Add a notification when custom support enforcers are not used due to supports being off

It is now emitted from Print::validate and has a hyperlink to enable supports

src/libslic3r/Print.cpp

@@ -1245,7 +1245,7 @@ static inline bool sequential_print_vertical_clearance_valid(const Print &print)
 }
 
 // Precondition: Print::validate() requires the Print::apply() to be called its invocation.
-std::string Print::validate() const
+std::string Print::validate(std::string* warning) const
 {
     if (m_objects.empty())
         return L("All objects are outside of the print volume.");
@@ -1440,7 +1440,22 @@ std::string Print::validate() const
     				}
                 }
             }
-            
+
+            // Do we have custom support data that would not be used?
+            // Notify the user in that case.
+            if (! object->has_support() && warning) {
+                for (const ModelVolume* mv : object->model_object()->volumes) {
+                    bool has_enforcers = mv->is_support_enforcer()
+                        || (mv->is_model_part()
+                            && ! mv->supported_facets.empty()
+                            && ! mv->supported_facets.get_facets(*mv, EnforcerBlockerType::ENFORCER).indices.empty());
+                    if (has_enforcers) {
+                        *warning = "_SUPPORTS_OFF";
+                        break;
+                    }
+                }
+            }
+
             // validate first_layer_height
             double first_layer_height = object->config().get_abs_value("first_layer_height");
             double first_layer_min_nozzle_diameter;

src/libslic3r/Print.hpp

@@ -444,7 +444,7 @@ public:
     bool                has_brim() const;
 
     // Returns an empty string if valid, otherwise returns an error message.
-    std::string         validate() const override;
+    std::string         validate(std::string* warning = nullptr) const override;
     double              skirt_first_layer_height() const;
     Flow                brim_flow() const;
     Flow                skirt_flow() const;

src/libslic3r/PrintBase.hpp

@@ -366,7 +366,7 @@ public:
     virtual std::vector<ObjectID> print_object_ids() const = 0;
 
     // Validate the print, return empty string if valid, return error if process() cannot (or should not) be started.
-    virtual std::string     validate() const { return std::string(); }
+    virtual std::string     validate(std::string* warning = nullptr) const { return std::string(); }
 
     enum ApplyStatus {
         // No change after the Print::apply() call.

src/libslic3r/PrintObject.cpp

@@ -430,6 +430,24 @@ void PrintObject::generate_support_material()
                 if (layer->empty())
                     throw Slic3r::SlicingError("Levitating objects cannot be printed without supports.");
 #endif
+
+            // Do we have custom support data that would not be used?
+            // Notify the user in that case.
+            if (! this->has_support()) {
+                for (const ModelVolume* mv : this->model_object()->volumes) {
+                    bool has_enforcers = mv->is_support_enforcer()
+                        || (mv->is_model_part()
+                            && ! mv->supported_facets.empty()
+                            && ! mv->supported_facets.get_facets(*mv, EnforcerBlockerType::ENFORCER).indices.empty());
+                    if (has_enforcers) {
+                        this->active_step_add_warning(PrintStateBase::WarningLevel::CRITICAL,
+                            L("An object has custom support enforcers which will not be used "
+                              "because supports are off. Consider turning them on.") + "\n" +
+                            (L("Object name")) + ": " + this->model_object()->name);
+                        break;
+                    }
+                }
+            }
         }
         this->set_done(posSupportMaterial);
     }

src/libslic3r/SLAPrint.cpp

@@ -617,7 +617,7 @@ std::string SLAPrint::output_filename(const std::string &filename_base) const
     return this->PrintBase::output_filename(m_print_config.output_filename_format.value, ".sl1", filename_base, &config);
 }
 
-std::string SLAPrint::validate() const
+std::string SLAPrint::validate(std::string*) const
 {
     for(SLAPrintObject * po : m_objects) {
 

src/libslic3r/SLAPrint.hpp

@@ -458,7 +458,7 @@ public:
 
     const SLAPrintStatistics&   print_statistics() const { return m_print_statistics; }
 
-    std::string validate() const override;
+    std::string validate(std::string* warning = nullptr) const override;
 
     // An aggregation of SliceRecord-s from all the print objects for each
     // occupied layer. Slice record levels dont have to match exactly.

src/slic3r/GUI/BackgroundSlicingProcess.cpp

@@ -430,10 +430,10 @@ bool BackgroundSlicingProcess::empty() const
 	return m_print->empty();
 }
 
-std::string BackgroundSlicingProcess::validate()
+std::string BackgroundSlicingProcess::validate(std::string* warning)
 {
 	assert(m_print != nullptr);
-	return m_print->validate();
+    return m_print->validate(warning);
 }
 
 // Apply config over the print. Returns false, if the new config values caused any of the already

src/slic3r/GUI/BackgroundSlicingProcess.hpp

@@ -131,7 +131,7 @@ public:
 	bool 		empty() const;
 	// Validate the print. Returns an empty string if valid, returns an error message if invalid.
 	// Call validate before calling start().
-	std::string validate();
+    std::string validate(std::string* warning = nullptr);
 
 	// Set the export path of the G-code.
 	// Once the path is set, the G-code 

src/slic3r/GUI/NotificationManager.hpp

@@ -71,7 +71,9 @@ enum class NotificationType
     // Notification that custom supports/seams were deleted after mesh repair.
     CustomSupportsAndSeamRemovedAfterRepair,
     // Notification that auto adding of color changes is impossible
-	EmptyAutoColorChange
+    EmptyAutoColorChange,
+    // Notification emitted by Print::validate
+    PrintValidateWarning
 };
 
 class NotificationManager

src/slic3r/GUI/Plater.cpp

@@ -1599,6 +1599,8 @@ struct Plater::priv
     void suppress_snapshots()   { this->m_prevent_snapshots++; }
     void allow_snapshots()      { this->m_prevent_snapshots--; }
 
+    void process_validation_warning(const std::string& warning) const;
+
     bool background_processing_enabled() const { return this->get_config("background_processing") == "1"; }
     void update_print_volume_state();
     void schedule_background_process();
@@ -2787,6 +2789,41 @@ void Plater::priv::update_print_volume_state()
     this->q->model().update_print_volume_state(print_volume);
 }
 
+
+void Plater::priv::process_validation_warning(const std::string& warning) const
+{
+    if (warning.empty())
+        notification_manager->close_notification_of_type(NotificationType::PrintValidateWarning);
+    else {
+        std::string text = warning;
+        std::string hypertext = "";
+        std::function<bool(wxEvtHandler*)> action_fn = [](wxEvtHandler*){ return false; };
+
+        if (text == "_SUPPORTS_OFF") {
+            text = _u8L("An object has custom support enforcers which will not be used "
+                        "because supports are disabled.")+"\n";
+            hypertext = _u8L("Enable supports for enforcers only");
+            action_fn = [](wxEvtHandler*) {
+                Tab* print_tab = wxGetApp().get_tab(Preset::TYPE_PRINT);
+                assert(print_tab);
+                DynamicPrintConfig& config = wxGetApp().preset_bundle->prints.get_edited_preset().config;
+                config.set_key_value("support_material", new ConfigOptionBool(true));
+                config.set_key_value("support_material_auto", new ConfigOptionBool(false));
+                print_tab->on_value_change("support_material", config.opt_bool("support_material"));
+                print_tab->on_value_change("support_material_auto", config.opt_bool("support_material_auto"));
+                return true;
+            };
+        }
+
+        notification_manager->push_notification(
+            NotificationType::PrintValidateWarning,
+            NotificationManager::NotificationLevel::ImportantNotification,
+            text, hypertext, action_fn
+        );
+    }
+}
+
+
 // Update background processing thread from the current config and Model.
 // Returns a bitmask of UpdateBackgroundProcessReturnState.
 unsigned int Plater::priv::update_background_process(bool force_validation, bool postpone_error_messages)
@@ -2829,17 +2866,23 @@ unsigned int Plater::priv::update_background_process(bool force_validation, bool
 		// The delayed error message is no more valid.
 		this->delayed_error_message.clear();
 		// The state of the Print changed, and it is non-zero. Let's validate it and give the user feedback on errors.
-        std::string err = this->background_process.validate();
+        std::string warning;
+        std::string err = this->background_process.validate(&warning);
         if (err.empty()) {
 			notification_manager->set_all_slicing_errors_gray(true);
             if (invalidated != Print::APPLY_STATUS_UNCHANGED && this->background_processing_enabled())
                 return_state |= UPDATE_BACKGROUND_PROCESS_RESTART;
+
+            // Pass a warning from validation and either show a notification,
+            // or hide the old one.
+            process_validation_warning(warning);
         } else {
 			// The print is not valid.
 			// Show error as notification.
             notification_manager->push_slicing_error_notification(err);
             return_state |= UPDATE_BACKGROUND_PROCESS_INVALID;
         }
+
     } else if (! this->delayed_error_message.empty()) {
     	// Reusing the old state.
         return_state |= UPDATE_BACKGROUND_PROCESS_INVALID;