Rework dialog closing on IsOpen = false

DialogHost.Avalonia/DialogClosingEventArgs.cs

@@ -6,11 +6,25 @@ namespace DialogHostAvalonia;
 /// <summary>
 /// Event args contains info about dialog closing
 /// </summary>
-public class DialogClosingEventArgs(DialogSession session, RoutedEvent routedEvent) : RoutedEventArgs(routedEvent) {
+public class DialogClosingEventArgs(DialogSession session, RoutedEvent routedEvent, bool canBeCancelled)
+    : RoutedEventArgs(routedEvent) {
+    /// <inheritdoc />
+    [Obsolete("Use constructor with canBeCancelled parameter")]
+    public DialogClosingEventArgs(DialogSession session, RoutedEvent routedEvent) : this(session, routedEvent, true) {
+    }
+
     /// <summary>
     /// Cancel the close.
     /// </summary>
-    public void Cancel() => IsCancelled = true;
+    public void Cancel() {
+        if (!CanBeCancelled) {
+            throw new InvalidOperationException(
+                $"Cannot cancel dialog closing after {nameof(DialogHost)}.{nameof(DialogHost.IsOpen)} " +
+                $"property has been set to {bool.FalseString}");
+        }
+
+        IsCancelled = true;
+    }
 
     /// <summary>
     /// Indicates if the close has already been cancelled.
@@ -26,4 +40,12 @@ public class DialogClosingEventArgs(DialogSession session, RoutedEvent routedEve
     /// Allows interaction with the current dialog session.
     /// </summary>
     public DialogSession Session { get; } = session ?? throw new ArgumentNullException(nameof(session));
+
+    /// <summary>
+    /// Indicates if the close can be canceled.
+    /// </summary>
+    /// <remarks>
+    /// Typically this is <c>true</c> unless closing is triggered by setting <see cref="DialogHost.IsOpen"/> to <c>false</c>.
+    /// </remarks>
+    public bool CanBeCancelled { get; } = canBeCancelled;
 }

DialogHost.Avalonia/DialogHost.axaml.cs

@@ -687,11 +687,13 @@ private void IsOpenPropertyChangedCallback(bool newValue) {
             OnDialogOpened(dialogOpenedEventArgs);
             DialogOpenedCallback?.Invoke(this, dialogOpenedEventArgs);
             CurrentSession?.ShowOpened(this, dialogOpenedEventArgs);
-
-            // dialogHost._overlayPopupHost?.ConfigurePosition(dialogHost._root, PlacementMode.AnchorAndGravity, new Point());
         }
         else {
-            RemoveAllHost();
+            for (var i = _overlayPopupHosts.Count - 1; i >= 0; i--)
+            {
+                var session = _overlayPopupHosts[i].Session;
+                InternalClose(session, session.CloseParameter, false);
+            }
 
             _restoreFocusDialogClose?.Focus();
         }
@@ -799,25 +801,9 @@ public void RemoveDispose(DialogOverlayPopupHost host) {
         return host.DialogTaskCompletionSource;
     }
 
-    private void RemoveHost(DialogOverlayPopupHost? host) {
-        if (host == null) {
-            return;
-        }
-
-        var session = host.Session;
-        if (!session.IsEnded) {
-            session.Close(session.CloseParameter);
-            return;
-        }
-
-        //DialogSession.Close may attempt to cancel the closing of the dialog.
-        //When the dialog is closed in this manner it is not valid
-        if (!session.IsEnded) {
-            throw new InvalidOperationException($"Cannot cancel dialog closing after {nameof(IsOpen)} property has been set to {bool.FalseString}");
-        }
-
+    private void RemoveHost(DialogOverlayPopupHost host) {
         //NB: _dialogTaskCompletionSource is only set in the case where the dialog is shown with Show
-        host.DialogTaskCompletionSource.TrySetResult(session.CloseParameter);
+        host.DialogTaskCompletionSource.TrySetResult(host.Session.CloseParameter);
         host.IsOpen = false;
         host.Content = null;
 
@@ -830,12 +816,6 @@ private void RemoveHost(DialogOverlayPopupHost? host) {
         }
     }
 
-    private void RemoveAllHost() {
-        foreach (var host in _overlayPopupHosts.ToArray().Reverse()) {
-            RemoveHost(host);
-        }
-    }
-
     private void ContentCoverGrid_OnPointerReleased(object sender, PointerReleasedEventArgs e) {
         if (CloseOnClickAway && CurrentSession != null) {
             InternalClose(CloseOnClickAwayParameter);
@@ -873,18 +853,18 @@ public event EventHandler<DialogClosingEventArgs> DialogClosing {
     internal void InternalClose(object? parameter) {
         var session = CurrentSession ?? throw new InvalidOperationException($"{nameof(DialogHost)} does not have a current session");
 
-        InternalClose(session, parameter);
+        InternalClose(session, parameter, true);
     }
 
-    internal void InternalClose(DialogSession session, object? parameter) {
+    internal void InternalClose(DialogSession session, object? parameter, bool canBeCancelled) {
         session.CloseParameter = parameter;
         session.IsEnded = true;
 
         //multiple ways of calling back that the dialog is closing:
         // * routed event
         // * straight forward IsOpen dependency property 
         // * handler provided to the async show method
-        var dialogClosingEventArgs = new DialogClosingEventArgs(session, DialogClosingEvent);
+        var dialogClosingEventArgs = new DialogClosingEventArgs(session, DialogClosingEvent, canBeCancelled);
         OnDialogClosing(dialogClosingEventArgs);
         DialogClosingCallback?.Invoke(this, dialogClosingEventArgs);
         session.ShowClosing(this, dialogClosingEventArgs);

DialogHost.Avalonia/DialogSession.cs

@@ -58,7 +58,7 @@ public void Close()
     {
         if (IsEnded) throw new InvalidOperationException("Dialog session has ended.");
 
-        _owner.InternalClose(this, null);
+        _owner.InternalClose(this, null, true);
     }
 
     /// <summary>
@@ -70,7 +70,7 @@ public void Close(object? parameter)
     {
         if (IsEnded) throw new InvalidOperationException("Dialog session has ended.");
 
-        _owner.InternalClose(this, parameter);
+        _owner.InternalClose(this, parameter, true);
     }
 
     internal void ShowOpened(object obj, DialogOpenedEventArgs args) {