8257414: Drag n Drop target area is wrong on high DPI systems

Backport-of: d3398324e9c3944d2f1558ff1becea9ed1d4e8a2

src/java.desktop/unix/classes/sun/awt/X11/XDnDDropTargetProtocol.java

@@ -37,6 +37,14 @@
 
 import jdk.internal.misc.Unsafe;
 
+import java.awt.Rectangle;
+
+import java.awt.GraphicsDevice;
+
+import java.awt.GraphicsEnvironment;
+
+import sun.awt.X11GraphicsConfig;
+
 /**
  * XDropTargetProtocol implementation for XDnD protocol.
  *
@@ -597,7 +605,25 @@ private boolean processXdndPosition(XClientMessageEvent xclient) {
         x = (int)(xclient.get_data(2) >> 16);
         y = (int)(xclient.get_data(2) & 0xFFFF);
 
-        if (xwindow == null) {
+        if (xwindow != null) {
+            x = xwindow.scaleDown(x);
+            y = xwindow.scaleDown(y);
+        } else {
+            GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
+            for (GraphicsDevice gd : ge.getScreenDevices()) {
+                X11GraphicsConfig gc = (X11GraphicsConfig)gd.getDefaultConfiguration();
+                Rectangle rt = gc.getBounds();
+                rt.x      = gc.scaleUp(rt.x);
+                rt.y      = gc.scaleUp(rt.y);
+                rt.width  = gc.scaleUp(rt.width);
+                rt.height = gc.scaleUp(rt.height);
+                if (rt.contains(x, y)) {
+                    x = gc.scaleDown(x);
+                    y = gc.scaleDown(y);
+                    break;
+                }
+            }
+
             long receiver =
                 XDropTargetRegistry.getRegistry().getEmbeddedDropSite(
                     xclient.get_window(), x, y);

src/java.desktop/unix/classes/sun/awt/X11/XDragSourceContextPeer.java

@@ -524,17 +524,17 @@ private void processMouseMove(XMotionEvent xmotion) {
         updateTargetWindow(xmotion);
 
         if (dragProtocol != null) {
-            dragProtocol.sendMoveMessage(scaleDown(xmotion.get_x_root()),
-                                         scaleDown(xmotion.get_y_root()),
+            dragProtocol.sendMoveMessage(xmotion.get_x_root(),
+                                         xmotion.get_y_root(),
                                          sourceAction, sourceActions,
                                          xmotion.get_time());
         }
     }
 
     private void processDrop(XButtonEvent xbutton) {
         try {
-            dragProtocol.initiateDrop(scaleDown(xbutton.get_x_root()),
-                                      scaleDown(xbutton.get_y_root()),
+            dragProtocol.initiateDrop(xbutton.get_x_root(),
+                                      xbutton.get_y_root(),
                                       sourceAction, sourceActions,
                                       xbutton.get_time());
         } catch (XException e) {