pixel.horse/src/ts/graphics/webgl/webglUtils.ts

import { WEBGL_CREATION_ERROR } from '../../common/errors';

export function getRenderTargetSize(width: number, height: number) {
  const max = Math.max(width, height);
  let pow = 256;

  while (pow < max) {
    pow *= 2;
  }

  return pow;
}

export function getWebGLContext(canvas: HTMLCanvasElement): WebGLRenderingContext {
  const options: WebGLContextAttributes = {
    alpha: false,
    premultipliedAlpha: false,
    antialias: false,
  };

  const gl = canvas.getContext('webgl2', options)
    || canvas.getContext('webgl', options)
    || canvas.getContext('experimental-webgl', options);

  if (!gl) {
    throw new Error(WEBGL_CREATION_ERROR);
  }

  return gl;
}

export function isWebGL2(gl: WebGLRenderingContext | undefined) {
  return !!(gl && gl.MAX_ELEMENT_INDEX);
}

export function getWebGLError(gl: WebGLRenderingContext) {
  const error = gl.getError();

  switch (error) {
    case gl.NO_ERROR: return 'NO_ERROR';
    case gl.INVALID_ENUM: return 'INVALID_ENUM';
    case gl.INVALID_VALUE: return 'INVALID_VALUE';
    case gl.INVALID_OPERATION: return 'INVALID_OPERATION';
    case gl.INVALID_FRAMEBUFFER_OPERATION: return 'INVALID_FRAMEBUFFER_OPERATION';
    case gl.OUT_OF_MEMORY: return 'OUT_OF_MEMORY';
    case gl.CONTEXT_LOST_WEBGL: return 'CONTEXT_LOST_WEBGL';
    default: return `${error}`;
  }
}

export function unbindAllTexturesAndBuffers(gl: WebGLRenderingContext) {
  try {
    const numTextureUnits = gl.getParameter(gl.MAX_TEXTURE_IMAGE_UNITS) | 0;

    for (let i = 0; i < numTextureUnits; i++) {
      gl.activeTexture(gl.TEXTURE0 + i);
      gl.bindTexture(gl.TEXTURE_2D, null);
    }

    gl.bindBuffer(gl.ARRAY_BUFFER, null);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, null);
    gl.bindRenderbuffer(gl.RENDERBUFFER, null);
    gl.bindFramebuffer(gl.FRAMEBUFFER, null);
  } catch (e) {
    DEVELOPMENT && console.error(e);
  }
}