Enum Priority 

#[non_exhaustive]
pub enum Priority {
    Optional,
    Secondary,
    Essential,
}

What a member is worth when there is not room for all of them.

Written for table columns and no longer only theirs. Three shapes ask the same question and this answers all three: a table too narrow for its columns, a row too narrow for its parts (see RowPart::priority), and a group of regions sharing one run of room – goingson’s tab strip and the Region::Band beside it, which is the case wiki layout-room-and-fallback was ruled on. It is what any member of a group is worth, not a table concept, and Fallback::Shed is what reads it.

The doc below is the column argument, which is where the type was measured; the sentence that gave it away is Priority::Essential’s, which was already written about a row.

Ordered: Priority::Optional drops first, Priority::Essential never drops. This replaces addressing columns by position, which is what both webview apps do today and is a live bug rather than only verbosity. goingson hides mobile columns with nth-child(n+5) against a seven-column table, so inserting a column silently hides the wrong one. #[non_exhaustive], same reasoning as Width. Note the ordering is the whole point of the type, so a new tier has to be declared in its place in the sequence rather than appended.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Optional

Dropped first.

Secondary

Dropped once the optional members are gone.

Essential

Never dropped. Without it the group does not identify itself.

Trait Implementations

impl Clone for Priority

fn clone(&self) -> Priority

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Priority

impl Debug for Priority

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

Formats the value using the given formatter.

impl Eq for Priority

impl Hash for Priority

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 Priority

fn cmp(&self, other: &Priority) -> 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 Priority

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

Equality operator ==.

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

Inequality operator !=.

impl PartialOrd for Priority

fn partial_cmp(&self, other: &Priority) -> 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 StructuralPartialEq for Priority