Add return value to wxSafeShowMessage()

This allows the caller to log the message to the console in addition to
showing the message box, for example. Previously, this would be
impossible to do without getting the duplicates if the message box was
not shown, but now it is.

include/wx/log.h

@@ -1459,7 +1459,7 @@ inline void wxLogNop() { }
 
 // wxLogFatalError helper: show the (fatal) error to the user in a safe way,
 // i.e. without using wxMessageBox() for example because it could crash
-void WXDLLIMPEXP_BASE
+bool WXDLLIMPEXP_BASE
 wxSafeShowMessage(const wxString& title, const wxString& text);
 
 // ----------------------------------------------------------------------------

interface/wx/log.h

@@ -1268,12 +1268,17 @@ public:
         message string.
     @param text
         The text to show to the user.
+    @return
+        @true If a message box was actually shown or @false if the message was
+        logged to the console because there is no safe to show it currently
+        (the return value is only available since wxWidgets 3.1.5, the function
+        doesn't return anything in the previous versions).
 
     @see wxLogFatalError()
 
     @header{wx/log.h}
 */
-void wxSafeShowMessage(const wxString& title, const wxString& text);
+bool wxSafeShowMessage(const wxString& title, const wxString& text);
 
 /**
     Returns the error code from the last system call. This function uses

src/common/log.cpp

@@ -180,13 +180,17 @@ private:
 // helper global functions
 // ----------------------------------------------------------------------------
 
-void wxSafeShowMessage(const wxString& title, const wxString& text)
+bool wxSafeShowMessage(const wxString& title, const wxString& text)
 {
     if ( !wxApp::GetValidTraits().SafeMessageBox(text, title) )
     {
         wxFprintf(stderr, wxS("%s: %s\n"), title.c_str(), text.c_str());
         fflush(stderr);
+        return false;
     }
+
+    // Message box actually shown.
+    return true;
 }
 
 // ----------------------------------------------------------------------------