Struct gtk4::PropertyExpression[−][src]

pub struct PropertyExpression(_);

Expand description

A GObject property value in a Expression.

Implementations

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impl PropertyExpression

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pub fn new<E: AsRef<Expression>>(
 this_type: Type,
 expression: Option<&E>,
 property_name: &str
) -> Self

Creates an expression that looks up a property.

The object to use is found by evaluating the expression, or using the this argument when expression is NULL.

If the resulting object conforms to this_type, its property named property_name will be queried. Otherwise, this expression’s evaluation will fail.

The given this_type must have a property with property_name.

`expression`

Expression to evaluate to get the object to query or NULL to query the this object

pub fn for_pspec<E: AsRef<Expression>>(
expression: Option<&E>,
pspec: ParamSpec
) -> Self

Creates an expression that looks up a property.

The object to use is found by evaluating the expression, or using the this argument when expression is NULL.

If the resulting object conforms to this_type, its property specified by pspec will be queried. Otherwise, this expression’s evaluation will fail.

`expression`

Expression to evaluate to get the object to query or NULL to query the this object

`pspec`

the GParamSpec for the property to query

pub fn expression(&self) -> Option<Expression>

Gets the expression specifying the object of a property expression.

pub fn pspec(&self) -> ParamSpec

Gets the GParamSpec specifying the property of a property expression.

Methods from Deref<Target = Expression>

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pub fn downcast_ref<E: IsExpression>(&self) -> Option<&E>

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pub fn type_(&self) -> Type

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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()

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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.

pub fn bind<T: IsA<Object>, U: IsA<Object>>(
 &self,
 target: &T,
 property_name: &str,
 this: Option<&U>
) -> 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.

`property`

name of the property on target to bind to

`this_`

the this argument for the evaluation of self

pub fn evaluate<T: IsA<Object>>(&self, this: Option<&T>) -> Option<Value>

Evaluates the given expression and on success stores the result in value.

The GType of value will be the type given by value_type().

It is possible that expressions cannot be evaluated - for example when the expression references objects that have been destroyed or set to NULL. In that case value will remain empty and FALSE will be returned.

`this_`

the this argument for the evaluation

`value`

an empty GValue

Returns

TRUE if the expression could be evaluated

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pub fn watch<T: IsA<Object>, F: Fn() + 'static>(
 &self,
 this: Option<&T>,
 notify: F
) -> 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.