microsoft / optical-reader

Optical Reader Library provides a simple easy-to-integrate optical reader task for QR-code and barcode reading purposes, and also provides a customizable optical reader framework for assisting in implementing own optical reader systems.

Optical Reader

Optical Reader Library provides a simple easy-to-integrate optical reader task for QR-code and barcode reading purposes, and also provides a customizable optical reader framework for assisting in implementing own optical reader systems.

The documentation for this project can be found from wiki: http://developer.nokia.com/community/wiki/Optical_Reader_Library_for_Windows_Phone_8

optical-reader's Issues

The link to the doku in the readme points to nowhere.

Can the documentation be seen somewhere else?

Potential Deadlock

The code in the InitializeCamera method in
optical-reader/OpticalReaderLib/Internal/OpticalReaderPage.xaml.cs waits synchronously on Tasks -- this code is reachable from an OnNavigatedTo handler, suggesting that it runs on the UI thread.
Here is the code in question:

optical-reader\OpticalReaderLib\Internal\OpticalReaderPage.xaml.cs(201): task.Wait();
optical-reader\OpticalReaderLib\Internal\OpticalReaderPage.xaml.cs(204): _device.SetPreviewResolutionAsync(previewResolution).AsTask().Wait();

Blocking the UI thread using the Wait() method can result in deadlock, if the code also
employs (asynchronous) await statements. The reason is that continuations following awaits
are posted to the UI thread - if the UI thread is blocked, these will never run. If the task blocking
the UI thread depends on these continuations to run in order to unblock it, the code deadlocks.
Please refer to http://blogs.msdn.com/b/pfxteam/archive/2011/01/13/10115163.aspx for a more
detailed discussion.

A possible fix is to offload the asynchronous operations to a non-UI thread, using the Task.Run
API call documented here: https://msdn.microsoft.com/en-us/library/system.threading.tasks.task.run(v=vs.110).aspx
Stephen Toub discusses this refactoring (and other possible refactorings) here: http://blogs.msdn.com/b/pfxteam/archive/2012/04/13/10293638.aspx