TM1640 Matrix + ArrayBuffer first column of letter does not appear in scrolling text

Hello @allObjects,

I think I understood the idea of a large ArrayBuffer with the entire line of text and display only part of it. Unfortunately, I am not comfortable with ArrayBuffers nor dataView
The idea is to measure the size of my sentence written in a buffer and generate the correct size Arraybuffer once (between 20 and 60 characters), then go and copy the useful portion to display on the matrix.
Did i well understood?

I read on MDN that there was an arrayBuffer.slice (start, end) but on espruino, the function does not return an arrayBuffer but just an array so I remain skeptical about the solution.
Any help would be great for a starting point to explore.
regards

the basic writing program

const phrases = ["Sourire aux cons","Aquiescer aux injonctions d'un supérieur","Mourir de honte","Mourir d'envie","Sourire aux jolies femmes","s'endormir devant la télévision"]; //it contains more sentence

function ecris() {
  phrase = "À quoi bon, ";
  tirage = Math.floor(Math.random()*phrases.length)­;
  phrase += phrases[tirage].toLowerCase()+".";
  return phrase;
}
console.log(ecris());

a try as you said

let bitIndex = 0;
let phraseAB;
g = Graphics.createArrayBuffer(8,8,1);

const phrases = ["Sourire aux cons","Aquiescer aux injonctions d'un supérieur","Mourir de honte","Mourir d'envie","Sourire aux jolies femmes","s'endormir devant la télévision"];

function ecris() {
  phrase = "À quoi bon, ";
  tirage = Math.floor(Math.random()*phrases.length)­;
  phrase += phrases[tirage].toLowerCase()+".";
  const width = g.stringWidth(phrase);
  phraseAB = Graphics.createArrayBuffer(width,8,1);
  phraseAB.drawString(laPhrase, 0, 0);
  sendDatas();
}

function sendDatas() {
  g = phraseAB.slice(bitIndex, bitIndex+8);
  g.setContrast(7); /* val entre 0 et 7 - TM1640*/
  g.setRotation(2,true); // TM1640
  // mise à jour du display
  g.flip();
  bitIndex++;
  setTimeout(sendDatas, 50);
  // do it til the end of phraseAB + ecris() + reset bitIndex
}

Am i on the good way?

regards
é.