merchant_seas/src/states/titlescreen.rs

use crate::resources::{font::FontResource, spritesheet::SpriteSheetMap};
use amethyst::{
    core::transform::Transform,
    prelude::*,
    renderer::{Camera, SpriteRender},
    ui::{Anchor, UiImage, UiText, UiTransform},
    window::ScreenDimensions,
};
use nalgebra::Vector3;

const DEFAULT_SPRITE_WIDTH: f32 = 256.0;
const DEFAULT_SPRITE_HEIGHT: f32 = 144.0;

/// struct for title screen state
pub struct TitleScreenState;

impl TitleScreenState {
    /// initialize the titlescreen
    fn init(&self, world: &mut World, dimensions: ScreenDimensions) {
        self.init_camera(world, &dimensions);
        self.init_ui(world);
        self.init_scenery(world, &dimensions);
    }

    // initialize the camera
    fn init_camera(&self, world: &mut World, dimensions: &ScreenDimensions) {
        let mut transform = Transform::default();
        transform.set_translation_xyz(dimensions.width() * 0.5, dimensions.height() * 0.5, 1.0);

        world
            .create_entity()
            .with(Camera::standard_2d(dimensions.width(), dimensions.height()))
            .with(transform)
            .build();
    }

    fn init_ui(&self, world: &mut World) {
        // get the font handle
        let font_handle = {
            if let Some(font_rsc) = world.try_fetch::<FontResource>() {
                font_rsc.get_handle().clone()
            } else {
                panic!("failed to get a handle on font resource");
            }
        };

        // create the button transforms
        let exit_btn_transform = UiTransform::new(
            "exit_button".into(),
            Anchor::BottomRight,
            Anchor::Middle,
            -100.0,
            50.0,
            0.0,
            100.0,
            50.0,
        );
        let settings_btn_transform = UiTransform::new(
            "settings_button".into(),
            Anchor::BottomRight,
            Anchor::Middle,
            0.0,
            0.0,
            0.0,
            200.0,
            50.0,
        );

        // create the button ui text
        let exit_btn_text =
            UiText::new(font_handle.clone(), "Exit".into(), [1.0, 1.0, 1.0, 1.0], 30.0);
        let settings_btn_text =
            UiText::new(font_handle, "Settings".into(), [1.0, 1.0, 1.0, 1.0], 30.0);

        // create ui image
        let btn_image = UiImage::SolidColor([0.0, 0.0, 0.0, 1.0]);

        // create the button
        world
            .create_entity()
            .with(exit_btn_transform)
            .with(exit_btn_text)
            .with(btn_image.clone())
            .build();
        world
            .create_entity()
            .with(settings_btn_transform)
            .with(settings_btn_text)
            .with(btn_image)
            .build();
    }

    // initialize the scenery
    fn init_scenery(&self, world: &mut World, dimensions: &ScreenDimensions) {
        // create the scale vector
        let scale_vector = Vector3::new(
            dimensions.width() / DEFAULT_SPRITE_WIDTH,
            dimensions.height() / DEFAULT_SPRITE_HEIGHT,
            0.0,
        );

        // create scenery transform
        let mut transform = Transform::default();
        transform.set_translation_xyz(dimensions.width() * 0.5, dimensions.height() * 0.5, 0.0);
        transform.set_scale(scale_vector);

        // get the sprite sheet from the map
        let spritesheet_handle = {
            if let Some(map) = world.try_fetch::<SpriteSheetMap>() {
                map.get_handle("title_screen".into())
                    .expect("could not find title_screen sprite sheet")
                    .clone()
            } else {
                panic!("failed to get a handle on the spritesheet map")
            }
        };

        // create a sprite render
        let mut sprite_render = SpriteRender { sprite_sheet: spritesheet_handle, sprite_number: 2 };

        // render background stuff
        world.create_entity().with(transform.clone()).with(sprite_render.clone()).build();
        sprite_render.sprite_number = 1;
        world.create_entity().with(transform.clone()).with(sprite_render.clone()).build();
        sprite_render.sprite_number = 0;
        world.create_entity().with(transform.clone()).with(sprite_render.clone()).build();
        sprite_render.sprite_number = 3;
        world.create_entity().with(transform.clone()).with(sprite_render.clone()).build();
        sprite_render.sprite_number = 4;
        world.create_entity().with(transform.clone()).with(sprite_render.clone()).build();
    }
}

impl SimpleState for TitleScreenState {
    fn on_start(&mut self, data: StateData<'_, GameData<'_, '_>>) {
        let world = data.world;
        let dimensions = (*world.read_resource::<ScreenDimensions>()).clone();

        self.init(world, dimensions);
    }
}