Rename "focus" in bevy_picking to "hover" (#16872)

# Objective

With the introduction of bevy_input_focus, the uses of "focus" in
bevy_picking are quite confusing and make searching hard.

Users will intuitively think these concepts are related, but they
actually aren't.

## Solution

Rename / rephrase all uses of "focus" in bevy_picking to refer to
"hover", since this is ultimately related to creating the `HoverMap`.

## Migration Guide

Various terms related to "focus" in `bevy_picking` have been renamed to
refer to "hover" to avoid confusion with `bevy_input_focus`. In
particular:

- The `update_focus` system has been renamed to `generate_hovermap`
- `PickSet::Focus` and `PostFocus` have been renamed to `Hover` and
`PostHover`
- The `bevy_picking::focus` module has been renamed to
`bevy_picking::hover`
- The `is_focus_enabled` field on `PickingPlugin` has been renamed to
`is_hover_enabled`
- The `focus_should_run` run condition has been renamed to
`hover_should_run`

crates/bevy_picking/src/events.rs

@@ -23,9 +23,9 @@
 //!
 //! The order in which interaction events are received is extremely important, and you can read more
 //! about it on the docs for the dispatcher system: [`pointer_events`]. This system runs in
-//! [`PreUpdate`](bevy_app::PreUpdate) in [`PickSet::Focus`](crate::PickSet::Focus). All pointer-event
+//! [`PreUpdate`](bevy_app::PreUpdate) in [`PickSet::Hover`](crate::PickSet::Hover). All pointer-event
 //! observers resolve during the sync point between [`pointer_events`] and
-//! [`update_interactions`](crate::focus::update_interactions).
+//! [`update_interactions`](crate::hover::update_interactions).
 //!
 //! # Events Types
 //!
@@ -49,7 +49,7 @@ use bevy_window::Window;
 
 use crate::{
     backend::{prelude::PointerLocation, HitData},
-    focus::{HoverMap, PreviousHoverMap},
+    hover::{HoverMap, PreviousHoverMap},
     pointer::{
         Location, PointerAction, PointerButton, PointerId, PointerInput, PointerMap, PressDirection,
     },
@@ -385,7 +385,7 @@ pub struct PickingEventWriters<'w> {
 /// receive [`Out`] and then entity B will receive [`Over`]. No entity will ever
 /// receive both an [`Over`] and and a [`Out`] event during the same frame.
 ///
-/// When we account for event bubbling, this is no longer true. When focus shifts
+/// When we account for event bubbling, this is no longer true. When the hovering focus shifts
 /// between children, parent entities may receive redundant [`Out`] → [`Over`] pairs.
 /// In the context of UI, this is especially problematic. Additional hierarchy-aware
 /// events will be added in a future release.

crates/bevy_picking/src/hover.rs

@@ -62,7 +62,7 @@ pub struct PreviousHoverMap(pub HashMap<PointerId, HashMap<Entity, HitData>>);
 
 /// Coalesces all data from inputs and backends to generate a map of the currently hovered entities.
 /// This is the final focusing step to determine which entity the pointer is hovering over.
-pub fn update_focus(
+pub fn generate_hovermap(
     // Inputs
     picking_behavior: Query<&PickingBehavior>,
     pointers: Query<&PointerId>,

crates/bevy_picking/src/lib.rs

@@ -128,12 +128,12 @@
 //! Bevy provides some backends out of the box, but you can even write your own. It's been
 //! made as easy as possible intentionally; the `bevy_mod_raycast` backend is 50 lines of code.
 //!
-//! #### Focus ([`focus`])
+//! #### Hover ([`hover`])
 //!
 //! The next step is to use the data from the backends, combine and sort the results, and determine
-//! what each cursor is hovering over, producing a [`HoverMap`](`crate::focus::HoverMap`). Note that
+//! what each cursor is hovering over, producing a [`HoverMap`](`crate::hover::HoverMap`). Note that
 //! just because a pointer is over an entity, it is not necessarily *hovering* that entity. Although
-//! multiple backends may be reporting that a pointer is hitting an entity, the focus system needs
+//! multiple backends may be reporting that a pointer is hitting an entity, the hover system needs
 //! to determine which entities are actually being hovered by this pointer based on the pick depth,
 //! order of the backend, and the optional [`PickingBehavior`] component of the entity. In other words,
 //! if one entity is in front of another, usually only the topmost one will be hovered.
@@ -154,7 +154,7 @@ extern crate alloc;
 
 pub mod backend;
 pub mod events;
-pub mod focus;
+pub mod hover;
 pub mod input;
 #[cfg(feature = "bevy_mesh_picking_backend")]
 pub mod mesh_picking;
@@ -201,9 +201,9 @@ pub struct PickingBehavior {
     ///
     /// For example, if a pointer is over a UI element, as well as a 3d mesh, backends will report
     /// hits for both of these entities. Additionally, the hits will be sorted by the camera order,
-    /// so if the UI is drawing on top of the 3d mesh, the UI will be "above" the mesh. When focus
+    /// so if the UI is drawing on top of the 3d mesh, the UI will be "above" the mesh. When hovering
     /// is computed, the UI element will be checked first to see if it this field is set to block
-    /// lower entities. If it does (default), the focus system will stop there, and only the UI
+    /// lower entities. If it does (default), the hovering system will stop there, and only the UI
     /// element will be marked as hovered. However, if this field is set to `false`, both the UI
     /// element *and* the mesh will be marked as hovered.
     ///
@@ -257,12 +257,12 @@ pub enum PickSet {
     ProcessInput,
     /// Reads inputs and produces [`backend::PointerHits`]s. In the [`PreUpdate`] schedule.
     Backend,
-    /// Reads [`backend::PointerHits`]s, and updates focus, selection, and highlighting states. In
+    /// Reads [`backend::PointerHits`]s, and updates the hovermap, selection, and highlighting states. In
     /// the [`PreUpdate`] schedule.
-    Focus,
-    /// Runs after all the focus systems are done, before event listeners are triggered. In the
+    Hover,
+    /// Runs after all the [`PickSet::Hover`] systems are done, before event listeners are triggered. In the
     /// [`PreUpdate`] schedule.
-    PostFocus,
+    PostHover,
     /// Runs after all other picking sets. In the [`PreUpdate`] schedule.
     Last,
 }
@@ -298,7 +298,7 @@ pub struct PickingPlugin {
     /// Enables and disables input collection.
     pub is_input_enabled: bool,
     /// Enables and disables updating interaction states of entities.
-    pub is_focus_enabled: bool,
+    pub is_hover_enabled: bool,
     /// Enables or disables picking for window entities.
     pub is_window_picking_enabled: bool,
 }
@@ -309,10 +309,10 @@ impl PickingPlugin {
         state.is_input_enabled && state.is_enabled
     }
 
-    /// Whether or not systems updating entities' [`PickingInteraction`](focus::PickingInteraction)
+    /// Whether or not systems updating entities' [`PickingInteraction`](hover::PickingInteraction)
     /// component should be running.
-    pub fn focus_should_run(state: Res<Self>) -> bool {
-        state.is_focus_enabled && state.is_enabled
+    pub fn hover_should_run(state: Res<Self>) -> bool {
+        state.is_hover_enabled && state.is_enabled
     }
 
     /// Whether or not window entities should receive pick events.
@@ -326,7 +326,7 @@ impl Default for PickingPlugin {
         Self {
             is_enabled: true,
             is_input_enabled: true,
-            is_focus_enabled: true,
+            is_hover_enabled: true,
             is_window_picking_enabled: true,
         }
     }
@@ -370,8 +370,8 @@ impl Plugin for PickingPlugin {
                 (
                     PickSet::ProcessInput.run_if(Self::input_should_run),
                     PickSet::Backend,
-                    PickSet::Focus.run_if(Self::focus_should_run),
-                    PickSet::PostFocus,
+                    PickSet::Hover.run_if(Self::hover_should_run),
+                    PickSet::PostHover,
                     PickSet::Last,
                 )
                     .chain(),
@@ -393,10 +393,10 @@ pub struct InteractionPlugin;
 impl Plugin for InteractionPlugin {
     fn build(&self, app: &mut App) {
         use events::*;
-        use focus::{update_focus, update_interactions};
+        use hover::{generate_hovermap, update_interactions};
 
-        app.init_resource::<focus::HoverMap>()
-            .init_resource::<focus::PreviousHoverMap>()
+        app.init_resource::<hover::HoverMap>()
+            .init_resource::<hover::PreviousHoverMap>()
             .init_resource::<PointerState>()
             .add_event::<Pointer<Cancel>>()
             .add_event::<Pointer<Click>>()
@@ -414,9 +414,9 @@ impl Plugin for InteractionPlugin {
             .add_event::<Pointer<Released>>()
             .add_systems(
                 PreUpdate,
-                (update_focus, update_interactions, pointer_events)
+                (generate_hovermap, update_interactions, pointer_events)
                     .chain()
-                    .in_set(PickSet::Focus),
+                    .in_set(PickSet::Hover),
             );
     }
 }

examples/testbed/ui.rs

@@ -7,7 +7,7 @@ use bevy::{
     a11y::AccessibilityNode,
     color::palettes::{basic::LIME, css::DARK_GRAY},
     input::mouse::{MouseScrollUnit, MouseWheel},
-    picking::focus::HoverMap,
+    picking::hover::HoverMap,
     prelude::*,
     ui::widget::NodeImageMode,
 };

examples/ui/scroll.rs

@@ -4,7 +4,7 @@ use accesskit::{Node as Accessible, Role};
 use bevy::{
     a11y::AccessibilityNode,
     input::mouse::{MouseScrollUnit, MouseWheel},
-    picking::focus::HoverMap,
+    picking::hover::HoverMap,
     prelude::*,
     winit::WinitSettings,
 };