It take a lots time when add freetype font into label

nguyenan-ble1 · June 22, 2022, 10:19am

Description

I am using freetype library via lv_freetype.
At the time of add font into label object, it takes a lots more time than using binary font.
Is there any way to reduce this processing time?

Create font：

static lv_ft_info_t s_font_12;
s_font_12.name = "f_12";
s_font_12.weight = 12;
s_font_12.style = FT_FONT_STYLE_NORMAL;
lv_ft_font_init(&s_font_12)

Create label object：

static lv_obj_t *label;
static lv_style_t s_style_label;

lv_style_set_text_font(&s_style_label, LV_STATE_DEFAULT, s_font_12.font);
lv_obj_add_style(label, LV_LABEL_PART_MAIN, &s_style_label);

kisvegabor · June 24, 2022, 9:31am

Exactly which function takes long time?

nguyenan-ble1 · June 27, 2022, 7:18am

Hi @kisvegabor

It is lv_label_set_text().
Sorry, it is not included in above of code.
This function will take longer as the font size increases.

kisvegabor · July 3, 2022, 1:02pm

It’s strange.

Have you setting some caching?

github.com

lvgl/lvgl/blob/6acbdaa53d941b891db377e65111bd999f04631d/lv_conf_template.h#L647-L657

    
      
          /*Memory used by FreeType to cache characters [bytes] (-1: no caching)*/
          #define LV_FREETYPE_CACHE_SIZE (16 * 1024)
          #if LV_FREETYPE_CACHE_SIZE >= 0
              /* 1: bitmap cache use the sbit cache, 0:bitmap cache use the image cache. */
              /* sbit cache:it is much more memory efficient for small bitmaps(font size < 256) */
              /* if font size >= 256, must be configured as image cache */
              #define LV_FREETYPE_SBIT_CACHE 0
              /* Maximum number of opened FT_Face/FT_Size objects managed by this cache instance. */
              /* (0:use system defaults) */
              #define LV_FREETYPE_CACHE_FT_FACES 0
              #define LV_FREETYPE_CACHE_FT_SIZES 0

nguyenan-ble1 · July 1, 2022, 5:19am

Hi @kisvegabor

Use cache is a solution for me.

My largest font is less than 256, so I use sbit cache.

If I use 10 fonts size in my app,
how many should I set LV_FREETYPE_CACHE_FT_FACES and LV_FREETYPE_CACHE_FT_SIZES ?

kisvegabor · July 3, 2022, 9:25am

I’m not an expert of FreeType (nor the details of how it’s integrated to LVGL) but if you are using the same font with 10 sizes you can set

LV_FREETYPE_CACHE_FT_FACES to 1
LV_FREETYPE_CACHE_FT_SIZES to 10

nguyenan-ble1 · July 3, 2022, 1:03pm

Thanks for your support.
Best regards!