Struct egui::Id

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pub struct Id(u64);
Expand description

egui tracks widgets frame-to-frame using Ids.

For instance, if you start dragging a slider one frame, egui stores the sliders Id as the current active id so that next frame when you move the mouse the same slider changes, even if the mouse has moved outside the slider.

For some widgets Ids are also used to persist some state about the widgets, such as Window position or whether not a collapsing header region is open.

This implies that the Ids must be unique.

For simple things like sliders and buttons that don’t have any memory and doesn’t move we can use the location of the widget as a source of identity. For instance, a slider only needs a unique and persistent ID while you are dragging the slider. As long as it is still while moving, that is fine.

For things that need to persist state even after moving (windows, collapsing headers) the location of the widgets is obviously not good enough. For instance, a collapsing region needs to remember whether or not it is open even if the layout next frame is different and the collapsing is not lower down on the screen.

Then there are widgets that need no identifiers at all, like labels, because they have no state nor are interacted with.

Tuple Fields§

§0: u64

Implementations§

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impl Id

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pub fn null() -> Self

A special Id, in particular as a key to crate::Memory::data for when there is no particular widget to attach the data.

The null Id is still a valid id to use in all circumstances, though obviously it will lead to a lot of collisions if you do use it!

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pub(crate) fn background() -> Self

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pub fn new(source: impl Hash) -> Id

Generate a new Id by hashing some source (e.g. a string or integer).

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pub fn with(self, child: impl Hash) -> Id

Generate a new Id by hashing the parent Id and the given argument.

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pub fn short_debug_format(&self) -> String

Short and readable summary

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pub(crate) fn value(&self) -> u64

Trait Implementations§

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impl Clone for Id

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fn clone(&self) -> Id

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Id

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

Formats the value using the given formatter. Read more
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impl From<&'static str> for Id

Convenience

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fn from(string: &'static str) -> Self

Converts to this type from the input type.
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impl From<String> for Id

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fn from(string: String) -> Self

Converts to this type from the input type.
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impl Hash for Id

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

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl PartialEq<Id> for Id

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

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

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impl Eq for Id

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impl StructuralEq for Id

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impl StructuralPartialEq for Id

Auto Trait Implementations§

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impl RefUnwindSafe for Id

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impl Send for Id

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impl Sync for Id

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impl Unpin for Id

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impl UnwindSafe for Id

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> ToOwned for Twhere T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> SerializableAny for Twhere T: 'static + Any + Clone + Send + Sync,