Settings: Eagerly install theme if invoked on the UI thread.

core/src/main/java/com/github/weisj/darklaf/settings/ThemeSettings.java

@@ -39,6 +39,7 @@ import com.github.weisj.darklaf.theme.info.AccentColorRule;
 import com.github.weisj.darklaf.theme.info.FontSizeRule;
 import com.github.weisj.darklaf.theme.info.PreferredThemeStyle;
 import com.github.weisj.darklaf.ui.util.DarkUIUtil;
+import com.github.weisj.darklaf.ui.util.UIThread;
 import com.github.weisj.darklaf.util.LazyValue;
 import com.github.weisj.darklaf.util.LogUtil;
 import com.github.weisj.darklaf.util.value.WeakShared;
@@ -510,7 +511,7 @@ public class ThemeSettings implements ThemePreferenceListener {
     protected void applyTheme(final Theme theme) {
         if (theme == null) return;
         if (LafManager.isInstalled() && LafManager.getTheme().appearsEqualTo(theme)) return;
-        SwingUtilities.invokeLater(() -> {
+        UIThread.runOnUIThread(() -> {
             LafManager.installTheme(theme);
             refresh();
         });

core/src/main/java/com/github/weisj/darklaf/ui/util/UIThread.java

@@ -0,0 +1,36 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2021 Jannis Weis
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+ * associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
+ * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+package com.github.weisj.darklaf.ui.util;
+
+import javax.swing.*;
+
+public final class UIThread {
+    private UIThread() {}
+
+    public static void runOnUIThread(final Runnable task) {
+        if (SwingUtilities.isEventDispatchThread()) {
+            task.run();
+        } else {
+            SwingUtilities.invokeLater(task);
+        }
+    }
+}