add Chapter14

Chapter14/sequencer/libs/etl/examples/platformio/src/main.cpp

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+#include <iostream>
+
+#include "etl/observer.h"
+
+// Position data.
+struct Position
+{
+  int x;
+  int y;
+};
+
+// Button data.
+struct Button
+{
+  enum
+  {
+    Down,
+    Up
+  };
+
+  int state;
+};
+
+// Wheel data.
+struct Wheel
+{
+  int delta;
+};
+
+// Definition of a mouse observer.
+typedef etl::observer<const Position&, Button, Wheel> Mouse_Observer;
+
+// Definition of an event handler for mouse notifications.
+class Event_Handler1 : public Mouse_Observer
+{
+public:
+
+  // Handle a position notification.
+  void notification(const Position& position)
+  {
+    std::cout << "Event_Handler1 : Position = " << position.x << "," << position.y << "\n";
+  }
+
+  // Handle a button notification.
+  void notification(Button button)
+  {
+    std::cout << "Event_Handler1 : Button = " << ((button.state == Button::Up) ? "Up\n" : "Down\n");
+  }
+
+  // Handle a wheel notification.
+  void notification(Wheel wheel)
+  {
+    std::cout << "Event_Handler1 : Wheel delta = " << wheel.delta << "\n";
+  }
+};
+
+// Definition of a second event handler for mouse notifications.
+class Event_Handler2 : public Mouse_Observer
+{
+public:
+
+  // Handler a position notification.
+  void notification(const Position& position)
+  {
+    std::cout << "Event_Handler2 : Position = " << position.x << "," << position.y << "\n";
+  }
+
+  // Handle a button notification.
+  void notification(Button button)
+  {
+    std::cout << "Event_Handler2 : Button = " << ((button.state == Button::Up) ? "Up\n" : "Down\n");
+  }
+
+  // Handle a wheel notification.
+  void notification(Wheel wheel)
+  {
+    // Not interested in wheel deltas.
+  }
+};
+
+// The observable mouse driver.
+const int MAX_MOUSE_OBSERVERS = 2;
+
+class Mouse_Driver : public etl::observable<Mouse_Observer, MAX_MOUSE_OBSERVERS>
+{
+public:
+
+  // Notify observers about a position event.
+  void Position_Event()
+  {
+    Position position = { 100, 200 };
+    notify_observers(position);
+  }
+
+  // Notify observers about a button up event.
+  void Button_Event_Up()
+  {
+    Button button = { Button::Up };
+    notify_observers(button);
+  }
+
+  // Notify observers about a button down event.
+  void Button_Event_Down()
+  {
+    Button button = { Button::Down };
+    notify_observers(button);
+  }
+
+  // Notify observers about a wheel up event.
+  void Wheel_Event_Up()
+  {
+    Wheel wheel = { 50 };
+    notify_observers(wheel);
+  }
+
+  // Notify observers about a wheel down event.
+  void Wheel_Event_Down()
+  {
+    Wheel wheel = { -25 };
+    notify_observers(wheel);
+  }
+};
+
+int main()
+{
+  Mouse_Driver   mouse_driver;
+  Event_Handler1 event_handler1;
+  Event_Handler2 event_handler2;
+
+  // Tell the mouse driver about the observers.
+  mouse_driver.add_observer(event_handler1);
+  mouse_driver.add_observer(event_handler2);
+
+  // Generate some events.
+  mouse_driver.Button_Event_Down();
+  mouse_driver.Button_Event_Up();
+  mouse_driver.Position_Event();
+  mouse_driver.Wheel_Event_Down();
+  mouse_driver.Wheel_Event_Up();
+ 
+  return 0;
+}