Font Engine, HELP

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1

Description

I want to create a LVGL font engine to display CJK because hardware limit. the font’s bitmap was stored in another flash and I get them by SPI. but it not work, either ascii or CJK.

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

RP2040 with it’s C-SDK

What do you want to achieve?

get them to work.

What have you tried so far?

Code to reproduce

font.c


  bool kbt_get_glyph_dsc(const lv_font_t *, lv_font_glyph_dsc_t *, uint32_t, uint32_t);
  const void *kbt_get_glyph_bitmap(lv_font_glyph_dsc_t *, lv_draw_buf_t *);
  lv_font_t *font_init();

lv_font_t *font_init()
{
  static lv_font_t font =
  {
    .get_glyph_dsc = kbt_get_glyph_dsc,
    .get_glyph_bitmap = kbt_get_glyph_bitmap,
    .line_height = 1 << 4,
    .base_line = 0,
  };
  return &font;
}
bool kbt_get_glyph_dsc(const lv_font_t *font, lv_font_glyph_dsc_t *dsc_out, uint32_t unicode_letter, uint32_t next_unicode_letter)
{
    (void)font;
    (void)next_unicode_letter;

    dsc_out->box_h = 1 << 4;
    dsc_out->ofs_x = 1 << 4;
    dsc_out->ofs_y =  1 << 4;
    dsc_out->format = LV_FONT_GLYPH_FORMAT_A1;
    dsc_out->gid.index = unicode_letter;
    if(dsc_out->gid.index < 0x7F)
        dsc_out->box_w = dsc_out->adv_w = 1 << 3;
    else if (dsc_out->gid.index > 0X4E00 && dsc_out->gid.index < 0X9FFF). // CJK font
        dsc_out->box_w = dsc_out->adv_w = 1 << 4;
    else
        return false;
    return true;
}
const void *kbt_get_glyph_bitmap(lv_font_glyph_dsc_t *dsc, lv_draw_buf_t *buf)
{
    // save bipmap data to buf->data as LVGL's description
  uint8_t sciibuf[16];
  uint8_t cjkbuf[32];
  return asciibuf;

The problem is how should I fill bytes to cjkbuf and asciibuf?

Screenshot and/or video

2

After a few days of dig, I changed function kbt_get_glyph_bitmap():

const void *kbt_get_glyph_bitmap(lv_font_glyph_dsc_t *dsc, lv_draw_buf_t *buf)
{
    buf = lv_draw_buf_create(width, height, LV_COLOR_FORMAT_NATIVE, 0);
    for (int i = 0; i < buf->data_size; i++)
            buf->data[i] = 0xFF;
    return buf;

it show a8 x 16 white block, is it correct? After a while (after showing a few letters), it crashes for memry alloc (lv_draw_buf_create() return NULL.

3

maybe it’s because lv_draw_buf_destroy() is not used to clear already used buffers and there is no space left in memory for new buffers