Visual hints in the 3D scene when sidebar matrix fields have focus (wip [position+scale+size] and disabled)

src/slic3r/GUI/3DScene.hpp

@@ -583,6 +583,41 @@ private:
     GLVolumeCollection& operator=(const GLVolumeCollection &);
 };
 
+#if ENABLE_SIDEBAR_VISUAL_HINTS
+class GLModel
+{
+protected:
+    GLVolume m_volume;
+    bool m_useVBOs;
+
+public:
+    GLModel();
+    virtual ~GLModel();
+
+    bool init(bool useVBOs) { return on_init(useVBOs); }
+
+    void set_color(float* color, unsigned int size);
+    void set_scale(const Vec3d& scale);
+
+    void render() const; 
+
+protected:
+    virtual bool on_init(bool useVBOs) = 0;
+
+private:
+    void render_VBOs() const;
+};
+
+class GLArrow : public GLModel
+{
+public:
+    GLArrow();
+
+protected:
+    virtual bool on_init(bool useVBOs);
+};
+#endif // ENABLE_SIDEBAR_VISUAL_HINTS
+
 class _3DScene
 {
     static GUI::GLCanvas3DManager s_canvas_mgr;