Add IGUIElement::isTrulyVisible which works like ISceneNode::isTrulyVisible.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@4462 dfc29bdd-3216-0410-991c-e03cc46cb475

changes.txt

@@ -1,6 +1,7 @@
 --------------------------
 Changes in 1.9 (not yet released)
 
+- Add IGUIElement::isTrulyVisible which works like ISceneNode::isTrulyVisible and checks for parent visibility as well.
 - Improved DDS loader and added support for DXTn (DXT1-5) compressed textures in OpenGL and Direct3D9 drivers.
 - Add function ISceneNode::getTransformedBoundingBoxEdges.
 - Improve automatic compiling under solaris (proposed by curaga)

include/IGUIElement.h

@@ -346,6 +346,20 @@ public:
 		return IsVisible;
 	}
 
+	//! Check whether the element is truly visible, taking into accounts its parents' visibility
+	/** \return true if the element and all its parents are visible,
+	false if this or any parent element is invisible. */
+	virtual bool isTrulyVisible() const
+	{
+		_IRR_IMPLEMENT_MANAGED_MARSHALLING_BUGFIX;
+		if(!IsVisible)
+			return false;
+
+		if(!Parent)
+			return true;
+
+		return Parent->isTrulyVisible();
+	}
 
 	//! Sets the visible state of this element.
 	virtual void setVisible(bool visible)