open small window to confirm closing the game when clicking the [X] o…

…n main game window

src/main/java/com/dreammaster/mixin/mixins/early/MixinMinecraft_PackIcon.java

@@ -1,5 +1,9 @@
 package com.dreammaster.mixin.mixins.early;
 
+import java.net.URL;
+
+import javax.swing.*;
+
 import net.minecraft.client.Minecraft;
 import net.minecraft.util.Util;
 
@@ -36,4 +40,37 @@ public class MixinMinecraft_PackIcon {
         return this.dreamcraft$loadedGTNHIcon ? Util.EnumOS.OSX : osType;
     }
 
+    @Unique
+    private boolean dreamcraft$isCloseRequested;
+
+    @ModifyExpressionValue(
+            method = "runGameLoop",
+            at = @At(value = "INVOKE", target = "Lorg/lwjgl/opengl/Display;isCloseRequested()Z", remap = false))
+    private boolean dreamcraft$confirmGameShutdown(boolean isCloseRequested) {
+        if (this.dreamcraft$isCloseRequested) {
+            return true;
+        }
+        if (isCloseRequested) {
+            new Thread(() -> {
+                final JFrame frame = new JFrame();
+                frame.setAlwaysOnTop(true);
+                final URL resource = IconLoader.class.getClassLoader()
+                        .getResource("assets/dreamcraft/textures/icon/GTNH_42x42.png");
+                final ImageIcon imageIcon = resource == null ? null : new ImageIcon(resource);
+                final int result = JOptionPane.showConfirmDialog(
+                        frame,
+                        "Are you sure you want to exit the game ?",
+                        Refstrings.NAME,
+                        JOptionPane.YES_NO_OPTION,
+                        JOptionPane.QUESTION_MESSAGE,
+                        imageIcon);
+                if (result == JOptionPane.YES_OPTION) {
+                    this.dreamcraft$isCloseRequested = true;
+                }
+            }).start();
+            return false;
+        }
+        return false;
+    }
+
 }