A11y basics - 9. Screen Reader live region

index.html

<h1>Golf Scorecard</h1>

<p class="score">
  You are at par
</p>

<div class="button-container">
  <button data-offset="-1"
          aria-labelledby="abc">
    ▼
  </button>
  <span class="tooltip"
        id="abc"
        aria-hidden="true">
    Lower score
  </span>
</div>

<div class="button-container">
  <div class="button"
       data-offset="1"
       tabindex="0"
       role="button"
       aria-labelledby="def">
    ▲
  </div>
  <span class="tooltip"
        id="def"
        aria-hidden="true">
    Increase score
  </span>
</div>

<footer>
  Triggering the button shouldn't have scrolled the page!
</footer>

main.dart

import 'dart:html';

final buttons = querySelectorAll('.button,button');
final customButton = querySelector('.button')!;
final scoreEl = querySelector('.score')!;
var score = 0;

void main() {
  buttons.onClick.listen(updateScore);
  buttons.onMouseUp.listen(blur);

  customButton.onKeyUp.listen(handleOnKeyUp);
  customButton.onKeyDown.listen(handleOnKeyDown);
}

void handleOnKeyUp(KeyboardEvent event) {
  var key = event.which ?? event.keyCode;

  if (key == KeyCode.ENTER || key == KeyCode.SPACE) {
    updateScore(event);
  }
}

void handleOnKeyDown(KeyboardEvent event) {
  var key = event.which ?? event.keyCode;

  if (key == KeyCode.SPACE) {
    event.preventDefault();
  }
}

void updateScore(Event event) {
  score += offset(event.target as HtmlElement);
  scoreEl.text = scoreText();
}

int offset(HtmlElement element) =>
    int.parse(element.attributes['data-offset']!);

String scoreText() {
  if (score > 0) return 'You are $score above par';
  if (score == 0) return 'You are at par';
  return 'You are ${score.abs()} below par';
}

void blur(MouseEvent event) {
  (event.target as HtmlElement).blur();
}

styles.css

body {
  background: #202124;
  color: #FFF;
  font-family: "Google Sans",Roboto,Arial,sans-serif;
  font-size: 14px;
  text-align: center;
}

button,
.button {
  background: #8AB4F8;
  color: #202124;
  font-size: 14px;
  font-weight: 500;
  height: 36px;
  min-width: 36px;
  padding: 0 23px;
  margin: 16px 4px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 0;
  border-radius: 4px;
  font-family: inherit;
  box-sizing: border-box;
}

button:hover,
.button:hover {
  background: #D2E3FC;
  cursor: pointer;
  user-select: none;
}

button:focus,
.button:focus {
  background: #D2E3FC;		
  outline: 0;
  box-shadow: 0 0 0 5px rgba(255,255,255, 0.3);
}

p {
  font-size: 18px;
}

.score {
  color: #AECBFA;
  color: #FDE293;
}

.button-container {
  display: inline-block;
  position: relative;
}

.tooltip {
  position: absolute;
  pointer-events: none;
  background: #FFF;
  color: black;
  padding: 4px 8px;
  border-radius: 4px;
  top: -5px;
  left: 50%;
  transform: translate(-50%, -50%);
  white-space: nowrap;
  opacity: 0;
}
.tooltip:after {
  content: '';
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -8px;
  width: 0;
  height: 0;
  border: 8px solid transparent;
  border-top-color: #FFF;
}

button:hover + .tooltip,
.button:hover + .tooltip,
button:focus + .tooltip,
.button:focus + .tooltip {
  animation: 1s ease 0s normal forwards 1 fadein;
  opacity: 1;
}

button:focus + .tooltip,
.button:focus + .tooltip {
  animation-duration: .3s;
}

@keyframes fadein{
  0% { opacity:0; }
  80% { opacity:0; }
  100% { opacity:1; }
}

footer {
  background: #F28B82;
  color: #202124;
  font-size: 24px;
  display: block;
  padding: 16px 32px;
  margin: 550px auto 32px;
  border-radius: 8px;
  max-width: 80%;
}