Struct DatasetMergeCallback 

#[repr(C)]
pub struct DatasetMergeCallback {
    pub cb: DatasetMergeCallbackType,
    pub callable: OptionRefAny,
}

A callback function used to merge the state of an old dataset into a new one.

This enables components with heavy internal state (video players, WebGL contexts) to preserve their resources across frames, while the DOM tree is recreated.

The callback receives both the old and new datasets as RefAny (cheap shallow clones) and returns the dataset that should be used for the new node.

Example

fn merge_video_state(new_data: RefAny, old_data: RefAny) -> RefAny {
    // Transfer heavy resources from old to new
    if let (Some(mut new), Some(old)) = (
        new_data.downcast_mut::<VideoState>(),
        old_data.downcast_ref::<VideoState>()
    ) {
        new.decoder = old.decoder.take();
        new.gl_texture = old.gl_texture.take();
    }
    new_data // Return the merged state
}

Fields

cb: DatasetMergeCallbackType

The function pointer that performs the merge. Signature: fn(new_data: RefAny, old_data: RefAny) -> RefAny

callable: OptionRefAny

Optional callable for FFI language bindings (Python, etc.) When set, the FFI layer can invoke this instead of cb.

Trait Implementations

impl Clone for DatasetMergeCallback

fn clone(&self) -> DatasetMergeCallback

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for DatasetMergeCallback

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

Formats the value using the given formatter.

impl From<extern "C" fn(RefAny, RefAny) -> RefAny> for DatasetMergeCallback

Allow creating DatasetMergeCallback from a raw function pointer. This enables the Into<DatasetMergeCallback> pattern for Python bindings.

fn from(cb: DatasetMergeCallbackType) -> Self

Converts to this type from the input type.

impl Hash for DatasetMergeCallback

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for DatasetMergeCallback

fn cmp(&self, other: &DatasetMergeCallback) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for DatasetMergeCallback

fn eq(&self, other: &DatasetMergeCallback) -> 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 PartialOrd for DatasetMergeCallback

fn partial_cmp(&self, other: &DatasetMergeCallback) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

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

Tests less than or equal to (for self and other) and is used by the <= operator.

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

Tests greater than (for self and other) and is used by the > operator.

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

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Eq for DatasetMergeCallback

impl StructuralPartialEq for DatasetMergeCallback