Source: tiny/core/textures/BaseRenderTexture.js

import BaseTexture from './BaseTexture';
import settings from '../settings';

/**
 * A BaseRenderTexture is a special texture that allows any display object to be rendered to it.
 *
 * __Hint__: All DisplayObjects (i.e. Sprites) that render to a BaseRenderTexture should be preloaded otherwise black rectangles will be drawn instead.
 *
 * A BaseRenderTexture takes a snapshot of any Display Object given to its render method. The position and rotation of the given Display Objects is ignored. For example:
 *
 * ```js
 * let baseRenderTexture = new Tiny.BaseRenderTexture(800, 600);
 * let sprite = Tiny.Sprite.fromImage('spinObj_01.png');
 *
 * sprite.position.x = 800/2;
 * sprite.position.y = 600/2;
 * sprite.anchor.x = 0.5;
 * sprite.anchor.y = 0.5;
 *
 * baseRenderTexture.render(sprite);
 * ```
 *
 * The Sprite in this case will be rendered using its local transform. To render this sprite at 0,0, you can clear the transform
 *
 * ```js
 * let app = new Tiny.Application();
 * let renderer = app.renderer;
 *
 * sprite.setTransform();
 *
 * let baseRenderTexture = new Tiny.BaseRenderTexture(100, 100);
 * let renderTexture = new Tiny.RenderTexture(baseRenderTexture);
 *
 * renderer.render(sprite, renderTexture);  // Renders to center of RenderTexture
 * ```
 *
 * @class
 * @extends Tiny.BaseTexture
 * @memberof Tiny
 */
export default class BaseRenderTexture extends BaseTexture {
  /**
   * @param {number} [width=100] - The width of the base render texture
   * @param {number} [height=100] - The height of the base render texture
   * @param {number} [scaleMode=Tiny.settings.SCALE_MODE] - See {@link Tiny.SCALE_MODES} for possible values
   * @param {number} [resolution=1] - The resolution / device pixel ratio of the texture being generated
   */
  constructor(width = 100, height = 100, scaleMode = 0, resolution = 1) {
    super(null, scaleMode);

    this.resolution = resolution || settings.RESOLUTION;

    this.width = Math.ceil(width);
    this.height = Math.ceil(height);

    this.realWidth = this.width * this.resolution;
    this.realHeight = this.height * this.resolution;

    this.scaleMode = scaleMode !== undefined ? scaleMode : settings.SCALE_MODE;
    this.hasLoaded = true;

    /**
     * A map of renderer IDs to webgl renderTargets
     *
     * @private
     * @member {object<number, WebGLTexture>}
     */
    this._glRenderTargets = {};

    /**
     * A reference to the canvas render target (we only need one as this can be shared across renderers)
     *
     * @private
     * @member {object<number, WebGLTexture>}
     */
    this._canvasRenderTarget = null;

    /**
     * This will let the renderer know if the texture is valid. If it's not then it cannot be rendered.
     *
     * @member {boolean}
     */
    this.valid = false;
  }

  /**
   * Resizes the BaseRenderTexture.
   *
   * @param {number} width - The width to resize to.
   * @param {number} height - The height to resize to.
   */
  resize(width, height) {
    width = Math.ceil(width);
    height = Math.ceil(height);

    if (width === this.width && height === this.height) {
      return;
    }

    this.valid = (width > 0 && height > 0);

    this.width = width;
    this.height = height;

    this.realWidth = this.width * this.resolution;
    this.realHeight = this.height * this.resolution;

    if (!this.valid) {
      return;
    }

    this.emit('update', this);
  }

  /**
   * Destroys this texture
   *
   */
  destroy() {
    super.destroy(true);
    this.renderer = null;
  }
}