RChehowski · October 10, 2019 20:17 · Oct 10, 2019
diff --git a/WindowsFlash.java b/WindowsFlash.java
@@ -0,0 +1,101 @@
+package com.vizor;
+
+import com.sun.jna.Pointer;
+import com.sun.jna.platform.win32.User32;
+import com.sun.jna.platform.win32.WinNT.HANDLE;
+import com.sun.jna.platform.win32.WinUser;
+import javafx.stage.Stage;
+
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
+import java.util.List;
+import java.util.Optional;
+
+import static com.sun.jna.platform.win32.WinUser.FLASHW_ALL;
+import static com.sun.jna.platform.win32.WinUser.FLASHW_TIMERNOFG;
+
+public class WindowsFlash
+{
+    /**
+     * This check greatly increases the probability to retrieve exactly the same window that you've required
+     * since the JavaFX stage title must be exactly the same string as the one from the glass window.
+     * Otherwise we might get the wrong window with exactly the same name.
+     *
+     * @param stageWindowName JavaFX Stage window name.
+     * @param glassWindowName Native glass window name.
+     *
+     * @return Whether the two strings are identical.
+     */
+    @SuppressWarnings("StringEquality")
+    private static boolean stringsAreIdentical(final String stageWindowName, final String glassWindowName)
+    {
+        return stageWindowName == glassWindowName;
+    }
+
+    /**
+     * Returns the JavaFX Stage native window handle for Windows.
+     *
+     * @param stage The JavaFX stage.
+     *
+     * @return An optional value containing the native window handle.
+     */
+    private static Optional<HANDLE> getStageHandle(final Stage stage)
+    {
+        try
+        {
+            final Class<?> glassWindowClass = Class.forName("com.sun.glass.ui.Window");
+
+            final MethodHandle getTitleMethodHandle = MethodHandles.lookup()
+                    .findVirtual(glassWindowClass, "getTitle", MethodType.methodType(String.class));
+
+            final MethodHandle getNativeHandleMethodHandle = MethodHandles.lookup()
+                    .findVirtual(glassWindowClass, "getNativeHandle", MethodType.methodType(long.class));
+
+            final MethodHandle getWindows = MethodHandles.lookup()
+                    .findStatic(glassWindowClass, "getWindows", MethodType.methodType(List.class));
+
+            // Iterate through glass windows and find the right one
+            final List<?> glassWindows = (List<?>) getWindows.invoke();
+            for (final Object glassWindow : glassWindows)
+            {
+                final String stageWindowName = stage.getTitle();
+                final String glassWindowName = (String) getTitleMethodHandle.invoke(glassWindow);
+
+                // Check strings identity, don't compare them
+                if (stringsAreIdentical(stageWindowName, glassWindowName))
+                {
+                    final long nativeHandle = (long)getNativeHandleMethodHandle.invoke(glassWindow);
+                    return Optional.of(new HANDLE(new Pointer(nativeHandle)));
+                }
+            }
+
+            // Unable to find the correct window
+            return Optional.empty();
+        }
+        catch (Throwable throwable)
+        {
+            // This may be a NPE, a reflective operation exception or a security exception
+            return Optional.empty();
+        }
+    }
+
+    /**
+     * Flashes the specified window. It does not change the active state of the window.
+     * Silently does nothing if any error occurred.
+     *
+     * @param stage JavaFX stage to flash.
+     */
+    public static void flashWindowIcon(final Stage stage)
+    {
+        getStageHandle(stage).ifPresent(windowHandle -> {
+            WinUser.FLASHWINFO info = new WinUser.FLASHWINFO();
+            info.hWnd = windowHandle;
+            info.dwFlags = FLASHW_ALL | FLASHW_TIMERNOFG;
+            info.uCount = Integer.MAX_VALUE;
+            info.dwTimeout = 0;
+
+            User32.INSTANCE.FlashWindowEx(info);
+        });
+    }
+}