Bug 518717 - [GTK3] Replace deprecated gdk_screen_width_mm()

Change-Id: Ibfa8e61d71f49dd0c64d0f94d79e403ec453542a
Signed-off-by: Sravan Kumar Lakkimsetti <sravankumarl@in.ibm.com>
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java
index 19357d1..0bff506 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java
@@ -467,9 +467,14 @@
 }
 
 Point getScreenDPI () {
-	int widthMM = GDK.gdk_screen_width_mm ();
-	int width = GDK.gdk_screen_width ();
-	int dpi = Compatibility.round (254 * width, widthMM * 10);
+	long /*int*/ screen = GDK.gdk_screen_get_default();
+	int dpi = (int) GDK.gdk_screen_get_resolution (screen);
+	if (dpi <= 0) dpi = 96; // gdk_screen_get_resolution returns -1 in case of error
+	if (GTK.GTK_VERSION > OS.VERSION(3, 9, 0)) {
+		int monitor_num = GDK.gdk_screen_get_monitor_at_point (screen, 0, 0);
+		int scale = GDK.gdk_screen_get_monitor_scale_factor (screen, monitor_num);
+		dpi = dpi * scale;
+	}
 	return new Point (dpi, dpi);
 }
 
@@ -1062,15 +1067,7 @@
  * @since 3.105
  */
 protected int getDeviceZoom() {
-	long /*int*/ screen = GDK.gdk_screen_get_default();
-	int dpi = (int) GDK.gdk_screen_get_resolution (screen);
-	if (dpi <= 0) dpi = 96; // gdk_screen_get_resolution returns -1 in case of error
-	if (GTK.GTK_VERSION > OS.VERSION(3, 9, 0)) {
-		int monitor_num = GDK.gdk_screen_get_monitor_at_point (screen, 0, 0);
-		int scale = GDK.gdk_screen_get_monitor_scale_factor (screen, monitor_num);
-		dpi = dpi * scale;
-	}
-	return DPIUtil.mapDPIToZoom (dpi);
+	return DPIUtil.mapDPIToZoom (getScreenDPI().x);
 }
 /**
  * @noreference This method is not intended to be referenced by clients.