resize using ALT+RMB

engine/canvas_modes.h

@@ -40,11 +40,15 @@ class CanvasModePen : public CanvasMode
     bool m_dragging = false;
     glm::vec2 m_pan_start;
     glm::vec2 m_cur_pos;
+    glm::vec2 m_size_pos_start;
+    float m_size_value_start;
     float m_camera_fov;
     float m_zoom_canvas = 1.f;
     float m_zoom_start;
     bool m_valid_brush = false;
     ui::Brush m_brush;
+    // resizing the tip
+    bool m_resizing = false;
 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;