Offline Web Applications support in Opera Presto 2.12

W3C reference:
W3C Offline Web Applications

Opera Presto offers support for Offline Web Applications implementing the user interface for caching. This allows documents to communicate with each other regardless of their source domain, and is designed in a way which does not enable cross-site scripting attacks. See this demo.

SQL

The client-side SQL database in HTML5 enables structured data storage. The API to interact with this database is asynchronous which ensures that the user interface does not lock up.

Method Arguments Support
openDatabase()
  • database name
  • database version
  • display name
  • estimated size (in bytes)
 Yes
transaction()
  • transaction callback
  • error callback
  • success callback
 Yes
executeSQL()
  • SQL statement
  • arguments
  • SQL statement callback
  • SQL statement error callback
 Yes

Offline Application Caching APIs

The mechanism for ensuring Web applications are available even when the user is not connected to their network is the manifest attribute on the html element. The attribute takes a URI to a manifest, which specifies which files are to be cached.

Element Attribute and value Support
html manifest="cache-manifest" Yes

► HTML5 markup

<!DOCTYPE HTML>
<html manifest="cache-manifest">
...

► Example manifest file

This manifest file specifies several files to cache, and then specifies that server.cgi should never be cached.

CACHE MANIFEST
index.html
help.html
style/default.css
images/logo.png
images/backgound.png

NETWORK:
server.cgi

Related APIs

Item Description Support
onLine attribute on the Navigator object
  • Determines whether you are currently online.
  • Example: var online = navigator.onLine;
 Yes
online and offline events Indicates changes made to the onLine attribute. Yes
localStorage attribute
  • Enables simple synchronous storage access.
  • Example: localStorage["status"] = "Idling.";
 Yes

Documentation

Opera Help

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