customize game startup for macOS platforms

Author: stephengold

common.gradle

@@ -8,7 +8,14 @@ java {
     targetCompatibility = JavaVersion.VERSION_11
 }
 
+import org.gradle.nativeplatform.platform.internal.DefaultNativePlatform
+Boolean isMacOS = DefaultNativePlatform.currentOperatingSystem.isMacOsX()
+
 tasks.withType(JavaExec) { // Java runtime options:
+    if (isMacOS) {
+        args '--noDialog'
+        jvmArgs '-XstartOnFirstThread'
+    }
     enableAssertions = true
 }
 

game/src/main/java/mygame/Main.java

@@ -45,9 +45,17 @@ public class Main extends GameApplication {
 
     /**
      * Start the jMonkeyEngine application
-     * @param args
+     *
+     * @param args might contain "--noDialog"
      */
     public static void main(String[] args) {
+        boolean showSettingsDialog = true;
+        for (String arg : args) {
+            if (arg.equals("--noDialog")) {
+                showSettingsDialog = false;
+            }
+        }
+
         // Mute the chatty loggers in certain packages.
         Heart.setLoggingLevels(Level.WARNING);
 
@@ -65,7 +73,7 @@ public static void main(String[] args) {
         //settings.setFrameRate(60);
 
         app.setSettings(settings);
-        app.setShowSettings(true);
+        app.setShowSettings(showSettingsDialog);
         app.setPauseOnLostFocus(false);
         app.start();
     }