Question and Answer Database
FAQ2501C.txt Trapping the Alt-F4 command.
Category :VCL
Platform :All
Product :C++Builder 3.x
Question:
How do I prevent someone from useing to shut down an
application that I have written?
Answer:
The answer lies in overriding the WndProc function of your form
calss thusly:
Add the following to the header file, right under the line that says
private: // User declarations
protected:
virtual void __fastcall WndProc(Messages::TMessage & msg);
and then add the following function to the .cpp file
void __fastcall TForm1::WndProc(Messages::TMessage & msg)
{
TWMSysCommand & syscmd = reinterpret_cast(msg);
if ( syscmd.Msg == WM_SYSCOMMAND
&& syscmd.CmdType == SC_CLOSE
&& syscmd.YPos <= 0
)
{
HMENU systemMenu = GetSystemMenu(Handle, FALSE);
MENUITEMINFO menuItemInfo;
ZeroMemory(&menuItemInfo, sizeof(menuItemInfo));
menuItemInfo.cbSize = sizeof(menuItemInfo);
menuItemInfo.fMask = MIIM_STATE;
if ( GetMenuItemInfo(systemMenu, SC_CLOSE, FALSE, &menuItemInfo)
&& menuItemInfo.fState & (MFS_DISABLED | MFS_GRAYED)
)
{
return;
}
}
TForm::WndProc(msg);
}
7/2/98 10:32:32 AM