Since relm is based on GTK , you need this library on your system in order to use it.
See this page for information on how to install GTK .
First, add this to your Cargo.toml
:
gtk = "^0.9.0"
relm = "^0.21.0"
relm-derive = "^0.21.0"
Next, add this to your crate:
use relm::{connect, Relm, Update, Widget};
use gtk::prelude::*;
use gtk::{Window, Inhibit, WindowType};
use relm_derive::Msg;
Then, create your model:
struct Model {
// …
}
The model contains the data related to a Widget
. It may be updated by the Widget::update
function.
Create your message enum
:
#[derive(Msg)]
enum Msg {
// …
Quit,
}
Messages are sent to Widget::update
to indicate that an event happened. The model can be updated when an event is received.
Create a struct
which represents a Widget
which contains the GTK widgets (in this case, the main window of the application) and the model:
struct Win {
// …
model: Model,
window: Window,
}
To make this struct
a relm Widget
that can be shown by the library, implement the Update
and Widget
traits:
impl Update for Win {
// Specify the model used for this widget.
type Model = Model;
// Specify the model parameter used to init the model.
type ModelParam = ();
// Specify the type of the messages sent to the update function.
type Msg = Msg;
// Return the initial model.
fn model(_: &Relm<Self>, _: ()) -> Model {
Model {
}
}
// The model may be updated when a message is received.
// Widgets may also be updated in this function.
fn update(&mut self, event: Msg) {
match event {
Msg::Quit => gtk::main_quit(),
}
}
}
impl Widget for Win {
// Specify the type of the root widget.
type Root = Window;
// Return the root widget.
fn root(&self) -> Self::Root {
self.window.clone()
}
// Create the widgets.
fn view(relm: &Relm<Self>, model: Self::Model) -> Self {
// GTK widgets are used normally within a `Widget`.
let window = Window::new(WindowType::Toplevel);
// Connect the signal `delete_event` to send the `Quit` message.
connect!(relm, window, connect_delete_event(_, _), return (Some(Msg::Quit), Inhibit(false)));
// There is also a `connect!()` macro for GTK events that do not need a
// value to be returned in the callback.
window.show_all();
Win {
model,
window,
}
}
}
Finally, show this Widget
by calling Win::run()
:
fn main() {
Win::run(()).unwrap();
}
A #[widget]
attribute is provided to simplify the creation of a widget.
This attribute does the following:
-
Provide a
view!
macro to create the widget with a declarative syntax. -
Automatically create the
fn root()
,type Msg
,type Model
,type ModelParam
andtype Root
items. -
Automatically insert the call to
Widget::set_property()
in theupdate()
function when assigning to an attribute of the model. -
Automatically create the
Widget
struct
. -
Update
andWidget
traits can be implemented at once.
To use this attribute, add the following code:
use relm_derive::widget;
Here is an example using this attribute:
#[derive(Msg)]
pub enum Msg {
Decrement,
Increment,
Quit,
}
pub struct Model {
counter: u32,
}
#[widget]
impl Widget for Win {
fn model() -> Model {
Model {
counter: 0,
}
}
fn update(&mut self, event: Msg) {
match event {
// A call to self.label1.set_text() is automatically inserted by the
// attribute every time the model.counter attribute is updated.
Msg::Decrement => self.model.counter -= 1,
Msg::Increment => self.model.counter = 1,
Msg::Quit => gtk::main_quit(),
}
}
view! {
gtk::Window {
gtk::Box {
orientation: Vertical,
gtk::Button {
// By default, an event with one paramater is assumed.
clicked => Msg::Increment,
// Hence, the previous line is equivalent to:
// clicked(_) => Increment,
label: " ",
},
gtk::Label {
// Bind the text property of this Label to the counter attribute
// of the model.
// Every time the counter attribute is updated, the text property
// will be updated too.
text: &self.model.counter.to_string(),
},
gtk::Button {
clicked => Msg::Decrement,
label: "-",
},
},
// Use a tuple when you want to both send a message and return a value to
// the GTK callback.
delete_event(_, _) => (Msg::Quit, Inhibit(false)),
}
}
}
Note
|
The struct Win is now automatically created by the attribute, as are the function root() and the associated types Model , ModelParam , Msg and Container .
You can still provide the method and the associated types if needed, but you cannot create the struct .
|
Warning
|
The #[widget] makes the generated struct public: hence, the corresponding model and message types must be public too.
|
Warning
|
Your program might be slower when using this attribute because the code generation is simple. For instance, the following code fn update(&mut self, event: Msg) {
for _ in 0..100 {
self.model.counter = 1;
}
} will generate this function: fn update(&mut self, event: Msg) {
for _ in 0..100 {
self.model.counter = 1;
self.label1.set_text(&self.model.counter.to_string());
}
} |
Warning
|
Also, the fn update(&mut self, event: Msg) {
self.model.text.push_str("Text");
} will not work as expected. Please use the following variation if needed. fn update(&mut self, event: Msg) {
self.model.text = "Text";
} |
For more information about how you can use relm, you can take a look at the examples.
If you want to add your project to this list, please create a pull request.