Source: packages/core/src/framebuffer/Framebuffer.js

import { Runner } from '@pixi/runner';
import { BaseTexture } from '../textures/BaseTexture';
import { DepthResource } from '../textures/resources/DepthResource';
import { FORMATS, TYPES, SCALE_MODES } from '@pixi/constants';
/**
 * Frame buffer used by the BaseRenderTexture
 *
 * @class
 * @memberof PIXI
 */
export class Framebuffer
{
    /**
     * @param {number} width - Width of the frame buffer
     * @param {number} height - Height of the frame buffer
     */
    constructor(width, height)
    {
        this.width = Math.ceil(width || 100);
        this.height = Math.ceil(height || 100);
        this.stencil = false;
        this.depth = false;
        this.dirtyId = 0;
        this.dirtyFormat = 0;
        this.dirtySize = 0;
        this.depthTexture = null;
        this.colorTextures = [];
        this.glFramebuffers = {};
        this.disposeRunner = new Runner('disposeFramebuffer', 2);
    }
    /**
     * Reference to the colorTexture.
     *
     * @member {PIXI.Texture[]}
     * @readonly
     */
    get colorTexture()
    {
        return this.colorTextures[0];
    }
    /**
     * Add texture to the colorTexture array
     *
     * @param {number} [index=0] - Index of the array to add the texture to
     * @param {PIXI.Texture} [texture] - Texture to add to the array
     */
    addColorTexture(index = 0, texture)
    {
        // TODO add some validation to the texture - same width / height etc?
        this.colorTextures[index] = texture || new BaseTexture(null, {
            scaleMode: SCALE_MODES.NEAREST,
            resolution: 1,
            mipmap: false,
            width: this.width,
            height: this.height,
        });
        this.dirtyId++;
        this.dirtyFormat++;

        return this;
    }
    /**
     * Add a depth texture to the frame buffer
     *
     * @param {PIXI.Texture} [texture] - Texture to add
     */
    addDepthTexture(texture)
    {
        /* eslint-disable max-len */
        this.depthTexture = texture || new BaseTexture(new DepthResource(null, { width: this.width, height: this.height }), {
            scaleMode: SCALE_MODES.NEAREST,
            resolution: 1,
            width: this.width,
            height: this.height,
            mipmap: false,
            format: FORMATS.DEPTH_COMPONENT,
            type: TYPES.UNSIGNED_SHORT,
        });
        this.dirtyId++;
        this.dirtyFormat++;

        return this;
    }
    /**
     * Enable depth on the frame buffer
     */
    enableDepth()
    {
        this.depth = true;
        this.dirtyId++;
        this.dirtyFormat++;

        return this;
    }
    /**
     * Enable stencil on the frame buffer
     */
    enableStencil()
    {
        this.stencil = true;
        this.dirtyId++;
        this.dirtyFormat++;

        return this;
    }
    /**
     * Resize the frame buffer
     *
     * @param {number} width - Width of the frame buffer to resize to
     * @param {number} height - Height of the frame buffer to resize to
     */
    resize(width, height)
    {
        width = Math.ceil(width);
        height = Math.ceil(height);
        if (width === this.width && height === this.height)
        { return; }
        this.width = width;
        this.height = height;
        this.dirtyId++;
        this.dirtySize++;
        for (let i = 0; i < this.colorTextures.length; i++)
        {
            const texture = this.colorTextures[i];
            const resolution = texture.resolution;
            // take into acount the fact the texture may have a different resolution..

            texture.setSize(width / resolution, height / resolution);
        }
        if (this.depthTexture)
        {
            const resolution = this.depthTexture.resolution;

            this.depthTexture.setSize(width / resolution, height / resolution);
        }
    }
    /**
     * disposes WebGL resources that are connected to this geometry
     */
    dispose()
    {
        this.disposeRunner.run(this, false);
    }
}