ENH: Add helper function for MRML translation with placeholders

Libs/MRML/Core/Testing/vtkMRMLI18NTest1.cxx

@@ -58,5 +58,12 @@ int vtkMRMLI18NTest1(int, char*[])
   // Use translation convenience function
   CHECK_STD_STRING(vtkMRMLTr("SomeContext", "SomeMessage"), "translated-SomeContextSomeMessage");
 
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some text without replacement", "aaa"), "Some text without replacement");
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some text with %1 replacement", "aaa"), "Some text with aaa replacement");
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some text %2 with %1 replacement", "aaa", "qwerty"), "Some text qwerty with aaa replacement");
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some text with missing %1 replacement %2 end", "aaa"), "Some text with missing aaa replacement  end");
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some %2 with %1 escaping %%2 and %% end", "aaa", "qwerty"), "Some qwerty with aaa escaping %2 and % end");
+  CHECK_STD_STRING(vtkMRMLI18N::Format("Some text edge case %", "aaa"), "Some text edge case %");
+
   return EXIT_SUCCESS;
 }

Libs/MRML/Core/vtkMRMLI18N.cxx

@@ -147,3 +147,45 @@ std::string vtkMRMLI18N::Translate(const char *context, const char *sourceText,
     return sourceText ? sourceText : "";
   }
 }
+
+//----------------------------------------------------------------------------
+std::string vtkMRMLI18N::Format(const std::string& input,
+  const char* arg1/*=nullptr*/, const char* arg2/*=nullptr*/, const char* arg3/*=nullptr*/,
+  const char* arg4/*=nullptr*/, const char* arg5/*=nullptr*/, const char* arg6/*=nullptr*/,
+  const char* arg7/*=nullptr*/, const char* arg8/*=nullptr*/, const char* arg9/*=nullptr*/)
+{
+  std::string output;
+
+  for (std::string::const_iterator it = input.cbegin(); it != input.cend(); ++it)
+  {
+    if ((*it == '%') && (it + 1 != input.end()))
+    {
+      const char nextChar = *(it + 1);
+      if (nextChar == '%')
+      {
+        // Escaped '%'
+        output += "%";
+        ++it;
+        continue;
+      }
+      else if (std::isdigit(nextChar))
+      {
+        // Found a valid placeholder (e.g., %1, %2, %3, ..., %9)
+        if (nextChar == '1' && arg1) { output += arg1; }
+        else if (nextChar == '2' && arg2) { output += arg2; }
+        else if (nextChar == '3' && arg3) { output += arg3; }
+        else if (nextChar == '4' && arg4) { output += arg4; }
+        else if (nextChar == '5' && arg5) { output += arg5; }
+        else if (nextChar == '6' && arg6) { output += arg6; }
+        else if (nextChar == '7' && arg7) { output += arg7; }
+        else if (nextChar == '8' && arg8) { output += arg8; }
+        else if (nextChar == '9' && arg9) { output += arg9; }
+        ++it;
+        continue;
+      }
+    }
+    output += (*it);
+  }
+
+  return output;
+}

Libs/MRML/Core/vtkMRMLI18N.h

@@ -50,6 +50,24 @@ class VTK_MRML_EXPORT vtkMRMLI18N : public vtkObject
   /// Translate message with the current translator
   static std::string Translate(const char *context, const char *sourceText, const char *disambiguation = nullptr, int n = -1);
 
+  /// Replace placeholders in strings, following Qt internationalization conventions.
+  ///
+  /// Accepted placeholders in the input string: %1, %2, %3, ..., %9.
+  /// Use %% instead of a single % to prevent replacement. For example "some %%3 thing" will result in "some %3 thing"
+  /// (and will not be replaced by the third replacement string argument).
+  ///
+  /// Example usage:
+  /// @code
+  ///   std::string displayableText = vtkMRMLI18N::Format(
+  ///     vtkMRMLTr("vtkMRMLVolumeArchetypeStorageNode", "Cannot read '%1' file as a volume of type '%2'."),
+  ///     filename.c_str(),
+  ///     volumeType.c_str());
+  /// @endcode
+  static std::string Format(const std::string& text,
+    const char* arg1 = nullptr, const char* arg2 = nullptr, const char* arg3 = nullptr,
+    const char* arg4 = nullptr, const char* arg5 = nullptr, const char* arg6 = nullptr,
+    const char* arg7 = nullptr, const char* arg8 = nullptr, const char* arg9 = nullptr);
+
   /// Set translator object. This class takes ownership of the translator
   /// and it releases it when the process quits.
   void SetTranslator(vtkMRMLTranslator* translator);