Drawable: Add layerOrderChanged signal

Resolves: #587

Author: adazem009

include/scratchcpp/drawable.h

@@ -3,6 +3,7 @@
 #pragma once
 
 #include "global.h"
+#include "signal.h"
 #include "spimpl.h"
 
 namespace libscratchcpp
@@ -27,6 +28,7 @@ class LIBSCRATCHCPP_EXPORT Drawable
 
         int layerOrder() const;
         virtual void setLayerOrder(int newLayerOrder);
+        sigslot::signal<int> &layerOrderChanged() const;
 
         IEngine *engine() const;
         virtual void setEngine(IEngine *engine);

src/scratch/drawable.cpp

@@ -22,6 +22,13 @@ int Drawable::layerOrder() const
 void Drawable::setLayerOrder(int newLayerOrder)
 {
     impl->layerOrder = newLayerOrder;
+    impl->layerOrderChanged(newLayerOrder);
+}
+
+/*! Emits when the layer number changes. */
+sigslot::signal<int> &Drawable::layerOrderChanged() const
+{
+    return impl->layerOrderChanged;
 }
 
 /*! Returns the engine. */

src/scratch/drawable_p.h

@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include <scratchcpp/signal.h>
+
 namespace libscratchcpp
 {
 
@@ -11,6 +13,7 @@ struct DrawablePrivate
 {
         int layerOrder = 0;
         IEngine *engine = nullptr;
+        mutable sigslot::signal<int> layerOrderChanged;
 };
 
 } // namespace libscratchcpp

test/scratch_classes/drawable_test.cpp

@@ -5,6 +5,12 @@
 
 using namespace libscratchcpp;
 
+class LayerOrderMock
+{
+    public:
+        MOCK_METHOD(void, f, (int));
+};
+
 TEST(DrawableTest, IsTarget)
 {
     Drawable drawable;
@@ -21,8 +27,17 @@ TEST(DrawableTest, LayerOrder)
 {
     Drawable drawable;
     ASSERT_EQ(drawable.layerOrder(), 0);
+
+    LayerOrderMock spy;
+    drawable.layerOrderChanged().connect(&LayerOrderMock::f, &spy);
+
+    EXPECT_CALL(spy, f(2));
     drawable.setLayerOrder(2);
     ASSERT_EQ(drawable.layerOrder(), 2);
+
+    EXPECT_CALL(spy, f(0));
+    drawable.setLayerOrder(0);
+    ASSERT_EQ(drawable.layerOrder(), 0);
 }
 
 TEST(TargetTest, Engine)