[Questions][Doc][Set-Style] How to know which "LV_PART_*" should I use when set a style?

How-to
1

Description

As a new comer to LVGL, I am learning the documents to set style of a object.

When I read the “Parts” section, I got it like this:

  1. Each object could be composed of parts which could have their own styles.
  2. Like a slider, I could know from the slider document that it have 3 parts and I could pass LV_PART_MAIN, LV_PART_INDICATOR, LV_PART_KNOB to set its style.

The question is that, for the function lv_obj_set_style_border_opa which need a selector param, which LV_PART_* is applicable to it? where could I find the reference?

void lv_obj_set_style_border_opa(struct _lv_obj_t *obj, lv_opa_t value, lv_style_selector_t selector)

Thx.

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

PC

What LVGL version are you using?

What do you want to achieve?

What have you tried so far?

Code to reproduce

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Screenshot and/or video

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2

Lets use lv_slider as an example.

You have to think about it this way. The lv_slider widget which is the slider control has a base of lv_obj. That base is the MAIN part. The INCICATOR is the portion of the slider that represents where the control is located. The KNOB is the part a user would touch/click and drag to change the value of the slider.

Not all widgets have all of those parts. an example is the lv_label widget. It is not going to have an INDICATOR or a KNOB.

3

Thanks!!! Got it.