Allow disabling saving wxFileConfig data when it is destroyed

This can be useful to avoid saving the changes performed by the user if
this turns out to be undesirable, for whatever reason.

Closes https://github.com/wxWidgets/wxWidgets/pull/1451

Closes #13788.

include/wx/fileconf.h

@@ -182,6 +182,9 @@ public:
   virtual bool Save(wxOutputStream& os, const wxMBConv& conv = wxConvAuto());
 #endif // wxUSE_STREAMS
 
+  void EnableAutoSave() { m_autosave = true; }
+  void DisableAutoSave() { m_autosave = false; }
+
 public:
   // functions to work with this list
   wxFileConfigLineList *LineListAppend(const wxString& str);
@@ -250,6 +253,7 @@ private:
 #endif // __UNIX__
 
   bool m_isDirty;                       // if true, we have unsaved changes
+  bool m_autosave;                      // if true, save changes on destruction
 
   wxDECLARE_NO_COPY_CLASS(wxFileConfig);
   wxDECLARE_ABSTRACT_CLASS(wxFileConfig);

interface/wx/fileconf.h

@@ -95,6 +95,29 @@ public:
     */
     virtual bool Save(wxOutputStream& os, const wxMBConv& conv = wxConvAuto());
 
+    /**
+        Enables saving data to the disk file when this object is destroyed.
+
+        This is the default behaviour and this function doesn't need to be
+        called explicitly unless DisableAutoSave() had been previously called.
+
+        @since 3.1.3
+    */
+    void EnableAutoSave();
+
+    /**
+        Prevent this object from saving data to the disk file when it is
+        destroyed.
+
+        By default, changes to this object are only saved permanently when
+        Flush() is explicitly called or when it is destroyed. If this method is
+        called, Flush() won't be called automatically from the destructor,
+        meaning that any non-explicitly-flushed changes will be lost.
+
+        @since 3.1.3
+    */
+    void DisableAutoSave();
+
     /**
         Allows setting the mode to be used for the config file creation. For example, to
         create a config file which is not readable by other users (useful if it stores

src/common/fileconf.cpp

@@ -346,6 +346,7 @@ void wxFileConfig::Init()
     }
 
     m_isDirty = false;
+    m_autosave = true;
 }
 
 // constructor supports creation of wxFileConfig objects of any type
@@ -487,7 +488,8 @@ void wxFileConfig::CleanUp()
 
 wxFileConfig::~wxFileConfig()
 {
-    Flush();
+    if ( m_autosave )
+        Flush();
 
     CleanUp();