Thread: popup menu in MFC?

I'm trying to get a popup menu working in my dialog app, I'm almost directly copying the code from a VC++ E-book that I got from a link on these forums, but I've run into a problem

the code :

void CAboutDlg::OnContextMenu(CWnd* pWnd, CPoint point)
{
CMenu *m_lMenu; // A pointer to the menu
CPoint m_pPoint; // A copy of the mouse position

m_pPoint = point; // Copy mouse position to a local variable
ClientToScreen(&m_pPoint); // Convert to an absolute screen position
m_lMenu - GetMenu(); //Get a pointer to the window menu
m_lMenu = m_lMenu->GetSubMenu(0); //Get a pointer to the first submenu
m_lMenu->TrackPopupMenu(TPM_CENTERALIGN + TPM_RIGHTBUTTON, m_pPoint.x, m_pPoint.y, this, NULL);//show the popup menu
}

the problem comes on the line

m_lMenu - GetMenu(); //Get a pointer to the window

I get the following warning

warning C4552: '>>' : operator has no effect; expected operator with side-effect

then a complaint that m_lMenu is being used on the next line without being initialized

Although the app compiles and runs OK, there is no popup menu functionality

Thanks

Merry christmas to all those who help !

Dude, change your line to

m_IMenu = GetMenu();
or
m_IMenu->GetMenu();

I don't know MFC so I am not sure what the correct call is. I suspect the first one is the correct one. Not everything you see in books is correct!

ok, changed it to m_lMenu = GetMenu(); and it compiles without warnings or errors, although the popup menu still isnt working?

I seem to have fixed the problem by simply not using the ClientToScreen() function, deleting this line makes the menu appear in the right place? No idea why, I thought the mouse position given was that relative to the dialog, not the screen, isnt that what ClientToScreen is for? Must be mistaken. Sorry for this thread it has been a bit pointless, but if anyone can offer an explanation as to why I dont need ClientToScreen I'd be happy to hear it.

thanks again

Heh, I happen to be learning from the same book, I spent a long time Googling for the answer to this evil problem and I found Sams' corrections. it's weird how it's just randomly in a FAQ in their book store.

The answer is:

• Line 18, "m_lMenu - GetMenu();" should be "m_lMenu = GetMenu();".
• Line 23, "m_pPoint.x, m_pPoint.y" should be "point.x, point.y".

Found at: http://www.samspublishing.com/bookst...409&rl=1#info3

I'm going to keep this FAQ nearby for the duration of this book in case there are more bugs later on.