codebits 2009 HTML5 JS APIs

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HTML5 JavaScript APIs
codebits.eu 2009

HTML5

Web Forms Offline History API

Audio/Video Drag & Drop Undo

Canvas Editable X-Domain
Messaging

“HTML5”
Web Forms Offline History API

Audio/Video Drag & Drop Undo

Canvas Editable X-Domain
Messaging
Storage Geolocation

Databases querySelector Workers

Sockets Server Events

“HTML5”

•Video •Storage
•Canvas •Workers
•Offline

http://html5demos.com/video

if (video.paused) {
if (video.ended) {
video.currentTime = 0;
}
video.play();
} else {
video.pause();
}

addEvent(
video,
'timeupdate',
function () {
positon.innerHTML =
➥ asTime(this.currentTime);
}
);


•play(), pause()
•paused, ended, currentTime
•canplay, timeupdate, ended
•and a bunch more.

•Bugs tend to be rather
quiet...shhh...

•Firefox needs the right
content-type

•
Safari will plough ahead

http://open.bbc.co.uk/rad/demos/html5/rdtv/episode2/

<!DOCTYPE html>
<html>
<head>
<title>Canvas</title>
</head>
<body>
<canvas></canvas>
</body>
</html>

var ctx = canvas.getContext('2d');


// Create radial gradient
var grad = ctx.createRadialGradient(0,0,0,0,0,600);


grad.addColorStop(0, '#E4E4E4');
grad.addColorStop(1, '#000');



// assign gradients to fill
ctx.fillStyle = grad;



// assign gradients to fill

// draw 600x600 fill
ctx.fillRect(0,0,600,600);

http://html5demos.com/canvas-grad

body.onmousemove = function (event) {
var width = window.innerWidth,
height = window.innerHeight,
x = event.clientX,
y = event.clientY,
rx = 600 * x / width,
ry = 600 * y / width;

var xc = parseInt(256 * x / width);
var yc = parseInt(256 * y / height);

grad = ctx.createRadialGradient(rx, ry, 0, rx, ry, 600);
grad.addColorStop(1, 'rgb('+xc+','+(255-xc)+','+yc+')');

};


height = window.innerHeight, Caclulate from
x = event.clientX, the mouse the
y = event.clientY,
rx = 600 * x / width, radius and
ry = 600 * y / width; colours


};


x = event.clientX,
y = event.clientY,
rx = 600 * x / width,
ry = 600 * y / width;
Re-render the
var xc = gradient
parseInt(256 * x / width);


};


x = event.clientX,
y = event.clientY,
rx = 600 * x / width,
ry = 600 * y / width;

Set 0, rx, ry, 600);
grad = ctx.createRadialGradient(rx, ry,
the new ﬁll
grad.addColorStop(0, '#000'); style and reﬁll -
the browser

handles the hard
ctx.fillRect(0,0,600,600); work
};


canvas.toDataURL("image/png");

canvas.toDataURL("image/png");
data:image/
png;base64,iVBORw0KGgoAAAANSUhEUgAAAMgAAADICAYAAACtWK6eAAAFxUlEQVR4Ae3dQW5jORAEUXvQ97+yez
CzNQpNyPwdIp+XJkVlRTKgheGvz69/fz78IIDAtwT+
+fa3fokAAv8RIIiLgMBAgCADHEsIEMQdQGAgQJABjiUECOIOIDAQIMgAxxICBHEHEBgIEGSAYwkBgrgDCAwECDLAs
YQAQdwBBAYCBBngWEKAIO4AAgMBggxwLCFAEHcAgYEAQQY4lhAgiDuAwECAIAMcSwj8+nEEn58/
fuQfHehf6/8Ik01rBHyCrPGy+zICBLmscOOuESDIGi+7LyNAkMsKN
data:image/png;base64,...
+4aAYKs8bL7MgIEuaxw464RIMgaL7svI0CQywo37hoBgqzxsvsyAgS5rHDjrhEgyBovuy8jQJDLCjfuGgGCrPGy
+zICBLmscOOuESDIGi+7LyNAkMsKN
+4aAYKs8bL7MgIEuaxw464RIMgaL7svI0CQywo37hoBgqzxsvsyAgS5rHDjrhEgyBovuy8jQJDLCjfuGgGCrPGy
+zICBLmscOOuESDIGi+7LyNAkMsKN+4aAYKs8bL7MgI//3R3T1m/
7AqdPa5PkLP7Nd2LBAjyIkAvP5sAQc7u13QvEiDIiwC9/
GwCBDm7X9O9SIAgLwL08rMJEOTsfk33IgGCvAjQy88mQJCz+zXdiwR+/i/pLwba/fLPj7/zPe5fH1+7R3P+BgI
+QTZAdeQ5BAhyTpcm2UCAIBugOvIcAgQ5p0uTbCBAkA1QHXkOAYKc06VJNhAgyAaojjyHAEHO6dIkGwgQZANUR55D
gCDndGmSDQQIsgGqI88hQJBzujTJBgIE2QDVkecQIMg5XZpkAwGCbIDqyHMIEOScLk2ygQBBNkB15DkECHJOlybZQ
IAgG6A68hwCBDmnS5NsIECQDVAdeQ4BgpzTpUk2ECDIBqiOPIcAQc7p0iQbCBBkA1RHnkOAIOd0aZINBAiyAaojzy
FAkHO6NMkGAgTZANWR5xC47ununrJ+zuV9YhKfIE9Q9h5vS4Agb1ud4E8QIMgTlL3H2xIgyNtWJ/
gTBAjyBGXv8bYECPK21Qn+BAGCPEHZe7wtAYK8bXWCP0GAIE9Q9h5vS+C6v6TXm/r8O1/j/vHla9y/vRo
+Qb7F4pcI/E
+AIG4CAgMBggxwLCFAEHcAgYEAQQY4lhAgiDuAwECAIAMcSwgQxB1AYCBAkAGOJQQI4g4gMBAgyADHEgIEcQcQGAg
QZIBjCQGCuAMIDAQIMsCxhABB3AEEBgIEGeBYQoAg7gACAwGCDHAsIUAQdwCBgQBBBjiWECCIO4DAQIAgAxxLCBDE
HUBgIECQAY4lBAjiDiAwECDIAMcSAgRxBxAYCBBkgGMJAU93j90BT1lvFeITpNWHNDECBIkVIk6LAEFafUgTI0CQW
CHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBI
kVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0C
QWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDEC
BIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI
0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHND
ECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUg
TI0CQWCHitAgQpNWHNDECBIkVIk6LAEFafUgTI0CQWCHitAgQpNWHNDECvwHnaxGSkEUPVAAAAABJRU5ErkJggg==

Canvas
+
drawImage
+
Video
=

http://blog.mozbox.org/post/2009/04/12/Firefox-35%3A-a-new-experiment-with-Canvas-Video

ctx.translate(canvas.width/2, canvas.height/2);
ctx.scale(-1, 1);
ctx.translate(-canvas.width/2, -canvas.height/2);

ctx.drawImage(
video, 0, 0,
video.width,
video.height,
0, 0,
canvas.width,
canvas.height);

http://html5demos.com/video-canvas

ctx.getImageData(0, 0, w, h);

0 1 2 3

0 r g b a

1 r g b a

... r g b a

pixels.data[i * 4 + 0];

0 1 2 3

0 r g b a

1 r g b a

... r g b a


0 1 2 3

0 r g b a

1 r g b a

... r g b a

for (i = 0; i < pixels.data.length / 4; i++) {
totals.r += pixels.data[i * 4 + 0]; // r
totals.g += pixels.data[i * 4 + 1]; // g
totals.b += pixels.data[i * 4 + 2]; // b
}

var r = parseInt(totals.r / (w*h)),
g = parseInt(totals.g / (w*h)),
b = parseInt(totals.b / (w*h)),
rgb = [r, g, b].join(',');

Storage

window based sessionStorage
localStorage

Storage

window based sessionStorage
domain based localStorage

Storage
var ss = sessionStorage;

ss.setItem('key', 12);

alert( ss.getItem('key') );

Storage
var ss = sessionStorage;

ss.key = 12;

alert( ss.key );

Values set with
expando syntax & that
overwrite methods:
are removed on reload

...but not removed
using setItem

// Safari debugger broken:
ss.setItem('key', 12);

Storage
• setItem(key, value)
• getItem(key)
• removeItem(key)
• key(index)
• clear()

Values are strings

Work around: JSON
(and http://www.json.org/json2.js)

Tweet stream
demo using
localStorage

•"Threads"
•Native or via Gears
•Sandboxed
•Debugging can be tricky

http://html5demos.com/worker

•importScripts

• postMessage

• onmessage

• onconnect

app.html
var w = new Worker('worker.js');

w.onmessage = function (event) {
alert("msg: " + event.data);
};

w.postMessage('run');

worker.js
onmessage = function (event) {
if (event.data == 'run') {
run();
}
};

function run() {
var data = doCrazyNumberCrunch();
postMessage(data);
}

Can dos

•Spawn more workers
•setTimeout/Interval & clear
•Access navigator
•Error handling onerror
•XHR (though responseXML is null)

Of ine Apps

•Application cache / manifest
•Events: of ine, online
•navigator.onLine property

http://icanhaz.com/rubiks

Using a Manifest
<!DOCTYPE html>
<html manifest="my.manifest">
<body>

</body>
</html>

my.manifest
CACHE MANIFEST
app.html
css/style.css
js/app.js
#version 13

The Manifest

1. Serve as text/manifest, by
adding to mime.types:

text/cache-manifest manifest

The Manifest

2. First line must be:

CACHE MANIFEST

The Manifest

3. Including page is
implicitly included in the
cache.

The Manifest

4. Two futher namespaces:
NETWORK & FALLBACK

FALLBACK:
/ offline.html

The Manifest

5. Include some versioning
to cache bust your
manifest

# version 16

Browser: I have a
Browser: request Server: serve all manifest, cache
assets

Browser:
Server: serve
applicationCache Browser: reload
manifest assets
updated

Browser: only
Browser: serve Server: 304 Not
request manifest
locally Modified
file

Browser: I have a
Problem:
Browser: request Server: serve all manifest, cache
assets
Change of content
requires 2 refreshes
Server: serve
Browser:
applicationCache Browser: reload
manifest assets
updated

Browser: only
Browser: serve Server: 304 Not
request manifest
locally Modified
file

applicationCache.onUpdateReady =
function () {
applicationCache.swapCache();
notice('reload');
};

window.onOnline =
function () {
// fire an update to the cache
applicationCache.update();
};

Attributes: data-*, itemProp,
sandbox (on iframes)

<progress> Microdata API,
<meter> datagrid, XHR2 &
<datalist> upload progress
<ruby>
querySelector
Drag & Drop,
History manager ARIA overlap

http://www.whatwg.org/html5/

http://tr.im/whatwg_complete

irc://irc.freenode.net/#whatwg

Remy
Sharp
@rem

icnhz.com/rs_talks
icnhz.com/rs_codebits
html5demos.com

The Dizzy HTML5 cat

codebits 2009 HTML5 JS APIs

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