LV_SPRINTF_USE_FLOAT missed in the LVGL 9.0

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1

Hi,

I have a code in LVGL 8.3 that uses lv_label_set_text_fmt to show a float number in a Label object.

up to LVGL 8.3, I was enabling the #define LV_SPRINTF_USE_FLOAT 1 in the lv_conf.h, however there is nothing like this in the config file of the LVGL-9.0, what should I do?

2

I fixed this. we should search for the float in the config

3

only find float in lv_conf_template.h and lv_conf_internal.h. I set it to 1
I still get f

Version would be v9.1.0

4

It’s missing in config but in code too ?

I m on V9.3, lv_snprintf is not using float, even with #define LV_SPRINTF_USE_FLOAT 1

5

Strange, just need to enable this in lv_conf.h

#define LV_USE_FLOAT            1
6

Have checked code and have found
#define PRINTF_DISABLE_SUPPORT_FLOAT (!LV_USE_FLOAT)

// support for the floating point type (%f)
// default: activated
#if !PRINTF_DISABLE_SUPPORT_FLOAT
    #define PRINTF_SUPPORT_FLOAT
#endif

So it need to be the same thing, but not working.

lv_snprintf(t, 10, "%.1f", i["Temp"].as<float>());

Here the minimal code I m using (working fine on V8)

            char *t = (char*)malloc(10);
            lv_snprintf(t, 10, "%.1f", 0.5f);
            Serial.println(t);

Have as result “f”

7

In my test, using v9.5, the only thing required was to change the LV_USE_FLOAT define #define LV_USE_FLOAT 1 in lv_conf.h, no more code changes where required.

If I do that, and open the file lvgl\src\stdlib\builtin\lv_sprintf_builtin.c on lines 776~794 i see in the IDE that the code is no longer “disabled” and lv_label_set_text_fmt works with %f ov lv_snprintf.

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Do you have this enabled in lv_conf, to use the builtin implementation?

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image793×173 6.5 KB

If using the standard lib, make sure you have enabled float support on compiler definition, since it may be optional depending on the compiler library in use…

I guess, a quick “hack” would be to change:

#define PRINTF_DISABLE_SUPPORT_FLOAT    (!LV_USE_FLOAT)

to

#define PRINTF_DISABLE_SUPPORT_FLOAT    1

to have support for floats just in printf functions…

8

Ok, so I have just changed the LVGL V9 version to the same than you (I m using platformio)

lvgl/lvgl@^9.5.0

And all is working now, so the problem was limited to 9.3 version (or something bad in cache, haven’t cleared the project on each tries)