Add empty EnableCloseButton() into wxTLW base class.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42503 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/latex/wx/tlw.tex

@@ -47,7 +47,10 @@ Returns \true if the platform supports making the window translucent.
 Enables or disables the Close button (most often in the right
 upper corner of a dialog) and the Close entry of the system
 menu (most often in the left upper corner of the dialog).
-Currently only implemented for wxMSW and wxGTK.
+Currently only implemented for wxMSW and wxGTK. Returns
+true if operation was successful. This may be wrong on
+X11 (including GTK+) where the window manager may not support
+this operation and there is no way to find out.
 
 \membersection{wxTopLevelWindow::GetDefaultItem}\label{wxtoplevelwindowgetdefaultitem}
 

include/wx/toplevel.h

@@ -167,6 +167,9 @@ public:
     virtual void SetTitle(const wxString& title) = 0;
     virtual wxString GetTitle() const = 0;
 
+    // enable/disable close button [x]
+    virtual bool EnableCloseButton(bool WXUNUSED(enable) ) { return false; } 
+
     // Set the shape of the window to the given region.
     // Returns true if the platform supports this feature (and the
     // operation is successful.)