diff -Naur a/gdk/quartz/gdkglobals-quartz.c b/gdk/quartz/gdkglobals-quartz.c
--- gdk/quartz/gdkglobals-quartz.c	2021-01-24 15:47:27.000000000 +0000
+++ gdk/quartz/gdkglobals-quartz.c	2021-01-24 15:40:36.000000000 +0000
@@ -34,9 +34,18 @@

   if (minor == GDK_OSX_UNSUPPORTED)
     {
-      OSErr err = Gestalt (gestaltSystemVersionMinor, (SInt32*)&minor);
+      gint32 major = GDK_OSX_UNSUPPORTED;
+      OSErr err = Gestalt (gestaltSystemVersionMajor, (SInt32*)&major);
+      g_return_val_if_fail (err == noErr, GDK_OSX_UNSUPPORTED);

+      err = Gestalt (gestaltSystemVersionMinor, (SInt32*)&minor);
       g_return_val_if_fail (err == noErr, GDK_OSX_UNSUPPORTED);
+
+      /* we should really move to NSProcessInfo instead of Gestalt, but its
+       * OS-version API exists in 10.10 and above, so we break 10.9 compat.
+       * So let's just fudge this for now, representing 11.x as 10.(15+x)
+       */
+      if(major > 10) minor += 15;
     }

   if (minor < GDK_OSX_MIN)
diff -Naur a/gdk/quartz/gdkwindow-quartz.c b/gdk/quartz/gdkwindow-quartz.c
--- gdk/quartz/gdkwindow-quartz.c	2021-01-24 15:47:27.000000000 +0000
+++ gdk/quartz/gdkwindow-quartz.c	2021-01-24 15:40:36.000000000 +0000
@@ -475,8 +475,10 @@
 _gdk_windowing_before_process_all_updates (void)
 {
   in_process_all_updates = TRUE;
-
-  NSDisableScreenUpdates ();
+
+  /* This API was deprecated in MacOS 10.14 */
+  if (gdk_quartz_osx_version() < GDK_OSX_MOJAVE)
+    NSDisableScreenUpdates ();
 }

 void
@@ -491,14 +493,11 @@
     {
       NSWindow *nswindow = tmp_list->data;

+      /* Revert to pre-2.24.33 behaviour.  The extra redraw introduced here really killed performance */
       [[nswindow contentView] displayIfNeeded];

       _gdk_quartz_drawable_flush (NULL);

-      /* 10.14 needs to be told that the view needs to be redrawn, see
-       * https://gitlab.gnome.org/GNOME/gtk/issues/1479 */
-      if (gdk_quartz_osx_version() >= GDK_OSX_MOJAVE)
-           [[nswindow contentView] setNeedsDisplay:YES];
       [nswindow enableFlushWindow];
       [nswindow flushWindow];
       [nswindow release];
@@ -510,7 +509,9 @@

   in_process_all_updates = FALSE;

-  NSEnableScreenUpdates ();
+  /* This API was deprecated in MacOS 10.14 */
+  if (gdk_quartz_osx_version() < GDK_OSX_MOJAVE)
+    NSEnableScreenUpdates ();
 }

 static void
diff -Naur a/gtk/gtkcontainer.c b/gtk/gtkcontainer.c
--- gtk/gtkcontainer.c	2021-01-24 15:47:28.000000000 +0000
+++ gtk/gtkcontainer.c	2021-01-24 15:40:36.000000000 +0000
@@ -42,6 +42,9 @@
 #include <gobject/gvaluecollector.h>
 #include "gtkalias.h"

+#ifdef GDK_WINDOWING_QUARTZ
+  #include "gdk/quartz/gdkquartz.h"
+#endif

 enum {
   ADD,
@@ -1357,7 +1360,17 @@
       gtk_container_check_resize (GTK_CONTAINER (widget));
     }

-  gdk_window_process_all_updates ();
+  #ifdef GDK_WINDOWING_QUARTZ
+    /* It seems that we process_all_updates (and redraw) here *and* in
+     * gdk_window_update_idle.  And that means full-window redraws in
+     * MacOS 11.  Disabling this does not seem to have any detrimental
+     * effects in my tests, but does cut down on processor use, so...
+     */
+    if(gdk_quartz_osx_version() < GDK_OSX_MOJAVE)
+      gdk_window_process_all_updates ();
+  #elif
+    gdk_window_process_all_updates ();
+  #endif

   return FALSE;
 }
diff -Naur a/gtk/gtkquartz.c b/gtk/gtkquartz.c
--- gtk/gtkquartz.c	2021-01-24 15:47:28.000000000 +0000
+++ gtk/gtkquartz.c	2021-01-24 15:40:36.000000000 +0000
@@ -67,7 +67,11 @@
     }
   [nsimage lockFocus];

-  context = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
+  if (gdk_quartz_osx_version () < GDK_OSX_YOSEMITE)
+       context = [[NSGraphicsContext currentContext] graphicsPort];
+  else
+       context = [[NSGraphicsContext currentContext] CGContext];
+
   CGContextDrawImage (context, CGRectMake (0, 0, pixbuf_width, pixbuf_height), image);

   [nsimage unlockFocus];