119 lines
3.9 KiB
Rust
119 lines
3.9 KiB
Rust
use crate::{read::Readable, ReadableRef};
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use dioxus_core::prelude::{IntoAttributeValue, ScopeId};
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use generational_box::UnsyncStorage;
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use std::{mem::MaybeUninit, ops::Deref};
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use crate::{ReadOnlySignal, Signal};
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use super::get_global_context;
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/// A signal that can be accessed from anywhere in the application and created in a static
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pub struct GlobalMemo<T: 'static> {
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selector: fn() -> T,
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}
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impl<T: PartialEq + 'static> GlobalMemo<T> {
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/// Create a new global signal
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pub const fn new(selector: fn() -> T) -> GlobalMemo<T>
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where
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T: PartialEq,
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{
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GlobalMemo { selector }
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}
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/// Get the signal that backs this global.
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pub fn signal(&self) -> ReadOnlySignal<T> {
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let key = self as *const _ as *const ();
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let context = get_global_context();
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let read = context.signal.borrow();
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match read.get(&key) {
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Some(signal) => *signal.downcast_ref::<ReadOnlySignal<T>>().unwrap(),
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None => {
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drop(read);
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// Constructors are always run in the root scope
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let signal = ScopeId::ROOT.in_runtime(|| Signal::selector(self.selector));
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context.signal.borrow_mut().insert(key, Box::new(signal));
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signal
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}
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}
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}
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/// Get the scope the signal was created in.
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pub fn origin_scope(&self) -> ScopeId {
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ScopeId::ROOT
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}
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/// Get the generational id of the signal.
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pub fn id(&self) -> generational_box::GenerationalBoxId {
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self.signal().id()
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}
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}
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impl<T: PartialEq + 'static> Readable for GlobalMemo<T> {
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type Target = T;
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type Storage = UnsyncStorage;
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#[track_caller]
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fn try_read(&self) -> Result<ReadableRef<Self>, generational_box::BorrowError> {
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self.signal().try_read()
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}
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#[track_caller]
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fn peek(&self) -> ReadableRef<Self> {
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self.signal().peek()
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}
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}
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impl<T: PartialEq + 'static> IntoAttributeValue for GlobalMemo<T>
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where
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T: Clone + IntoAttributeValue,
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{
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fn into_value(self) -> dioxus_core::AttributeValue {
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self.signal().into_value()
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}
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}
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impl<T: PartialEq + 'static> PartialEq for GlobalMemo<T> {
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fn eq(&self, other: &Self) -> bool {
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std::ptr::eq(self, other)
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}
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}
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/// Allow calling a signal with signal() syntax
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///
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/// Currently only limited to copy types, though could probably specialize for string/arc/rc
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impl<T: PartialEq + Clone + 'static> Deref for GlobalMemo<T> {
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type Target = dyn Fn() -> T;
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fn deref(&self) -> &Self::Target {
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// https://github.com/dtolnay/case-studies/tree/master/callable-types
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// First we create a closure that captures something with the Same in memory layout as Self (MaybeUninit<Self>).
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let uninit_callable = MaybeUninit::<Self>::uninit();
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// Then move that value into the closure. We assume that the closure now has a in memory layout of Self.
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let uninit_closure = move || Self::read(unsafe { &*uninit_callable.as_ptr() }).clone();
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// Check that the size of the closure is the same as the size of Self in case the compiler changed the layout of the closure.
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let size_of_closure = std::mem::size_of_val(&uninit_closure);
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assert_eq!(size_of_closure, std::mem::size_of::<Self>());
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// Then cast the lifetime of the closure to the lifetime of &self.
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fn cast_lifetime<'a, T>(_a: &T, b: &'a T) -> &'a T {
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b
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}
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let reference_to_closure = cast_lifetime(
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{
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// The real closure that we will never use.
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&uninit_closure
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},
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// We transmute self into a reference to the closure. This is safe because we know that the closure has the same memory layout as Self so &Closure == &self.
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unsafe { std::mem::transmute(self) },
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);
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// Cast the closure to a trait object.
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reference_to_closure as &Self::Target
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}
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}
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