Module quicksilver::tutorials::_10_views

Quicksilver uses the View structure as an abstraction for both graphical and input projection.

This means that a view can be thought of like a camera: it determines what coordinates in draw calls appear where on screen, as well as the relationship between the mouse location on the screen and the reported coordinates.

Important to understanding View is understanding world versus screen coordinates. Screen coordinates map the the window on the user's device. (0, 0) on the screen is the top-left, and screen coordinates span to the pixel width and height of the window. World coordinates are defined by the active view. By default, the world is a rectangle with the size of the initial window.

Here is a View in action (the camera example):

// Demonstrate adding a View to the draw-geometry example
// The camera can be controlled with the arrow keys
extern crate quicksilver;

use quicksilver::{
    Result,
    geom::{Circle, Line, Rectangle, Shape, Transform, Triangle, Vector},
    graphics::{Background::Col, Color, View},
    input::{Key},
    lifecycle::{Settings, State, Window, run},
};

struct Camera {
    view: Rectangle
}

impl State for Camera {
    // Initialize the struct
    fn new() -> Result<Camera> {
        Ok(Camera {
            view: Rectangle::new_sized((800, 600))
        })
    }

    fn update(&mut self, window: &mut Window) -> Result<()> {
        if window.keyboard()[Key::Left].is_down() {
            self.view = self.view.translate((-4, 0));
        }
        if window.keyboard()[Key::Right].is_down() {
            self.view = self.view.translate((4, 0));
        }
        if window.keyboard()[Key::Down].is_down() {
            self.view = self.view.translate((0, 4));
        }
        if window.keyboard()[Key::Up].is_down() {
            self.view = self.view.translate((0, -4));
        }
        window.set_view(View::new(self.view));
        Ok(())
    }

    fn draw(&mut self, window: &mut Window) -> Result<()> {
        window.clear(Color::WHITE)?;
        window.draw(&Rectangle::new((100, 100), (32, 32)), Col(Color::BLUE));
        window.draw_ex(&Rectangle::new((400, 300), (32, 32)), Col(Color::BLUE), Transform::rotate(45), 10);
        window.draw(&Circle::new((400, 300), 100), Col(Color::GREEN));
        window.draw_ex(
            &Line::new((50, 80),(600, 450)).with_thickness(2.0),
            Col(Color::RED),
            Transform::IDENTITY,
            5
        );
        window.draw_ex(
            &Triangle::new((500, 50), (450, 100), (650, 150)),
            Col(Color::RED),
            Transform::rotate(45) * Transform::scale((0.5, 0.5)),
            0
        );
        Ok(())
    }
}

fn main() {
    run::<Camera>("Camera", Vector::new(800, 600), Settings::default());
}