Example for how specs and tcod would work together

main.rs

extern crate tcod;
extern crate specs;

use tcod::console::{Root};
use specs::{System, VecStorage, Component, World, Builder, WriteStorage, DispatcherBuilder};

#[derive(Debug)]
enum Command {
    PutCharacter(char,i32,i32),
    Clear,
}

#[derive(Debug)]
struct Surface {
    commands: Vec<Command>,
}

impl Component for Surface {
    type Storage = VecStorage<Self>;
}

struct RootSystem {
    root: Root,
}

impl<'a> System<'a> for RootSystem {
    type SystemData = WriteStorage<'a, Surface>;

    fn run(&mut self, mut surfaces: Self::SystemData) {
        use specs::Join;
        use tcod::colors;
        use tcod::console::*;

        self.root.set_default_foreground(colors::WHITE); // Command

        for surface in (&mut surfaces).join() { // should be surfaces
            for command in &surface.commands {
                match command {
                    Command::Clear => self.root.clear(),
                    Command::PutCharacter(ascii, x, y) => self.root.put_char(*x, *y, *ascii,  BackgroundFlag::None),
                }
            }
            surface.commands.clear();
        }

        self.root.flush();
        self.root.wait_for_keypress(true); // Should be check instead of wait and should push into a Key resource
        //TODO resource for self.root.window_closed()
    }

    // fn setup(&mut self, res: &mut Resources) {
    //     use specs::prelude::SystemData;
    //     Self::SystemData::setup(res);
    // }
}

impl RootSystem {
    fn new() -> RootSystem {
        use tcod::console::*;
        let root = Root::initializer()
            .font("arial10x10.png", FontLayout::Tcod)
            .font_type(FontType::Greyscale)
            .size(80, 50)
            .title("Rust/libtcod tutorial")
            .init();
        RootSystem {
            root
        }
    }
}

fn main() {
    tcod::system::set_fps(20);

    let mut world = World::new();
    world.register::<Surface>();
    
    world.create_entity().with(Surface{commands: vec![Command::Clear, Command::PutCharacter('@', 1, 1)]}).build();

    let mut dispatcher = DispatcherBuilder::new()
        .with_thread_local(RootSystem::new())
        .build();

    loop {
        dispatcher.dispatch(&mut world.res);
    }
}