From 040c47e01760515fb320b9eded87208ff02091bc Mon Sep 17 00:00:00 2001
From: Bebo-Maker <bennetbo@gmx.de>
Date: Wed, 23 Mar 2022 08:35:28 +0100
Subject: [PATCH] Fix issue when showing previewer multiple times.

Previously when calling ShowPreviewer  in the same process multiple times lead to an Exception inside Avalonia.
---
 QuestPDF.Previewer/DocumentPreviewerExtensions.cs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/QuestPDF.Previewer/DocumentPreviewerExtensions.cs b/QuestPDF.Previewer/DocumentPreviewerExtensions.cs
index 1a335ac..29f3f70 100644
--- a/QuestPDF.Previewer/DocumentPreviewerExtensions.cs
+++ b/QuestPDF.Previewer/DocumentPreviewerExtensions.cs
@@ -1,4 +1,5 @@
 using Avalonia;
+using Avalonia.Controls.ApplicationLifetimes;
 using QuestPDF.Infrastructure;
 
 namespace QuestPDF.Previewer
@@ -17,6 +18,19 @@ namespace QuestPDF.Previewer
         {
             ArgumentNullException.ThrowIfNull(document);
 
+            //Currently there is no way to unitialize a previously run avalonia app.
+            //So we need to check if the previewer was already run and show the window again.
+            if(Application.Current?.ApplicationLifetime is ClassicDesktopStyleApplicationLifetime desktop)
+            {
+                desktop.MainWindow = new PreviewerWindow()
+                {
+                    Document = document,
+                };
+                desktop.MainWindow.Show();
+                desktop.Start(Array.Empty<string>());
+                return;
+            }
+
             AppBuilder
                 .Configure(() => new PreviewerApp()
                 {