Get size 0 from object

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Description

Hi,
I’m new to lvgl and tried to do some modification on the demo files. And this fits. Now I’m tried to do some more modification and run in a problem.
I generate just an object and set values for height, width and position. For simualtion is set display size 240x320. In simulation I can see an empty “body” at the expected position and with the expected size.
But when I read back the width and height of the object, I get 0 as height and width.
In cause of the “right looking” in simulation, I would expect to see the values in the object by debugger. But there is nothing to see. So I’m confused.
The nearly same code is used in lvgl-academy in the widget-base-object

What MCU/Processor/Board and compiler are you using?

WindowsSimulation, VisualStudio22

What do you want to achieve?

I would expect to see the setted values, if I use the lv_obj_get_height or _width

What have you tried so far?

Code to reproduce

    lv_obj_t* obj1 = lv_obj_create(lv_scr_act());
    lv_obj_set_width(obj1, 50);
    lv_obj_set_height(obj1, 50);
    lv_obj_set_pos(obj1, 100, 100);

    lv_coord_t w = lv_obj_get_width(obj1);
    lv_coord_t h = lv_obj_get_height(obj1);
    printf("width = %d, height = %d\n", w,h);

The output:
width = 0, height = 0

Screenshot and/or video

grafik

2

It’s the expected behavior. See
https://docs.lvgl.io/master/overview/coords.html#postponed-coordinate-calculation

3

Hi @kisvegabor,
thank you for your evidence. I wasn’t aware of this mechanism. This tip works.
Thank you

By this I have second question:
This “update” is triggered always topdown. If i would resize parent-object, all child-objects will recalculated/reordered/… . Right?

4

Actually the whole screen of obj will be updated as the position and size of an object can depend on both its children an parents.

5

Hi,

ok. That’s what I understand.

Thank you

6

The problem here, is that pair of set/get APIs is used to access what are actually two different variables: the requested width/height/x/y, and the actual computed values.

It’s documented, but the behaviour is wrong and should be fixed.