synchronize access to the bitmap and owning canvas used first by

jni-sourced drawing and then by doDraw to put the bits on the screen.
This should fix crashes when screen orientation changes while
board_draw is running in the JNI thread, but for some reason the
emulators aren't signaling config changes so I can't test.

xwords4/android/XWords4/src/org/eehouse/android/xw4/BoardActivity.java

@@ -13,7 +13,6 @@ import android.os.Handler;
 import android.os.Message;
 import java.io.FileOutputStream;
 import java.io.FileInputStream;
-import android.content.res.Configuration;
 import android.content.Intent;
 import java.util.concurrent.Semaphore;
 import android.net.Uri;
@@ -168,7 +167,7 @@ public class BoardActivity extends Activity implements UtilCtxt {
             }
 
             m_jniThread = new 
-                JNIThread( m_jniGamePtr, m_gi,
+                JNIThread( m_jniGamePtr, m_gi, m_view,
                            new Handler() {
                                public void handleMessage( Message msg ) {
                                    switch( msg.what ) {

xwords4/android/XWords4/src/org/eehouse/android/xw4/BoardView.java

@@ -16,8 +16,8 @@ import android.graphics.drawable.BitmapDrawable;
 import android.content.res.Resources;
 import android.graphics.Paint.FontMetricsInt;
 
-public class BoardView extends View implements DrawCtx, 
-                                               BoardHandler {
+public class BoardView extends View implements DrawCtx, BoardHandler,
+                                               SyncedDraw {
 
     private Paint m_fillPaint;
     private Paint m_strokePaint;
@@ -26,8 +26,8 @@ public class BoardView extends View implements DrawCtx,
     private CurGameInfo m_gi;
     private int m_layoutWidth = 0;
     private int m_layoutHeight = 0;
-    private Canvas m_canvas;
-    private Bitmap m_bitmap;
+    private Bitmap m_bitmap;    // the board
+    private Canvas m_canvas;    // owns the bitmap
     private int m_trayOwner;
     private Rect m_valRect;
     private Rect m_letterRect;
@@ -105,10 +105,14 @@ public class BoardView extends View implements DrawCtx,
         return true;             // required to get subsequent events
     }
 
+    // This will be called from the UI thread
+    @Override
     protected void onDraw( Canvas canvas ) 
     {
-        if ( layoutBoardOnce() ) {
-            canvas.drawBitmap( m_bitmap, m_left, m_top, new Paint() );
+        synchronized( this ) {
+            if ( layoutBoardOnce() ) {
+                canvas.drawBitmap( m_bitmap, m_left, m_top, new Paint() );
+            }
         }
     }
 
@@ -192,8 +196,9 @@ public class BoardView extends View implements DrawCtx,
             layoutDone = true;
         }
         return layoutDone;
-    }
+    } // layoutBoardOnce
 
+    // BoardHandler interface implementation
     public void startHandling( JNIThread thread, int gamePtr, CurGameInfo gi ) 
     {
         m_jniThread = thread;
@@ -201,6 +206,18 @@ public class BoardView extends View implements DrawCtx,
         m_gi = gi;
     }
 
+    // SyncedDraw interface implementation
+    public void doJNIDraw()
+    {
+        boolean drew;
+        synchronized( this ) {
+            drew = XwJNI.board_draw( m_jniGamePtr );
+        }
+        if ( !drew ) {
+            Utils.logf( "draw not complete" );
+        }
+    }
+
     // DrawCtxt interface implementation
     public void scoreBegin( Rect rect, int numPlayers, int[] scores, 
                             int remCount, int dfs )

xwords4/android/XWords4/src/org/eehouse/android/xw4/jni/JNIThread.java

@@ -51,6 +51,8 @@ public class JNIThread extends Thread {
     private int m_jniGamePtr;
     private CurGameInfo m_gi;
     private Handler m_handler;
+    private SyncedDraw m_drawer;
+
     LinkedBlockingQueue<QueueElem> m_queue;
 
     private class QueueElem {
@@ -62,10 +64,13 @@ public class JNIThread extends Thread {
         Object[] m_args;
     }
 
-    public JNIThread( int gamePtr, CurGameInfo gi, Handler handler ) {
+    public JNIThread( int gamePtr, CurGameInfo gi, SyncedDraw drawer, 
+                      Handler handler ) 
+    {
         m_jniGamePtr = gamePtr;
         m_gi = gi;
         m_handler = handler;
+        m_drawer = drawer;
 
         m_queue = new LinkedBlockingQueue<QueueElem>();
     }
@@ -303,9 +308,13 @@ public class JNIThread extends Thread {
             }
 
             if ( draw ) {
-                if ( !XwJNI.board_draw( m_jniGamePtr ) ) {
-                    Utils.logf( "draw not complete" );
-                }
+                // do the drawing in this thread but in BoardView
+                // where it can be synchronized with that class's use
+                // of the same bitmap for blitting.
+                m_drawer.doJNIDraw();
+
+                // main UI thread has to invalidate view as it created
+                // it.
                 Message.obtain( m_handler, DRAW ).sendToTarget();
             }
         }