From 687267b9db69ff312953c1c45fab044c1b0cc042 Mon Sep 17 00:00:00 2001
From: Paul Cornett <paulcor@users.noreply.github.com>
Date: Mon, 6 Jul 2020 23:13:33 -0700
Subject: [PATCH] Fix the default background color reported for toplevel
 windows with GTK3

See #18811
---
 include/wx/gtk/toplevel.h |  1 +
 src/gtk/toplevel.cpp      | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/include/wx/gtk/toplevel.h b/include/wx/gtk/toplevel.h
index 037a7498cb..19227ffa3f 100644
--- a/include/wx/gtk/toplevel.h
+++ b/include/wx/gtk/toplevel.h
@@ -74,6 +74,7 @@ public:
     virtual void SetLabel(const wxString& label) wxOVERRIDE { SetTitle( label ); }
     virtual wxString GetLabel() const wxOVERRIDE            { return GetTitle(); }
 
+    virtual wxVisualAttributes GetDefaultAttributes() const wxOVERRIDE;
 
     virtual bool SetTransparent(wxByte alpha) wxOVERRIDE;
     virtual bool CanSetTransparent() wxOVERRIDE;
diff --git a/src/gtk/toplevel.cpp b/src/gtk/toplevel.cpp
index d7f94d8b3a..74c6ed2e1b 100644
--- a/src/gtk/toplevel.cpp
+++ b/src/gtk/toplevel.cpp
@@ -35,6 +35,7 @@
 
 #include "wx/gtk/private.h"
 #include "wx/gtk/private/gtk3-compat.h"
+#include "wx/gtk/private/stylecontext.h"
 #include "wx/gtk/private/win_gtk.h"
 
 #ifdef GDK_WINDOWING_X11
@@ -1815,3 +1816,12 @@ bool wxTopLevelWindowGTK::CanSetTransparent()
                            "Composite", &opcode, &event, &error);
 #endif
 }
+
+wxVisualAttributes wxTopLevelWindowGTK::GetDefaultAttributes() const
+{
+    wxVisualAttributes attrs(GetClassDefaultAttributes());
+#ifdef __WXGTK3__
+    wxGtkStyleContext().AddWindow().Bg(attrs.colBg);
+#endif
+    return attrs;
+}