- refactored

- constify

source/AStack.cpp

@@ -26,6 +26,7 @@ AStack::AStack(StackType type, const std::string &name)
 : m_name(name)
 , m_type(type)
 , m_pLayers(nullptr)
+, m_numLayers(0)
 {
 }
 
@@ -50,16 +51,9 @@ void AStack::setName(const std::string& name)
 	m_name = name;
 }
 
-size_t AStack::numLayers()
+size_t AStack::numLayers() const
 {
-	size_t count = 0;
-	Layer *pLayer = m_pLayers;
-	while(pLayer)
-	{
-		count++;
-		pLayer = pLayer->next;
-	}
-	return count;
+	return m_numLayers;
 }
 
 void AStack::addLayer(Layer *pOtherLayer)
@@ -79,6 +73,7 @@ void AStack::addLayer(Layer *pOtherLayer)
 		pLayer->next = pOtherLayer;
 		pOtherLayer->prev = pLayer;
 	}
+	updateNumLayers();
 }
 
 void AStack::delLayer(Layer* pLayer)
@@ -86,6 +81,17 @@ void AStack::delLayer(Layer* pLayer)
 	assert(!"Stack::delLayer: Not implemented!");
 }
 
+void AStack::updateNumLayers()
+{
+	m_numLayers = 0;
+	Layer *pLayer = m_pLayers;
+	while(pLayer)
+	{
+		m_numLayers++;
+		pLayer = pLayer->next;
+	}
+}
+
 Layer* AStack::getLayer(size_t layerId) const
 {
 	Layer *pLayer = m_pLayers;
@@ -101,6 +107,16 @@ Layer* AStack::getLayer(size_t layerId) const
 	
 }
 
+Layer* AStack::getFirstLayer() const
+{
+	return getLayer(0);
+}
+
+Layer* AStack::getLastLayer() const
+{
+	return getLayer(numLayers()-1);
+}
+
 bool AStack::save(const std::string &dir)
 {
 	return StackCreator::toFile(this, dir, m_name);