Created
September 21, 2017 17:12
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scrolling captions
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body { | |
margin: 0; | |
padding: 0; | |
font-family: sans-serif; | |
background-color: rgba(0,0,0,0); | |
} | |
#transcriptContainer { | |
background-color: rgba(0,0,0,0.6); | |
width: 100%; | |
position: fixed; | |
bottom: 0px; | |
overflow: hidden; | |
clear: both; | |
} | |
#transcript { | |
color: white; | |
font-size: 18px; | |
position: absolute; | |
transform: translateY(0px); | |
width: 100%; | |
padding: 0 10px 0 10px; | |
-webkit-transition: transform .3s; | |
transition: transform .3s; | |
line-height: 1.5em; | |
} | |
#measure { | |
display: block; | |
} |
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<html> | |
<head> | |
<title>twitch a11y captions frontend</title> | |
<link rel="stylesheet" href="main.css"/> | |
</head> | |
<body> | |
<div id="transcriptContainer"> | |
<div id="transcript"> | |
<span id="measure">LOADING<br/>...</span> | |
</div> | |
</div> | |
<script src="viewer.js"></script> | |
</body> | |
</html> |
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const transcriptBox = document.getElementById('transcript'); | |
const measure = document.getElementById('measure'); | |
const tPadd = window.getComputedStyle(measure, null).getPropertyValue('height'); | |
const tPadding = Number(tPadd.substr(0, tPadd.length-2)); | |
// set height of the container dynamically | |
document.getElementById('transcriptContainer').style.height = tPadding + 'px'; | |
// cache current height of transcript box | |
let prevHeight = transcriptBox.clientHeight; | |
// reset content after measuring height | |
transcriptBox.innerHTML = ''; | |
// replaxce this with an on translation socket event | |
window.Twitch.ext.listen('broadcast',(target, contentType, message) => { | |
console.log('message!', message, target, contentType); | |
const parsedMessage = JSON.parse(message); | |
if (target === 'broadcast' && parsedMessage.type === 'caption') { | |
transcriptBox.innerHTML += `${parsedMessage.caption.toUpperCase()}<br/>`; | |
} | |
}); | |
// each time the transcript box receives new content, check if we need to scroll the text up | |
const observer = new MutationObserver((mutation) => { | |
const nextHeight = transcriptBox.clientHeight; | |
if (nextHeight > prevHeight) { | |
prevHeight = nextHeight; | |
transcriptBox.style.transform = `translateY(${tPadding - transcriptBox.clientHeight}px)`; | |
}; | |
}); | |
// start observing mutations | |
observer.observe(transcriptBox, {childList: true}); | |
// for testing | |
// const i = setInterval(() => {transcript.innerHTML += "ANOTHER CAPTION HAS ARRIVED "}, 500); |
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