Enum script::dom::event::EventDefault

pub enum EventDefault {
    Allowed,
    Prevented,
    Handled,
}

An enum to indicate whether the default action of an event is allowed.

This should’ve been a bool. Instead, it’s an enum, because, aside from the allowed/canceled states, we also need something to stop the event from being handled again (without cancelling the event entirely). For example, an Up/Down KeyEvent inside a textarea element will trigger the cursor to go up/down if the text inside the element spans multiple lines. This enum helps us to prevent such events from being sent to the constellation where it will be handled once again for page scrolling (which is definitely not what we’d want).

Variants

Allowed

The default action of the event is allowed (constructor’s default)

Prevented

The default action has been prevented by calling PreventDefault

Handled

The event has been handled somewhere in the DOM, and it should be prevented from being re-handled elsewhere. This doesn’t affect the judgement of DefaultPrevented

Trait Implementations

impl Clone for EventDefault

fn clone(&self) -> EventDefault

Returns a copy of the value.

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

Performs copy-assignment from source.

impl MallocSizeOf for EventDefault

fn size_of(&self, ops: &mut MallocSizeOfOps) -> usize

Measure the heap usage of all descendant heap-allocated structures, but not the space taken up by the value itself.

impl PartialEq<EventDefault> for EventDefault

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Traceable for EventDefault

unsafe fn trace(&self, tracer: *mut JSTracer)

Trace self.

impl Copy for EventDefault

impl StructuralPartialEq for EventDefault