docs: function _commitTextures(gl, cur, next) {
    for (let i = 0; i < next.maxTextureSlot + 1; ++i) {
      if (cur.textureUnits[i] !== next.textureUnits[i]) {
        let texture = next.textureUnits[i];
        if (texture !== undefined && texture._glID !== -1) {
          gl.activeTexture(gl.TEXTURE0 + i);
          gl.bindTexture(texture._target, texture._glID);
        }
      }
    }
  }