From a94325a76abe24a96ca0223f684b0ef3ca939c1f Mon Sep 17 00:00:00 2001
From: Stefan Csomor <csomor@advancedconcepts.ch>
Date: Tue, 23 Oct 2018 21:01:31 +0200
Subject: [PATCH] fix transparency problems on macOS

under mojave any backgroundColor destroys transparency
---
 src/osx/cocoa/nonownedwnd.mm | 7 ++++++-
 src/osx/nonownedwnd_osx.cpp  | 3 +--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/osx/cocoa/nonownedwnd.mm b/src/osx/cocoa/nonownedwnd.mm
index b21d2d2e14..64a6b3b74f 100644
--- a/src/osx/cocoa/nonownedwnd.mm
+++ b/src/osx/cocoa/nonownedwnd.mm
@@ -914,7 +914,12 @@ bool wxNonOwnedWindowCocoaImpl::SetTransparent(wxByte alpha)
 
 bool wxNonOwnedWindowCocoaImpl::SetBackgroundColour(const wxColour& col )
 {
-    [m_macWindow setBackgroundColor:col.OSXGetNSColor()];
+    // only set the native background color if the toplevel window's
+    // background is not supposed to be transparent, otherwise the
+    // transparency is lost
+    if( GetWXPeer()->GetBackgroundStyle() != wxBG_STYLE_TRANSPARENT &&
+       !(GetWXPeer()->GetWindowStyle() & wxFRAME_SHAPED) )
+        [m_macWindow setBackgroundColor:col.OSXGetNSColor()];
     return true;
 }
 
diff --git a/src/osx/nonownedwnd_osx.cpp b/src/osx/nonownedwnd_osx.cpp
index d8883120ac..3f46bca9e2 100644
--- a/src/osx/nonownedwnd_osx.cpp
+++ b/src/osx/nonownedwnd_osx.cpp
@@ -152,8 +152,7 @@ bool wxNonOwnedWindow::Create(wxWindow *parent,
     wxWindowCreateEvent event(this);
     HandleWindowEvent(event);
 
-    if ( GetBackgroundStyle() != wxBG_STYLE_TRANSPARENT )
-        SetBackgroundColour(wxSystemSettings::GetColour( wxSYS_COLOUR_APPWORKSPACE ));
+    SetBackgroundColour(wxSystemSettings::GetColour( wxSYS_COLOUR_APPWORKSPACE ));
 
     if ( parent )
         parent->AddChild(this);