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// This file was generated by gir (https://github.com/gtk-rs/gir)
// from gir-files (https://github.com/gtk-rs/gir-files)
// DO NOT EDIT
use crate::ExpressionWatch;
use glib::{prelude::*, translate::*};
use std::{boxed::Box as Box_, fmt};
glib::wrapper! {
/// [`Expression`][crate::Expression] provides a way to describe references to values.
///
/// An important aspect of expressions is that the value can be obtained
/// from a source that is several steps away. For example, an expression
/// may describe ‘the value of property A of `object1`, which is itself the
/// value of a property of `object2`’. And `object1` may not even exist yet
/// at the time that the expression is created. This is contrast to `GObject`
/// property bindings, which can only create direct connections between
/// the properties of two objects that must both exist for the duration
/// of the binding.
///
/// An expression needs to be "evaluated" to obtain the value that it currently
/// refers to. An evaluation always happens in the context of a current object
/// called `this` (it mirrors the behavior of object-oriented languages),
/// which may or may not influence the result of the evaluation. Use
/// [`evaluate()`][Self::evaluate()] for evaluating an expression.
///
/// Various methods for defining expressions exist, from simple constants via
/// [`ConstantExpression::new()`][crate::ConstantExpression::new()] to looking up properties in a `GObject`
/// (even recursively) via [`PropertyExpression::new()`][crate::PropertyExpression::new()] or providing
/// custom functions to transform and combine expressions via
/// [`ClosureExpression::new()`][crate::ClosureExpression::new()].
///
/// Here is an example of a complex expression:
///
/// **⚠️ The following code is in c ⚠️**
///
/// ```c
/// color_expr = gtk_property_expression_new (GTK_TYPE_LIST_ITEM,
/// NULL, "item");
/// expression = gtk_property_expression_new (GTK_TYPE_COLOR,
/// color_expr, "name");
/// ```
///
/// when evaluated with `this` being a [`ListItem`][crate::ListItem], it will obtain the
/// "item" property from the [`ListItem`][crate::ListItem], and then obtain the "name" property
/// from the resulting object (which is assumed to be of type `GTK_TYPE_COLOR`).
///
/// A more concise way to describe this would be
///
/// ```text
/// this->item->name
/// ```
///
/// The most likely place where you will encounter expressions is in the context
/// of list models and list widgets using them. For example, [`DropDown`][crate::DropDown] is
/// evaluating a [`Expression`][crate::Expression] to obtain strings from the items in its model
/// that it can then use to match against the contents of its search entry.
/// [`StringFilter`][crate::StringFilter] is using a [`Expression`][crate::Expression] for similar reasons.
///
/// By default, expressions are not paying attention to changes and evaluation is
/// just a snapshot of the current state at a given time. To get informed about
/// changes, an expression needs to be "watched" via a [`ExpressionWatch`][crate::ExpressionWatch],
/// which will cause a callback to be called whenever the value of the expression may
/// have changed; [`watch()`][Self::watch()] starts watching an expression, and
/// [`ExpressionWatch::unwatch()`][crate::ExpressionWatch::unwatch()] stops.
///
/// Watches can be created for automatically updating the property of an object,
/// similar to GObject's `GBinding` mechanism, by using [`bind()`][Self::bind()].
///
/// ## GtkExpression in GObject properties
///
/// In order to use a [`Expression`][crate::Expression] as a `GObject` property, you must use the
/// `gtk_param_spec_expression` when creating a `GParamSpec` to install in the
/// `GObject` class being defined; for instance:
///
/// **⚠️ The following code is in c ⚠️**
///
/// ```c
/// obj_props[PROP_EXPRESSION] =
/// gtk_param_spec_expression ("expression",
/// "Expression",
/// "The expression used by the widget",
/// G_PARAM_READWRITE |
/// G_PARAM_STATIC_STRINGS |
/// G_PARAM_EXPLICIT_NOTIFY);
/// ```
///
/// When implementing the `GObjectClass.set_property` and `GObjectClass.get_property`
/// virtual functions, you must use `gtk_value_get_expression`, to retrieve the
/// stored [`Expression`][crate::Expression] from the `GValue` container, and `gtk_value_set_expression`,
/// to store the [`Expression`][crate::Expression] into the `GValue`; for instance:
///
/// **⚠️ The following code is in c ⚠️**
///
/// ```c
/// // in set_property()...
/// case PROP_EXPRESSION:
/// foo_widget_set_expression (foo, gtk_value_get_expression (value));
/// break;
///
/// // in get_property()...
/// case PROP_EXPRESSION:
/// gtk_value_set_expression (value, foo->expression);
/// break;
/// ```
///
/// ## GtkExpression in .ui files
///
/// [`Builder`][crate::Builder] has support for creating expressions. The syntax here can be used where
/// a [`Expression`][crate::Expression] object is needed like in a `<property>` tag for an expression
/// property, or in a `<binding name="property">` tag to bind a property to an expression.
///
/// To create a property expression, use the `<lookup>` element. It can have a `type`
/// attribute to specify the object type, and a `name` attribute to specify the property
/// to look up. The content of `<lookup>` can either be an element specfiying the expression
/// to use the object, or a string that specifies the name of the object to use.
///
/// Example:
///
/// ```xml
/// <lookup name='search'>string_filter</lookup>
/// ```
///
/// To create a constant expression, use the `<constant>` element. If the type attribute
/// is specified, the element content is interpreted as a value of that type. Otherwise,
/// it is assumed to be an object. For instance:
///
/// ```xml
/// <constant>string_filter</constant>
/// <constant type='gchararray'>Hello, world</constant>
/// ```
///
/// To create a closure expression, use the `<closure>` element. The `type` and `function`
/// attributes specify what function to use for the closure, the content of the element
/// contains the expressions for the parameters. For instance:
///
/// ```xml
/// <closure type='gchararray' function='combine_args_somehow'>
/// <constant type='gchararray'>File size:</constant>
/// <lookup type='GFile' name='size'>myfile</lookup>
/// </closure>
/// ```
///
/// This is an Abstract Base Class, you cannot instantiate it.
#[doc(alias = "GtkExpression")]
pub struct Expression(Shared<ffi::GtkExpression>);
match fn {
ref => |ptr| ffi::gtk_expression_ref(ptr),
unref => |ptr| ffi::gtk_expression_unref(ptr),
}
}
impl glib::StaticType for Expression {
fn static_type() -> glib::Type {
unsafe { from_glib(ffi::gtk_expression_get_type()) }
}
}
impl Expression {
pub const NONE: Option<&'static Expression> = None;
/// 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`][crate::ExpressionWatch]
#[doc(alias = "gtk_expression_bind")]
pub fn bind(
&self,
target: &impl IsA<glib::Object>,
property: &str,
this_: Option<&impl IsA<glib::Object>>,
) -> ExpressionWatch {
unsafe {
from_glib_none(ffi::gtk_expression_bind(
self.as_ref().to_glib_full(),
target.as_ref().to_glib_none().0,
property.to_glib_none().0,
this_.map(|p| p.as_ref()).to_glib_none().0,
))
}
}
/// 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()`][Self::evaluate()]
#[doc(alias = "gtk_expression_get_value_type")]
#[doc(alias = "get_value_type")]
pub fn value_type(&self) -> glib::types::Type {
unsafe {
from_glib(ffi::gtk_expression_get_value_type(
self.as_ref().to_glib_none().0,
))
}
}
/// Checks if the expression is static.
///
/// A static expression will never change its result when
/// [`evaluate()`][Self::evaluate()] is called on it with the same arguments.
///
/// That means a call to [`watch()`][Self::watch()] is not necessary because
/// it will never trigger a notify.
///
/// # Returns
///
/// `TRUE` if the expression is static
#[doc(alias = "gtk_expression_is_static")]
pub fn is_static(&self) -> bool {
unsafe {
from_glib(ffi::gtk_expression_is_static(
self.as_ref().to_glib_none().0,
))
}
}
/// 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()`][crate::ExpressionWatch::unwatch()]. You should call `Gtk::ExpressionWatch::ref()`
/// if you want to keep the watch around.
#[doc(alias = "gtk_expression_watch")]
pub fn watch<P: Fn() + 'static>(
&self,
this_: Option<&impl IsA<glib::Object>>,
notify: P,
) -> ExpressionWatch {
let notify_data: Box_<P> = Box_::new(notify);
unsafe extern "C" fn notify_func<P: Fn() + 'static>(user_data: glib::ffi::gpointer) {
let callback: &P = &*(user_data as *mut _);
(*callback)()
}
let notify = Some(notify_func::<P> as _);
unsafe extern "C" fn user_destroy_func<P: Fn() + 'static>(data: glib::ffi::gpointer) {
let _callback: Box_<P> = Box_::from_raw(data as *mut _);
}
let destroy_call4 = Some(user_destroy_func::<P> as _);
let super_callback0: Box_<P> = notify_data;
unsafe {
from_glib_none(ffi::gtk_expression_watch(
self.as_ref().to_glib_none().0,
this_.map(|p| p.as_ref()).to_glib_none().0,
notify,
Box_::into_raw(super_callback0) as *mut _,
destroy_call4,
))
}
}
}
impl fmt::Display for Expression {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str("Expression")
}
}