cranpose 0.9.22

Build desktop, mobile and web apps with composable Rust functions
Documentation 
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use cranpose_core::{NodeId, collections::map::HashMap};

use crate::accessibility::AccessibilityElement;

#[derive(Debug, thiserror::Error, PartialEq, Eq)]
pub(crate) enum AccessibilityIdentityError {
    #[error("accessibility node IDs exhausted")]
    Exhausted,
    #[error("duplicate accessibility identity: node {0}, canvas key {1:?}")]
    Duplicate(NodeId, Option<u64>),
}

/// What [`AccessibilitySnapshot::update`] replaced: the elements and ids
/// published before, and for each new element the index its control had
/// among them.
#[cfg_attr(
    not(any(
        test,
        target_os = "android",
        target_os = "ios",
        all(feature = "desktop-shell", feature = "renderer-wgpu"),
        all(feature = "web", feature = "renderer-wgpu", target_arch = "wasm32")
    )),
    allow(
        dead_code,
        reason = "only the Android, iOS, desktop and web bridges diff against what an update replaced"
    )
)]
pub(crate) struct Replaced {
    pub(crate) elements: Vec<AccessibilityElement>,
    #[cfg_attr(
        not(any(
            test,
            target_os = "android",
            all(feature = "desktop-shell", feature = "renderer-wgpu")
        )),
        allow(
            dead_code,
            reason = "only the Android wire and the desktop tree read the ids an update replaced"
        )
    )]
    pub(crate) ids: Vec<i32>,
    pub(crate) was: Vec<Option<usize>>,
}

#[derive(Default)]
pub(crate) struct AccessibilitySnapshot {
    pub(crate) elements: Vec<AccessibilityElement>,
    pub(crate) ids: Vec<i32>,
    last_id: i32,
    indices: HashMap<i32, usize>,
    spare: Vec<AccessibilityElement>,
}

impl AccessibilitySnapshot {
    /// Moves on to `elements`, keeping the ids of controls it already held,
    /// and hands back what it replaced.
    pub(crate) fn update(
        &mut self,
        elements: Vec<AccessibilityElement>,
    ) -> Result<Replaced, AccessibilityIdentityError> {
        let mut identities: HashMap<_, usize> =
            HashMap::with_capacity_and_hasher(elements.len(), Default::default());
        for (index, element) in elements.iter().enumerate() {
            let identity = (element.node_id, element.canvas_key);
            if identities.insert(identity, index).is_some() {
                return Err(AccessibilityIdentityError::Duplicate(
                    identity.0, identity.1,
                ));
            }
        }
        // A control keeps its id while it is the same node: same identity and
        // generation.
        let mut was = vec![None; elements.len()];
        let mut ids = vec![0; elements.len()];
        for (old, (element, id)) in self.elements.iter().zip(&self.ids).enumerate() {
            if let Some(&index) = identities.get(&(element.node_id, element.canvas_key))
                && elements[index].node_generation == element.node_generation
            {
                was[index] = Some(old);
                ids[index] = *id;
            }
        }
        let mut last_id = self.last_id;
        for (id, was) in ids.iter_mut().zip(&was) {
            if was.is_none() {
                last_id = last_id
                    .checked_add(1)
                    .ok_or(AccessibilityIdentityError::Exhausted)?;
                *id = last_id;
            }
        }
        self.indices = ids
            .iter()
            .enumerate()
            .map(|(index, id)| (*id, index))
            .collect();
        self.last_id = last_id;
        Ok(Replaced {
            elements: std::mem::replace(&mut self.elements, elements),
            ids: std::mem::replace(&mut self.ids, ids),
            was,
        })
    }

    pub(crate) fn take_spare(&mut self) -> Vec<AccessibilityElement> {
        let spare = std::mem::take(&mut self.spare);
        if spare.capacity() == 0 {
            Vec::with_capacity(self.elements.len())
        } else {
            spare
        }
    }

    pub(crate) fn recycle(&mut self, elements: Vec<AccessibilityElement>) {
        if elements.capacity() >= self.spare.capacity() {
            self.spare = elements;
        }
    }

    pub(crate) fn changed(
        &mut self,
        elements: Vec<AccessibilityElement>,
        force: bool,
    ) -> Option<Vec<AccessibilityElement>> {
        if force || elements != self.elements {
            return Some(elements);
        }
        self.recycle(elements);
        None
    }

    pub(crate) fn element(&self, id: i32) -> Option<&AccessibilityElement> {
        self.elements.get(*self.indices.get(&id)?)
    }

    #[cfg(any(test, target_os = "android"))]
    pub(crate) fn identity(&self, id: i32) -> Option<(NodeId, Option<u64>)> {
        self.element(id)
            .map(|element| (element.node_id, element.canvas_key))
    }
}

#[cfg(test)]
#[path = "tests/accessibility_identity.rs"]
mod tests;