Better const correctness

src/libslic3r/Brim.cpp

@@ -564,7 +564,7 @@ ExtrusionEntityCollection make_brim(const Print &print, PrintTryCancel try_cance
     }
 #endif // BRIM_DEBUG_TO_SVG
 
-    const bool could_brim_intersects_skirt = std::any_of(print.objects().begin(), print.objects().end(), [&print](PrintObject *object) {
+    const bool could_brim_intersects_skirt = std::any_of(print.objects().begin(), print.objects().end(), [&print](const PrintObject *object) {
         const BrimType &bt = object->config().brim_type;
         return (bt == btOuterOnly || bt == btOuterAndInner) && print.config().skirt_distance.value < object->config().brim_width;
     });

src/libslic3r/TreeSupport.cpp

@@ -3908,7 +3908,7 @@ static void generate_support_areas(Print &print, const BuildVolume &build_volume
 void fff_tree_support_generate(PrintObject &print_object, std::function<void()> throw_on_cancel)
 {
     size_t idx = 0;
-    for (PrintObject* po : print_object.print()->objects()) {
+    for (const PrintObject *po : print_object.print()->objects()) {
         if (po == &print_object)
             break;
         ++idx;

src/slic3r/GUI/DoubleSlider.cpp

@@ -2123,13 +2123,13 @@ void Control::show_cog_icon_context_menu()
     GUI::wxGetApp().plater()->PopupMenu(&menu);
 }
 
-bool check_color_change(PrintObject* object, size_t frst_layer_id, size_t layers_cnt, bool check_overhangs, std::function<bool(Layer*)> break_condition)
+bool check_color_change(const PrintObject* object, size_t frst_layer_id, size_t layers_cnt, bool check_overhangs, std::function<bool(const Layer*)> break_condition)
 {
     double prev_area = area(object->get_layer(frst_layer_id)->lslices);
 
     bool detected = false;
     for (size_t i = frst_layer_id+1; i < layers_cnt; i++) {
-        Layer* layer = object->get_layer(i);
+        const Layer* layer = object->get_layer(i);
         double cur_area = area(layer->lslices);
 
         // check for overhangs
@@ -2169,7 +2169,7 @@ void Control::auto_color_change()
         if (object->layer_count() < 2)
             continue;
 
-        check_color_change(object, 1, object->layers().size(), false, [this, extruders_cnt](Layer* layer)
+        check_color_change(object, 1, object->layers().size(), false, [this, extruders_cnt](const Layer* layer)
         {
             int tick = get_tick_from_value(layer->print_z);
             if (tick >= 0 && !m_ticks.has_tick(tick)) {

src/slic3r/GUI/DoubleSlider.hpp

@@ -31,10 +31,10 @@ constexpr double epsilon() { return 0.0011; }
 bool equivalent_areas(const double& bottom_area, const double& top_area);
 
 // return true if color change was detected
-bool check_color_change(PrintObject* object, size_t frst_layer_id, size_t layers_cnt, bool check_overhangs,
+bool check_color_change(const PrintObject* object, size_t frst_layer_id, size_t layers_cnt, bool check_overhangs,
                         // what to do with detected color change
                         // and return true when detection have to be desturbed
-                        std::function<bool(Layer*)> break_condition);
+                        std::function<bool(const Layer*)> break_condition);
 
 // custom message the slider sends to its parent to notify a tick-change:
 wxDECLARE_EVENT(wxCUSTOMEVT_TICKSCHANGED, wxEvent);

src/slic3r/GUI/GUI_Preview.cpp

@@ -574,7 +574,7 @@ void Preview::update_layers_slider(const std::vector<double>& layers_z, bool kee
             if (i < min_solid_height)
                 continue;
 
-            if (DoubleSlider::check_color_change(object, i, num_layers, true, [this, object](Layer*) {
+            if (DoubleSlider::check_color_change(object, i, num_layers, true, [this, object](const Layer*) {
                 NotificationManager* notif_mngr = wxGetApp().plater()->get_notification_manager();
                 notif_mngr->push_notification(
                     NotificationType::SignDetected, NotificationManager::NotificationLevel::PrintInfoNotificationLevel,