add board_getActiveRect to jni, and use it to capture a thumbnail

that's smaller.  Scaling is still a problem, though: some but not all
grid lines show up.

xwords4/android/XWords4/jni/andutils.c

@@ -275,13 +275,25 @@ getIntFromArray( JNIEnv* env, jintArray arr, bool del )
 {
     jint* ints = (*env)->GetIntArrayElements(env, arr, 0);
     int result = ints[0];
-    (*env)->ReleaseIntArrayElements( env, arr, ints, 0);
+    (*env)->ReleaseIntArrayElements( env, arr, ints, 0 );
     if ( del ) {
         deleteLocalRef( env, arr );
     }
     return result;
 }
 
+void
+setIntInArray( JNIEnv* env, jintArray arr, int index, int val )
+{
+    jint* ints = (*env)->GetIntArrayElements( env, arr, 0 );
+#ifdef DEBUG
+    jsize len = (*env)->GetArrayLength( env, arr );
+    XP_ASSERT( len > index );
+#endif
+    ints[index] = val;
+    (*env)->ReleaseIntArrayElements( env, arr, ints, 0 );
+}
+
 jobjectArray
 makeStringArray( JNIEnv *env, int siz, const XP_UCHAR** vals )
 {

xwords4/android/XWords4/jni/andutils.h

@@ -48,6 +48,7 @@ bool getObject( JNIEnv* env, jobject obj, const char* name, const char* sig,
 
 jintArray makeIntArray( JNIEnv *env, int size, const jint* vals );
 int getIntFromArray( JNIEnv* env, jintArray arr, bool del );
+void setIntInArray( JNIEnv* env, jintArray arr, int index, int val );
 
 jbyteArray makeByteArray( JNIEnv* env, int size, const jbyte* vals );
 

xwords4/android/XWords4/jni/xwjni.c

@@ -640,6 +640,29 @@ Java_org_eehouse_android_xw4_jni_XwJNI_board_1setTrayLoc
     XWJNI_END();
 }
 
+#ifdef XWFEATURE_ACTIVERECT
+JNIEXPORT jboolean JNICALL 
+Java_org_eehouse_android_xw4_jni_XwJNI_board_1getActiveRect
+( JNIEnv* env, jclass C, jint gamePtr, jobject jrect, jintArray dims )
+{
+    jboolean result;
+    XWJNI_START();
+    XP_Rect rect;
+    XP_U16 nCols, nRows;
+    result = board_getActiveRect( state->game.board, &rect, &nCols, &nRows );
+    if ( result ) {
+        setInt( env, jrect, "left", rect.left );
+        setInt( env, jrect, "top", rect.top );
+        setInt( env, jrect, "right", rect.left + rect.width );
+        setInt( env, jrect, "bottom", rect.top + rect.height );
+        setIntInArray( env, dims, 0, nCols );
+        setIntInArray( env, dims, 1, nRows );
+    }
+    XWJNI_END();
+    return result;
+}
+#endif
+
 JNIEXPORT jboolean JNICALL
 Java_org_eehouse_android_xw4_jni_XwJNI_board_1handlePenDown
 (JNIEnv *env, jclass C, jint gamePtr, jint xx, jint yy, jbooleanArray barray )

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

@@ -940,12 +940,23 @@ public class BoardView extends View implements DrawCtx, BoardHandler,
     public Bitmap getScaledBoard()
     {
         Bitmap result = null;
-        int divisor = XWPrefs.getThumbScale( m_context );
-        if ( 0 < divisor ) {
-            result = Bitmap.createScaledBitmap( s_bitmap, 
-                                                m_layoutWidth / divisor,
-                                                m_layoutHeight / divisor,
-                                                false );
+        if ( GitVersion.THUMBNAIL_SUPPORTED ) {
+            int divisor = XWPrefs.getThumbScale( m_context );
+
+            if ( 0 < divisor ) {
+                int[] dims = new int[2];
+                Rect rect = new Rect();
+                XwJNI.board_getActiveRect( m_jniGamePtr, rect, dims );
+
+                Bitmap tmpb = 
+                    Bitmap.createBitmap( s_bitmap, rect.left, rect.top,
+                                         1 + rect.width(), 1 + rect.height() );
+
+                result = Bitmap.createScaledBitmap( tmpb,
+                                                    rect.width() / divisor,
+                                                    rect.height() / divisor,
+                                                    false );
+            }
         }
         return result;
     }

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

@@ -20,6 +20,9 @@
 
 package org.eehouse.android.xw4.jni;
 
+import android.graphics.Rect;
+
+
 // Collection of native methods
 public class XwJNI {
 
@@ -159,6 +162,8 @@ public class XwJNI {
     public static native void board_setTimerLoc( int gamePtr,
                                                  int timerLeft, int timerTop,
                                                  int timerWidth, int timerHeight );
+    public static native boolean board_getActiveRect( int gamePtr, Rect rect,
+                                                      int[] dims );
 
     public static native boolean board_handlePenDown( int gamePtr, 
                                                       int xx, int yy,