implement pen and erase as strategy pattern introducing the CanvasMode classes

engine/canvas_modes.h

@@ -0,0 +1,47 @@
+#pragma once
+#include "event.h"
+
+NS_START
+class Canvas;
+NS_END
+
+class CanvasMode
+{
+public:
+    static class NodeCanvas* node;
+    static ui::Canvas* canvas;
+    virtual void on_MouseDownL(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseUpL(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseDownR(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseUpR(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseMove(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseScroll(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_MouseCancel(MouseEvent* me, glm::vec2& loc) {}
+    virtual void on_KeyDown(KeyEvent* ke) {}
+    virtual void on_KeyUp(KeyEvent* ke) {}
+    virtual void on_GestureStart(GestureEvent* ge) {}
+    virtual void on_GestureMove(GestureEvent* ge) {}
+};
+
+class CanvasModePen : public CanvasMode
+{
+    bool m_dragging = false;
+    bool m_draggingR = false;
+    glm::vec2 m_dragR_start;
+    glm::vec2 m_pan_start;
+    glm::vec2 m_pan;
+    glm::vec2 m_cur;
+    float m_camera_fov;
+    float m_zoom_canvas = 1.f;
+    float m_zoom_start;
+public:
+    virtual void on_MouseDownL(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseUpL(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseDownR(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseUpR(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseMove(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseScroll(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_MouseCancel(MouseEvent* me, glm::vec2& loc) override;
+    virtual void on_GestureStart(GestureEvent* ge) override;
+    virtual void on_GestureMove(GestureEvent* ge) override;
+};