make BufferObject's regions getData() return a clean slice

Author: riccardobl

jme3-core/src/main/java/com/jme3/shader/bufferobject/BufferRegion.java

@@ -70,21 +70,15 @@ public BufferRegion() {
      * @return ByteBuffer
      */
     public ByteBuffer getData() {
-        ByteBuffer d = bo.getData();
-        if (source == null || d != source || slice == null) {
-            source = d;
-            int currentPos = source.position();
-            int currentLimit = source.limit();
-            assert end < source.capacity() : "Can't set limit at " + end + " on capacity " + source.capacity();
-            source.limit(end + 1);
-            source.position(start);
-            slice = source.slice();
-            slice.order(source.order());
-            assert slice.limit() == (end - start + 1) : "Capacity is " + slice.limit() + " but " + (end - start + 1) + " expected";
-            source.limit(currentLimit);
-            source.position(currentPos);
-        }
-        slice.rewind();
+        ByteBuffer source = bo.getData();
+        assert end < source.capacity() : "Can't set limit at " + end + " on capacity " + source.capacity();
+
+        ByteBuffer view = source.duplicate();
+        view.position(start);
+        view.limit(end + 1);
+
+        ByteBuffer slice = view.slice().order(source.order());
+        assert slice.limit() == (end - start + 1) : "Capacity is " + slice.limit() + " but " + (end - start + 1) + " expected";
         return slice;
     }
 

jme3-core/src/main/java/com/jme3/shader/bufferobject/DirtyRegionsIterator.java

@@ -48,20 +48,11 @@ private static class DirtyRegion extends BufferRegion {
 
         @Override
         public ByteBuffer getData() {
-            ByteBuffer d = bo.getData();
-            if (source == null || d != source || slice == null) {
-                source = d;
-                int currentPos = source.position();
-                int currentLimit = source.limit();
-                source.limit(source.capacity());
-                source.position(0);
-                slice = source.slice();
-                source.limit(currentLimit);
-                source.position(currentPos);
-            }
-            slice.limit(end + 1);
-            slice.position(start);
-            return slice;
+            ByteBuffer source = bo.getData();
+            ByteBuffer view = source.duplicate();
+            view.position(start);
+            view.limit(end + 1);
+            return view.slice().order(source.order());
         }
 
         public void clearDirty() {

jme3-core/src/test/java/com/jme3/shader/bufferobject/DirtyRegionsIteratorTest.java

@@ -3,10 +3,10 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
 import java.util.Arrays;
 
 import org.junit.jupiter.api.Test;
@@ -53,6 +53,28 @@ public void testMergedDirtyRegionSliceUsesInclusiveEnd() {
         assertEquals(8, region.getData().remaining());
     }
 
+    @Test
+    public void testMergedDirtyRegionGetDataUsesZeroBasedSliceAndPreservesOrder() {
+        BufferObject bo = new BufferObject();
+        bo.setRegions(Arrays.asList(
+                new BufferRegion(0, 3),
+                new BufferRegion(4, 7),
+                new BufferRegion(8, 11)));
+
+        bo.getData().order(ByteOrder.LITTLE_ENDIAN);
+        bo.getRegion(0).markDirty();
+        bo.getRegion(1).markDirty();
+        bo.getRegion(2).clearDirty();
+        bo.setUpdateNeeded(false);
+
+        BufferRegion region = bo.getDirtyRegions().next();
+        ByteBuffer data = region.getData();
+
+        assertEquals(0, data.position());
+        assertEquals(8, data.remaining());
+        assertEquals(ByteOrder.LITTLE_ENDIAN, data.order());
+    }
+
     @Test
     public void testNoRegionsHasNextContract() {
         BufferObject bo = new BufferObject();