Refresh rework

src/displayapp/screens/Screen.h

@@ -2,6 +2,7 @@
 
 #include <cstdint>
 #include "../TouchEvents.h"
+#include <lvgl/lvgl.h>
 
 namespace Pinetime {
   namespace Applications {
@@ -34,25 +35,20 @@ namespace Pinetime {
       };
 
       class Screen {
+      private:
+        virtual void Refresh() {
+        }
+
       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;
+        static void RefreshTaskCallback(lv_task_t* task);
+
+        bool IsRunning() const {
+          return running;
+        }
 
         /** @return false if the button hasn't been handled by the app, true if it has been handled */
         virtual bool OnButtonPushed() {