Set up extensions filter correctly in wxFileDialog in wxOSX

We need to call DoOnFilterSelected() to restrict the files that can be
initially selected by the user to the filter.

Closes #17415.

docs/changes.txt

@@ -69,6 +69,7 @@ wxMSW:
 wxOSX:
 
 - Remove extra borders around wxFilePickerCtrl (John Roberts).
+- Set up extensions filter correctly in wxFileDialog (nick863).
 - Turn off automatic quotes substitutions in wxTextCtrl (Xlord2).
 
 

src/osx/cocoa/filedlg.mm

@@ -606,7 +606,18 @@ int wxFileDialog::ShowModal()
         [oPanel setMessage:cf.AsNSString()];
         [oPanel setAllowsMultipleSelection: (HasFlag(wxFD_MULTIPLE) ? YES : NO )];
 
+        // Note that the test here is intentionally different from the one
+        // above, in the wxFD_SAVE case: we need to call DoOnFilterSelected()
+        // even for m_firstFileTypeFilter == 0, i.e. when using the default
+        // filter.
+        if ( m_firstFileTypeFilter >= 0 )
+        {
+            DoOnFilterSelected(m_firstFileTypeFilter);
+        }
+        else
+        {
             [oPanel setAllowedFileTypes: (m_delegate == nil ? types : nil)];
+        }
         if ( !m_dir.IsEmpty() )
             [oPanel setDirectoryURL:[NSURL fileURLWithPath:dir.AsNSString() 
                                                isDirectory:YES]];