GPU是否与CPU交换创建的纹理?

let contextLost = false;
function createCanvas(canvasWidth, canvasHeight) {
  const canvas = document.createElement('canvas');
  canvas.width = canvasWidth + 'px';
  canvas.height = canvasHeight + 'px';
	  
	canvas.addEventListener("webglcontextlost", function(event) {
		//event.preventDefault();
		console.log('context is lost');
		contextLost = true;
		
	}, false);
	canvas.addEventListener(
		"webglcontextrestored", function() { 
		console.log('context is restored'); 
		}, false);

  return canvas;
}
function getGLContext(canvas) {
  const attributes = { alpha: false, depth: false, antialias: false };
  // Only fetch a gl context if we haven't already
  const gl = canvas.getContext('webgl2', attributes);
  if(!gl) {
	  throw 'No support for WebGL2';
  }
  if(!gl.getExtension('EXT_color_buffer_float')) {
	  throw 'No support for floatingpoint output textures';
  }
  return gl;
}
function createTexture(gl, width, height, data) {
  const texture = gl.createTexture();
  // Bind the texture so the following methods effect this texture.
  gl.bindTexture(gl.TEXTURE_2D, texture);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
  gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
  // Pixel format and data for the texture
  gl.texImage2D(
    gl.TEXTURE_2D,  // Target, matches bind above.
    0,              // Level of detail.
    gl.R32F,        // Internal format.
    width,          // Width - normalized to s.
    height,         // Height - normalized to t.
    0,              // Always 0 in OpenGL ES.
    gl.RED,        // Format for each pixel.
    gl.FLOAT,           // Data type for each chanel.
    data);          // Image data in the described format, or null.
  // Unbind the texture.
  gl.bindTexture(gl.TEXTURE_2D, null);

  return texture;
}

let totalSize = 0;
const buffer = new Float32Array(1024*1024);
function createTexture2() {
	const texsize=1024 * 1024 * 4;
	const tex = createTexture(gl, 1024, 1024, buffer) ;
	if(!tex || contextLost) {
		console.log('context lost; stopping now');
		return;
	}
	totalSize += texsize;
	console.log('Total size = ' + totalSize);
	window.setTimeout(createTexture2, 0);
}
const canvas = createCanvas(1,1);
const gl = getGLContext(canvas);

createTexture2();

console.log('the end');