vba10/EventHandlerForDevice.cpp

#include "pch.h"
#include "EventHandlerForDevice.h"
#include "App.xaml.h"

using namespace VBA10;
using namespace Platform;
using namespace Concurrency;
using namespace Windows::ApplicationModel;
using namespace Windows::Devices;
using namespace Windows::Devices::Enumeration;
using namespace Windows::Devices::HumanInterfaceDevice;
using namespace Windows::Foundation;
using namespace Windows::Storage;
using namespace Windows::UI::Core;
using namespace Windows::UI::Xaml;

EventHandlerForDevice^ EventHandlerForDevice::eventHandlerForDevice = nullptr;

SRWLOCK EventHandlerForDevice::srwSingletonCreationLock = SRWLOCK_INIT;

/// <summary>
/// Enforces the singleton pattern so that there is only one object handling app events
/// as it relates to the UsbDevice because this sample app only supports communicating with one device at a time. 
///
/// An instance of EventHandlerForDevice is globally available because the device needs to persist across scenario pages.
///
/// If there is no instance of EventHandlerForDevice created before this property is called,
/// an EventHandlerForDevice will be created.
/// </summary>
EventHandlerForDevice^ EventHandlerForDevice::Current::get(void)
{
	// Acquiring Shared lock is much quicker than an exclusive lock, so avoid exclusive lock unless it's necessary
	AcquireSRWLockShared(&srwSingletonCreationLock);

	if (eventHandlerForDevice == nullptr)
	{
		// Multiple threads could have entered here, so acquire exclusive lock to make sure only one instance is created.
		ReleaseSRWLockShared(&srwSingletonCreationLock);

		AcquireSRWLockExclusive(&srwSingletonCreationLock);

		if (eventHandlerForDevice == nullptr)
		{
			CreateNewEventHandlerForDevice();
		}

		ReleaseSRWLockExclusive(&srwSingletonCreationLock);
	}
	else
	{
		ReleaseSRWLockShared(&srwSingletonCreationLock);
	}

	return eventHandlerForDevice;
}

/// <summary>
/// Creates a new instance of EventHandlerForDevice, enables auto reconnect, and uses it as the Current instance.
/// </summary>
void EventHandlerForDevice::CreateNewEventHandlerForDevice(void)
{
	eventHandlerForDevice = ref new EventHandlerForDevice();
}

/// <summary>
/// This method opens the device using the WinRT Hid API. After the device is opened, we will save the device
/// so that it can be used across scenarios.
///
/// It is important that the FromIdAsync call is made on the UI thread because the consent prompt can only be displayed
/// on the UI thread.
/// 
/// This method is used to reopen the device after the device reconnects to the computer and when the app resumes.
/// </summary>
/// <param name="deviceInfo">Device information of the device to be opened</param>
/// <param name="deviceSelector">The AQS used to find this device</param>
/// <returns>True if the device was successfully opened, false if the device could not be opened for well known reasons.
/// An exception may be thrown if the device could not be opened for extraordinary reasons.</returns>
IAsyncOperation<bool>^ EventHandlerForDevice::OpenDeviceAsync(Enumeration::DeviceInformation^ deviceInfo)
{
	// This sample uses FileAccessMode.ReadWrite to open the device because we do not want other apps opening our device and 
	// changing the state of our device. FileAccessMode.Read can be used instead.
	return create_async([this, deviceInfo]()
	{
		String^ test = deviceInfo->Id;
		return create_task(HidDevice::FromIdAsync(deviceInfo->Id, FileAccessMode::Read))
			.then([this, deviceInfo](task<HidDevice^> deviceTask)
		{
			bool successfullyOpenedDevice = false;
			//NotifyType notificationStatus;
			//String^ notificationMessage = nullptr;

			// This may throw an exception or return null if we could not open the device
			try
			{
				device = deviceTask.get();
			}
			catch (Platform::Exception^)
			{
				device = nullptr;
			}
			// Device could have been blocked by user or the device has already been opened by another app.
			if (device != nullptr)
			{
				successfullyOpenedDevice = true;

				deviceInformation = deviceInfo;
				//this->deviceSelector = deviceSelector;

				//notificationStatus = NotifyType::StatusMessage;
				//notificationMessage = "Device " + deviceInformation->Id + " opened";

				if (appSuspendEventToken.Value == 0 || appResumeEventToken.Value == 0)
				{
					RegisterForAppEvents();
				}

				// User can block the device after it has been opened in the Settings charm. We can detect this by registering for the 
				// DeviceAccessInformation->AccessChanged event
				if (deviceAccessInformation == nullptr)
				{
					RegisterForDeviceAccessStatusChange();
				}

				// Create and register device watcher events for the device to be opened unless we're reopening the device
				if (deviceWatcher == nullptr)
				{
					deviceWatcher = Enumeration::DeviceInformation::CreateWatcher(this->deviceSelector);

					RegisterForDeviceWatcherEvents();
				}

				if (!watcherStarted)
				{
					// Start the device watcher after we made sure that the device is opened.
					StartDeviceWatcher();
				}
			}
			else
			{
				successfullyOpenedDevice = false;

				//notificationStatus = NotifyType::ErrorMessage;

				auto deviceAccessStatus = Enumeration::DeviceAccessInformation::CreateFromId(deviceInfo->Id)->CurrentStatus;

				if (deviceAccessStatus == DeviceAccessStatus::DeniedByUser)
				{
					//notificationMessage = "Access to the device was blocked by the user : " + deviceInfo->Id;
				}
				else if (deviceAccessStatus == DeviceAccessStatus::DeniedBySystem)
				{
					// This status is most likely caused by app permissions (did not declare the device in the app's package.appxmanifest)
					// This status does not cover the case where the device is already opened by another app.
					//notificationMessage = "Access to the device was blocked by the system : " + deviceInfo->Id;
				}
				else
				{
					// Most likely the device is opened by another app, but cannot be sure
					//notificationMessage = "Unknown error, possibly opened by another app : " + deviceInfo->Id;
				}
			}

			//MainPage::Current->NotifyUser(notificationMessage, notificationStatus);

			// Notify registered callback handle whether or not the device has been opened
			if (deviceConnectedCallback != nullptr)
			{
				auto deviceConnectedEventArgs = ref new OnDeviceConnectedEventArgs(successfullyOpenedDevice, deviceInfo);

				deviceConnectedCallback(this, deviceConnectedEventArgs);
			}

			return successfullyOpenedDevice;
		});
	});
}

/// <summary>
/// Closes the device, stops the device watcher, stops listening for app events, and resets object state to before a device
/// was ever connected.
/// </summary>
void EventHandlerForDevice::CloseDevice(void)
{
	if (IsDeviceConnected)
	{
		CloseCurrentlyConnectedDevice();
	}

	if (deviceWatcher != nullptr)
	{
		if (watcherStarted)
		{
			StopDeviceWatcher();

			UnregisterFromDeviceWatcherEvents();
		}

		deviceWatcher = nullptr;
	}

	if (deviceAccessInformation != nullptr)
	{
		UnregisterFromDeviceAccessStatusChange();

		deviceAccessInformation = nullptr;
	}

	if (appSuspendEventToken.Value != 0 || appResumeEventToken.Value != 0)
	{
		UnregisterFromAppEvents();
	}

	deviceInformation = nullptr;
	deviceSelector = nullptr;

	deviceConnectedCallback = nullptr;
	deviceCloseCallback = nullptr;

	isEnabledAutoReconnect = true;
}

EventHandlerForDevice::EventHandlerForDevice(void) :
	watcherStarted(false),
	watcherSuspended(false),
	isEnabledAutoReconnect(true)
{
}

EventHandlerForDevice::~EventHandlerForDevice()
{
	if (IsDeviceConnected)
	{
		CloseDevice();
	}
}

/// <summary>
/// This method demonstrates how to close the device properly using the WinRT Hid API.
///
/// When the HidDevice is closing, it will cancel all IO operations that are still pending (not complete).
/// The close will not wait for any IO completion callbacks to be called, so the close call may complete before any of
/// the IO completion callbacks are called.
/// The pending IO operations will still call their respective completion callbacks with either a task 
/// cancelled error or the operation completed.
/// </summary>
void EventHandlerForDevice::CloseCurrentlyConnectedDevice(void)
{
	if (device != nullptr)
	{
		if (deviceCloseCallback != nullptr)
		{
			deviceCloseCallback(this, deviceInformation);
		}

		// This closes the handle to the device
		delete device;

		device = nullptr;

		// Save the deviceInformation->Id in case deviceInformation is set to null when closing the
		// device
		String^ deviceId = deviceInformation->Id;

		//MainPage::Current->Dispatcher->RunAsync(
		//	CoreDispatcherPriority::Normal,
		//	ref new DispatchedHandler([deviceId]()
		//{
		//	MainPage::Current->NotifyUser(deviceId + " is closed", NotifyType::StatusMessage);
		//}));
	}
}

/// <summary>
/// Register for app suspension/resume events. See the comments
/// for the event handlers for more information on what is being done to the device.
///
/// We will also register for when the app exists so that we may close the device handle.
/// </summary>
void EventHandlerForDevice::RegisterForAppEvents()
{
	// This event is raised when the app is exited and when the app is suspended
	appSuspendEventToken = App::Current->Suspending += ref new SuspendingEventHandler(this, &EventHandlerForDevice::OnAppSuspension);

	appResumeEventToken = App::Current->Resuming += ref new EventHandler<Object^>(this, &EventHandlerForDevice::OnAppResume);
}

void EventHandlerForDevice::UnregisterFromAppEvents()
{
	App::Current->Suspending -= appSuspendEventToken;
	appSuspendEventToken.Value = 0;

	App::Current->Resuming -= appResumeEventToken;
	appResumeEventToken.Value = 0;
}

/// <summary>
/// Register for Added and Removed events
/// Note that, when disconnecting the device, the device may be closed by the system before the OnDeviceRemoved callback is invoked.
/// </summary>
void EventHandlerForDevice::RegisterForDeviceWatcherEvents()
{
	deviceAddedEventToken = deviceWatcher->Added += ref new TypedEventHandler<DeviceWatcher^, Enumeration::DeviceInformation^>(
		this, &EventHandlerForDevice::OnDeviceAdded);

	deviceRemovedEventToken = deviceWatcher->Removed += ref new TypedEventHandler<DeviceWatcher^, DeviceInformationUpdate^>(
		this, &EventHandlerForDevice::OnDeviceRemoved);
}

void EventHandlerForDevice::UnregisterFromDeviceWatcherEvents()
{
	deviceWatcher->Added -= deviceAddedEventToken;
	deviceAddedEventToken.Value = 0;

	deviceWatcher->Removed -= deviceRemovedEventToken;
	deviceRemovedEventToken.Value = 0;
}

/// <summary>
/// Listen for any changed in device access permission. The user can block access to the device while the device is in use.
/// If the user blocks access to the device while the device is opened, the device's handle will be closed automatically by
/// the system; it is still a good idea to close the device explicitly so that resources are cleaned up.
/// 
/// Note that by the time the AccessChanged event is raised, the device handle may already be closed by the system.
/// </summary>
void EventHandlerForDevice::RegisterForDeviceAccessStatusChange()
{
	deviceAccessInformation = Enumeration::DeviceAccessInformation::CreateFromId(deviceInformation->Id);

	deviceAccessChangedEventToken = deviceAccessInformation->AccessChanged
		+= ref new TypedEventHandler<Enumeration::DeviceAccessInformation^, DeviceAccessChangedEventArgs^>(this, &EventHandlerForDevice::OnDeviceAccessChanged);
}

void EventHandlerForDevice::UnregisterFromDeviceAccessStatusChange()
{
	deviceAccessInformation->AccessChanged -= deviceAccessChangedEventToken;
	deviceAccessChangedEventToken.Value = 0;
}

void EventHandlerForDevice::StartDeviceWatcher(void)
{
	watcherStarted = true;

	if ((deviceWatcher->Status != DeviceWatcherStatus::Started)
		&& (deviceWatcher->Status != DeviceWatcherStatus::EnumerationCompleted))
	{
		deviceWatcher->Start();
	}
}

void EventHandlerForDevice::StopDeviceWatcher(void)
{
	if ((deviceWatcher->Status == DeviceWatcherStatus::Started)
		|| (deviceWatcher->Status == DeviceWatcherStatus::EnumerationCompleted))
	{
		deviceWatcher->Stop();
	}

	watcherStarted = false;
}

/// <summary>
/// If a HidDevice object has been instantiated (a handle to the device is opened), we must close it before the app 
/// goes into suspension because the API automatically closes it for us if we don't. When resuming, the API will
/// not reopen the device automatically, so we need to explicitly open the device in the app (Scenario1_DeviceConnect).
///
/// Since we have to reopen the device ourselves when the app resumes, it is good practice to explicitly call the close
/// in the app as well (For every open there is a close).
/// 
/// We must stop the DeviceWatcher because it will continue to raise events even if
/// the app is in suspension, which is not desired (drains battery). We resume the device watcher once the app resumes again.
/// </summary>
/// <param name="sender"></param>
/// <param name="eventArgs"></param>
void EventHandlerForDevice::OnAppSuspension(Object^ /* sender */, SuspendingEventArgs^ /* eventArgs */)
{
	if (watcherStarted)
	{
		watcherSuspended = true;
		StopDeviceWatcher();
	}
	else
	{
		watcherSuspended = false;
	}

	CloseCurrentlyConnectedDevice();
}

/// <summary>
/// When resume into the application, we should reopen a handle to the Usb device again. This will automatically
/// happen when we start the device watcher again; the device will be re-enumerated and we will attempt to reopen it
/// if IsEnabledAutoReconnect property is enabled.
/// 
/// See OnAppSuspension for why we are starting the device watcher again
/// </summary>
/// <param name="sender"></param>
/// <param name="args"></param>
void EventHandlerForDevice::OnAppResume(Object^ /* sender */, Object^ /* args */)
{
	if (watcherSuspended)
	{
		watcherSuspended = false;
		StartDeviceWatcher();
	}
}

/// <summary>
/// Close the device that is opened so that all pending operations are canceled properly.
/// </summary>
/// <param name="sender"></param>
/// <param name="deviceInformationUpdate"></param>
void EventHandlerForDevice::OnDeviceRemoved(DeviceWatcher^ /* sender */, DeviceInformationUpdate^ deviceInformationUpdate)
{
	if (IsDeviceConnected && (deviceInformationUpdate->Id == deviceInformation->Id))
	{
		// The main reasons to close the device explicitly is to clean up resources, to properly handle errors,
		// and stop talking to the disconnected device.
		CloseCurrentlyConnectedDevice();
	}
}

/// <summary>
/// Open the device that the user wanted to open if it hasn't been opened yet and auto reconnect is enabled.
/// </summary>
/// <param name="sender"></param>
/// <param name="deviceInfo"></param>
void EventHandlerForDevice::OnDeviceAdded(DeviceWatcher^ /* sender */, Enumeration::DeviceInformation^ deviceInfo)
{
	if ((deviceInformation != nullptr) && (deviceInfo->Id == deviceInformation->Id) && !IsDeviceConnected && isEnabledAutoReconnect)
	{
		//MainPage::Current->Dispatcher->RunAsync(
		//	CoreDispatcherPriority::Normal,
		//	ref new DispatchedHandler([this]()
		//{
			// If we failed to reconnect to the device, don't try to connect anymore
			create_task(OpenDeviceAsync(deviceInformation)).then([this](task<bool> openDeviceSuccess)
			{
				isEnabledAutoReconnect = openDeviceSuccess.get();
			});

			// Any app specific device intialization should be done here because we don't know the state of the device when it is re-enumerated.
		//}));
	}
}

/// <summary>
/// Close the device if the device access was denied by anyone (system or the user) and reopen it if permissions are allowed again
/// </summary>
/// <param name="sender"></param>
/// <param name="eventArgs"></param>
void EventHandlerForDevice::OnDeviceAccessChanged(Enumeration::DeviceAccessInformation^ sender, DeviceAccessChangedEventArgs^ eventArgs)
{
	if ((eventArgs->Status == DeviceAccessStatus::DeniedBySystem)
		|| (eventArgs->Status == DeviceAccessStatus::DeniedByUser))
	{
		CloseCurrentlyConnectedDevice();
	}
	else if ((eventArgs->Status == DeviceAccessStatus::Allowed) && (deviceInformation != nullptr) && isEnabledAutoReconnect)
	{
		//MainPage::Current->Dispatcher->RunAsync(
		//	CoreDispatcherPriority::Normal,
		//	ref new DispatchedHandler([this]()
		//{
			// If we failed to reconnect to the device, don't try to connect anymore
			create_task(OpenDeviceAsync(deviceInformation)).then([this](task<bool> openDeviceSuccess)
			{
				isEnabledAutoReconnect = openDeviceSuccess.get();
			});

			// Any app specific device intialization should be done here because we don't know the state of the device when it is re-enumerated.
		//}));
	}
}