src/java.desktop/unix/classes/sun/awt/X11GraphicsDevice.java

@@ -42,10 +42,11 @@
 import sun.java2d.xr.XRGraphicsConfig;
 import sun.java2d.loops.SurfaceType;
 
 import sun.awt.util.ThreadGroupUtils;
 import sun.misc.ManagedLocalsThread;
+import sun.security.action.GetPropertyAction;
 
 /**
  * This is an implementation of a GraphicsDevice object for a single
  * X11 screen.
  *

@@ -61,13 +62,15 @@
     private static Boolean xrandrExtSupported;
     private final Object configLock = new Object();
     private SunDisplayChanger topLevels = new SunDisplayChanger();
     private DisplayMode origDisplayMode;
     private boolean shutdownHookRegistered;
+    private int scale;
 
     public X11GraphicsDevice(int screennum) {
         this.screen = screennum;
+        this.scale = initScaleFactor();
     }
 
     /*
      * Initialize JNI field and method IDs for fields that may be
      * accessed from C.

@@ -277,10 +280,11 @@
                                                 ArrayList<DisplayMode> modes);
     private static native void configDisplayMode(int screen,
                                                  int width, int height,
                                                  int displayMode);
     private static native void resetNativeData(int screen);
+    private static native int getNativeScaleFactor(int screen);
 
     /**
      * Returns true only if:
      *   - the Xrandr extension is present
      *   - the necessary Xrandr functions were loaded successfully

@@ -507,10 +511,37 @@
      */
     public void addDisplayChangedListener(DisplayChangedListener client) {
         topLevels.add(client);
     }
 
+    public int getScaleFactor(){
+        return scale;
+    }
+
+    private int initScaleFactor() {
+
+        boolean hidpiEnabled = "true".equals(AccessController.doPrivileged(
+                new GetPropertyAction("sun.java2d.uiScale.enabled", "true")));
+
+        if (!hidpiEnabled) {
+            return 1;
+        }
+
+        String hidpiScale = AccessController.doPrivileged(
+                new GetPropertyAction("sun.java2d.uiScale", "-1"));
+        try {
+            int scale = Integer.parseInt(hidpiScale);
+            if (scale >= 1) {
+                return scale;
+            }
+        } catch (NumberFormatException ignore) {
+        }
+
+        int scale = getNativeScaleFactor(screen);
+        return scale >= 1 ? scale : 1;
+    }
+    
     /**
      * Remove a DisplayChangeListener from this X11GraphicsDevice.
      */
     public void removeDisplayChangedListener(DisplayChangedListener client) {
         topLevels.remove(client);