utils.js

/*
 * Copyright 2019 Gregg Tavares
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 */

/**
 * Gets the gl version as a number
 * @param {WebGLRenderingContext} gl A WebGLRenderingContext
 * @return {number} version of gl
 * @private
 */
//function getVersionAsNumber(gl) {
//  return parseFloat(gl.getParameter(gl.VERSION).substr(6));
//}

/**
 * Check if context is WebGL 2.0
 * @param {WebGLRenderingContext} gl A WebGLRenderingContext
 * @return {bool} true if it's WebGL 2.0
 * @memberOf module:twgl
 */
function isWebGL2(gl) {
  // This is the correct check but it's slow
  //  return gl.getParameter(gl.VERSION).indexOf("WebGL 2.0") === 0;
  // This might also be the correct check but I'm assuming it's slow-ish
  // return gl instanceof WebGL2RenderingContext;
  return !!gl.texStorage2D;
}

/**
 * Check if context is WebGL 1.0
 * @param {WebGLRenderingContext} gl A WebGLRenderingContext
 * @return {bool} true if it's WebGL 1.0
 * @memberOf module:twgl
 */
function isWebGL1(gl) {
  // This is the correct check but it's slow
  // const version = getVersionAsNumber(gl);
  // return version <= 1.0 && version > 0.0;  // because as of 2016/5 Edge returns 0.96
  // This might also be the correct check but I'm assuming it's slow-ish
  // return gl instanceof WebGLRenderingContext;
  return !gl.texStorage2D;
}

/**
 * Gets a string for WebGL enum
 *
 * Note: Several enums are the same. Without more
 * context (which function) it's impossible to always
 * give the correct enum. As it is, for matching values
 * it gives all enums. Checking the WebGL2RenderingContext
 * that means
 *
 *      0     = ZERO | POINT | NONE | NO_ERROR
 *      1     = ONE | LINES | SYNC_FLUSH_COMMANDS_BIT
 *      32777 = BLEND_EQUATION_RGB | BLEND_EQUATION_RGB
 *      36662 = COPY_READ_BUFFER | COPY_READ_BUFFER_BINDING
 *      36663 = COPY_WRITE_BUFFER | COPY_WRITE_BUFFER_BINDING
 *      36006 = FRAMEBUFFER_BINDING | DRAW_FRAMEBUFFER_BINDING
 *
 * It's also not useful for bits really unless you pass in individual bits.
 * In other words
 *
 *     const bits = gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT;
 *     twgl.glEnumToString(gl, bits);  // not going to work
 *
 * Note that some enums only exist on extensions. If you
 * want them to show up you need to pass the extension at least
 * once. For example
 *
 *     const ext = gl.getExtension('WEBGL_compressed_texture_s3tc');
 *     if (ext) {
 *        twgl.glEnumToString(ext, 0);  // just prime the function
 *
 *        ..later..
 *
 *        const internalFormat = ext.COMPRESSED_RGB_S3TC_DXT1_EXT;
 *        console.log(twgl.glEnumToString(gl, internalFormat));
 *
 * Notice I didn't have to pass the extension the second time. This means
 * you can have place that generically gets an enum for texture formats for example.
 * and as long as you primed the function with the extensions
 *
 * If you're using `twgl.addExtensionsToContext` to enable your extensions
 * then twgl will automatically get the extension's enums.
 *
 * @param {WebGLRenderingContext} gl A WebGLRenderingContext or any extension object
 * @param {number} value the value of the enum you want to look up.
 * @return {string} enum string or hex value
 * @memberOf module:twgl
 * @function glEnumToString
 */
const glEnumToString = (function() {
  const haveEnumsForType = {};
  const enums = {};

  function addEnums(gl) {
    const type = gl.constructor.name;
    if (!haveEnumsForType[type]) {
      for (const key in gl) {
        if (typeof gl[key] === 'number') {
          const existing = enums[gl[key]];
          enums[gl[key]] = existing ? `${existing} | ${key}` : key;
        }
      }
      haveEnumsForType[type] = true;
    }
  }

  return function glEnumToString(gl, value) {
    addEnums(gl);
    return enums[value] || (typeof value === 'number' ? `0x${value.toString(16)}` : value);
  };
}());

export {
  glEnumToString,
  isWebGL1,
  isWebGL2,
};