diff -r e199adc2d3cc modules/graphics/src/main/native-glass/gtk/glass_gtkcompat.cpp
--- a/modules/graphics/src/main/native-glass/gtk/glass_gtkcompat.cpp	Fri Oct 02 08:25:28 2015 -0700
+++ b/modules/graphics/src/main/native-glass/gtk/glass_gtkcompat.cpp	Sat Dec 22 00:33:14 2018 +0900
@@ -26,6 +26,7 @@
 #include "glass_general.h"
 #include <gdk/gdk.h>
 #include <gtk/gtk.h>
+#include <pthread.h>
 
 gboolean disableGrab = FALSE;
 
@@ -292,12 +293,41 @@
     gtk_widget_realize(window);
 }
 
+static GdkColormap* known_colormap = 0;
+static GdkVisual* known_visual = 0;
+static pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
+
 void
 glass_gtk_window_configure_from_visual(GtkWidget *widget, GdkVisual *visual) {
-    GdkColormap *colormap = gdk_colormap_new(visual, TRUE);
+    GdkColormap *colormap;
+    pthread_mutex_lock(&mtx);
+    if (known_visual == 0 || known_colormap == 0) {
+        colormap = gdk_colormap_new(visual, TRUE);
+        known_colormap = colormap;
+	known_visual = visual;
+    } else if (visual != known_visual) {
+        g_object_unref(known_colormap);
+        colormap = gdk_colormap_new(visual, TRUE);
+        known_visual = visual;
+        known_colormap = colormap;
+    } else {
+        colormap = known_colormap;
+    }
+    pthread_mutex_unlock(&mtx);
     gtk_widget_set_colormap(widget, colormap);
 }
 
+#ifdef __GNUC__
+__attribute__((destructor))
+static void destructor() {
+    if (known_colormap) {
+        g_object_unref(known_colormap);
+    }
+}
+#endif
+
 static gboolean
 configure_transparent_window(GtkWidget *window) {
     GdkScreen *default_screen = gdk_screen_get_default();