Can someone explain to me whats going on here.

Question

BOOL OGLWindow::MouseMove(int x, int y)
{
Listener *plistener = static_cast<Listener*>(m_rect);
plistener->MouseMove(x - m_width * 0.5, m_height * 0.5 - y);

return TRUE;
}

Answer 1

BOOL OGLWindow::MouseMove(int x, int y)
{
Listener *plistener = static_cast<Listener*>(m_rect);
plistener->MouseMove(x - m_width * 0.5, m_height * 0.5 - y);

return TRUE;
}

Please do not put the whole question in the subject.

But what is your question really? How can we answer without some information about the type of m_rect and the definition of thListener class?

I would say, though, that the cast looks rather odd.

---

David Wilkinson | Visual C++ MVP

Answer 2

Code is moving cursor to center of the rectangle.  Always returns true.

---

jdweng

Answer 3

Well, without knowing more about your inheritence heiarchy and the declaration of m_rect, I can only make some general statements.

Your OGLWindow class has a m_rect member variable.  That variable is not of type Listener*.  static_cast<Listener*> is used to cast m_rect to a pointer to Listener.  The compiler will prevent a nonsensical cast. For example,  if m_rect is something that couldn't be a Listener* that would be a compiler error.  Also, if m_rect were a const pointer, static_cast would prevent the cast from removing the const.  However, no runtime check will be performed, so you better be sure that m_rect really is a Listener.

Once the cast is made, a method is called on the Listener object.

class ListenerBase {};
class Listener : public ListenerBase{};
class Hearer :  public ListenerBase{};
class Other {};

ListenerBase *lb = new Listener();
Listener *l = static_cast<Listener*>(lb); // valid cast
Hearer *h = static_cast<Hearer*>(lb); // No compiler error, but undefined behavior.  lb is not a Hearer.
Other *o = static_cast<Other*>(lb); // compiler error.  No conversion from ListenerBase to Other

Also look up dynamic_cast while you are learning about this.