fix(widgets): make animations on state change more consistent (#9174)

Co-authored-by: Liam Howatt <30486941+liamHowatt@users.noreply.github.com>

docs/src/details/common-widget-features/events.rst

@@ -181,6 +181,9 @@ Special Events
 -  :cpp:enumerator:`LV_EVENT_REFRESH`: Notify Widget to refresh something on it (for the user)
 -  :cpp:enumerator:`LV_EVENT_READY`: A process has finished
 -  :cpp:enumerator:`LV_EVENT_CANCEL`: A process has been cancelled
+-  :cpp:enumerator:`LV_EVENT_STATE_CHANGED`: The state of a widget has been changed.
+   E.g. :cpp:enumerator:`LV_STATE_PRESSED` was added. In the event :cpp:expr:`lv_event_get_prev_state(e)`
+   returns the previous state and :cpp:expr:`lv_obj_get_state(obj)` returns the current state.
 
 
 Other Events
@@ -265,11 +268,11 @@ contains all data about the event. The following values can be retrieved from it
 - :cpp:expr:`lv_event_get_param(e)`: get the parameter passed as the last parameter of :cpp:func:`lv_obj_send_event_cb`
 
 .. tip::
-   When using C++, prefer :cpp:expr:`lv_event_get_target_obj(e)` over :cpp:expr:`lv_event_get_target(e)` 
+   When using C++, prefer :cpp:expr:`lv_event_get_target_obj(e)` over :cpp:expr:`lv_event_get_target(e)`
    when you know the target is a Widget, as it returns the correct type without requiring a cast.
 
 .. warning::
-   Only call :cpp:expr:`lv_event_get_target_obj(e)` when the event target is known to be a Widget. 
+   Only call :cpp:expr:`lv_event_get_target_obj(e)` when the event target is known to be a Widget.
    Calling it for Display or Indev targets is considered Undefined Behavior.
 
 

src/core/lv_obj.c

@@ -994,6 +994,7 @@ static void update_obj_state(lv_obj_t * obj, lv_state_t new_state)
     /*If there is no difference in styles there is nothing else to do*/
     if(cmp_res == LV_STYLE_STATE_CMP_SAME) {
         obj->state = new_state;
+        lv_obj_send_event(obj, LV_EVENT_STATE_CHANGED, &prev_state);
         return;
     }
 
@@ -1002,6 +1003,18 @@ static void update_obj_state(lv_obj_t * obj, lv_state_t new_state)
 
     obj->state = new_state;
     lv_obj_update_layer_type(obj);
+
+    /*Skip transitions if the widget is not rendered yet. */
+    if(!obj->rendered) {
+        lv_obj_invalidate(obj);
+        if(cmp_res == LV_STYLE_STATE_CMP_DIFF_DRAW_PAD) {
+            lv_obj_refresh_ext_draw_size(obj);
+        }
+
+        lv_obj_send_event(obj, LV_EVENT_STATE_CHANGED, &prev_state);
+        return;
+    }
+
     lv_obj_style_transition_dsc_t * ts = lv_malloc_zeroed(sizeof(lv_obj_style_transition_dsc_t) * STYLE_TRANSITION_MAX);
     uint32_t tsi = 0;
     uint32_t i;
@@ -1058,6 +1071,8 @@ static void update_obj_state(lv_obj_t * obj, lv_state_t new_state)
         lv_obj_invalidate(obj);
         lv_obj_refresh_ext_draw_size(obj);
     }
+
+    lv_obj_send_event(obj, LV_EVENT_STATE_CHANGED, &prev_state);
 }
 
 /**

src/core/lv_obj_event.c

@@ -346,7 +346,18 @@ lv_draw_task_t * lv_event_get_draw_task(lv_event_t * e)
         LV_LOG_WARN("Not interpreted with this event code");
         return NULL;
     }
+}
 
+lv_state_t lv_event_get_prev_state(lv_event_t * e)
+{
+    if(e->code == LV_EVENT_STATE_CHANGED) {
+        lv_state_t * state = lv_event_get_param(e);
+        return state ? *state : 0;
+    }
+    else {
+        LV_LOG_WARN("Not interpreted with this event code");
+        return 0;
+    }
 }
 
 /**********************

src/core/lv_obj_event.h

@@ -16,6 +16,7 @@ extern "C" {
 #include "../misc/lv_types.h"
 #include "../misc/lv_event.h"
 #include "../indev/lv_indev.h"
+#include "lv_obj_style.h"
 
 /*********************
  *      DEFINES
@@ -193,6 +194,14 @@ void lv_event_set_cover_res(lv_event_t * e, lv_cover_res_t res);
  */
 lv_draw_task_t * lv_event_get_draw_task(lv_event_t * e);
 
+/**
+ * Get the previous state before the state change.
+ * Can be used in `LV_EVENT_STATE_CHANGED` event
+ * @param e     pointer to an event
+ * @return      the previous state
+ */
+lv_state_t lv_event_get_prev_state(lv_event_t * e);
+
 /**********************
  *      MACROS
  **********************/

src/core/lv_obj_private.h

@@ -77,6 +77,10 @@ struct _lv_obj_t {
     uint16_t h_layout   : 1;
     uint16_t w_layout   : 1;
     uint16_t is_deleting : 1;
+
+    /** The widget is rendered at least once already.
+     * It's used to skip initial animations and transitions. */
+    uint16_t rendered : 1;
 };
 
 /**********************

src/core/lv_observer.c

@@ -856,7 +856,9 @@ lv_observer_t * lv_obj_bind_checked(lv_obj_t * obj, lv_subject_t * subject)
 {
     lv_observer_t * observable = bind_to_bitfield(subject, obj, obj_state_observer_cb, LV_STATE_CHECKED, 0, true,
                                                   FLAG_COND_EQ);
+
     lv_obj_add_event_cb(obj, obj_value_changed_event_cb, LV_EVENT_VALUE_CHANGED, subject);
+
     return observable;
 }
 
@@ -996,6 +998,7 @@ static lv_observer_t * bind_to_bitfield(lv_subject_t * subject, lv_obj_t * obj,
 
     lv_observer_t * observable = lv_subject_add_observer_obj(subject, cb, obj, p);
     observable->auto_free_user_data = 1;
+
     return observable;
 }
 

src/core/lv_refr.c

@@ -107,6 +107,10 @@ void lv_obj_redraw(lv_layer_t * layer, lv_obj_t * obj)
     lv_area_t clip_area_ori = layer->_clip_area;
     lv_area_t clip_coords_for_obj;
 
+    /*The widget will be rendered.
+     *So setters from now should use animations. */
+    obj->rendered = 1;
+
     /*Truncate the clip area to `obj size + ext size` area*/
     lv_area_t obj_coords_ext;
     lv_obj_get_coords(obj, &obj_coords_ext);
@@ -258,6 +262,7 @@ void lv_obj_redraw(lv_layer_t * layer, lv_obj_t * obj)
     }
 
     layer->_clip_area = clip_area_ori;
+
     LV_PROFILER_REFR_END;
 }
 

src/misc/lv_event.c

@@ -338,6 +338,7 @@ const char * lv_event_code_get_name(lv_event_code_t code)
             ENUM_CASE(EVENT_REFRESH);
             ENUM_CASE(EVENT_READY);
             ENUM_CASE(EVENT_CANCEL);
+            ENUM_CASE(EVENT_STATE_CHANGED);
 
             /** Other events*/
             ENUM_CASE(EVENT_CREATE);

src/misc/lv_event.h

@@ -78,6 +78,7 @@ typedef enum {
     LV_EVENT_REFRESH,             /**< Notify Widget to refresh something on it (for user)*/
     LV_EVENT_READY,               /**< A process has finished */
     LV_EVENT_CANCEL,              /**< A process has been cancelled */
+    LV_EVENT_STATE_CHANGED,       /**< The state of the widget changed*/
 
     /** Other events */
     LV_EVENT_CREATE,              /**< Object is being created */

src/widgets/bar/lv_bar.c

@@ -737,12 +737,15 @@ static void lv_bar_init_anim(lv_obj_t * obj, lv_bar_anim_t * bar_anim)
 
 static void bar_value_observer_cb(lv_observer_t * observer, lv_subject_t * subject)
 {
+    lv_obj_t * obj = lv_observer_get_target_obj(observer);
+    /*If the bar is not rendered yet show the new state immediately*/
+    lv_anim_enable_t anim_on = obj->rendered ? LV_ANIM_ON : LV_ANIM_OFF;
     if(subject->type == LV_SUBJECT_TYPE_INT) {
-        lv_bar_set_value(observer->target, subject->value.num, LV_ANIM_OFF);
+        lv_bar_set_value(observer->target, subject->value.num, anim_on);
     }
 #if LV_USE_FLOAT
     else {
-        lv_bar_set_value(observer->target, (int32_t)subject->value.float_v, LV_ANIM_OFF);
+        lv_bar_set_value(observer->target, (int32_t)subject->value.float_v, anim_on);
     }
 #endif
 }

src/widgets/roller/lv_roller.c

@@ -964,8 +964,11 @@ static void roller_value_changed_event_cb(lv_event_t * e)
 
 static void roller_value_observer_cb(lv_observer_t * observer, lv_subject_t * subject)
 {
+    /*If the roller is not rendered yet show the new state immediately*/
+    lv_obj_t * obj = lv_observer_get_target_obj(observer);
+    lv_anim_enable_t anim_on = obj->rendered ? LV_ANIM_ON : LV_ANIM_OFF;
     if((int32_t)lv_roller_get_selected(observer->target) != subject->value.num) {
-        lv_roller_set_selected(observer->target, subject->value.num, LV_ANIM_OFF);
+        lv_roller_set_selected(observer->target, subject->value.num, anim_on);
     }
 }
 

src/widgets/slider/lv_slider.c

@@ -234,7 +234,6 @@ lv_observer_t * lv_slider_bind_value(lv_obj_t * obj, lv_subject_t * subject)
     }
 
     lv_obj_add_event_cb(obj, slider_value_changed_event_cb, LV_EVENT_VALUE_CHANGED, subject);
-
     lv_observer_t * observer = lv_subject_add_observer_obj(subject, slider_value_observer_cb, obj, NULL);
     return observer;
 }
@@ -682,12 +681,15 @@ static void slider_value_changed_event_cb(lv_event_t * e)
 
 static void slider_value_observer_cb(lv_observer_t * observer, lv_subject_t * subject)
 {
+    lv_obj_t * obj = lv_observer_get_target_obj(observer);
+    /*If the slider is not rendered yet show the new state immediately*/
+    lv_anim_enable_t anim_on = obj->rendered ? LV_ANIM_ON : LV_ANIM_OFF;
     if(subject->type == LV_SUBJECT_TYPE_INT) {
-        lv_slider_set_value(observer->target, subject->value.num, LV_ANIM_OFF);
+        lv_slider_set_value(observer->target, subject->value.num, anim_on);
     }
 #if LV_USE_FLOAT
     else {
-        lv_slider_set_value(observer->target, (int32_t)subject->value.float_v, LV_ANIM_OFF);
+        lv_slider_set_value(observer->target, (int32_t)subject->value.float_v, anim_on);
     }
 #endif
 }

src/widgets/switch/lv_switch.c

@@ -163,9 +163,14 @@ static void lv_switch_event(const lv_obj_class_t * class_p, lv_event_t * e)
         *s = LV_MAX(*s, knob_size);
         *s = LV_MAX(*s, lv_obj_calculate_ext_draw_size(obj, LV_PART_INDICATOR));
     }
-    else if(code == LV_EVENT_VALUE_CHANGED) {
-        lv_switch_trigger_anim(obj);
-        lv_obj_invalidate(obj);
+    else if(code == LV_EVENT_STATE_CHANGED) {
+        lv_state_t prev_state = lv_event_get_prev_state(e);
+        lv_state_t diff = prev_state ^ lv_obj_get_state(obj);
+
+        if(diff & LV_STATE_CHECKED) {
+            lv_switch_trigger_anim(obj);
+            lv_obj_invalidate(obj);
+        }
     }
     else if(code == LV_EVENT_DRAW_MAIN) {
         draw_main(e);
@@ -296,6 +301,9 @@ static void lv_switch_anim_completed(lv_anim_t * a)
 static void lv_switch_trigger_anim(lv_obj_t * obj)
 {
     LV_ASSERT_OBJ(obj, MY_CLASS);
+    /*If the widget is not rendered yet show state changes immediately*/
+    if(!obj->rendered) return;
+
     lv_switch_t * sw = (lv_switch_t *)obj;
 
     uint32_t anim_dur_full = lv_obj_get_style_anim_duration(obj, LV_PART_MAIN);

src/xml/lv_xml_base_types.c

@@ -285,6 +285,7 @@ lv_event_code_t lv_xml_trigger_text_to_enum_value(const char * txt)
     if(lv_streq("child_changed", txt)) return LV_EVENT_CHILD_CHANGED;
     if(lv_streq("child_created", txt)) return LV_EVENT_CHILD_CREATED;
     if(lv_streq("child_deleted", txt)) return LV_EVENT_CHILD_DELETED;
+    if(lv_streq("state_changed", txt)) return LV_EVENT_STATE_CHANGED;
     if(lv_streq("screen_unload_start", txt)) return LV_EVENT_SCREEN_UNLOAD_START;
     if(lv_streq("screen_load_start", txt)) return LV_EVENT_SCREEN_LOAD_START;
     if(lv_streq("screen_loaded", txt)) return LV_EVENT_SCREEN_LOADED;

tests/src/test_cases/test_theme.c

@@ -141,6 +141,8 @@ static void test_widgets(const char * img_name)
 
     lv_spinner_create(scr_act);
 
+    lv_test_wait(1000); /*Wait for the transitions*/
+
     TEST_ASSERT_EQUAL_SCREENSHOT(img_name);
 
     lv_obj_clean(scr_act);

tests/src/test_cases/widgets/test_switch.c

@@ -156,6 +156,8 @@ void test_screeshots(void)
     lv_obj_add_state(sw, LV_STATE_CHECKED);
     lv_obj_set_size(sw, 50, 100);
 
+    lv_test_wait(1000); /*Wait for the transitions*/
+
     TEST_ASSERT_EQUAL_SCREENSHOT("widgets/switch_1.png");
 }
 

tests/src/test_cases/xml/test_xml_switch.c

@@ -33,6 +33,7 @@ void test_xml_switch_widget(void)
 
     lv_xml_create(scr, "lv_switch", attrs_1);
 
+    lv_test_wait(1000); /*Wait for the transitions*/
 
     TEST_ASSERT_EQUAL_SCREENSHOT("xml/lv_switch.png");
 }