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Revision as of 12:55, 20 October 2011 by isalento (Talk | contribs)

Porting between Symbian Web Runtime and Nokia Asha Web Apps

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This article explains the differences between Symbian Web Runtime and Series 40 Web Apps, and the changes you need to make to port between the two formats.

Contents

Overview

The Symbian Web Runtime (WRT) is the official Web Runtime offering by Nokia for Symbian devices. Series 40 Web Apps are W3C compliant widgets than run on Nokia Series 40 devices.

The two types of web apps are actually quite similar; they are both constructed from traditional web resources written in html, javascript and CSS, have a registration file, and are packaged in zip files. While the execution model is quite different, from a developer point of view the packaging and programming is much the same. As a result developers can port between the two types with little effort.

File name

Both types of web apps are packaged in a zip file containing much the same files. The main change in this area when porting is to use the correct file extension:

  • Series 40 Web App has extension .wgt
  • Symbian Web Runtime has extension .wgz

It is also necessary to change the registration file, as discussed below.

Registration file

Symbian and Series 40 Web Apps use similar but different registration files:

  • Symbian Web Runtime: info.plist
  • Series 40 Web Apps: config.xml

It is relatively easy to rename the file and convert the needed tags. An example is given below.

If the info.plist file of a Symbian Widget is

<xmlversion="1.0"encoding="UTF8">
<DOCTYPEplistPUBLIC "//Nokia//DTDPLIST1.0//EN" 
"http://www.nokia.com/NOKIA_COM_1/DTDs/plist-1.0.dtd">
<plist version="1.0"><dict>
<key>DisplayName</key>
<string>A Widget</string>
<key>Identifier</key>
<string>xxx.xxx.widget</string>
<key>MainHTML</key>
<string>AWidget.html</string>
</dict></plist>

and the config.xml of a S40 Web App must be altered as

<?xml version="1.0" encoding="UTF-8"?>
<widget xmlns=" http://www.w3.org/ns/widgets" height="200" 
id="http://nokia.com/simplemaps" version="0.1.0" 
viewmodes="windowed fullscreen" width="200">
    <name short="AW">A Widget</name>
    ...
    <icon src="icon.png"/>
    <content src="AWidget.html"/>
    ...
</widget>

If need be, developers can add other tags such as

<description>...</description>

<author email=" mailbox@email.com" 
href=" http://www.website.com/">
Corporation
</author>

<license>...</license>

etc.

Size of UI elements

The typical screen size of Series 40 device (240 x 320 px) is different from typical Symbian touch devices (640 x 360 px), so the application must change the width and height of some items in html or css in order to optimise the UI. This includes text, images and videos.

Comparison of recommended dimensions of a button on common devices running Symbian WRT and Series 40 Web App.

Device Physical size Pixel size
Nokia N8-00 (Symbian^3) 7 x 7 mm 60 x 60 px
Nokia X3-02 (Series 40) 6.1 x 6.1 mm 40 x 40 px


For more information see Series 40 Web App UX Guidelines.

Media file size

Series 40 devices are typically are less powerful than Symbian devices. In order to run applications at acceptable speeds, it may be necessary to use smaller media files, including images, audio and video.


Application structure

The most difficult part on porting a Symbian Web Runtime widget to Series 40 Web App is taking mobile web library (MWL) into use in a Web App. Symbian Web Runtime allows JavaScript to be executed on a device and thus you can e.g. switch element contents on the fly without user noticing. The situation is different in the Series 40 Web App, as all of the JavaScript is executed on a proxy server. Using JavaScript to switch elements contents in a Web App will result in a round trip to server and back. This is where MWL comes to help. What you should do is to generate most of the HTML ready in the server side using JavaScript and then use MWL methods to switch CSS properties to hide and show element contents. Methods provided by the MWL are only scripts that are executed on a device in a Series 40 Web Apps.

Application icons

Series 40 Web Apps have one more icon compared to Symbian WRT widget. They both share the main icon defined in the info.plist or config.xml. This icon is used in the application menus. In addition a favicon is needed in Series 40 Web Apps. The favicon is used in Nokia Browser history and favorites listing. The favicon is a 16x16 px pixel image. To include favicon add following line to index.html head-section:

<link rel="icon" type="image/png" href="favicon.png"/>


Storing Data

Series 40 Web Apps supports preferences attribute to store key-value pairs as defined in the W3C Widget interface specification. Preference should be defined in config.xml before using.

Config.xml: <preference name="key" value=""/>

JavaScript:

var val = widget.preferences.getItem("key");  
widget.preferences.setItem("key","value");
//or alternative way to access preferences
var val = widget.preferences["key"];
widget.preferences["key"] = "value”

Symbian WRT equivalent would be:

var val = widget.preferenceForKey("key");  
widget.setPreferenceForKey("value", "key");


Localization

Symbian WRT uses special “xx.lproj” folders for localization purposes. For example \MyWidget\fi.lproj\. Series 40 Web apps uses supports localization in compliance with the W3C widget specification. Basically it is folder based localization as well, but the folder structure is bit different. In a W3C widget localization folder is placed in the root of the widget folder and must be named “locales” (case sensitive). Localized files are placed inside subfolders of the locales folder. The names of subfolders must comply with values derived from the IANA Language Subtag Registry such as “fr”, ”fi” and “en-US”. E.g. \locales\fi-Fi\

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