fix #537: Move sprite to front when starting dragging

Author: adazem009

src/scratch/sprite.cpp

@@ -226,6 +226,11 @@ bool Sprite::dragging() const
 void Sprite::startDragging()
 {
     impl->dragging = true;
+
+    IEngine *eng = engine();
+
+    if (eng)
+        eng->moveSpriteToFront(this);
 }
 
 /*! Stops dragging. */

test/scratch_classes/sprite_test.cpp

@@ -400,6 +400,12 @@ TEST(SpriteTest, Dragging)
     sprite.setInterface(&handler);
     ASSERT_FALSE(sprite.dragging());
 
+    EngineMock engine;
+    sprite.setEngine(&engine);
+    EXPECT_CALL(engine, spriteFencingEnabled).WillRepeatedly(Return(false));
+    EXPECT_CALL(engine, requestRedraw).WillRepeatedly(Return());
+
+    EXPECT_CALL(engine, moveSpriteToFront(&sprite));
     sprite.startDragging();
     ASSERT_TRUE(sprite.dragging());