Timer App : add background label to ensure that the app will be displayed correctly after a full refresh (HW scrolling transition).

Code cleaning and rename methods.

src/displayapp/screens/Timer.h

@@ -8,32 +8,35 @@
 #include "components/timer/TimerController.h"
 
 namespace Pinetime::Applications::Screens {
-
   class Timer : public Screen {
   public:
     enum class Modes { Normal, Done };
 
     Timer(DisplayApp* app, Controllers::TimerController& timerController);
-
     ~Timer() override;
-
     void Refresh() override;
-
-    void setDone();
-
+    void SetDone();
     void OnButtonEvent(lv_obj_t* obj, lv_event_t event);
 
   private:
+    void CreateButtons();
     bool running;
     uint8_t secondsToSet = 0;
     uint8_t minutesToSet = 0;
     Controllers::TimerController& timerController;
-
-    void createButtons();
-
-    lv_obj_t *time, *msecTime, *btnPlayPause, *txtPlayPause, *btnMinutesUp, *btnMinutesDown, *btnSecondsUp, *btnSecondsDown, *txtMUp,
-      *txtMDown, *txtSUp, *txtSDown;
-
+    lv_obj_t* backgroundLabel;
+    lv_obj_t* time;
+    lv_obj_t* msecTime;
+    lv_obj_t* btnPlayPause;
+    lv_obj_t* txtPlayPause;
+    lv_obj_t* btnMinutesUp;
+    lv_obj_t* btnMinutesDown;
+    lv_obj_t* btnSecondsUp;
+    lv_obj_t* btnSecondsDown;
+    lv_obj_t* txtMUp;
+    lv_obj_t* txtMDown;
+    lv_obj_t* txtSUp;
+    lv_obj_t* txtSDown;
     lv_task_t* taskRefresh;
   };
 }