Cocoa: Apply retina window hint to Metal layer

Related to #1340.

src/cocoa_platform.h

@@ -110,6 +110,7 @@ typedef struct _GLFWwindowNS
     id              layer;
 
     GLFWbool        maximized;
+    GLFWbool        retina;
 
     // Cached window properties to filter out duplicate events
     int             width, height;

src/cocoa_window.m

@@ -534,7 +534,7 @@ static const NSRange kEmptyRange = { NSNotFound, 0 };
         window->ns.yscale = yscale;
         _glfwInputWindowContentScale(window, xscale, yscale);
 
-        if (window->ns.layer)
+        if (window->ns.retina && window->ns.layer)
             [window->ns.layer setContentsScale:[window->ns.object backingScaleFactor]];
     }
 }
@@ -842,9 +842,7 @@ static GLFWbool createNativeWindow(_GLFWwindow* window,
         [window->ns.object setFrameAutosaveName:@(wndconfig->ns.frameName)];
 
     window->ns.view = [[GLFWContentView alloc] initWithGlfwWindow:window];
-
-    if (wndconfig->ns.retina)
-        [window->ns.view setWantsBestResolutionOpenGLSurface:YES];
+    window->ns.retina = wndconfig->ns.retina;
 
     if (fbconfig->transparent)
     {
@@ -1728,7 +1726,9 @@ VkResult _glfwPlatformCreateWindowSurface(VkInstance instance,
         return VK_ERROR_EXTENSION_NOT_PRESENT;
     }
 
-    [window->ns.layer setContentsScale:[window->ns.object backingScaleFactor]];
+    if (window->ns.retina)
+        [window->ns.layer setContentsScale:[window->ns.object backingScaleFactor]];
+
     [window->ns.view setLayer:window->ns.layer];
     [window->ns.view setWantsLayer:YES];
 

src/nsgl_context.m

@@ -360,6 +360,9 @@ GLFWbool _glfwCreateContextNSGL(_GLFWwindow* window,
                                   forParameter:NSOpenGLContextParameterSurfaceOpacity];
     }
 
+    if (window->ns.retina)
+        [window->ns.view setWantsBestResolutionOpenGLSurface:YES];
+
     [window->context.nsgl.object setView:window->ns.view];
 
     window->context.nsgl.swapIntervalCond = [NSCondition new];