implemented forcing state change of settingsVM when UnintentionalDisconnect happened,

made Sending and Receiving with USB HID more robust

MultiTerm.Core/ViewModel/TerminalViewModel.cs

@@ -108,6 +108,7 @@ public abstract partial class TerminalViewModel : ObservableObject, ITerminalVie
             // unsubscribe events
             this.CommunicationProtocol.ReceivedDataEvent -= CommunicationProtocol_ReceivedDataEvent;
             this.CommunicationProtocol.SentDataEvent -= CommunicationProtocol_SentDataEvent;
+            this.CommunicationProtocol.DisconnectedEvent -= CommunicationProtocol_DisconnectedEvent;
             // remove reference to object
             this.CommunicationProtocol = null;
         }
@@ -125,6 +126,7 @@ public abstract partial class TerminalViewModel : ObservableObject, ITerminalVie
         {
             this.CommunicationProtocol.ReceivedDataEvent += CommunicationProtocol_ReceivedDataEvent;
             this.CommunicationProtocol.SentDataEvent += CommunicationProtocol_SentDataEvent;
+            this.CommunicationProtocol.DisconnectedEvent += CommunicationProtocol_DisconnectedEvent;
         }
 
         // initializes default newline separators, updates them directly inside ReceivedData and SentData objects
@@ -151,6 +153,16 @@ public abstract partial class TerminalViewModel : ObservableObject, ITerminalVie
         this.SentData.HandleNewData(e.SentData);
     }
 
+    private void CommunicationProtocol_DisconnectedEvent(object? sender, DisconnectedEventArgs e)
+    {
+        // on unintentional disconnect the view model may still display connected => force to disconnected state
+        // allows user to change settings
+        if(e.Unintentional == true && this.ProtocolSettings!.DisplaysConnected == true)
+        {
+            this.ProtocolSettings.ForceConnectedState(false);
+        }
+    }
+
     #endregion
 
     /// <summary>

MultiTerm.Protocols/CommunicationProtocol.cs

@@ -48,6 +48,9 @@ public abstract class CommunicationProtocol : ICommunicationProtocol
     /// To be called whenever the protocol detected that it is disconnected, but this is not a known fact.
     /// </summary>
     protected void OnUnintentionallyDisconnected()
+    {
+        // perform all steps in a task, to prevent deadlock when this method is called from a thread that is joined.
+        Task.Run(() =>
         {
             // update state
             this.IsConnected = false;
@@ -57,6 +60,7 @@ public abstract class CommunicationProtocol : ICommunicationProtocol
 
             // raise event indicating an unintentional disconnect
             this.DisconnectedEvent?.Invoke(this, new DisconnectedEventArgs(true));
+        });
     }
 
     /// <summary>
@@ -84,7 +88,7 @@ public abstract class CommunicationProtocol : ICommunicationProtocol
         if (success == false)
         {
             this.logger.LogError($"'{nameof(SendBytes)}()' failed to send during {nameof(InternalSendBytes)}.", nameof(CommunicationProtocol));
-            this.messenger.Send<IUserInterfaceMessage>(new GenericUserInterfaceMessage("Failed to send message", MessageImportance.High));
+            this.messenger.Send<IUserInterfaceMessage>(new GenericUserInterfaceMessage("Failed to send data, for more information please check logfile.", MessageImportance.High));
         }
 
         return success;

MultiTerm.Protocols/IProtocolSettingsViewModel.cs

@@ -1,4 +1,5 @@
-using MultiTerm.Protocols.Types;
+using CommunityToolkit.Mvvm.Input;
+using MultiTerm.Protocols.Types;
 
 namespace MultiTerm.Protocols;
 
@@ -9,6 +10,11 @@ public interface IProtocolSettingsViewModel
     /// </summary>
     ProtocolType ProtocolType { get; }
 
+    /// <summary>
+    /// Indicates if the <see cref="IProtocolSettingsViewModel"/> displays ifself as if the protocol is connected.
+    /// </summary>
+    bool DisplaysConnected { get; }
+
     /// <summary>
     /// Indicates wether the settings can currently be edited.
     /// </summary>
@@ -24,4 +30,14 @@ public interface IProtocolSettingsViewModel
     /// Event that is thrown when the user requested to disconnect from the device.
     /// </summary>
     event EventHandler? DisconnectRequested;
+
+    /// <summary>
+    /// Change the state from connected to disconnected or from disconnected to connected.
+    /// Does not throw <see cref="ConnectRequested"/> or <see cref="DisconnectRequested"/>.
+    /// </summary>
+    /// <param name="connected">
+    /// if true changes the state from disconnected to connected.
+    /// if false changes the state from connected to disconnected.
+    /// </param>
+    void ForceConnectedState(bool connected);
 }

MultiTerm.Protocols/ProtocolSettingsViewModel.cs

@@ -19,6 +19,15 @@ public abstract partial class ProtocolSettingsViewModel : ObservableObject, IPro
     public event EventHandler<ConnectionRequestEventArgs>? ConnectRequested;
     public event EventHandler? DisconnectRequested;
 
+    public bool DisplaysConnected {
+        get
+        {
+            if (this.ConnectDisconnectButtonText == connectedStateButtonText) return true;
+            else if (this.ConnectDisconnectButtonText == disconnectedStateButtonText) return false;
+            else { throw new Exception($"'{nameof(DisplaysConnected)}' has not recognized button text, cannot identify state of connection."); }
+        }
+    }
+
     public abstract ProtocolType ProtocolType { get; }
 
     [ObservableProperty]
@@ -44,7 +53,7 @@ public abstract partial class ProtocolSettingsViewModel : ObservableObject, IPro
         await Task.Factory.StartNew(() =>
         {
             // if currently disconnected
-            if (this.ConnectDisconnectButtonText == disconnectedStateButtonText)
+            if (this.DisplaysConnected == false)
             {
                 // CONNECT
                 this.AreEditable = false;
@@ -64,20 +73,31 @@ public abstract partial class ProtocolSettingsViewModel : ObservableObject, IPro
                 {
                     // rollback
                     this.AreEditable = true;
+                    
                 }
             }
             // if currently connected
-            else if (this.ConnectDisconnectButtonText == connectedStateButtonText)
+            else
             {
                 // DISCONNECT
                 this.DisconnectRequested?.Invoke(this, EventArgs.Empty);
                 this.ConnectDisconnectButtonText = disconnectedStateButtonText;
                 this.AreEditable = true;
             }
+        });
+    }
+
+    public void ForceConnectedState(bool connected)
+    {
+        if (connected)
+        {
+            this.ConnectDisconnectButtonText = connectedStateButtonText;
+            this.AreEditable = false;
+        }
         else
         {
-                throw new Exception($"'{nameof(ConnectDisconnectAsync)}()' has not recognized button text, cannot identify state of connection.");
+            this.ConnectDisconnectButtonText = disconnectedStateButtonText;
+            this.AreEditable = true;
         }
-        });
     }
 }

MultiTerm.Protocols/UsbHid/UsbHidProtocol.cs

@@ -77,11 +77,25 @@ public class UsbHidProtocol : CommunicationProtocol
     {
         while (ct.IsCancellationRequested == false)
         {
+            // if usb hid device is null => something is wrong => break loop
+            if (this.usbHidDevice == null)
+            {
+                this.OnUnintentionallyDisconnected();
+                break;
+            }
+
             ReadOnlySpan<byte> readData;
-            if (this.usbHidDevice != null)
+            try
             {
                 // read with timeout
                 readData = this.usbHidDevice.ReadTimeout(200, (int)ReadTimeoutMs);
+            }
+            catch  // on exception => break loop
+            {
+                this.OnUnintentionallyDisconnected();
+                break;
+            }
+
             // any data received?
             if (readData.Length > 0)
             {
@@ -92,13 +106,6 @@ public class UsbHidProtocol : CommunicationProtocol
                 }
             }
         }
-            // if usb hid device is null => something is wrong => break loop
-            else
-            {
-                this.OnUnintentionallyDisconnected();
-                break;
-            }
-        }
     }
 
     protected override bool InternalSendBytes(byte[] bytes)
@@ -137,10 +144,19 @@ public class UsbHidProtocol : CommunicationProtocol
                 return false;
             }
 
-            this.usbHidDevice.Write(bytes);
+            try
+            {
+                this.usbHidDevice.Write(sendableBytes.ToArray());
+            }
+            catch(Exception ex) 
+            {
+                this.logger.LogException(ex, $"Failed to Write Data to USB HID device " +
+                    $"VID={this.usbHidSettings!.VendorId}, PID={this.usbHidSettings.ProductId}.", nameof(UsbHidProtocol));
+                return false;
+            }
 
             // report sent bytes
-            foreach (byte b in bytes)
+            foreach (byte b in sendableBytes)
             {
                 this.OnSentData(new ExtendedByte(b));
             }