WIP: Invalidating shared support spots in Print::apply()

src/libslic3r/Print.hpp

@@ -609,6 +609,12 @@ private:
     // Return 4 wipe tower corners in the world coordinates (shifted and rotated), including the wipe tower brim.
     std::vector<Point>  first_layer_wipe_tower_corners() const;
 
+    // Returns true if any of the print_objects has print_object_step valid.
+    // That means data shared by all print objects of the print_objects span may still use the shared data.
+    // Otherwise the shared data shall be released.
+    // Unguarded variant, thus it shall only be called from main thread with background processing stopped.
+    static bool         is_shared_print_object_step_valid_unguarded(SpanOfConstPtrs<PrintObject> print_objects, PrintObjectStep print_object_step);
+
     PrintConfig                             m_config;
     PrintObjectConfig                       m_default_object_config;
     PrintRegionConfig                       m_default_region_config;

src/libslic3r/PrintApply.cpp

@@ -1451,6 +1451,21 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
     for (PrintObject *object : m_objects)
         object->update_slicing_parameters();
 
+    if (apply_status == APPLY_STATUS_INVALIDATED) {
+        // Invalidate data of a single ModelObject shared by multiple PrintObjects.
+        // Find spans of PrintObjects sharing the same PrintObjectRegions.
+        std::vector<PrintObject*> all_objects(m_objects);
+        std::sort(all_objects.begin(), all_objects.end(), [](const PrintObject *l, const PrintObject *r){ return l->shared_regions() < r->shared_regions(); } );
+        for (auto it = all_objects.begin(); it != all_objects.end();) {
+            PrintObjectRegions *shared_regions = (*it)->m_shared_regions;
+            auto it_begin = it;
+            for (++ it; it != all_objects.end() && shared_regions == (*it)->shared_regions(); ++ it);
+            auto this_objects = SpanOfConstPtrs<PrintObject>(const_cast<const PrintObject* const* const>(&(*it_begin)), it - it_begin);
+            if (Print::is_shared_print_object_step_valid_unguarded(this_objects, posSupportSpotsSearch))
+                shared_regions->generated_support_points.reset();
+        }
+    }
+
 #ifdef _DEBUG
     check_model_ids_equal(m_model, model);
 #endif /* _DEBUG */
@@ -1458,4 +1473,9 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
 	return static_cast<ApplyStatus>(apply_status);
 }
 
+bool Print::is_shared_print_object_step_valid_unguarded(SpanOfConstPtrs<PrintObject> print_objects, PrintObjectStep print_object_step)
+{
+    return std::any_of(print_objects.begin(), print_objects.end(), [print_object_step](auto po){ return po->is_step_done_unguarded(print_object_step); });
+}
+
 } // namespace Slic3r