diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7e094a85f..44b77de48 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,13 +42,6 @@ if (MSVC)
     add_compile_options(-bigobj -Zm316)
 endif ()
 
-# CMAKE_PREFIX_PATH is used to point CMake to the remaining dependencies (Boost, TBB, ...)
-# We pick it from environment if it is not defined in another way
-if (NOT DEFINED CMAKE_PREFIX_PATH)
-	if (DEFINED ENV{CMAKE_PREFIX_PATH})
-		set(CMAKE_PREFIX_PATH "$ENV{CMAKE_PREFIX_PATH}")
-	endif ()
-endif ()
 message(STATUS "CMAKE_PREFIX_PATH: ${CMAKE_PREFIX_PATH}")
 
 # Add our own cmake module path.
diff --git a/deps/deps-unix-common.cmake b/deps/deps-unix-common.cmake
index 7ad1b4290..e4c718d21 100644
--- a/deps/deps-unix-common.cmake
+++ b/deps/deps-unix-common.cmake
@@ -26,6 +26,7 @@ ExternalProject_Add(dep_nlopt
     URL_HASH SHA256=c6dd7a5701fff8ad5ebb45a3dc8e757e61d52658de3918e38bab233e7fd3b4ae
     CMAKE_GENERATOR "${DEP_MSVC_GEN}"
     CMAKE_ARGS
+        -DBUILD_SHARED_LIBS=OFF
         -DNLOPT_PYTHON=OFF
         -DNLOPT_OCTAVE=OFF
         -DNLOPT_MATLAB=OFF
@@ -35,18 +36,7 @@ ExternalProject_Add(dep_nlopt
     INSTALL_COMMAND ""
 )
 
-ExternalProject_Add(dep_zlib
-    EXCLUDE_FROM_ALL 1
-    URL "https://zlib.net/zlib-1.2.11.tar.xz"
-    URL_HASH SHA256=4ff941449631ace0d4d203e3483be9dbc9da454084111f97ea0a2114e19bf066
-    CMAKE_GENERATOR "${DEP_MSVC_GEN}"
-    CMAKE_ARGS ${DEP_CMAKE_OPTS}
-    INSTALL_COMMAND make install "DESTDIR=${DESTDIR}"
-    INSTALL_COMMAND ""
-)
-
 ExternalProject_Add(dep_libpng
-    DEPENDS dep_zlib
     EXCLUDE_FROM_ALL 1
     URL "http://prdownloads.sourceforge.net/libpng/libpng-1.6.35.tar.xz?download"
     URL_HASH SHA256=23912ec8c9584917ed9b09c5023465d71709dce089be503c7867fec68a93bcd7
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index f228723da..3ab08b773 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -3885,6 +3885,7 @@ void GLCanvas3D::render()
 void GLCanvas3D::select_all()
 {
     m_selection.add_all();
+    m_dirty = true;
 }
 
 void GLCanvas3D::delete_selected()
diff --git a/src/slic3r/GUI/GUI_App.cpp b/src/slic3r/GUI/GUI_App.cpp
index 52426c12d..121044729 100644
--- a/src/slic3r/GUI/GUI_App.cpp
+++ b/src/slic3r/GUI/GUI_App.cpp
@@ -520,7 +520,7 @@ void GUI_App::update_mode()
 
     obj_list()->get_sizer()->Show(mode == ConfigMenuModeExpert);
     sidebar().set_mode_value(mode);
-    sidebar().show_buttons(mode == ConfigMenuModeExpert);
+//    sidebar().show_buttons(mode == ConfigMenuModeExpert);
     obj_list()->update_selections();
 
     sidebar().Layout();
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index 10d9d0eb3..5a98c5254 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -263,6 +263,7 @@ void ObjectList::selection_changed()
         event.SetEventObject(this);
         wxPostEvent(this, event);
     }
+    wxGetApp().sidebar().enable_buttons(!m_objects_model->IsEmpty());
 
     part_selection_changed();
 
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index b57e4e01c..5e921921e 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -565,6 +565,7 @@ Sidebar::Sidebar(Plater *parent)
     p->btn_export_gcode->SetFont(wxGetApp().bold_font());
     p->btn_reslice = new wxButton(this, wxID_ANY, _(L("Slice now")));
     p->btn_reslice->SetFont(wxGetApp().bold_font());
+    enable_buttons(false);
 
     auto *btns_sizer = new wxBoxSizer(wxVERTICAL);
     btns_sizer->Add(p->btn_reslice, 0, wxEXPAND | wxTOP, 5);
@@ -820,15 +821,9 @@ void Sidebar::show_sliced_info_sizer(const bool show)
 void Sidebar::show_buttons(const bool show)
 {
     p->btn_reslice->Show(show);
-    for (size_t i = 0; i < wxGetApp().tab_panel()->GetPageCount(); ++i) {
-        TabPrinter *tab = dynamic_cast<TabPrinter*>(wxGetApp().tab_panel()->GetPage(i));
-        if (!tab)
-            continue;
-		if (p->plater->printer_technology() == ptFFF) {
-            p->btn_send_gcode->Show(show && !tab->m_config->opt_string("print_host").empty());
-        }
-        break;
-    }
+    TabPrinter *tab = dynamic_cast<TabPrinter*>(wxGetApp().get_tab(Preset::TYPE_PRINTER));
+	if (tab && p->plater->printer_technology() == ptFFF)
+        p->btn_send_gcode->Show(show && !tab->m_config->opt_string("print_host").empty());
 }
 
 void Sidebar::enable_buttons(bool enable)
@@ -1819,6 +1814,8 @@ unsigned int Plater::priv::update_background_process()
         // Some previously calculated data on the Print was invalidated.
         // Hide the slicing results, as the current slicing status is no more valid.
         this->sidebar->show_sliced_info_sizer(false);
+        // Disable buttons during background process.
+        this->sidebar->enable_buttons(false);
         // Reset preview canvases. If the print has been invalidated, the preview canvases will be cleared.
         // Otherwise they will be just refreshed.
         this->gcode_preview_data.reset();
@@ -2062,6 +2059,7 @@ void Plater::priv::on_process_completed(wxCommandEvent &evt)
 		this->statusbar()->set_status_text(L("Cancelled"));
 
     this->sidebar->show_sliced_info_sizer(success);
+    this->sidebar->enable_buttons(success);
 
     // This updates the "Slice now", "Export G-code", "Arrange" buttons status.
     // Namely, it refreshes the "Out of print bed" property of all the ModelObjects, and it enables