feat(event) add LV_SCREEN_(UN)LOAD_START

docs/overview/event.md

@@ -110,8 +110,10 @@ The following event codes exist:
 - `LV_EVENT_STYLE_CHANGED`    Object's style has changed
 - `LV_EVENT_BASE_DIR_CHANGED` The base dir has changed
 - `LV_EVENT_GET_SELF_SIZE`    Get the internal size of a widget
-- `LV_EVENT_SCREEN_LOADED`    A screen was loaded
+- `LV_EVENT_SCREEN_UNLOAD_START` A screen unload started, fired immediately when lv_scr_load/lv_scr_load_anim is called
-- `LV_EVENT_SCREEN_UNLOADED`  A screen was unloaded
+- `LV_EVENT_SCREEN_LOAD_START` A screen load started, fired when the screen change delay is expired
+- `LV_EVENT_SCREEN_LOADED`    A screen was loaded, called when all animations are finished
+- `LV_EVENT_SCREEN_UNLOADED`  A screen was unloaded, called when all animations are finished
 
 ### Special events
 - `LV_EVENT_VALUE_CHANGED`    The object's value has changed (i.e. slider moved)

src/core/lv_disp.c

@@ -83,11 +83,15 @@ void lv_disp_load_scr(lv_obj_t * scr)
     lv_disp_t * d = lv_obj_get_disp(scr);
     if(!d) return;  /*Shouldn't happen, just to be sure*/
 
-    if(d->act_scr) lv_event_send(d->act_scr, LV_EVENT_SCREEN_UNLOADED, NULL);
+    lv_obj_t * old_scr = d->act_scr;
+
+    if(d->act_scr) lv_event_send(old_scr, LV_EVENT_SCREEN_UNLOAD_START, NULL);
+    if(d->act_scr) lv_event_send(scr, LV_EVENT_SCREEN_LOAD_START, NULL);
 
     d->act_scr = scr;
 
-    if(d->act_scr) lv_event_send(d->act_scr, LV_EVENT_SCREEN_LOADED, NULL);
+    if(d->act_scr) lv_event_send(scr, LV_EVENT_SCREEN_LOADED, NULL);
+    if(d->act_scr) lv_event_send(old_scr, LV_EVENT_SCREEN_UNLOADED, NULL);
 
     lv_obj_invalidate(scr);
 }
@@ -227,6 +231,8 @@ void lv_scr_load_anim(lv_obj_t * new_scr, lv_scr_load_anim_t anim_type, uint32_t
     lv_disp_t * d = lv_obj_get_disp(new_scr);
     lv_obj_t * act_scr = lv_scr_act();
 
+    /*If an other screen load animation is in progress
+     *make target screen loaded immediately. */
     if(d->scr_to_load && act_scr != d->scr_to_load) {
         lv_disp_load_scr(d->scr_to_load);
         lv_anim_del(d->scr_to_load, NULL);
@@ -329,8 +335,11 @@ void lv_scr_load_anim(lv_obj_t * new_scr, lv_scr_load_anim_t anim_type, uint32_t
             break;
     }
 
+    lv_event_send(act_scr, LV_EVENT_SCREEN_UNLOAD_START, NULL);
+
     lv_anim_start(&a_new);
     lv_anim_start(&a_old);
+
 }
 
 /**
@@ -409,9 +418,11 @@ lv_timer_t * _lv_disp_get_refr_timer(lv_disp_t * disp)
 static void scr_load_anim_start(lv_anim_t * a)
 {
     lv_disp_t * d = lv_obj_get_disp(a->var);
-    d->prev_scr = lv_scr_act();
 
-    lv_disp_load_scr(a->var);
+    d->prev_scr = lv_scr_act();
+    d->act_scr = a->var;
+
+    lv_event_send(d->act_scr, LV_EVENT_SCREEN_LOAD_START, NULL);
 }
 
 static void opa_scale_anim(void * obj, int32_t v)
@@ -433,6 +444,9 @@ static void scr_anim_ready(lv_anim_t * a)
 {
     lv_disp_t * d = lv_obj_get_disp(a->var);
 
+    lv_event_send(d->act_scr, LV_EVENT_SCREEN_LOADED, NULL);
+    lv_event_send(d->prev_scr, LV_EVENT_SCREEN_UNLOADED, NULL);
+
     if(d->prev_scr && d->del_prev) lv_obj_del(d->prev_scr);
     d->prev_scr = NULL;
     d->scr_to_load = NULL;

src/core/lv_event.h

@@ -75,9 +75,10 @@ typedef enum {
     LV_EVENT_CHILD_CHANGED,       /**< Child was removed, added, or its size, position were changed */
     LV_EVENT_CHILD_CREATED,       /**< Child was created, always bubbles up to all parents*/
     LV_EVENT_CHILD_DELETED,       /**< Child was deleted, always bubbles up to all parents*/
+    LV_EVENT_SCREEN_UNLOAD_START, /**< A screen unload started, fired immediately when scr_load is called*/
+    LV_EVENT_SCREEN_LOAD_START,   /**< A screen load started, fired when the screen change delay is expired*/
     LV_EVENT_SCREEN_LOADED,       /**< A screen was loaded*/
     LV_EVENT_SCREEN_UNLOADED,     /**< A screen was unloaded*/
-
     LV_EVENT_SIZE_CHANGED,        /**< Object coordinates/size have changed*/
     LV_EVENT_STYLE_CHANGED,       /**< Object's style has changed*/
     LV_EVENT_LAYOUT_CHANGED,      /**< The children position has changed due to a layout recalculation*/