Merge branch 'safe-show-message'

Show message box from wxSafeShowMessage() in the other ports too, if
possible.

Currently this is done using wxMessageBox() if it can be sure that it's
safe to call and only MSW uses native function which is always safe to
call. Ideal would be to also use a native function under Mac, where it
should also be the case, but this doesn't seem to work for whichever
reason.

See https://github.com/wxWidgets/wxWidgets/pull/2270

interface/wx/app.h

@@ -859,6 +859,18 @@ public:
     */
     bool GetUseBestVisual() const;
 
+    /**
+        Returns a pointer to the top application window if any.
+
+        This function is safe to call even before creating, or after
+        destroying, the application object, as it simply returns @NULL if it
+        doesn't exist. Otherwise it's equivalent to calling
+        @c wxTheApp->GetTopWindow().
+
+        @since 3.1.5
+     */
+    static wxWindow* GetMainTopWindow();
+
     /**
         Returns a pointer to the top window.
 

interface/wx/apptrait.h

@@ -133,5 +133,28 @@ public:
         Returns @true to suppress subsequent asserts, @false to continue as before.
     */
     virtual bool ShowAssertDialog(const wxString& msg) = 0;
+
+    /**
+        Shows a message box with the given text and title if possible.
+
+        In some ports, e.g. wxMSW, a message box will always be shown, while in
+        the other ones it will be only done if the GUI is available (e.g. X11
+        display was successfully opened for X11-based ports) and the function
+        simply returns @false without doing anything otherwise.
+
+        This function is safe in the sense that it can always be called, even
+        before creating wxApp, similarly to wxSafeShowMessage() which is
+        implemented by calling this function and then logging the message to
+        standard error stream if it returned @false.
+
+        @since 3.1.5
+
+        @param text
+            The text to show to the user.
+        @param title
+            The title of the message box shown to the user.
+        @return @true if the message box was shown or @false otherwise.
+     */
+    virtual bool SafeMessageBox(const wxString& text, const wxString& title) = 0;
 };
 

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