Assign default/restore tagname format in Export Sprite Sheet UI

src/app/commands/cmd_export_sprite_sheet.cpp

@@ -974,7 +974,15 @@ private:
   }
 
   void updateDefaultDataTagnameFormat() {
-    m_tagnameFormatDefault = "{tag}";
+    m_tagnameFormatDefault =
+      get_default_tagname_format_for_sheet();
+
+    if (m_tagnameFormat.empty()) {
+      dataTagnameFormat()->setText(m_tagnameFormatDefault);
+    }
+    else {
+      dataTagnameFormat()->setText(m_tagnameFormat);
+    }
   }
 
   void updateDataFields() {

src/app/filename_formatter.cpp

@@ -217,4 +217,9 @@ std::string get_default_filename_format_for_sheet(
   return format;
 }
 
+std::string get_default_tagname_format_for_sheet()
+{
+  return "{tag}";
+}
+
 } // namespace app

src/app/filename_formatter.h

@@ -114,6 +114,8 @@ namespace app {
     const bool hasLayer,
     const bool hasTag);
 
+  std::string get_default_tagname_format_for_sheet();
+
 } // namespace app
 
 #endif