Struct DirectionalNavigationMap 

pub struct DirectionalNavigationMap {
    pub neighbors: EntityHashMap<NavNeighbors>,
}

A resource that stores the traversable graph of focusable entities.

Each entity can have up to 8 neighbors, one for each CompassOctant.

To ensure that your graph is intuitive to navigate and generally works correctly, it should be:

• Connected: Every focusable entity should be reachable from every other focusable entity.
• Symmetric: If entity A is a neighbor of entity B, then entity B should be a neighbor of entity A, ideally in the reverse direction.
• Physical: The direction of navigation should match the layout of the entities when possible, although looping around the edges of the screen is also acceptable.
• Not self-connected: An entity should not be a neighbor of itself; use None instead.

For now, this graph must be built manually, and the developer is responsible for ensuring that it meets the above criteria.

Fields

neighbors: EntityHashMap<NavNeighbors>

A directed graph of focusable entities.

Pass in the current focus as a key, and get back a collection of up to 8 neighbors, each keyed by a CompassOctant.

Implementations

impl DirectionalNavigationMap

pub fn remove(&mut self, entity: Entity)

Adds a new entity to the navigation map, overwriting any existing neighbors for that entity.

Removes an entity from the navigation map, including all connections to and from it.

Note that this is an O(n) operation, where n is the number of entities in the map, as we must iterate over each entity to check for connections to the removed entity.

If you are removing multiple entities, consider using remove_multiple instead.

pub fn remove_multiple(&mut self, entities: EntityHashSet)

Removes a collection of entities from the navigation map.

While this is still an O(n) operation, where n is the number of entities in the map, it is more efficient than calling remove multiple times, as we can check for connections to all removed entities in a single pass.

An EntityHashSet must be provided as it is noticeably faster than the standard hasher or a Vec.

pub fn clear(&mut self)

Completely clears the navigation map, removing all entities and connections.

pub fn add_edge(&mut self, a: Entity, b: Entity, direction: CompassOctant)

Adds an edge between two entities in the navigation map. Any existing edge from A in the provided direction will be overwritten.

The reverse edge will not be added, so navigation will only be possible in one direction. If you want to add a symmetrical edge, use add_symmetrical_edge instead.

pub fn add_symmetrical_edge( &mut self, a: Entity, b: Entity, direction: CompassOctant, )

Adds a symmetrical edge between two entities in the navigation map. The A -> B path will use the provided direction, while B -> A will use the CompassOctant::opposite variant.

Any existing connections between the two entities will be overwritten.

pub fn add_edges(&mut self, entities: &[Entity], direction: CompassOctant)

Add symmetrical edges between each consecutive pair of entities in the provided slice.

Unlike add_looping_edges, this method does not loop back to the first entity.

Examples found in repository

examples/ui/directional_navigation.rs (line 222)

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: percent(100),
            height: percent(100),
            ..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: px(300),
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                margin: UiRect::all(px(12)),
                ..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: percent(100),
            height: 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: px(200),
                        height: px(120),
                        // Add a border so we can show which element is focused
                        border: UiRect::all(px(4)),
                        // 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(px(16)),
                    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: Justify::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 add_looping_edges( &mut self, entities: &[Entity], direction: CompassOctant, )

Add symmetrical edges between each consecutive pair of entities in the provided slice, looping back to the first entity at the end.

This is useful for creating a circular navigation path between a set of entities, such as a menu.

Examples found in repository

examples/ui/directional_navigation.rs (line 210)

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: percent(100),
            height: percent(100),
            ..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: px(300),
                justify_content: JustifyContent::Center,
                align_items: AlignItems::Center,
                margin: UiRect::all(px(12)),
                ..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: percent(100),
            height: 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: px(200),
                        height: px(120),
                        // Add a border so we can show which element is focused
                        border: UiRect::all(px(4)),
                        // 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(px(16)),
                    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: Justify::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 get_neighbor( &self, focus: Entity, octant: CompassOctant, ) -> Option<Entity>

Gets the entity in a given direction from the current focus, if any.

pub fn get_neighbors(&self, entity: Entity) -> Option<&NavNeighbors>

Looks up the neighbors of a given entity.

If the entity is not in the map, None will be returned. Note that the set of neighbors is not guaranteed to be non-empty though!

Trait Implementations

impl Clone for DirectionalNavigationMap

fn clone(&self) -> DirectionalNavigationMap

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for DirectionalNavigationMap

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

Formats the value using the given formatter.

impl Default for DirectionalNavigationMap

fn default() -> DirectionalNavigationMap

Returns the “default value” for a type.

impl FromArg for DirectionalNavigationMap

type This<'from_arg> = DirectionalNavigationMap

The type to convert into.

fn from_arg( arg: Arg<'_>, ) -> Result<<DirectionalNavigationMap as FromArg>::This<'_>, ArgError>

Creates an item from an argument.

impl FromReflect for DirectionalNavigationMap

fn from_reflect( reflect: &(dyn PartialReflect + 'static), ) -> Option<DirectionalNavigationMap>

Constructs a concrete instance of Self from a reflected value.

fn take_from_reflect( reflect: Box<dyn PartialReflect>, ) -> Result<Self, Box<dyn PartialReflect>>

Attempts to downcast the given value to Self using, constructing the value using from_reflect if that fails.

impl GetOwnership for DirectionalNavigationMap

fn ownership() -> Ownership

Returns the ownership of Self.

impl GetTypeRegistration for DirectionalNavigationMap

fn get_type_registration() -> TypeRegistration

Returns the default TypeRegistration for this type.

fn register_type_dependencies(registry: &mut TypeRegistry)

Registers other types needed by this type.

impl IntoReturn for DirectionalNavigationMap

fn into_return<'into_return>(self) -> Return<'into_return>

where DirectionalNavigationMap: 'into_return,

Converts Self into a Return value.

impl PartialEq for DirectionalNavigationMap

fn eq(&self, other: &DirectionalNavigationMap) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialReflect for DirectionalNavigationMap

fn get_represented_type_info(&self) -> Option<&'static TypeInfo>

Returns the TypeInfo of the type represented by this value.

fn try_apply( &mut self, value: &(dyn PartialReflect + 'static), ) -> Result<(), ApplyError>

Tries to apply a reflected value to this value.

fn reflect_kind(&self) -> ReflectKind

Returns a zero-sized enumeration of “kinds” of type.

fn reflect_ref(&self) -> ReflectRef<'_>

Returns an immutable enumeration of “kinds” of type.

fn reflect_mut(&mut self) -> ReflectMut<'_>

Returns a mutable enumeration of “kinds” of type.

fn reflect_owned(self: Box<DirectionalNavigationMap>) -> ReflectOwned

Returns an owned enumeration of “kinds” of type.

fn try_into_reflect( self: Box<DirectionalNavigationMap>, ) -> Result<Box<dyn Reflect>, Box<dyn PartialReflect>>

Attempts to cast this type to a boxed, fully-reflected value.

fn try_as_reflect(&self) -> Option<&(dyn Reflect + 'static)>

Attempts to cast this type to a fully-reflected value.

fn try_as_reflect_mut(&mut self) -> Option<&mut (dyn Reflect + 'static)>

Attempts to cast this type to a mutable, fully-reflected value.

fn into_partial_reflect( self: Box<DirectionalNavigationMap>, ) -> Box<dyn PartialReflect>

Casts this type to a boxed, reflected value.

fn as_partial_reflect(&self) -> &(dyn PartialReflect + 'static)

Casts this type to a reflected value.

fn as_partial_reflect_mut(&mut self) -> &mut (dyn PartialReflect + 'static)

Casts this type to a mutable, reflected value.

fn reflect_partial_eq( &self, value: &(dyn PartialReflect + 'static), ) -> Option<bool>

Returns a “partial equality” comparison result.

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

Debug formatter for the value.

fn reflect_clone(&self) -> Result<Box<dyn Reflect>, ReflectCloneError>

Attempts to clone Self using reflection.

fn apply(&mut self, value: &(dyn PartialReflect + 'static))

Applies a reflected value to this value.

fn to_dynamic(&self) -> Box<dyn PartialReflect>

Converts this reflected value into its dynamic representation based on its kind.

fn reflect_clone_and_take<T>(&self) -> Result<T, ReflectCloneError>

where T: 'static, Self: Sized + TypePath,

For a type implementing PartialReflect, combines reflect_clone and take in a useful fashion, automatically constructing an appropriate ReflectCloneError if the downcast fails.

fn reflect_hash(&self) -> Option<u64>

Returns a hash of the value (which includes the type).

fn is_dynamic(&self) -> bool

Indicates whether or not this type is a dynamic type.

impl Reflect for DirectionalNavigationMap

fn into_any(self: Box<DirectionalNavigationMap>) -> Box<dyn Any>

Returns the value as a Box<dyn Any>.

fn as_any(&self) -> &(dyn Any + 'static)

Returns the value as a &dyn Any.

fn as_any_mut(&mut self) -> &mut (dyn Any + 'static)

Returns the value as a &mut dyn Any.

fn into_reflect(self: Box<DirectionalNavigationMap>) -> Box<dyn Reflect>

Casts this type to a boxed, fully-reflected value.

fn as_reflect(&self) -> &(dyn Reflect + 'static)

Casts this type to a fully-reflected value.

fn as_reflect_mut(&mut self) -> &mut (dyn Reflect + 'static)

Casts this type to a mutable, fully-reflected value.

fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>>

Performs a type-checked assignment of a reflected value to this value.

impl Struct for DirectionalNavigationMap

fn field(&self, name: &str) -> Option<&(dyn PartialReflect + 'static)>

Returns a reference to the value of the field named name as a &dyn PartialReflect.

fn field_mut( &mut self, name: &str, ) -> Option<&mut (dyn PartialReflect + 'static)>

Returns a mutable reference to the value of the field named name as a &mut dyn PartialReflect.

fn field_at(&self, index: usize) -> Option<&(dyn PartialReflect + 'static)>

Returns a reference to the value of the field with index index as a &dyn PartialReflect.

fn field_at_mut( &mut self, index: usize, ) -> Option<&mut (dyn PartialReflect + 'static)>

Returns a mutable reference to the value of the field with index index as a &mut dyn PartialReflect.

fn name_at(&self, index: usize) -> Option<&str>

Returns the name of the field with index index.

fn field_len(&self) -> usize

Returns the number of fields in the struct.

fn iter_fields(&self) -> FieldIter<'_>

Returns an iterator over the values of the reflectable fields for this struct.

fn to_dynamic_struct(&self) -> DynamicStruct

Creates a new DynamicStruct from this struct.

fn get_represented_struct_info(&self) -> Option<&'static StructInfo>

Will return None if TypeInfo is not available.

impl TypePath for DirectionalNavigationMap

fn type_path() -> &'static str

Returns the fully qualified path of the underlying type.

fn short_type_path() -> &'static str

Returns a short, pretty-print enabled path to the type.

fn type_ident() -> Option<&'static str>

Returns the name of the type, or None if it is anonymous.

fn crate_name() -> Option<&'static str>

Returns the name of the crate the type is in, or None if it is anonymous.

fn module_path() -> Option<&'static str>

Returns the path to the module the type is in, or None if it is anonymous.

impl Typed for DirectionalNavigationMap

fn type_info() -> &'static TypeInfo

Returns the compile-time info for the underlying type.

impl Resource for DirectionalNavigationMap

where DirectionalNavigationMap: Send + Sync + 'static,

impl StructuralPartialEq for DirectionalNavigationMap