From af8acfce0dbab0864affb5bc8ee4e45bc8c9f4a9 Mon Sep 17 00:00:00 2001
From: Dariusz Komosinski <darek.komosinski@gmail.com>
Date: Thu, 9 Jul 2020 21:49:34 +0200
Subject: [PATCH] Prevent crashes caused by null locked framebuffer.

---
 src/Windows/Avalonia.Win32/FramebufferManager.cs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/Windows/Avalonia.Win32/FramebufferManager.cs b/src/Windows/Avalonia.Win32/FramebufferManager.cs
index 87c5a1bb02..f4c3a80799 100644
--- a/src/Windows/Avalonia.Win32/FramebufferManager.cs
+++ b/src/Windows/Avalonia.Win32/FramebufferManager.cs
@@ -17,16 +17,18 @@ namespace Avalonia.Win32
 
         public ILockedFramebuffer Lock()
         {
-            UnmanagedMethods.RECT rc;
-            UnmanagedMethods.GetClientRect(_hwnd, out rc);
-            var width = rc.right - rc.left;
-            var height = rc.bottom - rc.top;
-            if ((_fb == null || _fb.Size.Width != width || _fb.Size.Height != height) && width > 0 && height > 0)
+            UnmanagedMethods.GetClientRect(_hwnd, out var rc);
+
+            var width = Math.Max(1, rc.right - rc.left);
+            var height = Math.Max(1, rc.bottom - rc.top);
+
+            if ((_fb == null || _fb.Size.Width != width || _fb.Size.Height != height))
             {
                 _fb?.Deallocate();
                 _fb = null;
                 _fb = new WindowFramebuffer(_hwnd, new PixelSize(width, height));
             }
+
             return _fb;
         }
     }