Add parameter to control if engine keeps pixel scale.

Author: EMaksymenko

worldwind/src/main/java/gov/nasa/worldwind/WorldWindow.java

@@ -92,6 +92,8 @@ public class WorldWindow extends GLSurfaceView implements Choreographer.FrameCal
 
     protected Viewport viewport = new Viewport();
 
+    protected boolean keepScale = true;
+
     protected int depthBits;
 
     protected Pool<Frame> framePool = new SynchronizedPool<>();
@@ -116,7 +118,7 @@ public boolean handleMessage(Message msg) {
             } else if (msg.what == MSG_ID_SET_VIEWPORT) {
                 Viewport newViewport = (Viewport) msg.obj;
                 // Keep map scale by adopting field of view on view port resize
-                if (viewport.height != 0) {
+                if (keepScale && viewport.height != 0) {
                     try {
                         camera.setFieldOfView(camera.getFieldOfView() * newViewport.height / viewport.height);
                     } catch (IllegalArgumentException ignore) {
@@ -306,6 +308,15 @@ public Navigator getNavigator() {
         return this.navigator;
     }
 
+    /**
+     * Keep pixel scale when changing the height of viewport by adapting field of view
+     *
+     * @param keepScale if true, then field of view will be changed on viewport height change to keep pixel scale
+     */
+    public void setKeepScale(boolean keepScale) {
+        this.keepScale = keepScale;
+    }
+
     public void addNavigatorListener(NavigatorListener listener) {
         if (listener == null) {
             throw new IllegalArgumentException(