Host does not try to change ingame speed if game is out of focus

pom.xml

@@ -88,6 +88,18 @@
             <version>13</version>
         </dependency>
 
+        <dependency>
+            <groupId>net.java.dev.jna</groupId>
+            <artifactId>jna</artifactId>
+            <version>5.6.0</version>
+        </dependency>
+
+        <dependency>
+            <groupId>net.java.dev.jna</groupId>
+            <artifactId>jna-platform</artifactId>
+            <version>5.6.0</version>
+        </dependency>
+
         <dependency>
             <groupId>com.1stleg</groupId>
             <artifactId>jnativehook</artifactId>

src/main/java/com/github/davue/pss/server/SpeedNegotiator.java

@@ -44,6 +44,9 @@ public void check() {
         if (clients.isEmpty())
             return;
 
+        if (!WindowFocusListener.isGameFocused())
+            return;
+
         boolean doNothing = false;
         if (server.SPEED_UP_KEY == 0) {
             server.LOGGER.warn("No ingame speed up key set!");
@@ -83,9 +86,9 @@ public void check() {
                 robot.keyRelease(server.SPEED_UP_KEY);
                 server.hostSpeed++;
             }
-
-            server.LOGGER.info("Host is now running at speed: {}", server.hostSpeed);
         }
+
+        server.LOGGER.info("Host is now running at speed: {}", server.hostSpeed);
     }
 
     /**

src/main/java/com/github/davue/pss/server/WindowFocusListener.java

@@ -0,0 +1,59 @@
+/*
+ * A cross-platform tool to overcome the limitations of the speed controls of Paradox Interactive games.
+ * Copyright (C) 2020 David Enderlin
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.github.davue.pss.server;
+
+import com.sun.jna.Platform;
+import com.sun.jna.platform.win32.*;
+import com.sun.jna.ptr.IntByReference;
+
+public class WindowFocusListener {
+    private static final User32 user32 = User32.INSTANCE;
+    private static final Kernel32 kernel32 = Kernel32.INSTANCE;
+    private static final Psapi psapi = Psapi.INSTANCE;
+
+    private static final String[] validGames = {"ck2game", "stellaris", "hoi4", "eu4"};
+
+    public static boolean isGameFocused() {
+        if (Platform.isWindows()) {
+            String processPath = getFocusedProcess();
+            String[] split = processPath.split("\\\\");
+            String executableName = split[split.length - 1].toLowerCase();
+            for (String game : validGames) {
+                String validName = game + ".exe";
+                if (executableName.substring(0, validName.length()).equals(validName))
+                    return true;
+            }
+
+            return false;
+        } else
+            return true;
+    }
+
+    private static String getFocusedProcess() {
+        int PROCESS_QUERY_INFORMATION = 0x0400;
+        WinDef.HWND windowHandle = user32.GetForegroundWindow();
+        IntByReference pid = new IntByReference();
+        user32.GetWindowThreadProcessId(windowHandle, pid);
+        WinNT.HANDLE processHandle = kernel32.OpenProcess(PROCESS_QUERY_INFORMATION, true, pid.getValue());
+
+        byte[] filename = new byte[512];
+        Psapi.INSTANCE.GetModuleFileNameExA(processHandle, null, filename, filename.length);
+        return new String(filename);
+    }
+}