#[repr(transparent)]
pub struct ConstantExpression { /* private fields */ }
Expand description

A constant value in a Expression.

Implementations

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

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

value_type

The type of the object

Returns

a new Expression

Similar to Self::value but panics if the value is of a different type.

Methods from Deref<Target = Expression>

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

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

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.

Similar to Self::evaluate but panics if the value is of a different type.

Create a PropertyExpression that looks up for property_name with self as parameter. This is useful in long chains of Expressions.

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 Expressions 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");

Create a ClosureExpression with self as the second parameter. This is useful in long chains of Expressions.

Trait Implementations

Converts this type into a shared reference of the (usually inferred) input type.

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.

Formats the value using the given formatter. Read more

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

Returns the argument unchanged.

Calls U::from(self).

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

Ensures that the type has been registered with the type system.

The resulting type after obtaining ownership.

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

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

Converts the given value to a String. 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.