Module quicksilver::tutorials::_03_input

Now we can draw all manner of colorful geometry, but that's not enough for an interesting application.

If we wanted to add keyboard support to our previous example, so that the user can use the left and right arrow keys to move the square back ond forth, it would look like this:

extern crate quicksilver;

use quicksilver::{
    Result,
    geom::{Rectangle, Vector},
    graphics::{Background, Color},
    input::Key, // We need the Key enum
    lifecycle::{State, Window, run}
};

struct Screen {
    position: Vector // We need to store the position as state
}

impl State for Screen {
    fn new() -> Result<Screen> {
        Ok(Screen {
            position: Vector::new(50, 50)
        })
    }

    fn update(&mut self, window: &mut Window) -> Result<()> {
        if window.keyboard()[Key::Right].is_down() {
            self.position.x += 2.5;
        }
        if window.keyboard()[Key::Left].is_down() {
            self.position.x -= 2.5;
        }
        Ok(())
    }

    fn draw(&mut self, window: &mut Window) -> Result<()> {
        window.clear(Color::WHITE)?;
        window.draw(&Rectangle::new(self.position, (100, 200)), Background::Col(Color::RED));
        Ok(())
    }
}

fn main() {
    run::<Screen>("Hello World", Vector::new(800, 600), Default::default());
}

Now we have very basic keyboard input controls. Every frame that the right arrow is held down, the box will move 2.5 pixels to the right, and the same for left.

The input API generally follows this principal: an input source is indexed by a button enum, and returns a ButtonState enum. A button state can be Pressed, Held, Released or NotPressed, and a convenience method is_down checks if the button is either pressed or held.

If we wanted to give the user more freedom, and allow them to use the mouse buttons or gamepad triggers instead of the arrow keys, we could do that fairly easily:

extern crate quicksilver;

use quicksilver::{
    Result,
    geom::{Rectangle, Vector},
    graphics::{Background, Color},
    input::{GamepadButton, Key, MouseButton}, // We need the mouse and gamepad buttons
    lifecycle::{State, Window, run}
};

struct Screen {
    position: Vector // We need to store the position as state
}

impl State for Screen {
    fn new() -> Result<Screen> {
        Ok(Screen {
            position: Vector::new(50, 50)
        })
    }

    fn update(&mut self, window: &mut Window) -> Result<()> {
        if window.keyboard()[Key::Right].is_down() ||
            window.mouse()[MouseButton::Right].is_down() ||
            window.gamepads().iter().any(|pad| pad[GamepadButton::TriggerRight].is_down())
            {
            self.position.x += 2.5;
        }
        if window.keyboard()[Key::Left].is_down() ||
            window.mouse()[MouseButton::Left].is_down() ||
            window.gamepads().iter().any(|pad| pad[GamepadButton::TriggerLeft].is_down())
            {
            self.position.x -= 2.5;
        }
        Ok(())
    }

    fn draw(&mut self, window: &mut Window) -> Result<()> {
        window.clear(Color::WHITE)?;
        window.draw(&Rectangle::new(self.position, (100, 200)), Background::Col(Color::RED));
        Ok(())
    }
}

fn main() {
    run::<Screen>("Hello World", Vector::new(800, 600), Default::default());
}

Unlike mice and keyboards, which generally are one-per-system, a machine may have many gamepads connected. More advanced applications may wish to assign specific gamepads to specific The input API generally follows this principal: an input source is indexed by a button enum, and returns a ButtonState enum. A button state can be Pressed, Held, Released or NotPressed, and a convenience method is_down checks if the button is either pressed or held. functions or specific users, but for our case checking against any gamepad does just fine.

If we want to only apply an effect once per input submission, we have two options. One is to check if the button state is exactly Pressed: that is, the button was not pressed the last update, but now is. The other is to implement the event method of State, and listen for a keypress event. To compare, here is an implementation that checks for Pressed for up and uses an event for down:

extern crate quicksilver;

use quicksilver::{
    Result,
    geom::{Rectangle, Vector},
    graphics::{Background, Color},
    input::{ButtonState, GamepadButton, Key, MouseButton}, // We need to match ButtonState
    lifecycle::{Event, State, Window, run} // We need to match against Event
};

struct Screen {
    position: Vector // We need to store the position as state
}

impl State for Screen {
    fn new() -> Result<Screen> {
        Ok(Screen {
            position: Vector::new(50, 50)
        })
    }

    fn event(&mut self, event: &Event, window: &mut Window) -> Result<()> {
        if let Event::Key(Key::Down, ButtonState::Pressed) = event {
            self.position.y += 10.0;
        }
        Ok(())
    }

    fn update(&mut self, window: &mut Window) -> Result<()> {
        if window.keyboard()[Key::Right].is_down() ||
            window.mouse()[MouseButton::Right].is_down() ||
            window.gamepads().iter().any(|pad| pad[GamepadButton::TriggerRight].is_down())
            {
            self.position.x += 2.5;
        }
        if window.keyboard()[Key::Left].is_down() ||
            window.mouse()[MouseButton::Left].is_down() ||
            window.gamepads().iter().any(|pad| pad[GamepadButton::TriggerLeft].is_down())
            {
            self.position.x -= 2.5;
        }
        if window.keyboard()[Key::Up] == ButtonState::Pressed {
            self.position.y -= 10.0;
        }
        Ok(())
    }

    fn draw(&mut self, window: &mut Window) -> Result<()> {
        window.clear(Color::WHITE)?;
        window.draw(&Rectangle::new(self.position, (100, 200)), Background::Col(Color::RED));
        Ok(())
    }
}

fn main() {
    run::<Screen>("Hello World", Vector::new(800, 600), Default::default());
}