Fix for #12877 - Color Change Added After Moving Slider

+ Fixed update of the ruler, when it was hidden and than shown
+ Added messed include in RulerForDoubleSlider.cpp (#12882)
+ Fixed some warnings

src/slic3r/GUI/DoubleSliderForLayers.cpp

@@ -969,8 +969,7 @@ void DSForLayers::Render(const int canvas_width, const int canvas_height, float
 
 void DSForLayers::force_ruler_update()
 {
-    if (m_show_ruler)
-        m_ruler.invalidate();
+    m_ruler.invalidate();
 }
 
 bool DSForLayers::is_wipe_tower_layer(int tick) const

src/slic3r/GUI/GUI_Preview.cpp

@@ -408,7 +408,7 @@ void Preview::create_sliders()
 
     m_layers_slider->set_callback_on_thumb_move( [this]() -> void { Preview::on_layers_slider_scroll_changed(); } );
 
-    m_layers_slider->set_callback_on_change_app_config([this](const std::string& key, const std::string& val)   -> void {
+    m_layers_slider->set_callback_on_change_app_config([](const std::string& key, const std::string& val)   -> void {
         wxGetApp().app_config->set(key, val);
     });
 

src/slic3r/GUI/ImGuiDoubleSlider.cpp

@@ -545,6 +545,11 @@ bool ImGuiControl::draw_slider( int* higher_pos, int* lower_pos,
                 m_lclick_on_selected_thumb = true;
             }
         }
+
+        if (ImGui::ItemHoverable(active_thumb, id) && ImGui::IsMouseDragging(0)) {
+            // invalidate active thumb clicking
+            m_active_thumb = ImRect(0.f, 0.f, 0.f, 0.f);
+        }
     }
 
     // update thumb position
@@ -621,7 +626,8 @@ bool ImGuiControl::draw_slider( int* higher_pos, int* lower_pos,
     }
 
     // draw label on mouse move
-    draw_label(move_label, mouse_pos_rc, false, true);
+    if (m_show_move_label)
+        draw_label(move_label, mouse_pos_rc, false, true);
 
     return pos_changed;
 }

src/slic3r/GUI/RulerForDoubleSlider.cpp

@@ -4,6 +4,7 @@
 ///|/
 #include "RulerForDoubleSlider.hpp"
 #include "libslic3r/CustomGCode.hpp"
+#include "libslic3r/libslic3r.h"
 
 using namespace Slic3r;
 using namespace CustomGCode;