Wrong Text alignment

Bug (archived)
1

Description

Hi,
i am facing an issue with labels

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

ARM

What do you experience?

when i set text from handleHumidity function the text is not showing as written. as per the code the text is set to below to temp_decrease img button. but the text is setting to right alignment.
but when i hardcode the text in humidity object it showing perfect.

What do you expect?

i want to print this text exactly below the img button.

Code to reproduce

static lv_obj_t * humidity;
static lv_obj_t * temp_decrease;
void test_screen(void)
{
              temp_decrease=lv_imgbtn_create(lv_scr_act(), NULL);
              lv_imgbtn_set_src(temp_decrease,LV_BTN_STATE_RELEASED,&temp_down);
              lv_imgbtn_set_src(temp_decrease,LV_BTN_STATE_PRESSED,&temp_down);
              lv_obj_align(temp_decrease,NULL,LV_ALIGN_CENTER,0,0);

              humidity = lv_label_create(lv_scr_act(), NULL);
              lv_label_set_text(humidity, "");
              lv_obj_align(humidity,temp_decrease,LV_ALIGN_OUT_BOTTOM_MID,0,30);
}
int handleHumidity(char *message){

    printf("### Message Arrived [Humidity]: %s",message); //Here message value is 36
    char curr_humidity[64];
    sprintf(curr_humidity,"Humidity is %s",message);
    lv_label_set_text(humidity,curr_humidity);
    return 0;
}

Screenshot and/or video

If possible, add screenshots and/or videos about the current issue.

2

Maybe a little difficult to explain:

The alignment of text within a label is closely linked.
It means, when you change the address of the string buffer the alignment is lost.

Or said differently, when you link a new string buffer to a label (or other control!?), you have to
set the alignment again.
Which means after the call of lv_label_set_text in handleHumidity, you have to call lv_obj_align
again.

If you write your code this way:

static lv_obj_t* humidity;
static lv_obj_t* temp_decrease;

char curr_humidity[64];

void test_screen (void)
{
    temp_decrease = lv_imgbtn_create (lv_scr_act(), NULL);

    lv_imgbtn_set_src (temp_decrease, LV_BTN_STATE_RELEASED, &temp_down);
    lv_imgbtn_set_src (temp_decrease, LV_BTN_STATE_PRESSED,  &temp_down);
    lv_obj_align      (temp_decrease, NULL, LV_ALIGN_CENTER, 0, 0);

    snprintf (curr_humidity, 64, "Humidity is 000000"); // just as an example, you also can use ""

    humidity = lv_label_create (lv_scr_act(), NULL);
    lv_label_set_text (humidity, curr_humidity);
    lv_obj_align      (humidity, temp_decrease, LV_ALIGN_OUT_BOTTOM_MID, 0, 30);
}

int handleHumidity (char *message)
{
    snprintf (curr_humidity, 64, "Humidity is %s", message);
    lv_label_set_text (humidity, curr_humidity);

    return 0;
}

Now, the label is always linked with the same string buffer (curr_humidity), and so the alignment is kept.

Some additional hint: For string printing use snprintf!
With snprintf you avoid string overflows (in case you set the size in sprintf to the same value as of your string buffer).

3

Thanks Robekras. Issue resolved.