p5 resize window without clearing the background - p5.js

Question

The following code makes use of the p5dom add-on to position the canvas in the centre of the window. To dynamically resize the canvas I'm using the windowResized() function. I want to keep the background function in setup. How do I prevent the background colour from clearing when I resize the window? Many thanks.
var cnv;
function centerCanvas() {
var x = (windowWidth - width) / 2;
var y = (windowHeight - height) / 2;
cnv.position(x, y);
}
function setup() {
cnv = createCanvas(windowWidth,windowHeight);
centerCanvas();
background(255, 0, 200);
}
function draw(){
}
function windowResized() {
centerCanvas();
resizeCanvas(windowWidth,windowHeight)
}

Answer 1

One thing you might do is draw everything to a buffer instead of directly to the screen. The createGraphics() function is your friend here. From the P5.js reference:
var pg;
function setup() {
createCanvas(100, 100);
pg = createGraphics(100, 100);
}
function draw() {
background(200);
pg.background(100);
pg.noStroke();
pg.ellipse(pg.width/2, pg.height/2, 50, 50);
image(pg, 50, 50);
image(pg, 0, 0, 50, 50);
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.5.16/p5.js"></script>
You would want to draw everything to a buffer, and then when the screen is resized, redraw that buffer.

Answer 2

Simply by adding the background function to the draw one too.
Try this:
var cnv;
function centerCanvas() {
var x = (windowWidth - width) / 2;
var y = (windowHeight - height) / 2;
cnv.position(x, y);
}
function setup() {
cnv = createCanvas(windowWidth,windowHeight);
centerCanvas();
background(255, 0, 200);
}
function draw(){
//HERE:
background(255, 0, 200);
}
function windowResized() {
//(you can add it here too...)
centerCanvas();
resizeCanvas(windowWidth,windowHeight);
}

Answer 3

I would simply set the background in the windowResized function.
function windowResized() {
centerCanvas();
resizeCanvas(windowWidth,windowHeight)
background(255, 0, 200);
}

Answer 4

For an alternative method, you could use CSS to edit the dimensions using something similar to the following:
<style>
canvas {
width: 100%;
height: 100%;
}
</style>