Infinite loop bug with lists.

[hydra]

This code causes an infinite loop:

    lv_obj_t *list = lv_list_create(panel, NULL);
    lv_obj_clean(list);
    lv_list_add(list, SYMBOL_EDIT, "TEST", NULL);

stackstrace:

Thread #1 57005 (Suspended : Signal : SIGTRAP:Trace/breakpoint trap)    
    lv_obj_get_screen() at lv_obj.c:1,057 0x801118a 
    lv_obj_invalidate() at lv_obj.c:357 0x801067c   
    lv_obj_set_parent() at lv_obj.c:436 0x80107d8   
    lv_page_signal() at lv_page.c:469 0x801ecf6 
    lv_list_signal() at lv_list.c:495 0x801df96 
    lv_obj_create() at lv_obj.c:258 0x8010528   
    lv_cont_create() at lv_cont.c:67 0x801a61e  
    lv_btn_create() at lv_btn.c:57 0x8019e46    
    lv_list_add() at lv_list.c:155 0x801dbd2    
    userCode() at userCode.c:57 0x802e9f6   
    <...more frames...> 

the infinite loop in question is this:

https://github.com/littlevgl/lvgl/blob/master/lv_core/lv_obj.c#L1045-L1049

I encountered this issue when attempting to remove old and add new buttons to a list view object.

What I want to do this this:

void createElements() {
    lv_obj_t *list = lv_list_create(panel, NULL);
}

then at any random time later on in the life of the program

void refreshElements() {
    lv_obj_clean(list);
    lv_list_add(list, SYMBOL_EDIT, "some element name", someHandler);
    lv_list_add(list, SYMBOL_EDIT, "some element name", someHandler);
    // ...
}

[hydra]

for the record, using lv_obj_del(item) on the list items works instead of lv_ovj_clean(list), but I don't want/need to keep a reference to each item (lv is already doing that for me...).

I'm feeling that the list API needs a lv_list_remove_all() method.

[kisvegabor]

Hi,

See: https://github.com/littlevgl/lvgl/issues/161

In summary: In dev-v5.2 there are functions (lv_..._clean()) to clean the content of the objects where lv_obj_clean is not working. So you should use lv_list_clean for this purpose.

[hydra]

ok, I missed #161 when I did a search for other bug reports, sorry for duplicate.

[kisvegabor]

No problem! :)