InfiniTime/src/displayapp/screens/Screen.h

#pragma once

#include <cstdint>
#include "../TouchEvents.h"

namespace Pinetime {
  namespace Applications {
    class DisplayApp;
    namespace Screens {

      template <class T>
      class DirtyValue {
        public:
          DirtyValue() = default;                      // Use NSDMI
          explicit DirtyValue(T const& v):value{v}{}   // Use MIL and const-lvalue-ref
          bool IsUpdated() const { return isUpdated; }
          T const& Get() { this->isUpdated = false; return value; }  // never expose a non-const lvalue-ref
          DirtyValue& operator=(const T& other) {
            if (this->value != other) {
              this->value = other;
              this->isUpdated = true;
            }
            return *this;
          }
        private:
          T value{};            // NSDMI - default initialise type
          bool isUpdated{true}; // NSDMI - use brace initilisation
      };
      
      class Screen {
        public:
          explicit Screen(DisplayApp* app) : app{app} {}
          virtual ~Screen() = default;

          /**
           * Most of the time, apps only react to events (touch events, for example).
           * In this case you don't need to do anything in this method.
           *
           * For example, InfiniPaint does nothing in Refresh().
           * But, if you want to update your display periodically, draw an animation...
           * you cannot do it in a touch event handler because these handlers are not
           * called if the user does not touch the screen.
           *
           * That's why Refresh() is there: update the display periodically.
           *
           * @return false if the app can be closed, true if it must continue to run
           **/
          virtual bool Refresh() = 0;

          /** @return false if the button hasn't been handled by the app, true if it has been handled */
          virtual bool OnButtonPushed() { return false; }

          /** @return false if the event hasn't been handled by the app, true if it has been handled */
          virtual bool OnTouchEvent(TouchEvents event) { return false; }
          virtual bool OnTouchEvent(uint16_t x, uint16_t y) { return false; }

        protected:
          DisplayApp* app;
      };
    }
  }
}