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

@@ -36,10 +36,12 @@
 
 import sun.awt.X11GraphicsConfig;
 import sun.awt.X11GraphicsDevice;
 import sun.awt.X11GraphicsEnvironment;
 
+import sun.java2d.pipe.Region;
+
 /*
  * This class is a collection of utility methods that operate
  * with native windows.
  */
 public class XlibUtil

@@ -412,8 +414,8 @@
             return 1 << (7 + button);
         }
     }
 
     static int scaleDown(int x, int scale) {
-        return x / scale;
+        return Region.clipRound(x / (double)scale);
     }
 }