Reduced context menus

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• Download demo project - 14 Kb

Introduction

This code provides a simple way to remove disabled items from a context menu. It is not good coding practice to remove disabled menu items from an application's main menus but it is often desirable to do this for popup context menus.

Using the code

Using the code is very simple. Add the two files "ReducedMenu.h" and "ReducedMenu.cpp" to your project.

Cast the menu you wish to popup to a CReducedMenu so that our custom  TrackPopupMenu function is called

((CReducedMenu*) menu.GetSubMenu(0))->TrackPopupMenu(TPM_LEFTALIGN | TPM_RIGHTBUTTON, x, y ,AfxGetMainWnd());

Points of Interest

The CReducedMenu class uses the internal class CEnabledCmdUI derived from CCmdUI to check the enabled state for each menu item using the MFC command update handlers. You can find the same class definition in MFC's WinCore.cpp.

class CReducedMenu: public CMenu
{
public:
    CReducedMenu() {}
    BOOL TrackPopupMenu( UINT nFlags, int x, int y, CWnd* pWnd, 
                         LPCRECT lpRect = NULL );

protected:
    void CullDisabledItems(CMenu* pMenu);


    // class to test if a command is enabled or not. Taken from MFC's WinCore.cpp
    class CEnabledCmdUI : public CCmdUI
    {
    public:
        CEnabledCmdUI():m_bEnabled(false) {}
        virtual void Enable(BOOL bOn)
        {
            m_bEnabled = bOn;
            m_bEnableChanged = TRUE;
        }

        virtual void SetCheck(int nCheck) {}
        virtual void SetRadio(BOOL bOn) {}
        virtual void SetText(LPCTSTR) {}

        BOOL m_bEnabled;
    }

};

The actual removal of disabled items is called recursively for any sub menus. After the disabled items are removed, surplus separators are then removed.

BOOL CReducedMenu::TrackPopupMenu( UINT nFlags, int x, int y, CWnd* pWnd, LPCRECT lpRect )
{
    CullDisabledItems(this);
    return CMenu::TrackPopupMenu( nFlags,x,y,pWnd,lpRect);
}


void CReducedMenu::CullDisabledItems(CMenu* pMenu)
{
    CEnabledCmdUI state;
    UINT n;

    // go through each menu item and remove disabled items
    for(n =0; n < pMenu->GetMenuItemCount(); n++)
    {
        state.m_nID = pMenu->GetMenuItemID( n );

        // menu separator or invalid cmd - ignore it
        if (state.m_nID == 0)
            continue;
        if (state.m_nID == (UINT)-1)
        {
            // possibly a popup menu, route to child menu if so
            CMenu* pSub=pMenu->GetSubMenu(n);
            if(pSub)
                CullDisabledItems(pSub);
        }
        else
        {
            // normal menu item, Remove it if the command is disabled
            AfxGetMainWnd()->OnCmdMsg(state.m_nID, CN_UPDATE_COMMAND_UI, &state, NULL);
            if( !state.m_bEnabled )
            {
                pMenu->DeleteMenu( n--, MF_BYPOSITION );
            }
        }
    }
    
    // now remove spare separators
    for (n =0; n < pMenu->GetMenuItemCount(); n++)
    {
        UINT nID = pMenu->GetMenuItemID( n );
        
        // if separator is first or last item in menu- remove it
        if (nID == 0 && (n == 0 || n == pMenu->GetMenuItemCount()-1) )
        {
            pMenu->DeleteMenu( n--, MF_BYPOSITION );
        }
        
        // if two adjacent separators, remove one
        if (n > 0 && nID == 0 && pMenu->GetMenuItemID( n-1 ) == 0 )
        {
            pMenu->DeleteMenu( n--, MF_BYPOSITION );
        }
    }
}

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