Windows Phone 7

Windows Phone 7: how to reset the idle detection countdown

Windows Phone 7 like every other phone OS turns off the screen after a period of inactivity. This is not a problem most of the time because any user activity (namely finger interactions on the screen) resets the countdown, so if you are using an application the screen saver will not get in the way. However there are some particular cases where it is useful to disable the idle detection, for example in games or apps that require long reading (or watching). In that case you can completely disable idle detection:

PhoneApplicationService.Current.UserIdleDetectionMode =

Keep in mind that this disables the “screen saver” at all, so be careful because you could drain the poor user’s battery if you do it without valid reason.

There is another more interesting case, though: suppose your app uses the accelerometer as its main user input. In this case there won’t be any user activity to trigger a countdown reset, but disabling it at all also doesn’t look like the best idea (what if the user puts the phone on the table to go grab a beer?).

The best in this case would be to reset the count-down when a movement is detected, i.e. treating accelerometer events like screen user input. How to do this?

The answer is extremely simple: you can just disable the IdleDetection and re-enable it again. This will reset the count-down. One little caveat: you cannot re-enable it immediately after having disabled it, the OS is smart enough not to be fooled and will ignore your two commands. You’ll have to wait a short while before re-enabling idle detection.

Here is an example: when I get a new reading from the accelerometer (I’m using the AccelerometerHelper) I check if there has been a large enough movement and in that case I disable the idle detection. Otherwise I enable it –this effectively resets the countdown every time the movement goes above a given threshold. Keep in mind that the accelerometer fires 50 times per second, that’s why I used a bool field to avoid unnecessary calls to the system setting. I’m not sure this prevents an actual performance loss, but it would be worth it to experiment and measure a little if you are using this technique in your apps.

double _currentValue;
bool _screenSaverEnabled = true;

private void OnAccelerometerHelperReadingChanged(object sender, AccelerometerHelperReadingEventArgs e)
    Dispatcher.BeginInvoke(() =>
            // you'll have something more useful in your app
            computedValue = e.OptimallyFilteredAcceleration.X;

            var delta = Math.Abs(computedValue - _currentValue);
            if (_screenSaverEnabled)
                if (delta > SOME_ARBITRARY_THRESOLD)
                    _screenSaverEnabled = false;
                    PhoneApplicationService.Current.UserIdleDetectionMode = IdleDetectionMode.Disabled;
                    Debug.WriteLine("Screen saver disabled");
                _screenSaverEnabled = true;
                PhoneApplicationService.Current.UserIdleDetectionMode = IdleDetectionMode.Enabled;
                Debug.WriteLine("Screen saver enabled");
            _currentValue = computedValue;

Happy coding!

WP7 icons quick and undirty

An unexpectedly time consuming part of Windows Phone 7 development are icons. Developers often don’t put much care into icons, and they are wrong. Your app is listed in the marketplace with an icon and most users just skip the crappy ones. If you make a bad icon most users won’t even read what the application is about, let alone download and install it.

That said, as a developer with some occasional design inspirations I found Expression Blend to be the perfect tool to generate WP7 graphics. The simple, minimalist style of WP7 icons just fits well with Blend and XAML in general.  Pro designers will probably be better off with specific graphic tools, but to me it’s just easier and faster to “program” my icons in Blend. I’ve had some decent results to support this approach but of course YMMV (the smile below is a placeholder and should be judged as such :-) ).


The main issue in creating the graphics with Blend is that you spend a lot of time cropping pictures to the correct size. That’s why I built myself a raw tool that is now decent enough to share with the world. It’s really raw, but it does the job. In fact it’s nothing more than a Blend/VS solution with correctly sized canvas and the ability to export all the images in one shot. The code is horrible and all, but it saved me a lot of time.



The Windows Phone 7 marketplace requires you to create several icons in different sizes. Don’t take this as an unnecessary hassle, it is in fact an opportunity: it means you can create a pixel-perfect image for every size. Do not create an image and just resize it to each size. There are good reasons against this:

1. The tile image is not a simple icon. It will be shown on the main phone page and includes at least the application name. That’s why your image must have an offset to take this into account. My solution overlays the system settings icon, so that you can check if your logo is correctly centered. If your icons are full-width you can ignore this.


2. You can (and should) use a different detail level for every size. A good looking 173×173 icon may look like an undefined mass of blurry pixels when resized to 62×62. Just keep the general theme and image consistent.

3. Straight lines will become anti-aliased and look blurry when you resize them (in XAML when you use a viewbox). It’s simple: the width of a line when stretched could become a non-integer value (for ex. 3.5 pixels) and will look blurry. If you have a different image for every size you have full control and can make one-pixel changes to avoid this effect. Look at this example: it may not look obvious but on a close look you’ll see that the left picture is not as well defined as the right one. On the phone, the difference is even more obvious.



Usage is simple: open the solution in Blend 4 or Visual Studio 2010 (it’s a WPF application), delete the placeholder smile and put your graphics in its place. Run the application and hit the export button to save the images. Tip: use resources for colors, shapes, etc. so that you can change them in one shot.
Enough said: download WP7IconBuddy and use it at your own risk. I’d love to hear some feedback.

Simple Error Reporting on WP7 RE-REDUX

If you haven’t read Rudi Grobler’s Simple Error Reporting on WP7 and Simple Error Reporting on WP7 Redux, please go read them now. Basically it’s about reporting errors at runtime from a Windows Phone 7 application. I always incorporate this kind of functionality in my applications (not only on Windows Phone) and it has proven to be very useful in these years.

While Rudi’s implementation uses the EmailComposeTask to send an error report, I do it in a slightly different and by submitting the report as http POST to a web page that then sends the email. This way the process is entirely silent and nothing is shown to the user (except the prompt). My reasoning is that the less steps she has to perform, the more likely she is to send the report.

In order to use this method you’ll need some server, but nothing fancy is required. I suspect you already have something adequate in place (for example the one hosting your blog).

Client Side

This is the code I put on the phone:

public void Application_UnhandledException(object sender, ApplicationUnhandledExceptionEventArgs e)
    if (MessageBoxResult.OK != MessageBox.Show("We encountered a problem and need to close. Would you like to tell us?",
                                "Oh no!",

        var subj = e.ExceptionObject.Message;
        var body = new StringBuilder("Stacktrace:");

        var wc = new WebClient();
        wc.Headers[HttpRequestHeader.UserAgent] = "Mozilla/5.0";
        wc.Headers[HttpRequestHeader.ContentType] = "application/x-www-form-urlencoded";
        wc.UploadStringCompleted += (s, er) => MessageBox.Show("Thanks for your report!");
            new Uri(""),
    catch (WebException)
        MessageBox.Show("The report could not be sent (no network available?).");

Don’t forget to replace the messages with something better. You can add whatever you like to the report, just keep in mind that if you query DeviceExtendedProperties to get the peak memory usage, your app will need the Identity Capability (which looks a bit scary in the marketplace in my opinion).

Server Side

On the server side you can do pretty much anything: you could insert the report in a database or fill in a ticket in your bug tracker. I keep it simple and send an email (please set up a dedicated address if you do this). My server is rather fast but only supports PHP, so that’s what I use:

	if (isset($_POST["subject"]) &amp;amp;amp;amp;amp;amp;&amp;amp;amp;amp;amp;amp; isset($_POST["body"]))
		mail("", "wp7 app bug report: ".$_POST["subject"], $_POST["body"]);
		echo "ok.";
		echo "missing parameters.";

Please notice that this is not the most secure practice in the world as someone could sniff the traffic generated by your app and exploit this page to flood your mailbox. A simple solution is to limit this page to send a maximum of say 10 emails/hour. Anyways if you are getting a much larger number of legit hits, chances are that the exception is always the same one (or your app is really buggy and you deserve to be flooded :-P).

Is this method better than using the EmailComposeTask? I don’t know, but it’s just another option at your disposal.

Windows Phone 7: internet tethering with Swisscom (now!)

While internet to USB tethering is not officially supported by Windows Phone 7 until the promised Q1 2011 update, it seems that devices and OS already support it. Probably Microsoft has not yet reached an agreement with some carriers and their idiotic pricing plans, so the feature is just hidden.

The good news is that if you own a Samsung or an LG you can already enable it without waiting for the update: just follow these direction. The only problem is that those settings apply to Orange France.

Being Swiss and having a Swisscom subscription (thankfully they allow tethering without any restriction) I had to play a bit but in the end I found out that these settings work fine with Swisscom:

Modem configuration: +cgdcont=1,”IP”,””
Call number: *99#***1# (instead of *99#)


An error occurred while accessing IsolatedStorage.

While developing a Silverlight Windows Phone 7 app I ran into this problem: when the application closes, an internal  IsolatedStorageException is raised:

An error occurred while accessing IsolatedStorage.
   at System.IO.IsolatedStorage.IsolatedStorageSecurityState.EnsureState()
   at System.IO.IsolatedStorage.IsolatedStorageFile.get_AvailableFreeSpace()
   at System.IO.IsolatedStorage.IsolatedStorageSettings.Save()
   at System.IO.IsolatedStorage.IsolatedStorageSettings.TrySave()
   at System.IO.IsolatedStorage.IsolatedStorageSettings.SaveAllSettings()
   at MS.Internal.FrameworkCallbacks.ShutdownAllPeers()

IsolatedStorageSettings seemed to be the cause of the problem. Very weird because I wasn’t even using it! Just adding this line in my App class would cause the problem:

private System.IO.IsolatedStorage.IsolatedStorageSettings appSettings = System.IO.IsolatedStorage.IsolatedStorageSettings.ApplicationSettings;

Now I created a new, empty, project (Windows Phone Application) and inserted that line. Weird: no problems.
I thought there was something wrong in my solution, so I made a backup copy and started removing stuff. At some point my solution was identical to the default one (except for the IsolatedStorageSettings line and the project’s GUID). Not “almost identical”, but completely, literally identical, i.e. WinMerge found no difference except the two mentioned. And of course the default solution worked while mine gave the IsolatedStorageException on shutdown.

I honestly haven’t understood the cause of the problem, but at least I’ve found a solution: change the project GUID:

  • close Visual Studio
  • open your solution’s .sln file with notepad
  • replace a couple of numbers in the Project(“{<your GUID here>}”)
  • open the .csproj with notepad
  • apply the same change to the GUID (in the first line after the comment and in all the Build Configurations)
  • Re-open your solution with Visual Studio and the problem is gone.

I suspect the problem has something to do with the emulator but I haven’t had a chance to try a real device yet. I hope I saved you an evening of head scratching.

Windows Phone 7 Marketplace subscription for Swiss individuals

Lately I’ve been busy coding stuff for Windows Phone 7 –really fun! If you are a Swiss individual (i.e. you are not developing your apps for a company) then joining the Marketplace is not very straightforward. If you reside in another non-U.S. country you may as well read this post, I suppose you will only have to make minor changes to the procedure.

Sascha Corti of Microsoft Switzerland has provided a great walkthrough, but I whish to add a couple of things, in particular re. obtaining your notarized passport copy.

Sign up

First, you can sign-up to the App Hub on You need a credit card to pay the CHF 129 annual fee. Be careful: the publisher name is final and cannot be changed later. So think about it for a minute and if you are not sure wait until you’ve decided what to display as your apps’ publisher.

Payee Details

When you are signed-up and have clicked on all the confirmation links you receive, you have to log into your account and fill in your bank account data under my account/payee details. If you only have a Post account, no problem, use the Post’s IBAN calculator –they also provide the BIC and correct address.

At this point you are ready to submit your applications to the marketplace, but you may want to continue reading. In fact as you probably already know, you will receive 70% of your app’s total sales, the other 30% being kept by Microsoft. The problem is that as a non-U.S. resident, another 30% will be removed from your part –which is a rather big hit IMO! Keep in mind that you will have to pay Swiss taxes on the income, so in the end not much will be left in your hands.

That’s why you have to provide some documentation proving that you are indeed paying taxes on your country –so that the U.S. won’t charge you that infamous additional 30%. In practice, it means asking an ITIN number to the U.S. International Revenue Service and giving it to Microsoft.

Notarized Copy

To ask an ITIN number you need a certified true copy of your passport. The IRS is rather strict on this aspect and won’t accept notarized copies from entities not in their list. This excludes the Swiss Post and probably anything else except the U.S. Embassy.

So -unless you live in Bern or Zurich and can take an appointment- you will have to send the following:

  • your passport
  • a copy of your passport
  • the filled-in W7 form (more on that later)
  • the Microsoft printed letter (more on that later)
  • a CHF 1.00 stamped envelope with your address

to this address:

U.S. Embassy
Consular Section
P.O. Box
3001 Bern

and at the same time, pay CHF 50.- (plus the 18.- postal fee) to

American Consular Services
Sulgeneckstrasse 19
3007 Bern

Yiikes! This will probably be the most expensive photocopy of your life (also considering that you made the copy itself :-) ), but they don’t have a post/bank account so you cannot avoid the 18.- fee.

W7 Form

In some days you will receive your notarized passport copy (and hopefully your passport) back. You are now ready to forward the W7 form. If you sent it to the embassy, they will probably have checked it for obvious mistakes, but I have not yet received mine back so I cannot tell at this time.

Anyways the W7 form can be downloaded here. Fill it in as explained in Sascha Corti’s presentation. In particular make sure that you check point a. and h., and enter “Exception 1 (d) – Royalty Income”  at point h., plus “12” as treaty article number.

Now log into your Marketplace account, go to the payee details page, scroll down until you find “Click here to download the Microsoft letter”, download the letter, print it and hand-write the date and your full name. Make sure the letter includes Todd Biggs signature at the end. A previous version did not include the signature and applications were rejected because of it.

Now send W7 and the letter to

International Revenue Service
ITIN Operations
P.O. Box 149342
Austin, TX 78714-9342
United States of America

After n weeks they will hopefully assign you an ITIN number.

W-8BEN form

With your ITIN in hand, you can finally fill in the W-8BEN form, print it, sign it and send it to

’Windows Marketplace for Mobile’
One Microsoft Way
Redmond WA 98052
United States of America

Once they receive and process it you should be free of the 30% tax and receive your full 70% royalties. As far as I understand it this is not retro-active, i.e. the taxes you previously paid won’t be reimbursed.

That’s all

This should be all (I never said it was simple ;-) ). It takes some effort, time and money (about CHF 80.- one-time plus the annual 129.- fee), but if you are doing some interesting apps it may be worth it as you will hopefully earn it back soon.


Getting your ITIN number from the IRS can take a long time. It took me more than 3 months since I sent the W7 form. Send it with signed mail for piece of mind, and be patient, they will eventually answer.