the current capacity is smaller than the supplied minimum capacity.

Examples

use hashbrown::HashMap;

let mut map: HashMap<i32, i32> = HashMap::with_capacity(100);
map.insert(1, 2);
map.insert(3, 4);
assert!(map.capacity() >= 100);
map.shrink_to(10);
assert!(map.capacity() >= 10);
map.shrink_to(0);
assert!(map.capacity() >= 2);
map.shrink_to(10);
assert!(map.capacity() >= 2);

pub fn entry(&mut self, key: K) -> Entry<'_, K, V, S, A>

Gets the given key’s corresponding entry in the map for in-place manipulation.

Examples

use hashbrown::HashMap;

let mut letters = HashMap::new();

for ch in "a short treatise on fungi".chars() {
    let counter = letters.entry(ch).or_insert(0);
    *counter += 1;
}

assert_eq!(letters[&'s'], 2);
assert_eq!(letters[&'t'], 3);
assert_eq!(letters[&'u'], 1);
assert_eq!(letters.get(&'y'), None);

pub fn entry_ref<'a, 'b, Q>( &'a mut self, key: &'b Q, ) -> EntryRef<'a, 'b, K, Q, V, S, A>

where Q: Hash + Equivalent<K> + ?Sized,

Gets the given key’s corresponding entry by reference in the map for in-place manipulation.

Examples

use hashbrown::HashMap;

let mut words: HashMap<String, usize> = HashMap::new();
let source = ["poneyland", "horseyland", "poneyland", "poneyland"];
for (i, &s) in source.iter().enumerate() {
    let counter = words.entry_ref(s).or_insert(0);
    *counter += 1;
}

assert_eq!(words["poneyland"], 3);
assert_eq!(words["horseyland"], 1);

pub fn get<Q>(&self, k: &Q) -> Option<&V>

where Q: Hash + Equivalent<K> + ?Sized,

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get(&1), Some(&"a"));
assert_eq!(map.get(&2), None);

pub fn get_key_value<Q>(&self, k: &Q) -> Option<(&K, &V)>

where Q: Hash + Equivalent<K> + ?Sized,

Returns the key-value pair corresponding to the supplied key.

The supplied key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.get_key_value(&1), Some((&1, &"a")));
assert_eq!(map.get_key_value(&2), None);

pub fn get_key_value_mut<Q>(&mut self, k: &Q) -> Option<(&K, &mut V)>

where Q: Hash + Equivalent<K> + ?Sized,

Returns the key-value pair corresponding to the supplied key, with a mutable reference to value.

The supplied key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
let (k, v) = map.get_key_value_mut(&1).unwrap();
assert_eq!(k, &1);
assert_eq!(v, &mut "a");
*v = "b";
assert_eq!(map.get_key_value_mut(&1), Some((&1, &mut "b")));
assert_eq!(map.get_key_value_mut(&2), None);

pub fn contains_key<Q>(&self, k: &Q) -> bool

where Q: Hash + Equivalent<K> + ?Sized,

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
assert_eq!(map.contains_key(&1), true);
assert_eq!(map.contains_key(&2), false);

pub fn get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>

where Q: Hash + Equivalent<K> + ?Sized,

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
map.insert(1, "a");
if let Some(x) = map.get_mut(&1) {
    *x = "b";
}
assert_eq!(map[&1], "b");

assert_eq!(map.get_mut(&2), None);

pub fn get_many_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once.

Returns an array of length N with the results of each query. For soundness, at most one mutable reference will be returned to any value. None will be used if the key is missing.

Panics

Panics if any keys are overlapping.

Examples

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);

// Get Athenæum and Bodleian Library
let [Some(a), Some(b)] = libraries.get_many_mut([
    "Athenæum",
    "Bodleian Library",
]) else { panic!() };

// Assert values of Athenæum and Library of Congress
let got = libraries.get_many_mut([
    "Athenæum",
    "Library of Congress",
]);
assert_eq!(
    got,
    [
        Some(&mut 1807),
        Some(&mut 1800),
    ],
);

// Missing keys result in None
let got = libraries.get_many_mut([
    "Athenæum",
    "New York Public Library",
]);
assert_eq!(
    got,
    [
        Some(&mut 1807),
        None
    ]
);

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Athenæum".to_string(), 1807);

// Duplicate keys panic!
let got = libraries.get_many_mut([
    "Athenæum",
    "Athenæum",
]);

pub unsafe fn get_many_unchecked_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<&mut V>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, without validating that the values are unique.

Returns an array of length N with the results of each query. None will be used if the key is missing.

For a safe alternative see get_many_mut.

Safety

Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.

Examples

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);

// SAFETY: The keys do not overlap.
let [Some(a), Some(b)] = (unsafe { libraries.get_many_unchecked_mut([
    "Athenæum",
    "Bodleian Library",
]) }) else { panic!() };

// SAFETY: The keys do not overlap.
let got = unsafe { libraries.get_many_unchecked_mut([
    "Athenæum",
    "Library of Congress",
]) };
assert_eq!(
    got,
    [
        Some(&mut 1807),
        Some(&mut 1800),
    ],
);

// SAFETY: The keys do not overlap.
let got = unsafe { libraries.get_many_unchecked_mut([
    "Athenæum",
    "New York Public Library",
]) };
// Missing keys result in None
assert_eq!(got, [Some(&mut 1807), None]);

pub fn get_many_key_value_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<(&K, &mut V)>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, with immutable references to the corresponding keys.

Returns an array of length N with the results of each query. For soundness, at most one mutable reference will be returned to any value. None will be used if the key is missing.

Panics

Panics if any keys are overlapping.

Examples

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);

let got = libraries.get_many_key_value_mut([
    "Bodleian Library",
    "Herzogin-Anna-Amalia-Bibliothek",
]);
assert_eq!(
    got,
    [
        Some((&"Bodleian Library".to_string(), &mut 1602)),
        Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut 1691)),
    ],
);
// Missing keys result in None
let got = libraries.get_many_key_value_mut([
    "Bodleian Library",
    "Gewandhaus",
]);
assert_eq!(got, [Some((&"Bodleian Library".to_string(), &mut 1602)), None]);

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);

// Duplicate keys result in panic!
let got = libraries.get_many_key_value_mut([
    "Bodleian Library",
    "Herzogin-Anna-Amalia-Bibliothek",
    "Herzogin-Anna-Amalia-Bibliothek",
]);

pub unsafe fn get_many_key_value_unchecked_mut<Q, const N: usize>( &mut self, ks: [&Q; N], ) -> [Option<(&K, &mut V)>; N]

where Q: Hash + Equivalent<K> + ?Sized,

Attempts to get mutable references to N values in the map at once, with immutable references to the corresponding keys, without validating that the values are unique.

Returns an array of length N with the results of each query. None will be returned if any of the keys are missing.

For a safe alternative see get_many_key_value_mut.

Safety

Calling this method with overlapping keys is undefined behavior even if the resulting references are not used.

Examples

use hashbrown::HashMap;

let mut libraries = HashMap::new();
libraries.insert("Bodleian Library".to_string(), 1602);
libraries.insert("Athenæum".to_string(), 1807);
libraries.insert("Herzogin-Anna-Amalia-Bibliothek".to_string(), 1691);
libraries.insert("Library of Congress".to_string(), 1800);

let got = libraries.get_many_key_value_mut([
    "Bodleian Library",
    "Herzogin-Anna-Amalia-Bibliothek",
]);
assert_eq!(
    got,
    [
        Some((&"Bodleian Library".to_string(), &mut 1602)),
        Some((&"Herzogin-Anna-Amalia-Bibliothek".to_string(), &mut 1691)),
    ],
);
// Missing keys result in None
let got = libraries.get_many_key_value_mut([
    "Bodleian Library",
    "Gewandhaus",
]);
assert_eq!(
    got,
    [
        Some((&"Bodleian Library".to_string(), &mut 1602)),
        None,
    ],
);

pub fn insert(&mut self, k: K, v: V) -> Option<V>

Inserts a key-value pair into the map.

If the map did not have this key present, None is returned.

If the map did have this key present, the value is updated, and the old value is returned. The key is not updated, though; this matters for types that can be == without being identical. See the std::collections module-level documentation for more.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
assert_eq!(map.insert(37, "a"), None);
assert_eq!(map.is_empty(), false);

map.insert(37, "b");
assert_eq!(map.insert(37, "c"), Some("b"));
assert_eq!(map[&37], "c");

pub unsafe fn insert_unique_unchecked(&mut self, k: K, v: V) -> (&K, &mut V)

Insert a key-value pair into the map without checking if the key already exists in the map.

This operation is faster than regular insert, because it does not perform lookup before insertion.

This operation is useful during initial population of the map. For example, when constructing a map from another map, we know that keys are unique.

Returns a reference to the key and value just inserted.

Safety

This operation is safe if a key does not exist in the map.

However, if a key exists in the map already, the behavior is unspecified: this operation may panic, loop forever, or any following operation with the map may panic, loop forever or return arbitrary result.

That said, this operation (and following operations) are guaranteed to not violate memory safety.

However this operation is still unsafe because the resulting HashMap may be passed to unsafe code which does expect the map to behave correctly, and would cause unsoundness as a result.

Examples

use hashbrown::HashMap;

let mut map1 = HashMap::new();
assert_eq!(map1.insert(1, "a"), None);
assert_eq!(map1.insert(2, "b"), None);
assert_eq!(map1.insert(3, "c"), None);
assert_eq!(map1.len(), 3);

let mut map2 = HashMap::new();

for (key, value) in map1.into_iter() {
    unsafe {
        map2.insert_unique_unchecked(key, value);
    }
}

let (key, value) = unsafe { map2.insert_unique_unchecked(4, "d") };
assert_eq!(key, &4);
assert_eq!(value, &mut "d");
*value = "e";

assert_eq!(map2[&1], "a");
assert_eq!(map2[&2], "b");
assert_eq!(map2[&3], "c");
assert_eq!(map2[&4], "e");
assert_eq!(map2.len(), 4);

pub fn try_insert( &mut self, key: K, value: V, ) -> Result<&mut V, OccupiedError<'_, K, V, S, A>>

Tries to insert a key-value pair into the map, and returns a mutable reference to the value in the entry.

Errors

If the map already had this key present, nothing is updated, and an error containing the occupied entry and the value is returned.

Examples

Basic usage:

use hashbrown::HashMap;
use hashbrown::hash_map::OccupiedError;

let mut map = HashMap::new();
assert_eq!(map.try_insert(37, "a").unwrap(), &"a");

match map.try_insert(37, "b") {
    Err(OccupiedError { entry, value }) => {
        assert_eq!(entry.key(), &37);
        assert_eq!(entry.get(), &"a");
        assert_eq!(value, "b");
    }
    _ => panic!()
}

pub fn remove<Q>(&mut self, k: &Q) -> Option<V>

where Q: Hash + Equivalent<K> + ?Sized,

Removes a key from the map, returning the value at the key if the key was previously in the map. Keeps the allocated memory for reuse.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

map.insert(1, "a");

assert_eq!(map.remove(&1), Some("a"));
assert_eq!(map.remove(&1), None);

// Now map holds none elements
assert!(map.is_empty());

pub fn remove_entry<Q>(&mut self, k: &Q) -> Option<(K, V)>

where Q: Hash + Equivalent<K> + ?Sized,

Removes a key from the map, returning the stored key and value if the key was previously in the map. Keeps the allocated memory for reuse.

The key may be any borrowed form of the map’s key type, but Hash and Eq on the borrowed form must match those for the key type.

Examples

use hashbrown::HashMap;

let mut map = HashMap::new();
// The map is empty
assert!(map.is_empty() && map.capacity() == 0);

map.insert(1, "a");

assert_eq!(map.remove_entry(&1), Some((1, "a")));
assert_eq!(map.remove(&1), None);

// Now map hold none elements
assert!(map.is_empty());

pub fn allocation_size(&self) -> usize

Returns the total amount of memory allocated internally by the hash set, in bytes.

The returned number is informational only. It is intended to be primarily used for memory profiling.

pub fn raw_entry_mut(&mut self) -> RawEntryBuilderMut<'_, K, V, S, A>

Creates a raw entry builder for the HashMap.

Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched. After this, insertions into a vacant entry still require an owned key to be provided.

Raw entries are useful for such exotic situations as:

• Hash memoization
• Deferring the creation of an owned key until it is known to be required
• Using a search key that doesn’t work with the Borrow trait
• Using custom comparison logic without newtype wrappers

Because raw entries provide much more low-level control, it’s much easier to put the HashMap into an inconsistent state which, while memory-safe, will cause the map to produce seemingly random results. Higher-level and more foolproof APIs like entry should be preferred when possible.

In particular, the hash used to initialized the raw entry must still be consistent with the hash of the key that is ultimately stored in the entry. This is because implementations of HashMap may need to recompute hashes when resizing, at which point only the keys are available.

Raw entries give mutable access to the keys. This must not be used to modify how the key would compare or hash, as the map will not re-evaluate where the key should go, meaning the keys may become “lost” if their location does not reflect their state. For instance, if you change a key so that the map now contains keys which compare equal, search may start acting erratically, with two keys randomly masking each other. Implementations are free to assume this doesn’t happen (within the limits of memory-safety).

Examples

use core::hash::{BuildHasher, Hash};
use hashbrown::hash_map::{HashMap, RawEntryMut};

let mut map = HashMap::new();
map.extend([("a", 100), ("b", 200), ("c", 300)]);

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

// Existing key (insert and update)
match map.raw_entry_mut().from_key(&"a") {
    RawEntryMut::Vacant(_) => unreachable!(),
    RawEntryMut::Occupied(mut view) => {
        assert_eq!(view.get(), &100);
        let v = view.get_mut();
        let new_v = (*v) * 10;
        *v = new_v;
        assert_eq!(view.insert(1111), 1000);
    }
}

assert_eq!(map[&"a"], 1111);
assert_eq!(map.len(), 3);

// Existing key (take)
let hash = compute_hash(map.hasher(), &"c");
match map.raw_entry_mut().from_key_hashed_nocheck(hash, &"c") {
    RawEntryMut::Vacant(_) => unreachable!(),
    RawEntryMut::Occupied(view) => {
        assert_eq!(view.remove_entry(), ("c", 300));
    }
}
assert_eq!(map.raw_entry().from_key(&"c"), None);
assert_eq!(map.len(), 2);

// Nonexistent key (insert and update)
let key = "d";
let hash = compute_hash(map.hasher(), &key);
match map.raw_entry_mut().from_hash(hash, |q| *q == key) {
    RawEntryMut::Occupied(_) => unreachable!(),
    RawEntryMut::Vacant(view) => {
        let (k, value) = view.insert("d", 4000);
        assert_eq!((*k, *value), ("d", 4000));
        *value = 40000;
    }
}
assert_eq!(map[&"d"], 40000);
assert_eq!(map.len(), 3);

match map.raw_entry_mut().from_hash(hash, |q| *q == key) {
    RawEntryMut::Vacant(_) => unreachable!(),
    RawEntryMut::Occupied(view) => {
        assert_eq!(view.remove_entry(), ("d", 40000));
    }
}
assert_eq!(map.get(&"d"), None);
assert_eq!(map.len(), 2);

pub fn raw_entry(&self) -> RawEntryBuilder<'_, K, V, S, A>

Creates a raw immutable entry builder for the HashMap.

Raw entries provide the lowest level of control for searching and manipulating a map. They must be manually initialized with a hash and then manually searched.

This is useful for

• Hash memoization
• Using a search key that doesn’t work with the Borrow trait
• Using custom comparison logic without newtype wrappers

Unless you are in such a situation, higher-level and more foolproof APIs like get should be preferred.

Immutable raw entries have very limited use; you might instead want raw_entry_mut.

Examples

use core::hash::{BuildHasher, Hash};
use hashbrown::HashMap;

let mut map = HashMap::new();
map.extend([("a", 100), ("b", 200), ("c", 300)]);

fn compute_hash<K: Hash + ?Sized, S: BuildHasher>(hash_builder: &S, key: &K) -> u64 {
    use core::hash::Hasher;
    let mut state = hash_builder.build_hasher();
    key.hash(&mut state);
    state.finish()
}

for k in ["a", "b", "c", "d", "e", "f"] {
    let hash = compute_hash(map.hasher(), k);
    let v = map.get(&k).cloned();
    let kv = v.as_ref().map(|v| (&k, v));

    println!("Key: {} and value: {:?}", k, v);

    assert_eq!(map.raw_entry().from_key(&k), kv);
    assert_eq!(map.raw_entry().from_hash(hash, |q| *q == k), kv);
    assert_eq!(map.raw_entry().from_key_hashed_nocheck(hash, &k), kv);
}

Trait Implementations

impl Debug for HoverMap

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for HoverMap

fn default() -> HoverMap

Returns the “default value” for a type.

impl Deref for HoverMap

type Target = HashMap<PointerId, HashMap<Entity, HitData>>

The resulting type after dereferencing.

fn deref(&self) -> &<HoverMap as Deref>::Target

Dereferences the value.

impl DerefMut for HoverMap

fn deref_mut(&mut self) -> &mut <HoverMap as Deref>::Target

Mutably dereferences the value.

impl Resource for HoverMap

where HoverMap: Send + Sync + 'static,