can't save preferances from injected script

Hi, I need to save information to a local file, I tried to do it thought of saving extension's settings , but I can not correctly call the save function, through the injected script. please help ...
P.S. Sorry for my bad english

There is no way to save to a local file. You can of course load and save preferences with the widget.preferences object. widget.preferences is available in the background script, popups, extension pages and injected scripts.

Of course, from my experience with using widget.preferences in injected scripts, it doesn't seem to work in private tabs. If you need your extension to work in private tabs, you will have to use opera.extension.postMessage from the injected script to send data back to the background script, then save the data to widget.preferences from the background script.

I tried to "use opera.extension.postMessage from the injected script to send data back to the background script",
but background script cant read my message...

I did it so:
//injected
window.opera.postError('Sending message to background.js');
opera.extension.postMessage('LOAD');

//////////////////background
window.addEventListener('DOMContentLoaded', function() {

// Listen for messages from the UserJS.
opera.extension.onmessage = function(event){
window.opera.postError('Received message from base.js');
if (event.data === 'LOAD') {
button.badge.textContent = parseInt(button.badge.textContent) + 1;
window.alert("test");
}
}
}, false);

one more:
//injected
opera.extension.bgProcess.SavePrefs(mailz);

//bckgnd
function SavePrefs()
{
something to do
}

and more:
//bckgnd

window.addEventListener("load", setupConnection, false);

function setupConnection(){
opera.extension.onconnect = function(event){
opera.postError("sent message to injected script");
}
opera.extension.onmessage = function(event){
opera.postError("This is what I got from injected script: "+event.data);
}

//injected
opera.extension.onmessage = function(event){
// Get content of incoming message.
alert("test");
var message = event.data;
window.opera.postError("background process sent: " + message);

// Replies back to background process.
var reply = "background process's message only had " + (message ? message.length : 0) + " characters.";
event.source.postMessage(reply);
};

I don't see why the first example there wouldn't work, except that window.alert() doesn't do anything in the background process.

As for the second, injected scripts cannot use opera.extension.bgProcess (see the article on bgProcess). What you want to do is something like this:

//background script

addEventListener('load', function() {
	
	// Listen for messages
	opera.extension.onmessage = function(e) {
		switch (e.data.action) {
			case 'save prefs':
				savePrefs(e.data.prefs);
				break;
				
			default: break;
		}
	}
		
	// Saves all the values in the object "prefs" to widget.preferences
	function savePrefs(prefs) {
		for (var name in prefs) {
			if (prefs.hasOwnProperty(name)) {
				widget.preferences[name] = prefs[name];
				console.log('saved: ' + name + ' = ' + prefs[name]);
			}
		}
	}

}, false);


//injected script

// Send a request to save preferences
opera.extension.postMessage({
	action: 'save prefs',
	prefs: {
		some_preference: 'some preference value',
		color: '#FF0000',
		rainbows: 2,
		narwhals: 1,
	},
});

You can send and receive entire objects as well as strings, which makes messaging much easier.


Also, on the third example, you are never sending a message from the background script to the injected script, so it will never respond. This should send a message when the script connects:

opera.extension.onconnect = function(e){
	opera.postError("sent message to injected script");
	e.source.postMessage('some message');
}

There is a bug in current versions of Opera though where onconnect may not fire for every page when you start Opera and Opera restores a session with a large number of tabs.