Struct gtk4::ConstantExpression[][src]

pub struct ConstantExpression(_);
Expand description

A constant value in a Expression.

Implementations

Creates a Expression that evaluates to the object given by the arguments.

value_type

The type of the object

Returns

a new Expression

Creates an expression that always evaluates to the given value.

value

a GValue

Returns

a new Expression

Gets the value that a constant expression evaluates to.

Returns

the value

Methods from Deref<Target = Expression>

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()

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

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

a ExpressionWatch

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

Installs a watch for the given expression that calls the notify function 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.

Trait Implementations

Performs the conversion.

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Value type checker.

Get the contained value from a Value. Read more

Returns the type identifier of Self.

Convert a value to a Value.

Returns the type identifer of self. Read more

Convert an Option to a Value.

Type to get the Type from. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Performs the conversion.

Performs the conversion.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.