Enum BackendError 

pub enum BackendError {
    NotSupported(String),
    Unavailable(String),
    InvalidRequest(String),
    Internal(String),
}

Why a backend call could not be satisfied. Each variant maps to exactly one JSON-RPC error code (see BackendError::to_rpc_error), so a backend picks the variant and never has to know the code.

Hand-rolled Display/Error rather than thiserror-derived (the usual convention in docs/CODE_STANDARDS.md’s Error Handling) because this crate keeps a deliberately minimal dependency set — the same trade its sibling frust-devtools-protocol makes for DecodeError.

Variants

NotSupported(String)

The backend does not implement this capability at all (the default screenshot answer). Distinct from a transient failure: a client that reads the handshake capability set should never have asked.

Unavailable(String)

The capability exists but nothing can serve it right now (no attached window, no live widget tree yet, app backgrounded).

InvalidRequest(String)

The request itself was wrong (an id that names no widget, an out-of-range coordinate).

Internal(String)

Anything else the backend failed at.

Implementations

impl BackendError

pub fn not_supported(what: impl Into<String>) -> Self

pub fn unavailable(what: impl Into<String>) -> Self

pub fn invalid_request(what: impl Into<String>) -> Self

pub fn internal(what: impl Into<String>) -> Self

pub fn to_rpc_error(&self) -> RpcError

The wire error this failure becomes.

Trait Implementations

impl Clone for BackendError

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for BackendError

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

Formats the value using the given formatter.

impl Display for BackendError

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

Formats the value using the given formatter.

impl Eq for BackendError

impl Error for BackendError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for BackendError

fn eq(&self, other: &Self) -> bool

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for BackendError