# Starting with cursive: (1/3)
## Target goal
In this first tutorial, we'll learn the basics of cursive,
and write a very basic first application:
```rust,no_run
extern crate cursive;
use cursive::Cursive;
use cursive::views::TextView;
fn main() {
let mut siv = Cursive::new();
siv.add_global_callback('q', |s| s.quit());
siv.add_layer(TextView::new("Hello cursive! Press <q> to quit."));
siv.run();
}
```
Run this application, and you should have something like that:
Now that you have an idea of what we'll do, let's start from scratch.
## Project configuration
Let's create a new project
(this is basic cargo stuff I hope you're familiar with):
```text
% cargo new --bin cursive_example
```
Now, we'll add cursive to the list of dependencies in `Cargo.toml`:
```toml
[package]
name = "cursive_example"
version = "0.1.0"
[dependencies]
cursive = "*"
```
Finally, update `src/main.rs` to import it:
```rust,no_run
extern crate cursive;
fn main() {
}
```
This simple application is now ready to use cursive. So let's do just that!
## The Cursive root
The cursive library is configured through a main [`Cursive`] root.
A typical cursive application will consist of three phases,
all centered around this object:
1. Create a `Cursive` object.
2. Configure the `Cursive` object.
3. Run the `Cursive` object.
Of these, the configuration phase is often the largest one,
so let's skip it for now.
In its simplest form, a cursive application is therefore:
```rust,no_run
extern crate cursive;
use cursive::Cursive;
fn main() {
let mut siv = Cursive::new();
siv.run();
}
```
It's rather easy to identify the two steps involved.
If you run this, you'll get an empty blue terminal, with no way of properly
leaving the application (you'll have to press <Ctrl-C> to kill it).
[`Cursive`]: http://gyscos.github.io/Cursive/cursive/struct.Cursive.html
## Interactivity
Let's first add a way to stop the application. We want to quit when the user
presses the letter `q`.
Cursive sends an event for every user input ; most of these are just ignored
and have no effect. The `Cursive` root has a [`add_global_callback`] method to
call a function anytime a certain event is fired.
This method takes 2 arguments: a trigger, and a callback.
* The trigger needs to implement `Into<event::Event>`. In addition to
[`event::Event`] itself, this includes [`event::Key`], or simply `char`.
These will trigger when the corresponding key (or letter) is pressed.
* The callback should be a function taking a `&mut Cursive` as argument. Here,
we want to quit, so we'll use [`Cursive::quit`] in a closure: `|s| s.quit()`.
In the end, we have:
```rust,no_run
extern crate cursive;
use cursive::Cursive;
fn main() {
let mut siv = Cursive::new();
siv.add_global_callback('q', |s| s.quit());
siv.run();
}
```
As expected, running it show no visible change, but hitting the `q` key at
least closes the application.
[`add_global_callback`]: http://gyscos.github.io/Cursive/cursive/struct.Cursive.html#method.add_global_callback
[`event::Event`]: http://gyscos.github.io/Cursive/cursive/event/enum.Event.html
[`event::Key`]: http://gyscos.github.io/Cursive/cursive/event/enum.Key.html
[`Cursive::quit`]: http://gyscos.github.io/Cursive/cursive/struct.Cursive.html#method.quit
## Views
[`View`s] are the main components of the user interface in a cursive
application. At their core, they define what to draw in a rectangle of the
terminal. For instance, a view can print a line of text, or a checkbox, etc.
Here, we'll be using a [`TextView`] to show a short message. `TextView` itself
can also deal with long text and do proper word-wrapping, but we won't need
that today.
The `TextView` constructor just takes the text to use: `TextView::new("...")`.
The `Cursive` root itself uses a [`StackView`] on the entire screen. This
`StackView` unsurprisingly stacks views in layers. It starts empty, so we'll
just need to add our `TextView` as a layer. The [`Cursive::add_layer`] does
exactly that.
Once we've added this line, our first application is complete:
```rust,no_run
extern crate cursive;
use cursive::Cursive;
use cursive::views::TextView;
fn main() {
let mut siv = Cursive::new();
siv.add_global_callback('q', |s| s.quit());
siv.add_layer(TextView::new("Hello cursive! Press <q> to quit."));
siv.run();
}
```
[`View`s]: http://gyscos.github.io/Cursive/cursive/view/trait.View.html
[`TextView`]: http://gyscos.github.io/Cursive/cursive/views/struct.TextView.html
[`StackView`]: http://gyscos.github.io/Cursive/cursive/views/struct.StackView.html
[`Cursive::add_layer`]: http://gyscos.github.io/Cursive/cursive/struct.Cursive.html#method.add_layer
Next: [Starting with Cursive (2/3)](./tutorial_2.md)
