[Bug 15055] New: implement undocumented window message 0x0313 (WM_POPUPSYSTEMMENU)

http://bugs.winehq.org/show_bug.cgi?id=15055

Summary: implement undocumented window message 0x0313
                    (WM_POPUPSYSTEMMENU)
           Product: Wine
           Version: 1.1.3
          Platform: Other
        OS/Version: other
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: user32
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

Created an attachment (id=15711)
 --> (http://bugs.winehq.org/attachment.cgi?id=15711)
test application (C source)

In order to display the system menu of a window that belongs to a different
process, the Windows taskbar sends the undocumented message 0x313 to the window
with the following parameters:

wparam = always 0 (changing it seems to make no difference)
lparam = MAKELONG(x,y), where x and y are screen coordinates where the menu
should be displayed

I've found that sending this message on Windows does cause a window to display
its system menu.

WM_POPUPSYSTEMMENU is a popular name for it according to Google.