Example: Hello World

/*

Hello World: the smallest possible BLIT386 program - one line of text, nothing else.
@description The smallest possible BLIT386 program: one line of text, nothing else on screen.

Part of the BLIT386 demo series.

Live version: https://demos.blit386.dev/hello-world

Guides:
  - Palette: https://blit386.dev/docs/guides/palette#create-and-activate-a-palette

Reference:
  - Rendering: https://blit386.dev/docs/api/rendering#system-font

---

A dark blue screen with "Hello, World!" centered on it in the built-in system font. That
is the whole program: a palette with two colors, one clear, one print.

*/

import { bootstrap, BT, Color32, Vector2i } from 'blit386';

// Palette slots. Slot 0 is always transparent, so our colors start at 1.
const C_BG = 1;
const C_TEXT = 2;

class Demo {
    palette = null;

    async init() {
        // A palette is a numbered list of colors. Draw calls name a slot number,
        // not a color.
        this.palette = BT.paletteCreate(16);
        this.palette.set(C_BG, new Color32(18, 22, 40));
        this.palette.set(C_TEXT, Color32.white);

        // Make this palette the one the engine draws with.
        BT.paletteSet(this.palette);

        return true;
    }

    // Nothing moves, so there is no game logic to run each tick.
    update() {}

    render() {
        BT.clear(C_BG);

        // Measure the text first, then place its top-left corner so the text is centered.
        const text = 'Hello, World!';
        const size = BT.systemPrintMeasure(text);
        const x = Math.round(BT.displaySize.x / 2 - size.x / 2);
        const y = Math.round(BT.displaySize.y / 2 - size.y / 2);

        BT.systemPrint(new Vector2i(x, y), C_TEXT, text);
    }
}

bootstrap(Demo);