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dioxus/packages/core/src/scopes.rs

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Rust
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use crate::{
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any_props::AnyProps,
arena::ElementId,
bump_frame::BumpFrame,
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factory::RenderReturn,
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innerlude::{Scheduler, SchedulerMsg},
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lazynodes::LazyNodes,
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Element, TaskId,
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};
use bumpalo::Bump;
use std::future::Future;
use std::{
any::{Any, TypeId},
cell::{Cell, RefCell},
collections::{HashMap, HashSet},
rc::Rc,
sync::Arc,
};
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/// A wrapper around the [`Scoped`] object that contains a reference to the [`ScopeState`] and properties for a given
/// component.
///
/// The [`Scope`] is your handle to the [`VirtualDom`] and the component state. Every component is given its own
/// [`ScopeState`] and merged with its properties to create a [`Scoped`].
///
/// The [`Scope`] handle specifically exists to provide a stable reference to these items for the lifetime of the
/// component render.
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pub type Scope<'a, T = ()> = &'a Scoped<'a, T>;
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// This ScopedType exists because we want to limit the amount of monomorphization that occurs when making inner
// state type generic over props. When the state is generic, it causes every method to be monomorphized for every
// instance of Scope<T> in the codebase.
//
//
/// A wrapper around a component's [`ScopeState`] and properties. The [`ScopeState`] provides the majority of methods
/// for the VirtualDom and component state.
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pub struct Scoped<'a, T = ()> {
/// The component's state and handle to the scheduler.
///
/// Stores things like the custom bump arena, spawn functions, hooks, and the scheduler.
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pub scope: &'a ScopeState,
/// The component's properties.
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pub props: &'a T,
}
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impl<'a, T> std::ops::Deref for Scoped<'a, T> {
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type Target = &'a ScopeState;
fn deref(&self) -> &Self::Target {
&self.scope
}
}
/// A component's unique identifier.
///
/// `ScopeId` is a `usize` that is unique across the entire [`VirtualDom`] and across time. [`ScopeID`]s will never be reused
/// once a component has been unmounted.
#[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, PartialOrd, Ord)]
pub struct ScopeId(pub usize);
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/// A component's state.
///
/// This struct stores all the important information about a component's state without the props.
pub struct ScopeState {
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pub(crate) render_cnt: Cell<usize>,
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pub(crate) node_arena_1: BumpFrame,
pub(crate) node_arena_2: BumpFrame,
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pub(crate) parent: Option<*mut ScopeState>,
pub(crate) id: ScopeId,
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pub(crate) height: u32,
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pub(crate) hook_arena: Bump,
pub(crate) hook_list: RefCell<Vec<*mut dyn Any>>,
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pub(crate) hook_idx: Cell<usize>,
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pub(crate) shared_contexts: RefCell<HashMap<TypeId, Box<dyn Any>>>,
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pub(crate) tasks: Rc<Scheduler>,
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pub(crate) spawned_tasks: HashSet<TaskId>,
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pub(crate) props: *const dyn AnyProps<'static>,
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pub(crate) placeholder: Cell<Option<ElementId>>,
}
impl ScopeState {
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pub fn current_frame(&self) -> &BumpFrame {
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match self.render_cnt.get() % 2 {
0 => &self.node_arena_1,
1 => &self.node_arena_2,
_ => unreachable!(),
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}
}
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pub fn previous_frame(&self) -> &BumpFrame {
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match self.render_cnt.get() % 2 {
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1 => &self.node_arena_1,
0 => &self.node_arena_2,
_ => unreachable!(),
}
}
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/// Get the current render since the inception of this component
///
/// This can be used as a helpful diagnostic when debugging hooks/renders, etc
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pub fn generation(&self) -> usize {
self.render_cnt.get()
}
/// Get a handle to the currently active bump arena for this Scope
///
/// This is a bump memory allocator. Be careful using this directly since the contents will be wiped on the next render.
/// It's easy to leak memory here since the drop implementation will not be called for any objects allocated in this arena.
///
/// If you need to allocate items that need to be dropped, use bumpalo's box.
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pub fn bump(&self) -> &Bump {
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&self.current_frame().bump
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}
/// Get a handle to the currently active head node arena for this Scope
///
/// This is useful for traversing the tree outside of the VirtualDom, such as in a custom renderer or in SSR.
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///
/// Panics if the tree has not been built yet.
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pub fn root_node<'a>(&'a self) -> &'a RenderReturn<'a> {
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self.try_root_node()
.expect("The tree has not been built yet. Make sure to call rebuild on the tree before accessing its nodes.")
}
/// Try to get a handle to the currently active head node arena for this Scope
///
/// This is useful for traversing the tree outside of the VirtualDom, such as in a custom renderer or in SSR.
///
/// Returns [`None`] if the tree has not been built yet.
pub fn try_root_node<'a>(&'a self) -> Option<&'a RenderReturn<'a>> {
let ptr = self.current_frame().node.get();
if ptr.is_null() {
return None;
}
let r: &RenderReturn = unsafe { &*ptr };
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unsafe { std::mem::transmute(r) }
}
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/// Get the height of this Scope - IE the number of scopes above it.
///
/// A Scope with a height of `0` is the root scope - there are no other scopes above it.
///
/// # Example
///
/// ```rust, ignore
/// let mut dom = VirtualDom::new(|cx| cx.render(rsx!{ div {} }));
/// dom.rebuild();
///
/// let base = dom.base_scope();
///
/// assert_eq!(base.height(), 0);
/// ```
pub fn height(&self) -> u32 {
self.height
}
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/// Get the Parent of this [`Scope`] within this Dioxus [`VirtualDom`].
///
/// This ID is not unique across Dioxus [`VirtualDom`]s or across time. IDs will be reused when components are unmounted.
///
/// The base component will not have a parent, and will return `None`.
///
/// # Example
///
/// ```rust, ignore
/// let mut dom = VirtualDom::new(|cx| cx.render(rsx!{ div {} }));
/// dom.rebuild();
///
/// let base = dom.base_scope();
///
/// assert_eq!(base.parent(), None);
/// ```
pub fn parent(&self) -> Option<ScopeId> {
// safety: the pointer to our parent is *always* valid thanks to the bump arena
self.parent.map(|p| unsafe { &*p }.id)
}
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/// Get the ID of this Scope within this Dioxus [`VirtualDom`].
///
/// This ID is not unique across Dioxus [`VirtualDom`]s or across time. IDs will be reused when components are unmounted.
///
/// # Example
///
/// ```rust, ignore
/// let mut dom = VirtualDom::new(|cx| cx.render(rsx!{ div {} }));
/// dom.rebuild();
/// let base = dom.base_scope();
///
/// assert_eq!(base.scope_id(), 0);
/// ```
pub fn scope_id(&self) -> ScopeId {
self.id
}
/// Create a subscription that schedules a future render for the reference component
///
/// ## Notice: you should prefer using [`schedule_update_any`] and [`scope_id`]
pub fn schedule_update(&self) -> Arc<dyn Fn() + Send + Sync + 'static> {
let (chan, id) = (self.tasks.sender.clone(), self.scope_id());
Arc::new(move || drop(chan.unbounded_send(SchedulerMsg::Immediate(id))))
}
/// Schedule an update for any component given its [`ScopeId`].
///
/// A component's [`ScopeId`] can be obtained from `use_hook` or the [`ScopeState::scope_id`] method.
///
/// This method should be used when you want to schedule an update for a component
pub fn schedule_update_any(&self) -> Arc<dyn Fn(ScopeId) + Send + Sync> {
let chan = self.tasks.sender.clone();
Arc::new(move |id| drop(chan.unbounded_send(SchedulerMsg::Immediate(id))))
}
/// Mark this scope as dirty, and schedule a render for it.
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pub fn needs_update(&self) {
self.needs_update_any(self.scope_id());
}
/// Get the [`ScopeId`] of a mounted component.
///
/// `ScopeId` is not unique for the lifetime of the [`VirtualDom`] - a [`ScopeId`] will be reused if a component is unmounted.
pub fn needs_update_any(&self, id: ScopeId) {
self.tasks
.sender
.unbounded_send(SchedulerMsg::Immediate(id))
.expect("Scheduler to exist if scope exists");
}
/// Return any context of type T if it exists on this scope
pub fn has_context<T: 'static + Clone>(&self) -> Option<T> {
self.shared_contexts
.borrow()
.get(&TypeId::of::<T>())
.and_then(|shared| shared.downcast_ref::<T>())
.cloned()
}
/// Try to retrieve a shared state with type `T` from any parent scope.
///
/// The state will be cloned and returned, if it exists.
///
/// We recommend wrapping the state in an `Rc` or `Arc` to avoid deep cloning.
pub fn consume_context<T: 'static + Clone>(&self) -> Option<T> {
if let Some(this_ctx) = self.has_context() {
return Some(this_ctx);
}
let mut search_parent = self.parent;
while let Some(parent_ptr) = search_parent {
// safety: all parent pointers are valid thanks to the bump arena
let parent = unsafe { &*parent_ptr };
if let Some(shared) = parent.shared_contexts.borrow().get(&TypeId::of::<T>()) {
return Some(
shared
.downcast_ref::<T>()
.expect("Context of type T should exist")
.clone(),
);
}
search_parent = parent.parent;
}
None
}
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/// This method enables the ability to expose state to children further down the [`VirtualDom`] Tree.
///
/// This is a "fundamental" operation and should only be called during initialization of a hook.
///
/// For a hook that provides the same functionality, use `use_provide_context` and `use_consume_context` instead.
///
/// When the component is dropped, so is the context. Be aware of this behavior when consuming
/// the context via Rc/Weak.
///
/// # Example
///
/// ```rust, ignore
/// struct SharedState(&'static str);
///
/// static App: Component = |cx| {
/// cx.use_hook(|| cx.provide_context(SharedState("world")));
/// render!(Child {})
/// }
///
/// static Child: Component = |cx| {
/// let state = cx.consume_state::<SharedState>();
/// render!(div { "hello {state.0}" })
/// }
/// ```
pub fn provide_context<T: 'static + Clone>(&self, value: T) -> T {
self.shared_contexts
.borrow_mut()
.insert(TypeId::of::<T>(), Box::new(value.clone()))
.and_then(|f| f.downcast::<T>().ok());
value
}
/// Pushes the future onto the poll queue to be polled after the component renders.
pub fn push_future(&self, fut: impl Future<Output = ()> + 'static) -> TaskId {
self.tasks.spawn(self.id, fut)
}
/// Spawns the future but does not return the [`TaskId`]
pub fn spawn(&self, fut: impl Future<Output = ()> + 'static) {
self.push_future(fut);
}
/// Spawn a future that Dioxus won't clean up when this component is unmounted
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///
/// This is good for tasks that need to be run after the component has been dropped.
pub fn spawn_forever(&self, fut: impl Future<Output = ()> + 'static) -> TaskId {
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// The root scope will never be unmounted so we can just add the task at the top of the app
let id = self.tasks.spawn(ScopeId(0), fut);
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// wake up the scheduler if it is sleeping
self.tasks
.sender
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.unbounded_send(SchedulerMsg::TaskNotified(id))
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.expect("Scheduler should exist");
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id
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}
/// Informs the scheduler that this task is no longer needed and should be removed.
///
/// This drops the task immediately.
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pub fn remove_future(&self, id: TaskId) {
self.tasks.remove(id);
}
/// Take a lazy [`VNode`] structure and actually build it with the context of the efficient [`Bump`] allocator.
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///
/// ## Example
///
/// ```ignore
/// fn Component(cx: Scope<Props>) -> Element {
/// // Lazy assemble the VNode tree
/// let lazy_nodes = rsx!("hello world");
///
/// // Actually build the tree and allocate it
/// cx.render(lazy_tree)
/// }
///```
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pub fn render<'src>(&'src self, rsx: LazyNodes<'src, '_>) -> Element<'src> {
Ok(rsx.call(self))
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}
/// Store a value between renders. The foundational hook for all other hooks.
///
/// Accepts an `initializer` closure, which is run on the first use of the hook (typically the initial render). The return value of this closure is stored for the lifetime of the component, and a mutable reference to it is provided on every render as the return value of `use_hook`.
///
/// When the component is unmounted (removed from the UI), the value is dropped. This means you can return a custom type and provide cleanup code by implementing the [`Drop`] trait
///
/// # Example
///
/// ```
/// use dioxus_core::ScopeState;
///
/// // prints a greeting on the initial render
/// pub fn use_hello_world(cx: &ScopeState) {
/// cx.use_hook(|| println!("Hello, world!"));
/// }
/// ```
#[allow(clippy::mut_from_ref)]
pub fn use_hook<State: 'static>(&self, initializer: impl FnOnce() -> State) -> &mut State {
let cur_hook = self.hook_idx.get();
let mut hook_list = self.hook_list.borrow_mut();
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if cur_hook >= hook_list.len() {
hook_list.push(self.hook_arena.alloc(initializer()));
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}
hook_list
.get(cur_hook)
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.and_then(|inn| {
self.hook_idx.set(cur_hook + 1);
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let raw_box = unsafe { &mut **inn };
raw_box.downcast_mut::<State>()
})
.expect(
r###"
Unable to retrieve the hook that was initialized at this index.
Consult the `rules of hooks` to understand how to use hooks properly.
You likely used the hook in a conditional. Hooks rely on consistent ordering between renders.
Functions prefixed with "use" should never be called conditionally.
"###,
)
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}
}