JRE-616 [linux] notify when dpi correction factor is applied to fonts

(cherry picked from commit f57d41f3118bfd773c99ce32d58cfae16931be6a)
(cherry picked from commit 6246abc72f)

src/java.desktop/share/classes/com/sun/java/swing/plaf/gtk/PangoFonts.java

@@ -30,6 +30,7 @@ import java.awt.geom.AffineTransform;
 import javax.swing.plaf.FontUIResource;
 import java.util.StringTokenizer;
 
+import sun.awt.AWTAccessor;
 import sun.font.FontConfigManager;
 import sun.font.FontUtilities;
 
@@ -161,8 +162,8 @@ class PangoFonts {
          */
         double dsize = size;
         int dpi = 96;
-        Object value =
-            Toolkit.getDefaultToolkit().getDesktopProperty("gnome.Xft/DPI");
+        Object xftDPI = Toolkit.getDefaultToolkit().getDesktopProperty("gnome.Xft/DPI");
+        Object value = xftDPI;
 
         if (!(value instanceof Integer)) {
             value = GTKEngine.INSTANCE.getSetting(GTKEngine.Settings.GTK_XFT_DPI);
@@ -179,6 +180,12 @@ class PangoFonts {
              * 72 dpi, so we need to adjust for that.
              */
             dsize = ((double)(dpi * size)/ 72.0);
+
+            if (xftDPI == null) {
+                // [tav] used to indicate the 96/72 scale correction to the client app
+                AWTAccessor.getToolkitAccessor().setDesktopProperty(
+                    Toolkit.getDefaultToolkit(), "gnome.Xft/DPI", value);
+            }
         } else {
             /* If there's no property, GTK scales for the resolution
              * reported by the Xserver using the formula listed above.

src/java.desktop/share/classes/java/awt/Toolkit.java

@@ -1397,6 +1397,11 @@ public abstract class Toolkit {
                     public void setPlatformResources(ResourceBundle bundle) {
                         Toolkit.setPlatformResources(bundle);
                     }
+
+                    @Override
+                    public void setDesktopProperty(Toolkit tk, String prop, Object value) {
+                        tk.setDesktopProperty(prop, value);
+                    }
                 });
 
         java.security.AccessController.doPrivileged(

src/java.desktop/share/classes/sun/awt/AWTAccessor.java

@@ -767,6 +767,7 @@ public final class AWTAccessor {
      */
     public interface ToolkitAccessor {
         void setPlatformResources(ResourceBundle bundle);
+        void setDesktopProperty(Toolkit tk, String prop, Object value);
     }
 
     /*