added Normal lines mode for perspective aligned lines

engine/canvas_modes.h

@@ -59,13 +59,15 @@ public:
 class CanvasModeNormal : public CanvasMode
 {
     ui::LineSegment m_line;
+    glm::vec3 origin;
+    glm::vec3 dir;
+    int m_plane_id;
     bool m_dragging = false;
-    glm::vec2 m_drag_start;
-    glm::vec2 m_drag_pos;
 public:
     virtual void on_MouseEvent(MouseEvent* me, glm::vec2& loc) override;
     virtual void on_Draw(const glm::mat4& ortho, const glm::mat4& proj, const glm::mat4& camera) override;
     virtual void init() override;
+    void commit();
 };
 
 class CanvasModeCamera : public CanvasMode