lv_disp: invoke scr_load_internal upon completion

[Lzw655]

Description of the feature or fix

[Version] release/v8.3
[Bugfix] An error involving accessing a null pointer occurs when using the following program:

    lv_obj_t *screen1 = lv_obj_create(NULL);
    lv_obj_set_style_bg_color(screen1, lv_palette_main(LV_PALETTE_BLUE), 0);

    lv_obj_t *screen2 = lv_obj_create(NULL);
    lv_obj_set_style_bg_color(screen2, lv_palette_main(LV_PALETTE_GREEN), 0);

    lv_scr_load_anim(screen1, LV_SCR_LOAD_ANIM_OVER_LEFT, 2000, 0, false);
    lv_scr_load_anim(screen2, LV_SCR_LOAD_ANIM_OVER_RIGHT, 1000, 500, false);

I think the reason is: If call the lv_scr_load_anim() function consecutively twice, and meet the condition time != 0 || delay != 0, on the second call, because scr_load_internal() sets d->scr_to_load = 0, immediately following functions like lv_obj_set_pos() will operate on d->scr_to_load.

Checkpoints

• Run code-format.py from the scripts folder. astyle needs to be installed.
• Update the Documentation if needed
• Add Examples if relevant.
• Add Tests if applicable.
• If you added new options to lv_conf_template.h run lv_conf_internal_gen.py and update Kconfig.

Be sure the following conventions are followed:

• Follow the Styling guide
• Prefer enums instead of macros. If inevitable to use defines export them with LV_EXPORT_CONST_INT(defined_value) right after the define.
• In function arguments prefer type name[] declaration for array parameters instead of type * name
• Use typed pointers instead of void * pointers
• Do not malloc into a static or global variables. Instead declare the variable in lv_global_t structure in lv_global.h and mark the variable with (LV_GLOBAL_DEFAULT()->variable) when it's used. See a detailed description here.
• Widget constructor must follow the lv_<widget_name>_create(lv_obj_t * parent) pattern.
• Widget members function must start with lv_<module_name> and should receive lv_obj_t * as first argument which is a pointer to widget object itself.
• structs should be used via an API and not modified directly via their elements.
• struct APIs should follow the widgets' conventions. That is to receive a pointer to the struct as the first argument, and the prefix of the struct name should be used as the prefix of the function name too (e.g. lv_disp_set_default(lv_disp_t * disp))
• Functions and structs which are not part of the public API must begin with underscore in order to mark them as "private".
• Arguments must be named in H files too.
• To register and use callbacks one of the following needs to be followed (see a detailed description here):
  • For both the registration function and the callback pass a pointer to a struct as the first argument. The struct must contain void * user_data field.
  • The last argument of the registration function must be void * user_data and the same user_data needs to be passed as the last argument of the callback.
  • Callback types not following these conventions should end with xcb_t.

[XuNeo]

Could you add your program to test cases?
See here:

lvgl/tests/src/test_cases/test_screen_load.c

Line 6 in 5e3fb68

void test_screen_load_no_crash(void)

[Lzw655]

@XuNeo The release/v8.3 branch seems to lack this file. Should I make the modifications in the master branch?

[XuNeo]

Should I make the modifications in the master branch?

Yes. Please add another PR with fix and test to master branch.

[Lzw655]

Should I make the modifications in the master branch?

Yes. Please add another PR with fix and test to master branch.

Done. #5066

[kisvegabor]

Thank you! Please add test_screen_load.c from master here as well so that we have a basic confidence about this feature is still working well.

[Lzw655]

Thank you! Please add test_screen_load.c from master here as well so that we have a basic confidence about this feature is still working well.

Ok, added it.

[kisvegabor]

Cool, thank you!