Example of a simple drawing machine

telegraphic_style_line_partition.pde

// renaud.jean-francois(arobas)uqam(point)ca
// Syntaxe Processing version 3.3.7
// mercredi, 9 mai 2018

// Press spacebar to draw white lines segment while caret is moving.

color c = color(40);
int posX, posY;
int stepLength = 2;
int margin = 50;

void setup() {
  size(600, 600);
  background(0);
  noStroke();
  posX = margin;
  posY = margin;
  rectMode(CENTER);
}

void draw() {
  //background(0); // keep uncommented to leave a trace of the moving rectangle

  posX += stepLength; // moving forward
  
  if (posX >= width-margin) {
    posX = margin;
    posY+= 50;
  }
  if (posY > height-margin) {
    background(0); // arrived at bottom, erase all lines
    posY = margin; // move back to top
  }

  fill(c);
  rect(posX, posY, stepLength+1, 4);
}

void keyPressed() {
  if (key==' ') {
    c = color(255);
  }
}

void keyReleased() {
  c = color(40);
}

Example of render :