hide cursor on canvas, add mouse focus event, brush preview solid when small

src/canvas_modes.h

@@ -88,6 +88,7 @@ public:
     bool m_picking = false;
     glm::vec2 m_cur_pos;
     bool m_draw_tip = false;
+    bool m_draw_outline = true;
 };
 
 class CanvasModeLine : public CanvasMode
@@ -98,6 +99,8 @@ class CanvasModeLine : public CanvasMode
     glm::vec2 m_drag_pos;
     std::shared_ptr<Brush> m_brush;
 public:
+    glm::vec2 m_cur_pos;
+    bool m_draw_tip = false;
     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;