From dd4edb23ed72fb2dcc54b1d89aa5dba73bd62052 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bla=C5=BE=20Toma=C5=BEi=C4=8D?= <blaz.tomazic@gmail.com>
Date: Fri, 28 Dec 2018 10:57:47 +0100
Subject: [PATCH] Use existing metal layer if present on NSWindow

If we create and assign a new metal layer to NSWindow, when another one
was already assigned, the window content stays black.
---
 src/renderer_mtl.mm | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/renderer_mtl.mm b/src/renderer_mtl.mm
index 62714537c..09988fc0d 100644
--- a/src/renderer_mtl.mm
+++ b/src/renderer_mtl.mm
@@ -2868,9 +2868,17 @@ namespace bgfx { namespace mtl
 				else
 				{
 					NSWindow* nsWindow = (NSWindow*)_nwh;
-					[nsWindow.contentView setWantsLayer:YES];
-					m_metalLayer = [CAMetalLayer layer];
-					[nsWindow.contentView setLayer:m_metalLayer];
+					CALayer* layer = nsWindow.contentView.layer;
+					if(NULL != layer && [layer isKindOfClass:NSClassFromString(@"CAMetalLayer")])
+					{
+						m_metalLayer = (CAMetalLayer*)layer;
+					}
+					else
+					{
+						[nsWindow.contentView setWantsLayer:YES];
+						m_metalLayer = [CAMetalLayer layer];
+						[nsWindow.contentView setLayer:m_metalLayer];
+					}
 				}
 			}
 #endif // BX_PLATFORM_*