Struct gtk4::ConstantExpression
source · [−]#[repr(transparent)]pub struct ConstantExpression { /* private fields */ }
Expand description
A constant value in a Expression
.
Implementations
sourceimpl ConstantExpression
impl ConstantExpression
pub fn upcast(self) -> Expression
pub fn upcast_ref(&self) -> &Expression
sourceimpl ConstantExpression
impl ConstantExpression
sourcepub fn new<V: ToValue>(value: &V) -> Self
pub fn new<V: ToValue>(value: &V) -> Self
Creates a Expression
that evaluates to the
object given by the arguments.
value_type
The type of the object
Returns
a new Expression
sourcepub fn value_as<V: for<'b> FromValue<'b> + 'static>(&self) -> V
pub fn value_as<V: for<'b> FromValue<'b> + 'static>(&self) -> V
Similar to Self::value
but panics if the value is of a different type.
Methods from Deref<Target = Expression>
pub const NONE: Option<&'static Expression> = None
sourcepub fn bind(
&self,
target: &impl IsA<Object>,
property: &str,
this_: Option<&impl IsA<Object>>
) -> ExpressionWatch
pub fn bind(
&self,
target: &impl IsA<Object>,
property: &str,
this_: Option<&impl IsA<Object>>
) -> ExpressionWatch
Bind target
’s property named property
to self
.
The value that self
evaluates to is set via g_object_set()
on
target
. This is repeated whenever self
changes to ensure that
the object’s property stays synchronized with self
.
If self
’s evaluation fails, target
’s property
is not updated.
You can ensure that this doesn’t happen by using a fallback
expression.
Note that this function takes ownership of self
. If you want
to keep it around, you should Gtk::Expression::ref()
it beforehand.
target
the target object to bind to
property
name of the property on target
to bind to
this_
the this argument for
the evaluation of self
Returns
sourcepub fn value_type(&self) -> Type
pub fn value_type(&self) -> Type
Gets the GType
that this expression evaluates to.
This type is constant and will not change over the lifetime of this expression.
Returns
The type returned from evaluate()
sourcepub fn is_static(&self) -> bool
pub fn is_static(&self) -> bool
Checks if the expression is static.
A static expression will never change its result when
evaluate()
is called on it with the same arguments.
That means a call to watch()
is not necessary because
it will never trigger a notify.
Returns
TRUE
if the expression is static
sourcepub fn watch<P: Fn() + 'static>(
&self,
this_: Option<&impl IsA<Object>>,
notify: P
) -> ExpressionWatch
pub fn watch<P: Fn() + 'static>(
&self,
this_: Option<&impl IsA<Object>>,
notify: P
) -> ExpressionWatch
Watch the given expression
for changes.
The @notify function will be called whenever the evaluation of self
may have changed.
GTK cannot guarantee that the evaluation did indeed change when the @notify gets invoked, but it guarantees the opposite: When it did in fact change, the @notify will be invoked.
this_
the this
argument to
watch
notify
callback to invoke when the expression changes
Returns
The newly installed watch. Note that the only
reference held to the watch will be released when the watch is unwatched
which can happen automatically, and not just via
ExpressionWatch::unwatch()
. You should call Gtk::ExpressionWatch::ref()
if you want to keep the watch around.
pub fn is<E: IsExpression>(&self) -> bool
pub fn downcast_ref<E: IsExpression>(&self) -> Option<&E>
pub fn type_(&self) -> Type
pub fn evaluate(&self, this: Option<&impl IsA<Object>>) -> Option<Value>
sourcepub fn evaluate_as<V: for<'b> FromValue<'b> + 'static, T: IsA<Object>>(
&self,
this: Option<&T>
) -> Option<V>
pub fn evaluate_as<V: for<'b> FromValue<'b> + 'static, T: IsA<Object>>(
&self,
this: Option<&T>
) -> Option<V>
Similar to Self::evaluate
but panics if the value is of a different type.
sourcepub fn chain_property<T: IsA<Object>>(
&self,
property_name: &str
) -> PropertyExpression
pub fn chain_property<T: IsA<Object>>(
&self,
property_name: &str
) -> PropertyExpression
Create a PropertyExpression
that looks up for
property_name
with self as parameter. This is useful in long chains of
Expression
s.
sourcepub fn chain_closure<R>(&self, closure: RustClosure) -> ClosureExpression where
R: ValueType,
pub fn chain_closure<R>(&self, closure: RustClosure) -> ClosureExpression where
R: ValueType,
Create a ClosureExpression
from a glib::Closure
with self
as the second parameter and R
as the return type. The return type is checked at run-time
and must always be specified. This is useful in long chains of
Expression
s when using the [glib::closure!
] macro.
Note that the first parameter will always be the this
object bound to the expression. If
None
is passed as this
then the type of the first parameter must be
Option<glib::Object>
otherwise type checking will panic.
use gtk::prelude::*;
use gtk::glib;
use glib::{closure, Object};
let button = gtk::Button::new();
button.set_label("Hello");
let label = button
.property_expression("label")
.chain_closure::<String>(closure!(|_: Option<Object>, label: &str| {
format!("{} World", label)
}))
.evaluate_as::<String, _>(gtk::Widget::NONE);
assert_eq!(label.unwrap(), "Hello World");
sourcepub fn chain_closure_with_callback<F, R>(&self, f: F) -> ClosureExpression where
F: Fn(&[Value]) -> R + 'static,
R: ValueType,
pub fn chain_closure_with_callback<F, R>(&self, f: F) -> ClosureExpression where
F: Fn(&[Value]) -> R + 'static,
R: ValueType,
Create a ClosureExpression
with self as the second parameter.
This is useful in long chains of Expression
s.
Trait Implementations
sourceimpl AsRef<Expression> for ConstantExpression
impl AsRef<Expression> for ConstantExpression
sourcefn as_ref(&self) -> &Expression
fn as_ref(&self) -> &Expression
Converts this type into a shared reference of the (usually inferred) input type.
sourceimpl Clone for ConstantExpression
impl Clone for ConstantExpression
sourceimpl Debug for ConstantExpression
impl Debug for ConstantExpression
sourceimpl Deref for ConstantExpression
impl Deref for ConstantExpression
type Target = Expression
type Target = Expression
The resulting type after dereferencing.
sourceimpl Display for ConstantExpression
impl Display for ConstantExpression
sourceimpl<'a> FromValue<'a> for ConstantExpression
impl<'a> FromValue<'a> for ConstantExpression
type Checker = GenericValueTypeOrNoneChecker<ConstantExpression>
type Checker = GenericValueTypeOrNoneChecker<ConstantExpression>
Value type checker.
sourceunsafe fn from_value(value: &'a Value) -> Self
unsafe fn from_value(value: &'a Value) -> Self
Get the contained value from a Value
. Read more
sourceimpl StaticType for ConstantExpression
impl StaticType for ConstantExpression
sourcefn static_type() -> Type
fn static_type() -> Type
Returns the type identifier of Self
.
sourceimpl ToValue for ConstantExpression
impl ToValue for ConstantExpression
sourceimpl ToValueOptional for ConstantExpression
impl ToValueOptional for ConstantExpression
sourcefn to_value_optional(s: Option<&Self>) -> Value
fn to_value_optional(s: Option<&Self>) -> Value
Convert an Option
to a Value
.
sourceimpl ValueType for ConstantExpression
impl ValueType for ConstantExpression
type Type = ConstantExpression
type Type = ConstantExpression
Type to get the Type
from. Read more
impl IsExpression for ConstantExpression
Auto Trait Implementations
impl RefUnwindSafe for ConstantExpression
impl !Send for ConstantExpression
impl !Sync for ConstantExpression
impl Unpin for ConstantExpression
impl UnwindSafe for ConstantExpression
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<T> StaticTypeExt for T where
T: StaticType,
impl<T> StaticTypeExt for T where
T: StaticType,
sourcefn ensure_type()
fn ensure_type()
Ensures that the type has been registered with the type system.