DoubleSlider modes(states) are extended and implemented mode detection from model

+ Some code refactoring

src/slic3r/GUI/Plater.cpp

@@ -5358,6 +5358,38 @@ bool Plater::is_export_gcode_scheduled() const
     return p->background_process.is_export_scheduled();
 }
 
+bool Plater::is_one_extruder_printed_model()
+{
+    if (wxGetApp().extruders_edited_cnt() == 1)
+        return true;    
+
+    // check if model use just one extruder
+    const ModelObjectPtrs& objects = p->model.objects;
+    if (!objects.empty())
+    {
+        const size_t extruder = objects[0]->config.has("extruder") ? 
+                                objects[0]->config.option("extruder")->getInt() : 0;
+        for (ModelObject* object : objects)
+        {
+            if (object->config.has("extruder") &&
+                object->config.option("extruder")->getInt() != extruder)
+                return false;
+
+            for (ModelVolume* volume : object->volumes)
+                if (volume->config.has("extruder") &&
+                    volume->config.option("extruder")->getInt() != extruder)
+                    return false;
+
+            for (const auto& range : object->layer_config_ranges)
+                if (range.second.has("extruder") &&
+                    range.second.option("extruder")->getInt() != extruder)
+                return false;
+        }
+    }
+
+    return true;
+}
+
 int Plater::get_selected_object_idx()
 {
     return p->get_selected_object_idx();