jumpstorm/engine/systems/Render.ts

import { System, SystemNames } from ".";
import { BoundingBox, ComponentNames, Sprite } from "../components";
import type { Entity } from "../entities";
import { Game } from "../Game";
import type { DrawArgs } from "../interfaces";
import { clamp } from "../utils";

export class Render extends System {
  private ctx: CanvasRenderingContext2D;

  constructor(ctx: CanvasRenderingContext2D) {
    super(SystemNames.Render);
    this.ctx = ctx;
  }

  public update(dt: number, game: Game) {
    this.ctx.clearRect(0, 0, this.ctx.canvas.width, this.ctx.canvas.height);

    game.componentEntities.get(ComponentNames.Sprite)?.forEach((entityId) => {
      const entity = game.entities.get(entityId);
      const sprite = entity.getComponent<Sprite>(ComponentNames.Sprite);
      sprite.update(dt);

      let drawArgs: DrawArgs;
      if (entity.hasComponent(ComponentNames.BoundingBox)) {
        const boundingBox = entity.getComponent<BoundingBox>(
          ComponentNames.BoundingBox
        );

        // don't render if we're outside the screen
        if (
          clamp(
            boundingBox.center.y,
            -boundingBox.dimension.height / 2,
            this.ctx.canvas.height + boundingBox.dimension.height / 2
          ) != boundingBox.center.y ||
          clamp(
            boundingBox.center.x,
            -boundingBox.dimension.width / 2,
            this.ctx.canvas.width + boundingBox.dimension.width / 2
          ) != boundingBox.center.x
        ) {
          return;
        }

        drawArgs = {
          center: boundingBox.center,
          dimension: boundingBox.dimension,
          rotation: boundingBox.rotation,
        };
      }
      sprite.draw(this.ctx, drawArgs);
    });
  }
}