GCodeViewer -> Imgui slider for sequential view replaced by DoubleSlider::Control (wip)

src/slic3r/GUI/Plater.hpp

@@ -320,6 +320,9 @@ public:
 
 #if ENABLE_GCODE_VIEWER
     void update_preview_bottom_toolbar();
+#if ENABLE_GCODE_USE_WXWIDGETS_SLIDER
+    void update_preview_horz_slider();
+#endif // ENABLE_GCODE_USE_WXWIDGETS_SLIDER
 #endif // ENABLE_GCODE_VIEWER
 
     const Mouse3DController& get_mouse3d_controller() const;