The Mobile Web - HTML5 on mobile devices

transcript

The Mobile Web - HTML5 on mobile devicesHTML5 User Group - AtlantaBy: Wesley Hales@wesleyhales

• Senior Developer at Red Hat

• W3C Member

• JSR 301/329 Rep.

• HTML5 User Group Founder

• html5rocks.com, DZone Refcard, and author of many other articles around the web.

Wesley Hales@wesleyhales

Mobile Web Apps Live (or DIE) by the UI

Top 5 Best Practices1) Use client side DBs instead of server round trips 2) Use CSS transitions instead of JavaScript animations (Enable hardware acceleration)3) Boost performance with JavaScript 1.6 (no more "for loops")4) Use cache manifests for live sites, not just offline apps5) HTML5 Form attributes and input styles (paceholder, pattern, etc...)

When working with HTML5

Device & Feature Detection

• MobileESP (server-side)

• Modernizr (client-side)

• CSS3 Media Queries

Device & Feature Detection

• Parsing the USER_AGENT

• WURFL APIs

Device Detection

WURFLWireless Universal Resource File

• Up to date list of all mobile devices

• Available as XML file

• Wrappers for most languages

• <html class="js canvas canvastext no-geolocation rgba hsla multiplebgs borderimage borderradius boxshadow opacity cssanimations csscolumns cssgradients cssreflections csstransforms csstransforms3d csstransitions video audio localstorage sessionstorage webworkers applicationcache fontface">

Modernizr

Feature Detection

• Adds classnames of available features to DOM

• Allows use of browser features with fallback options

• shiv & polyfills

Modernizr

Feature Detection

Feature Detection“Cascading” the detection:#nice { background: url(background-one.png) top left repeat-x; background: url(background-one.png) top left repeat-x, url(background-two.png) bottom left repeat-x;}

Using Modernizr:

#nice { background: url(background-one.png) top left repeat-x;}.multiplebgs #nice { background: url(background-one.png) top left repeat-x, url(background-two.png) bottom left repeat-x;}

The Mobile Web

Mobile Platforms

Mobile Frameworks

And many more...

Todays Focus

Mobile Basics

• Hardware Acceleration

• Page Transitions: Sliding, Flipping, and Rotating

• Fetching and Caching

• Network Detection

• Debugging & Profiling

Hardware Acceleration

• Page Layout

• Memory allocation (Compositing)

• Power Consumption

• Conflicts

Hardware AccelerationDemo

Hardware AccelerationUnderstanding Page Layout

Hardware AccelerationSliding and Staging

Hardware AccelerationBased on device

Hardware AccelerationCompositing Visuals

• Safari Command Line Flags

• Chrome about:flags

• Safari/WebKit Command Line Flags$> export CA_COLOR_OPAQUE=1$> export CA_LOG_MEMORY_USAGE=1$> /Applications/Safari.app/Contents/MacOS/Safari

Hardware AccelerationCompositing Visuals - WebKit CoreAnimation

• Chrome about:flags

Hardware AccelerationKeep In Mind

• Don’t composite every DOM element

• When you make use of the GPU, you’realso using the battery

• Beware of overlapping acceleration

DemoFetching and Caching

Fetching and Caching

• Pre-fetch content for smooth transitions

• Setup for offline capability

• Concurrent Ajax

Caching

appCache unlimited 10MB

Web Storage 5MB 5MB

by device

Fetching content and parsing the DOM

External page parsed via AJAX call:

Fetching and CachinglocalStorage used within the AJAX call:

innerHTML()

Douglas Crockford - Javascript The Good Parts

“If the HTML text contains a <script> tag or its equivalent, then an evil script will run. ..

Java Mobile Web Settings• Causes browser memory leaks

• You don’t get a reference to the element you just created

• Problems with some elements setting their innerHTML

• And it fails on iOS...

Not only is innerHTML() bad...

Java Mobile Web Settings

• Stops working randomly

• It’s a 4 year old problem in Safari

• there are hacks to workaround

• setTimeout(‘yuck’)

Beware of innerHTML on

Java Mobile Web Settings• get the xhr.responseText

• send it to an automatically generated HTML5 sandbox iframe

• pull from the iframe DOM and use document.adoptNode

The Solution

Java Mobile Web SettingsThe Solutionfunction getFrame() { var frame = document.getElementById("temp-frame"); if (!frame) { // create frame frame = document.createElement("iframe"); frame.setAttribute("id", "temp-frame"); frame.setAttribute("name", "temp-frame"); frame.setAttribute("seamless", ""); frame.setAttribute("sandbox", ""); frame.style.display = 'none'; document.documentElement.appendChild(frame); } return frame.contentDocument;}

Java Mobile Web SettingsThe Solution

var frame = getFrame();frame.write(responseText);

Java Mobile Web SettingsThe Solution

document.getElementById(elementId).appendChild(document.adoptNode(incomingElements));

Fetching and CachingRecap

• Get all fetchable links on the parent page

• Concurrently get the external pages

• Cache pages with localStorage

• Do not use innerHTML

• Write fetched content into iframe

• Place it into parent using adoptNode()

Network Detection and Handling

• Offline access through applicationCache

• Offline/Online events

• Content fetching based on network speed

Network Detection and Handling

applicationCache

appCache unlimited 10MB

by device

Offline AccessappCache Mime Mappings

<mime-mapping> <extension>appcache</extension> <mime-type>text/cache-manifest</mime-type></mime-mapping>

web.xml

Apache config

applicationCachedemo.appcache

applicationCachePage usage

Updating the cache

Offline & Online eventsevent listeners

Offline & Online eventsappCache error event

Fetching based on network speednavigator.connection (The Network Information API)

Fetching based on network speed

WIFI (Asynchronous) Request Timeline

Edge (Synchronous) Request Timeline

Questions?@wesleyhales

#atlhtml5

Note - All code and demos presented here will be available on October 4, 2011 www.html5rocks.com/en/mobile/optimization-and-performance.html

The Mobile Web - HTML5 on mobile devices

Technology