diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index bc37300269..9e5d5c4fab 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -1,4 +1,5 @@
 #include "libslic3r.h"
+#include "I18N.hpp"
 #include "GCode.hpp"
 #include "ExtrusionEntity.hpp"
 #include "EdgeGrid.hpp"
@@ -36,6 +37,11 @@
 
 namespace Slic3r {
 
+//! macro used to mark string used at localization,
+//! return same string
+#define L(s) (s)
+#define _(s) Slic3r::I18N::translate(s)
+
 // Only add a newline in case the current G-code does not end with a newline.
 static inline void check_add_eol(std::string &gcode)
 {
@@ -405,7 +411,8 @@ std::string WipeTowerIntegration::tool_change(GCode &gcodegen, int extruder_id,
 	assert(m_layer_idx >= 0 && size_t(m_layer_idx) <= m_tool_changes.size());
     if (! m_brim_done || gcodegen.writer().need_toolchange(extruder_id) || finish_layer) {
 		if (m_layer_idx < (int)m_tool_changes.size()) {
-			assert(size_t(m_tool_change_idx) < m_tool_changes[m_layer_idx].size());
+			if (! (size_t(m_tool_change_idx) < m_tool_changes[m_layer_idx].size()))
+                throw std::runtime_error("Wipe tower generation failed, possibly due to empty first layer.");
 			gcode += append_tcr(gcodegen, m_tool_changes[m_layer_idx][m_tool_change_idx++], extruder_id);
 		}
         m_brim_done = true;
@@ -448,6 +455,17 @@ std::vector<GCode::LayerToPrint> GCode::collect_layers_to_print(const PrintObjec
                 -- idx_object_layer;
             }
         }
+
+        // Let's make sure that the last layer is not empty, so we don't build on top of it.
+        if (! layers_to_print.empty()
+         && ((layer_to_print.object_layer && layer_to_print.object_layer->has_extrusions())
+          || (layer_to_print.support_layer && layer_to_print.support_layer->has_extrusions()))
+         && (! layers_to_print.back().object_layer  || ! layers_to_print.back().object_layer->has_extrusions())
+         && (! layers_to_print.back().support_layer || ! layers_to_print.back().support_layer->has_extrusions()))
+            throw std::runtime_error(_(L("Empty layers detected, the output would not be printable.")) + "\n\n" +
+                                     _(L("Object name: ")) + object.model_object()->name + "\n" + _(L("Print z: ")) +
+                                     std::to_string(layers_to_print.back().print_z()));
+
         layers_to_print.emplace_back(layer_to_print);
     }
 
@@ -1138,9 +1156,9 @@ void GCode::_do_export(Print &print, FILE *file)
     print.m_print_statistics.clear();
     print.m_print_statistics.estimated_normal_print_time = m_normal_time_estimator.get_time_dhms();
     print.m_print_statistics.estimated_silent_print_time = m_silent_time_estimator_enabled ? m_silent_time_estimator.get_time_dhms() : "N/A";
-    print.m_print_statistics.estimated_normal_color_print_times = m_normal_time_estimator.get_color_times_dhms();
+    print.m_print_statistics.estimated_normal_color_print_times = m_normal_time_estimator.get_color_times_dhms(true);
     if (m_silent_time_estimator_enabled)
-        print.m_print_statistics.estimated_silent_color_print_times = m_silent_time_estimator.get_color_times_dhms();
+        print.m_print_statistics.estimated_silent_color_print_times = m_silent_time_estimator.get_color_times_dhms(true);
 
     std::vector<Extruder> extruders = m_writer.extruders();
     if (! extruders.empty()) {
diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index f10b45723a..18437c8e16 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -78,8 +78,13 @@ ToolOrdering::ToolOrdering(const Print &print, unsigned int first_extruder, bool
                 zs.emplace_back(layer->print_z);
             for (auto layer : object->support_layers())
                 zs.emplace_back(layer->print_z);
-            if (! object->layers().empty())
-                object_bottom_z = object->layers().front()->print_z - object->layers().front()->height;
+
+            // Find first object layer that is not empty and save its print_z
+            for (const Layer* layer : object->layers())
+                if (layer->has_extrusions()) {
+                    object_bottom_z = layer->print_z - layer->height;
+                    break;
+                }
         }
         this->initialize_layers(zs);
     }
@@ -324,6 +329,7 @@ void ToolOrdering::fill_wipe_tower_partitions(const PrintConfig &config, coordf_
 						m_layer_tools[j].has_wipe_tower = true;
 					} else {
 						LayerTools &lt_extra = *m_layer_tools.insert(m_layer_tools.begin() + j, lt_new);
+                        //LayerTools &lt_prev  = m_layer_tools[j];
                         LayerTools &lt_next  = m_layer_tools[j + 1];
                         assert(! m_layer_tools[j - 1].extruders.empty() && ! lt_next.extruders.empty());
                         // FIXME: Following assert tripped when running combine_infill.t. I decided to comment it out for now.
diff --git a/src/libslic3r/GCode/WipeTower.cpp b/src/libslic3r/GCode/WipeTower.cpp
index 55a6c4437e..e1b34fdeae 100644
--- a/src/libslic3r/GCode/WipeTower.cpp
+++ b/src/libslic3r/GCode/WipeTower.cpp
@@ -1242,6 +1242,8 @@ void WipeTower::generate(std::vector<std::vector<WipeTower::ToolChangeResult>> &
     for (auto& used : m_used_filament_length) // reset used filament stats
         used = 0.f;
 
+    m_old_temperature = -1; // reset last temperature written in the gcode
+
     std::vector<WipeTower::ToolChangeResult> layer_result;
 	for (auto layer : m_plan)
 	{
diff --git a/src/libslic3r/GCodeTimeEstimator.cpp b/src/libslic3r/GCodeTimeEstimator.cpp
index 33dc9f4b7d..8a2e1266a8 100644
--- a/src/libslic3r/GCodeTimeEstimator.cpp
+++ b/src/libslic3r/GCodeTimeEstimator.cpp
@@ -694,22 +694,39 @@ namespace Slic3r {
         return m_color_times;
     }
 
-    std::vector<std::string> GCodeTimeEstimator::get_color_times_dhms() const
+    std::vector<std::string> GCodeTimeEstimator::get_color_times_dhms(bool include_remaining) const
     {
         std::vector<std::string> ret;
+        float total_time = 0.0f;
         for (float t : m_color_times)
         {
-            ret.push_back(_get_time_dhms(t));
+            std::string time = _get_time_dhms(t);
+            if (include_remaining)
+            {
+                time += " (";
+                time += _get_time_dhms(m_time - total_time);
+                time += ")";
+            }
+            total_time += t;
+            ret.push_back(time);
         }
         return ret;
     }
 
-    std::vector<std::string> GCodeTimeEstimator::get_color_times_minutes() const
+    std::vector<std::string> GCodeTimeEstimator::get_color_times_minutes(bool include_remaining) const
     {
         std::vector<std::string> ret;
+        float total_time = 0.0f;
         for (float t : m_color_times)
         {
-            ret.push_back(_get_time_minutes(t));
+            std::string time = _get_time_minutes(t);
+            if (include_remaining)
+            {
+                time += " (";
+                time += _get_time_minutes(m_time - total_time);
+                time += ")";
+            }
+            total_time += t;
         }
         return ret;
     }
diff --git a/src/libslic3r/GCodeTimeEstimator.hpp b/src/libslic3r/GCodeTimeEstimator.hpp
index 840d587784..8d794af1e4 100644
--- a/src/libslic3r/GCodeTimeEstimator.hpp
+++ b/src/libslic3r/GCodeTimeEstimator.hpp
@@ -346,14 +346,16 @@ namespace Slic3r {
         // Returns the estimated time, in minutes (integer)
         std::string get_time_minutes() const;
 
-       // Returns the estimated time, in seconds, for each color
+        // Returns the estimated time, in seconds, for each color
         std::vector<float> get_color_times() const;
 
         // Returns the estimated time, in format DDd HHh MMm SSs, for each color
-        std::vector<std::string> get_color_times_dhms() const;
+        // If include_remaining==true the strings will be formatted as: "time for color (remaining time at color start)"
+        std::vector<std::string> get_color_times_dhms(bool include_remaining) const;
 
         // Returns the estimated time, in minutes (integer), for each color
-        std::vector<std::string> get_color_times_minutes() const;
+        // If include_remaining==true the strings will be formatted as: "time for color (remaining time at color start)"
+        std::vector<std::string> get_color_times_minutes(bool include_remaining) const;
 
         // Return an estimate of the memory consumed by the time estimator.
         size_t memory_used() const;
diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 25cd92d865..d6489d6780 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -99,8 +99,7 @@ Model Model::read_from_file(const std::string &input_file, DynamicPrintConfig *c
         result = load_stl(input_file.c_str(), &model);
     else if (boost::algorithm::iends_with(input_file, ".obj"))
         result = load_obj(input_file.c_str(), &model);
-    else if (!boost::algorithm::iends_with(input_file, ".zip.amf") && (boost::algorithm::iends_with(input_file, ".amf") ||
-        boost::algorithm::iends_with(input_file, ".amf.xml")))
+    else if (boost::algorithm::iends_with(input_file, ".amf") || boost::algorithm::iends_with(input_file, ".amf.xml"))
         result = load_amf(input_file.c_str(), config, &model);
     else if (boost::algorithm::iends_with(input_file, ".3mf"))
         result = load_3mf(input_file.c_str(), config, &model);
diff --git a/src/libslic3r/Print.cpp b/src/libslic3r/Print.cpp
index c423afeb94..e53f498106 100644
--- a/src/libslic3r/Print.cpp
+++ b/src/libslic3r/Print.cpp
@@ -1723,7 +1723,7 @@ void Print::_make_wipe_tower()
                     break;
                 lt.has_support = true;
                 // Insert the new support layer.
-                double height    = lt.print_z - m_wipe_tower_data.tool_ordering.layer_tools()[i-1].print_z;
+                double height    = lt.print_z - (i == 0 ? 0. : m_wipe_tower_data.tool_ordering.layer_tools()[i-1].print_z);
                 //FIXME the support layer ID is set to -1, as Vojtech hopes it is not being used anyway.
                 it_layer = m_objects.front()->insert_support_layer(it_layer, -1, height, lt.print_z, lt.print_z - 0.5 * height);
                 ++ it_layer;
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 304f6f749f..e49c81f460 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -422,6 +422,7 @@ void PrintConfigDef::init_fff_params()
     def->cli = "bottom-fill-pattern|external-fill-pattern|solid-fill-pattern";
     def->enum_keys_map = &ConfigOptionEnum<InfillPattern>::get_enum_values();
     def->enum_values = def_top_fill_pattern->enum_values;
+    def->enum_labels = def_top_fill_pattern->enum_labels;
     def->aliases = def_top_fill_pattern->aliases;
     def->set_default_value(new ConfigOptionEnum<InfillPattern>(ipRectilinear));
 
diff --git a/src/slic3r/GUI/Camera.cpp b/src/slic3r/GUI/Camera.cpp
index 242d00a071..8e3a6d1f12 100644
--- a/src/slic3r/GUI/Camera.cpp
+++ b/src/slic3r/GUI/Camera.cpp
@@ -22,10 +22,10 @@ namespace Slic3r {
 namespace GUI {
 
 const double Camera::DefaultDistance = 1000.0;
-double Camera::FrustrumMinZSize = 50.0;
+double Camera::FrustrumMinZRange = 50.0;
+double Camera::FrustrumMinNearZ = 100.0;
 double Camera::FrustrumZMargin = 10.0;
-double Camera::FovMinDeg = 0.5;
-double Camera::FovMaxDeg = 75.0;
+double Camera::MaxFovDeg = 60.0;
 
 Camera::Camera()
     : phi(45.0f)
@@ -186,7 +186,8 @@ void Camera::apply_view_matrix() const
 
 void Camera::apply_projection(const BoundingBoxf3& box) const
 {
-    m_distance = DefaultDistance;
+    set_distance(DefaultDistance);
+
     double w = 0.0;
     double h = 0.0;
 
@@ -194,15 +195,14 @@ void Camera::apply_projection(const BoundingBoxf3& box) const
     {
         m_frustrum_zs = calc_tight_frustrum_zs_around(box);
 
-        w = (double)m_viewport[2];
-        h = (double)m_viewport[3];
+        w = 0.5 * (double)m_viewport[2];
+        h = 0.5 * (double)m_viewport[3];
 
-        double two_zoom = 2.0 * m_zoom;
-        if (two_zoom != 0.0)
+        if (m_zoom != 0.0)
         {
-            double inv_two_zoom = 1.0 / two_zoom;
-            w *= inv_two_zoom;
-            h *= inv_two_zoom;
+            double inv_zoom = 1.0 / m_zoom;
+            w *= inv_zoom;
+            h *= inv_zoom;
         }
 
         switch (m_type)
@@ -226,21 +226,16 @@ void Camera::apply_projection(const BoundingBoxf3& box) const
 
         if (m_type == Perspective)
         {
-            double fov_rad = 2.0 * std::atan(h / m_frustrum_zs.first);
-            double fov_deg = Geometry::rad2deg(fov_rad);
+            double fov_deg = Geometry::rad2deg(2.0 * std::atan(h / m_frustrum_zs.first));
 
             // adjust camera distance to keep fov in a limited range
-            if (fov_deg > FovMaxDeg + 0.001)
+            if (fov_deg > MaxFovDeg)
             {
-                double new_near_z = h / ::tan(0.5 * Geometry::deg2rad(FovMaxDeg));
-                m_distance += (new_near_z - m_frustrum_zs.first);
-                apply_view_matrix();
-            }
-            else if (fov_deg < FovMinDeg - 0.001)
-            {
-                double new_near_z = h / ::tan(0.5 * Geometry::deg2rad(FovMinDeg));
-                m_distance += (new_near_z - m_frustrum_zs.first);
-                apply_view_matrix();
+                double delta_z = h / ::tan(0.5 * Geometry::deg2rad(MaxFovDeg)) - m_frustrum_zs.first;
+                if (delta_z > 0.001)
+                    set_distance(m_distance + delta_z);
+                else
+                    break;
             }
             else
                 break;
@@ -328,42 +323,50 @@ void Camera::debug_render() const
 
 std::pair<double, double> Camera::calc_tight_frustrum_zs_around(const BoundingBoxf3& box) const
 {
-    std::pair<double, double> ret = std::make_pair(DBL_MAX, -DBL_MAX);
+    std::pair<double, double> ret;
 
-    Vec3d bb_min = box.min;
-    Vec3d bb_max = box.max;
-
-    // box vertices in world space
-    std::vector<Vec3d> vertices;
-    vertices.reserve(8);
-    vertices.push_back(bb_min);
-    vertices.emplace_back(bb_max(0), bb_min(1), bb_min(2));
-    vertices.emplace_back(bb_max(0), bb_max(1), bb_min(2));
-    vertices.emplace_back(bb_min(0), bb_max(1), bb_min(2));
-    vertices.emplace_back(bb_min(0), bb_min(1), bb_max(2));
-    vertices.emplace_back(bb_max(0), bb_min(1), bb_max(2));
-    vertices.push_back(bb_max);
-    vertices.emplace_back(bb_min(0), bb_max(1), bb_max(2));
-
-    // set the Z range in eye coordinates (negative Zs are in front of the camera)
-    for (const Vec3d& v : vertices)
+    while (true)
     {
-        double z = -(m_view_matrix * v)(2);
-        ret.first = std::min(ret.first, z);
-        ret.second = std::max(ret.second, z);
-    }
+        ret = std::make_pair(DBL_MAX, -DBL_MAX);
 
-    // apply margin
-    ret.first -= FrustrumZMargin;
-    ret.second += FrustrumZMargin;
+        // box vertices in world space
+        std::vector<Vec3d> vertices;
+        vertices.reserve(8);
+        vertices.push_back(box.min);
+        vertices.emplace_back(box.max(0), box.min(1), box.min(2));
+        vertices.emplace_back(box.max(0), box.max(1), box.min(2));
+        vertices.emplace_back(box.min(0), box.max(1), box.min(2));
+        vertices.emplace_back(box.min(0), box.min(1), box.max(2));
+        vertices.emplace_back(box.max(0), box.min(1), box.max(2));
+        vertices.push_back(box.max);
+        vertices.emplace_back(box.min(0), box.max(1), box.max(2));
 
-    // ensure min size
-    if (ret.second - ret.first < FrustrumMinZSize)
-    {
-        double mid_z = 0.5 * (ret.first + ret.second);
-        double half_size = 0.5 * FrustrumMinZSize;
-        ret.first = mid_z - half_size;
-        ret.second = mid_z + half_size;
+        // set the Z range in eye coordinates (negative Zs are in front of the camera)
+        for (const Vec3d& v : vertices)
+        {
+            double z = -(m_view_matrix * v)(2);
+            ret.first = std::min(ret.first, z);
+            ret.second = std::max(ret.second, z);
+        }
+
+        // apply margin
+        ret.first -= FrustrumZMargin;
+        ret.second += FrustrumZMargin;
+
+        // ensure min size
+        if (ret.second - ret.first < FrustrumMinZRange)
+        {
+            double mid_z = 0.5 * (ret.first + ret.second);
+            double half_size = 0.5 * FrustrumMinZRange;
+            ret.first = mid_z - half_size;
+            ret.second = mid_z + half_size;
+        }
+
+        if (ret.first >= FrustrumMinNearZ)
+            break;
+
+        // ensure min Near Z
+        set_distance(m_distance + FrustrumMinNearZ - ret.first);
     }
 
     return ret;
@@ -385,21 +388,19 @@ double Camera::calc_zoom_to_bounding_box_factor(const BoundingBoxf3& box, int ca
     Vec3d up = get_dir_up();
     Vec3d forward = get_dir_forward();
 
-    Vec3d bb_min = box.min;
-    Vec3d bb_max = box.max;
     Vec3d bb_center = box.center();
 
     // box vertices in world space
     std::vector<Vec3d> vertices;
     vertices.reserve(8);
-    vertices.push_back(bb_min);
-    vertices.emplace_back(bb_max(0), bb_min(1), bb_min(2));
-    vertices.emplace_back(bb_max(0), bb_max(1), bb_min(2));
-    vertices.emplace_back(bb_min(0), bb_max(1), bb_min(2));
-    vertices.emplace_back(bb_min(0), bb_min(1), bb_max(2));
-    vertices.emplace_back(bb_max(0), bb_min(1), bb_max(2));
-    vertices.push_back(bb_max);
-    vertices.emplace_back(bb_min(0), bb_max(1), bb_max(2));
+    vertices.push_back(box.min);
+    vertices.emplace_back(box.max(0), box.min(1), box.min(2));
+    vertices.emplace_back(box.max(0), box.max(1), box.min(2));
+    vertices.emplace_back(box.min(0), box.max(1), box.min(2));
+    vertices.emplace_back(box.min(0), box.min(1), box.max(2));
+    vertices.emplace_back(box.max(0), box.min(1), box.max(2));
+    vertices.push_back(box.max);
+    vertices.emplace_back(box.min(0), box.max(1), box.max(2));
 
     double max_x = 0.0;
     double max_y = 0.0;
@@ -430,6 +431,12 @@ double Camera::calc_zoom_to_bounding_box_factor(const BoundingBoxf3& box, int ca
     return std::min((double)canvas_w / (2.0 * max_x), (double)canvas_h / (2.0 * max_y));
 }
 
+void Camera::set_distance(double distance) const
+{
+    m_distance = distance;
+    apply_view_matrix();
+}
+
 } // GUI
 } // Slic3r
 
diff --git a/src/slic3r/GUI/Camera.hpp b/src/slic3r/GUI/Camera.hpp
index 79e87c7264..839d0d6cf1 100644
--- a/src/slic3r/GUI/Camera.hpp
+++ b/src/slic3r/GUI/Camera.hpp
@@ -10,10 +10,10 @@ namespace GUI {
 struct Camera
 {
     static const double DefaultDistance;
-    static double FrustrumMinZSize;
+    static double FrustrumMinZRange;
+    static double FrustrumMinNearZ;
     static double FrustrumZMargin;
-    static double FovMinDeg;
-    static double FovMaxDeg;
+    static double MaxFovDeg;
 
     enum EType : unsigned char
     {
@@ -101,6 +101,7 @@ private:
     // the camera MUST be outside of the bounding box in eye coordinate of the given box
     std::pair<double, double> calc_tight_frustrum_zs_around(const BoundingBoxf3& box) const;
     double calc_zoom_to_bounding_box_factor(const BoundingBoxf3& box, int canvas_w, int canvas_h) const;
+    void set_distance(double distance) const;
 };
 
 } // GUI
diff --git a/src/slic3r/GUI/FirmwareDialog.cpp b/src/slic3r/GUI/FirmwareDialog.cpp
index 7865aecf2e..d1f2da040c 100644
--- a/src/slic3r/GUI/FirmwareDialog.cpp
+++ b/src/slic3r/GUI/FirmwareDialog.cpp
@@ -354,7 +354,7 @@ bool FirmwareDialog::priv::check_model_id()
 	// Therefore, regretably, so far the check cannot be used and we just return true here.
 	// TODO: Rewrite Serial using more platform-native code.
 	return true;
-	
+
 	// if (hex_file.model_id.empty()) {
 	// 	// No data to check against, assume it's ok
 	// 	return true;
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 5e505bb416..c74207123d 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1529,7 +1529,7 @@ void GLCanvas3D::render()
     }
 
     m_camera.apply_view_matrix();
-    m_camera.apply_projection(_max_bounding_box(true));
+    m_camera.apply_projection(_max_bounding_box(true, true));
 
     GLfloat position_cam[4] = { 1.0f, 0.0f, 1.0f, 0.0f };
     glsafe(::glLightfv(GL_LIGHT1, GL_POSITION, position_cam));
@@ -3273,7 +3273,7 @@ void GLCanvas3D::do_mirror(const std::string& snapshot_type)
 void GLCanvas3D::set_camera_zoom(double zoom)
 {
     const Size& cnv_size = get_canvas_size();
-    m_camera.set_zoom(zoom, _max_bounding_box(false), cnv_size.get_width(), cnv_size.get_height());
+    m_camera.set_zoom(zoom, _max_bounding_box(false, false), cnv_size.get_width(), cnv_size.get_height());
     m_dirty = true;
 }
 
@@ -3699,9 +3699,20 @@ void GLCanvas3D::_resize(unsigned int w, unsigned int h)
     m_dirty = false;
 }
 
-BoundingBoxf3 GLCanvas3D::_max_bounding_box(bool include_bed_model) const
+BoundingBoxf3 GLCanvas3D::_max_bounding_box(bool include_gizmos, bool include_bed_model) const
 {
     BoundingBoxf3 bb = volumes_bounding_box();
+
+    // The following is a workaround for gizmos not being taken in account when calculating the tight camera frustrum
+    // A better solution would ask the gizmo manager for the bounding box of the current active gizmo, if any
+    if (include_gizmos && m_gizmos.is_running())
+    {
+        BoundingBoxf3 sel_bb = m_selection.get_bounding_box();
+        Vec3d sel_bb_center = sel_bb.center();
+        Vec3d extend_by = sel_bb.max_size() * Vec3d::Ones();
+        bb.merge(BoundingBoxf3(sel_bb_center - extend_by, sel_bb_center + extend_by));
+    }
+
     bb.merge(m_bed.get_bounding_box(include_bed_model));
     return bb;
 }
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index c9803f9db8..bd33dbef78 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -652,7 +652,7 @@ private:
     bool _set_current();
     void _resize(unsigned int w, unsigned int h);
 
-    BoundingBoxf3 _max_bounding_box(bool include_bed_model) const;
+    BoundingBoxf3 _max_bounding_box(bool include_gizmos, bool include_bed_model) const;
 
     void _zoom_to_box(const BoundingBoxf3& box);
 
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index c0af7a41e7..c714b6797c 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -494,7 +494,7 @@ void ObjectList::update_name_in_model(const wxDataViewItem& item) const
     if (obj_idx < 0) return;
     const int volume_id = m_objects_model->GetVolumeIdByItem(item);
 
-    take_snapshot(wxString::Format(_(L("Rename %s")), volume_id < 0 ? _(L("Object")) : _(L("Sub-object"))));
+    take_snapshot(volume_id < 0 ? _(L("Rename Object")) : _(L("Rename Sub-object")));
 
     if (m_objects_model->GetItemType(item) & itObject) {
         (*m_objects)[obj_idx]->name = m_objects_model->GetName(item).ToUTF8().data();
@@ -1049,8 +1049,10 @@ void ObjectList::get_settings_choice(const wxString& category_name)
     wxArrayInt selections;
     wxDataViewItem item = GetSelection();
 
+    const ItemType item_type = m_objects_model->GetItemType(item);
+
     settings_menu_hierarchy settings_menu;
-    const bool is_part = m_objects_model->GetItemType(item) & (itVolume | itLayer);
+    const bool is_part = item_type & (itVolume | itLayer);
     get_options_menu(settings_menu, is_part);
     std::vector< std::pair<std::string, std::string> > *settings_list = nullptr;
 
@@ -1127,7 +1129,10 @@ void ObjectList::get_settings_choice(const wxString& category_name)
     }
 #endif
 
-    take_snapshot(wxString::Format(_(L("Add Settings for %s")), is_part ? _(L("Sub-object")) : _(L("Object"))));
+    const wxString snapshot_text =  item_type & itLayer   ? _(L("Add Settings for Layers")) :
+                                    item_type & itVolume  ? _(L("Add Settings for Sub-object")) :
+                                                            _(L("Add Settings for Object"));
+    take_snapshot(snapshot_text);
 
     std::vector <std::string> selected_options;
     selected_options.reserve(selection_cnt);
@@ -1159,7 +1164,7 @@ void ObjectList::get_settings_choice(const wxString& category_name)
 
 
     // Add settings item for object/sub-object and show them 
-    if (!(m_objects_model->GetItemType(item) & (itObject | itVolume | itLayer)))
+    if (!(item_type & (itObject | itVolume | itLayer)))
         item = m_objects_model->GetTopParent(item);
     show_settings(add_settings_item(item, m_config));
 }
@@ -1169,11 +1174,13 @@ void ObjectList::get_freq_settings_choice(const wxString& bundle_name)
     std::vector<std::string> options = get_options_for_bundle(bundle_name);
     wxDataViewItem item = GetSelection();
 
+    ItemType item_type = m_objects_model->GetItemType(item);
+
     /* Because of we couldn't edited layer_height for ItVolume from settings list,
      * correct options according to the selected item type :
      * remove "layer_height" option
      */
-    if ((m_objects_model->GetItemType(item) & itVolume) && bundle_name == _("Layers and Perimeters")) {
+    if ((item_type & itVolume) && bundle_name == _("Layers and Perimeters")) {
         const auto layer_height_it = std::find(options.begin(), options.end(), "layer_height");
         if (layer_height_it != options.end())
             options.erase(layer_height_it);
@@ -1185,7 +1192,10 @@ void ObjectList::get_freq_settings_choice(const wxString& bundle_name)
     assert(m_config);
     auto opt_keys = m_config->keys();
 
-    take_snapshot(wxString::Format(_(L("Add Settings Bundle for %s")), m_objects_model->GetItemType(item) & (itVolume|itLayer) ? _(L("Sub-object")) : _(L("Object"))));
+    const wxString snapshot_text = item_type & itLayer  ? _(L("Add Settings Bundle for Layers")) :
+                                   item_type & itVolume ? _(L("Add Settings Bundle for Sub-object")) :
+                                                          _(L("Add Settings Bundle for Object"));
+    take_snapshot(snapshot_text);
 
     const DynamicPrintConfig& from_config = wxGetApp().preset_bundle->prints.get_edited_preset().config;
     for (auto& opt_key : options)
@@ -1202,7 +1212,7 @@ void ObjectList::get_freq_settings_choice(const wxString& bundle_name)
     }
 
     // Add settings item for object/sub-object and show them 
-    if (!(m_objects_model->GetItemType(item) & (itObject | itVolume | itLayer)))
+    if (!(item_type & (itObject | itVolume | itLayer)))
         item = m_objects_model->GetTopParent(item);
     show_settings(add_settings_item(item, m_config));
 }
@@ -1217,26 +1227,6 @@ void ObjectList::show_settings(const wxDataViewItem settings_item)
     // update object selection on Plater
     if (!m_prevent_canvas_selection_update)
         update_selections_on_canvas();
-/*    auto item = GetSelection();
-    if (item) {
-        if (m_objects_model->GetItemType(item) == itInstance)
-            item = m_objects_model->GetTopParent(item);
-        const auto settings_item = m_objects_model->IsSettingsItem(item) ? item : m_objects_model->GetSettingsItem(item);
-        select_item(settings_item ? settings_item :
-            m_objects_model->AddSettingsChild(item));
-
-        // update object selection on Plater
-        if (!m_prevent_canvas_selection_update)
-            update_selections_on_canvas();
-    }
-    else { 
-        //# ys_FIXME ??? use case ???
-        auto panel = wxGetApp().sidebar().scrolled_panel();
-        panel->Freeze();
-        wxGetApp().obj_settings()->UpdateAndShow(true);
-        panel->Thaw();
-    }
-    */
 }
 
 wxMenu* ObjectList::append_submenu_add_generic(wxMenu* menu, const ModelVolumeType type) {
@@ -1778,7 +1768,19 @@ void ObjectList::del_subobject_item(wxDataViewItem& item)
     if (type & itVolume && (*m_objects)[obj_idx]->get_mesh_errors_count() == 0)
         m_objects_model->DeleteWarningIcon(m_objects_model->GetParent(item));
 
+    // If last two Instances of object is selected, show the message about impossible action
+    bool show_msg = false;
+    if (type & itInstance) { 
+        wxDataViewItemArray instances;
+        m_objects_model->GetChildren(m_objects_model->GetParent(item), instances);
+        if (instances.Count() == 2 && IsSelected(instances[0]) && IsSelected(instances[1]))
+            show_msg = true;
+    }
+
     m_objects_model->Delete(item);
+
+    if (show_msg)
+        Slic3r::GUI::show_error(nullptr, _(L("From Object List You can't delete the last intance from object.")));
 }
 
 void ObjectList::del_settings_from_config(const wxDataViewItem& parent_item)
@@ -1861,7 +1863,7 @@ bool ObjectList::del_subobject_from_object(const int obj_idx, const int idx, con
             if (vol->is_model_part())
                 ++solid_cnt;
         if (volume->is_model_part() && solid_cnt == 1) {
-            Slic3r::GUI::show_error(nullptr, _(L("You can't delete the last solid part from object.")));
+            Slic3r::GUI::show_error(nullptr, _(L("From Object List You can't delete the last solid part from object.")));
             return false;
         }
 
@@ -1880,7 +1882,7 @@ bool ObjectList::del_subobject_from_object(const int obj_idx, const int idx, con
     }
     else if (type == itInstance) {
         if (object->instances.size() == 1) {
-            Slic3r::GUI::show_error(nullptr, _(L("You can't delete the last intance from object.")));
+            Slic3r::GUI::show_error(nullptr, _(L("From Object List You can't delete the last intance from object.")));
             return false;
         }
 
@@ -2435,6 +2437,8 @@ void ObjectList::remove()
 
     for (auto& item : sels)
     {
+        if (m_objects_model->InvalidItem(item)) // item can be deleted for this moment (like last 2 Instances or Volumes)
+            continue;
         if (m_objects_model->GetParent(item) == wxDataViewItem(0))
             delete_from_model_and_list(itObject, m_objects_model->GetIdByItem(item), -1);
         else {
@@ -3181,33 +3185,6 @@ void ObjectList::last_volume_is_deleted(const int obj_idx)
     volume->config.set_key_value("extruder", new ConfigOptionInt(0));
 }
 
-/* #lm_FIXME_delete_after_testing
-void ObjectList::update_settings_items()
-{
-    m_prevent_canvas_selection_update = true;
-    wxDataViewItemArray sel;
-    GetSelections(sel); // stash selection
-
-    wxDataViewItemArray items;
-    m_objects_model->GetChildren(wxDataViewItem(0), items);
-
-    for (auto& item : items) {        
-        const wxDataViewItem& settings_item = m_objects_model->GetSettingsItem(item);
-        select_item(settings_item ? settings_item : m_objects_model->AddSettingsChild(item));
-
-        // If settings item was deleted from the list, 
-        // it's need to be deleted from selection array, if it was there
-        if (settings_item != m_objects_model->GetSettingsItem(item) && 
-            sel.Index(settings_item) != wxNOT_FOUND) {
-            sel.Remove(settings_item);
-        }
-    }
-
-    // restore selection:
-    SetSelections(sel);
-    m_prevent_canvas_selection_update = false;
-}
-*/
 void ObjectList::update_and_show_object_settings_item()
 {
     const wxDataViewItem item = GetSelection();
diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index d3da148a05..f5da43aee9 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -279,6 +279,18 @@ bool MainFrame::can_export_gcode() const
     return true;
 }
 
+bool MainFrame::can_send_gcode() const
+{
+    if (m_plater == nullptr)
+        return false;
+
+    if (m_plater->model().objects.empty())
+        return false;
+
+    const auto prin_host_opt =wxGetApp().preset_bundle->printers.get_edited_preset().config.option<ConfigOptionString>("print_host");
+    return prin_host_opt != nullptr && !prin_host_opt->value.empty();
+}
+
 bool MainFrame::can_slice() const
 {
     bool bg_proc = wxGetApp().app_config->get("background_processing") == "1";
@@ -451,6 +463,10 @@ void MainFrame::init_menubar()
             [this](wxCommandEvent&) { if (m_plater) m_plater->export_gcode(); }, menu_icon("export_gcode"), nullptr,
             [this](){return can_export_gcode(); }, this);
         m_changeable_menu_items.push_back(item_export_gcode);
+        wxMenuItem* item_send_gcode = append_menu_item(export_menu, wxID_ANY, _(L("S&end G-code")) + dots +"\tCtrl+Shift+G", _(L("Send to print current plate as G-code")),
+            [this](wxCommandEvent&) { if (m_plater) m_plater->send_gcode(); }, menu_icon("export_gcode"), nullptr,
+            [this](){return can_send_gcode(); }, this);
+        m_changeable_menu_items.push_back(item_send_gcode);
         export_menu->AppendSeparator();
         append_menu_item(export_menu, wxID_ANY, _(L("Export plate as &STL")) + dots, _(L("Export current plate as STL")),
             [this](wxCommandEvent&) { if (m_plater) m_plater->export_stl(); }, menu_icon("export_plater"), nullptr,
@@ -689,7 +705,8 @@ void MainFrame::update_menubar()
 {
     const bool is_fff = plater()->printer_technology() == ptFFF;
 
-    m_changeable_menu_items[miExport]       ->SetItemLabel((is_fff ? _(L("Export &G-code"))         : _(L("Export"))                    )   + dots + "\tCtrl+G");
+    m_changeable_menu_items[miExport]       ->SetItemLabel((is_fff ? _(L("Export &G-code"))         : _(L("E&xport"))       ) + dots     + "\tCtrl+G");
+    m_changeable_menu_items[miSend]         ->SetItemLabel((is_fff ? _(L("S&end G-code"))           : _(L("S&end to print"))) + dots    + "\tCtrl+Shift+G");
 
     m_changeable_menu_items[miMaterialTab]  ->SetItemLabel((is_fff ? _(L("&Filament Settings Tab")) : _(L("Mate&rial Settings Tab")))   + "\tCtrl+3");
     m_changeable_menu_items[miMaterialTab]  ->SetBitmap(create_scaled_bitmap(this, menu_icon(is_fff ? "spool": "resin")));
diff --git a/src/slic3r/GUI/MainFrame.hpp b/src/slic3r/GUI/MainFrame.hpp
index a41f33824d..5d34be48ef 100644
--- a/src/slic3r/GUI/MainFrame.hpp
+++ b/src/slic3r/GUI/MainFrame.hpp
@@ -67,6 +67,7 @@ class MainFrame : public DPIFrame
     bool can_export_model() const;
     bool can_export_supports() const;
     bool can_export_gcode() const;
+    bool can_send_gcode() const;
     bool can_slice() const;
     bool can_change_view() const;
     bool can_select() const;
@@ -79,6 +80,7 @@ class MainFrame : public DPIFrame
     enum MenuItems
     {                   //   FFF                  SLA
         miExport = 0,   // Export G-code        Export
+        miSend,         // Send G-code          Send to print
         miMaterialTab,  // Filament Settings    Material Settings
     };
 
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index 1a49466378..ea74cdf208 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -1175,10 +1175,10 @@ void Sidebar::show_sliced_info_sizer(const bool show)
                 if (ps.estimated_silent_print_time != "N/A") {
                     new_label += wxString::Format("\n    - %s", _(L("stealth mode")));
                     info_text += wxString::Format("\n%s", ps.estimated_silent_print_time);
-                    for (int i = (int)ps.estimated_normal_color_print_times.size() - 1; i >= 0; --i)
+                    for (int i = (int)ps.estimated_silent_color_print_times.size() - 1; i >= 0; --i)
                     {
                         new_label += wxString::Format("\n      - %s%d", _(L("Color ")), i + 1);
-                        info_text += wxString::Format("\n%s", ps.estimated_normal_color_print_times[i]);
+                        info_text += wxString::Format("\n%s", ps.estimated_silent_color_print_times[i]);
                     }
                 }
                 p->sliced_info->SetTextAndShow(siEstimatedTime,  info_text,      new_label);
diff --git a/src/slic3r/GUI/Selection.cpp b/src/slic3r/GUI/Selection.cpp
index 630ecd1d4a..85f154e959 100644
--- a/src/slic3r/GUI/Selection.cpp
+++ b/src/slic3r/GUI/Selection.cpp
@@ -402,8 +402,10 @@ void Selection::remove_all()
 
     if (is_empty())
         return;
-    
-    if (!wxGetApp().plater()->can_redo())
+  
+// Not taking the snapshot with non-empty Redo stack will likely be more confusing than losing the Redo stack.
+// Let's wait for user feedback.
+//    if (!wxGetApp().plater()->can_redo())
         wxGetApp().plater()->take_snapshot(_(L("Selection-Remove All")));
 
     m_mode = Instance;
diff --git a/src/slic3r/GUI/wxExtensions.cpp b/src/slic3r/GUI/wxExtensions.cpp
index 7ddf1c2732..3da6997a79 100644
--- a/src/slic3r/GUI/wxExtensions.cpp
+++ b/src/slic3r/GUI/wxExtensions.cpp
@@ -1385,6 +1385,18 @@ int ObjectDataViewModel::GetRowByItem(const wxDataViewItem& item) const
     return -1;
 }
 
+bool ObjectDataViewModel::InvalidItem(const wxDataViewItem& item)
+{
+    if (!item)
+        return true;
+
+    ObjectDataViewModelNode* node = (ObjectDataViewModelNode*)item.GetID();
+    if (!node || node->invalid()) 
+        return true;
+
+    return false;
+}
+
 wxString ObjectDataViewModel::GetName(const wxDataViewItem &item) const
 {
 	ObjectDataViewModelNode *node = (ObjectDataViewModelNode*)item.GetID();
diff --git a/src/slic3r/GUI/wxExtensions.hpp b/src/slic3r/GUI/wxExtensions.hpp
index b04c6c9c06..5b9bdee023 100644
--- a/src/slic3r/GUI/wxExtensions.hpp
+++ b/src/slic3r/GUI/wxExtensions.hpp
@@ -367,6 +367,7 @@ public:
 #ifndef NDEBUG
 	bool 		valid();
 #endif /* NDEBUG */
+    bool        invalid() const { return m_idx < -1; }
 
 private:
     friend class ObjectDataViewModel;
@@ -430,6 +431,7 @@ public:
     void GetItemInfo(const wxDataViewItem& item, ItemType& type, int& obj_idx, int& idx);
     int  GetRowByItem(const wxDataViewItem& item) const;
     bool IsEmpty() { return m_objects.empty(); }
+    bool InvalidItem(const wxDataViewItem& item);
 
 	// helper method for wxLog
 
diff --git a/src/slic3r/Utils/Serial.cpp b/src/slic3r/Utils/Serial.cpp
index cd2a01cbfd..acfd5fafd0 100644
--- a/src/slic3r/Utils/Serial.cpp
+++ b/src/slic3r/Utils/Serial.cpp
@@ -353,6 +353,8 @@ void Serial::set_baud_rate(unsigned baud_rate)
 	}
 }
 
+
+/*
 void Serial::set_DTR(bool on)
 {
 	auto handle = native_handle();
@@ -495,6 +497,7 @@ std::string Serial::printer_format_line(const std::string &line, unsigned line_n
 
 	return (boost::format("N%1% %2%*%3%\n") % line_num_str % line % checksum).str();
 }
+*/
 
 
 } // namespace Utils
diff --git a/src/slic3r/Utils/Serial.hpp b/src/slic3r/Utils/Serial.hpp
index 67d64b4ec1..8bad75b315 100644
--- a/src/slic3r/Utils/Serial.hpp
+++ b/src/slic3r/Utils/Serial.hpp
@@ -46,6 +46,17 @@ public:
 	~Serial();
 
 	void set_baud_rate(unsigned baud_rate);
+
+	// The Serial implementation is currently in disarray and therefore commented out.
+	// The boost implementation seems to have several problems, such as lack of support
+	// for custom baud rates, few weird implementation bugs and a history of API breakages.
+	// It's questionable whether it solves more problems than causes. Probably not.
+	// TODO: Custom implementation not based on asio.
+	//
+	// As of now, this class is only kept for the purpose of rebooting AVR109,
+	// see FirmwareDialog::priv::avr109_reboot()
+
+/*
 	void set_DTR(bool on);
 
 	// Resets the line number both internally as well as with the firmware using M110
@@ -68,7 +79,7 @@ public:
 
 	// Same as above, but with internally-managed line number
 	size_t printer_write_line(const std::string &line);
-	
+
 	// Toggles DTR to reset the printer
 	void printer_reset();
 
@@ -76,6 +87,7 @@ public:
 	static std::string printer_format_line(const std::string &line, unsigned line_num);
 private:
 	unsigned m_line_num = 0;
+*/
 };