Flickering Problem - Screen Buffering but also turn off Display

Okay, now I mixed up a sample of your two suggestions. But now I have heavy flickering again:

require("FontDylex7x13").add(Graphics);

let fnt = 'Dylex7x13';

let pal2color = new Uint16Array([0x0000,0xffff,0x07ff,0xC618],0,2);
let buf = Graphics.createArrayBuffer(240,192,2,{msb:true});

const pad = (number, length) => {
    let str = '' + number;
    while (str.length < length) {
        str = '0' + str;
    }

    return str;
};

const printClock = ts => {
  if(ts === undefined) {
    ts = new Date();
  }
  
  h = ts.getHours();
  m = ts.getMinutes();
  s = ts.getSeconds();
  
  return `${pad(h,2)}:${pad(m,2)}:${pad(s,2)}`;
};

const renderMain = () => {
  g.clear();

  buf.clear();
  buf.setColor(1);
  buf.setFontAlign(0,-1);
  buf.setFont(fnt,5);
  buf.drawLine(0,0,240,0);
  buf.drawString("Hello",120,0);

  buf.setFont(fnt,3);
  buf.setColor(2);
  buf.drawString(printClock(),120,60);

  g.drawImage({width:buf.getWidth(),height:buf.getHeight(),bpp:2,buffer:buf.buffer,palette:pal2color},0,48);
};

const ticker = () => {
  renderMain();
  // g.flip();
};

setInterval(ticker,1000);

I guess I have still a big misunderstanding of the usage of rendering with the Bangle.js.