lvgl/src/lv_misc/lv_bidi.c

/**
 * @file lv_bidi.c
 *
 */

/*********************
 *      INCLUDES
 *********************/
#include "lv_bidi.h"
#include <stddef.h>
#include "lv_txt.h"

#if LV_USE_BIDI

/*********************
 *      DEFINES
 *********************/
#define LV_BIDI_BRACKLET_DEPTH   4

/**********************
 *      TYPEDEFS
 **********************/
typedef struct
{
    uint32_t bracklet_pos;
    lv_bidi_dir_t dir;
}bracket_stack_t;

/**********************
 *  STATIC PROTOTYPES
 **********************/
static lv_bidi_dir_t get_next_run(const char * txt, lv_bidi_dir_t base_dir, uint32_t max_len, uint32_t * len);
static void rtl_reverse(char * dest, const char * src, uint32_t len);
static uint32_t char_change_to_pair(uint32_t letter);
static lv_bidi_dir_t bracket_process(const char * txt, uint32_t next_pos, uint32_t len, uint32_t letter, lv_bidi_dir_t base_dir);

/**********************
 *  STATIC VARIABLES
 **********************/
static const uint8_t bracket_left[] = {"<({["};
static const uint8_t bracket_right[] = {">)}]"};
static bracket_stack_t br_stack[LV_BIDI_BRACKLET_DEPTH];
static uint8_t br_stack_p;

/**********************
 *      MACROS
 **********************/

/**********************
 *   GLOBAL FUNCTIONS
 **********************/

void lv_bidi_process(const char * str_in, char * str_out, lv_bidi_dir_t base_dir)
{
    if(base_dir == LV_BIDI_DIR_AUTO) base_dir = lv_bidi_detect_base_dir(str_in);

    uint32_t par_start = 0;
    uint32_t par_len;

    while(str_in[par_start] == '\n' || str_in[par_start] == '\r') {
        str_out[par_start] = str_in[par_start];
        par_start ++;
    }

    while(str_in[par_start] != '\0') {
        par_len = lv_bidi_get_next_paragraph(&str_in[par_start]);
        lv_bidi_process_paragraph(&str_in[par_start], &str_out[par_start], par_len, base_dir);
        par_start += par_len;

        while(str_in[par_start] == '\n' || str_in[par_start] == '\r') {
            str_out[par_start] = str_in[par_start];
            par_start ++;
        }
    }

    str_out[par_start] = '\0';
}

lv_bidi_dir_t lv_bidi_detect_base_dir(const char * txt)
{
    uint32_t i = 0;
    uint32_t letter;
    while(txt[i] != '\0') {
        letter = lv_txt_encoded_next(txt, &i);

        lv_bidi_dir_t dir;
        dir = lv_bidi_get_letter_dir(letter);
        if(dir == LV_BIDI_DIR_RTL || dir == LV_BIDI_DIR_LTR) return dir;
    }

    /*If there were no strong char earlier return with the default base dir */
    if(LV_BIDI_BASE_DIR_DEF == LV_BIDI_DIR_AUTO) return LV_BIDI_DIR_LTR;
    else return LV_BIDI_BASE_DIR_DEF;
}

lv_bidi_dir_t lv_bidi_get_letter_dir(uint32_t letter)
{
    if(lv_bidi_letter_is_rtl(letter)) return LV_BIDI_DIR_RTL;
    if(lv_bidi_letter_is_neutral(letter)) return LV_BIDI_DIR_NEUTRAL;
    if(lv_bidi_letter_is_weak(letter)) return LV_BIDI_DIR_WEAK;

    return LV_BIDI_DIR_LTR;
}

bool lv_bidi_letter_is_weak(uint32_t letter)
{
    uint32_t i = 0;
    static const char weaks[] = "0123456789";

    do {
        uint32_t x = lv_txt_encoded_next(weaks, &i);
        if(letter == x) {
            return true;
        }
    } while(weaks[i] != '\0');

    return false;
}

bool lv_bidi_letter_is_rtl(uint32_t letter)
{
     if(letter >= 0x5d0 && letter <= 0x5ea) return true;
    if(letter == 0x202E) return true;               /*Unicode of LV_BIDI_RLO*/
//    if(letter >= 'a' && letter <= 'z') return true;

    return false;
}

bool lv_bidi_letter_is_neutral(uint32_t letter)
{
    uint16_t i;
    static const char neutrals[] = " \t\n\r.,:;'\"`!?%/\\-=()[]{}<>@#&$|";
    for(i = 0; neutrals[i] != '\0'; i++) {
        if(letter == (uint32_t)neutrals[i]) return true;
    }

    return false;
}


/**********************
 *   STATIC FUNCTIONS
 **********************/

void lv_bidi_process_paragraph(const char * str_in, char * str_out, uint32_t len, lv_bidi_dir_t base_dir)
{
    uint32_t run_len = 0;
    lv_bidi_dir_t run_dir;
    uint32_t rd = 0;
    uint32_t wr;

    if(base_dir == LV_BIDI_DIR_AUTO) base_dir = lv_bidi_detect_base_dir(str_in);
    if(base_dir == LV_BIDI_DIR_RTL) wr = len;
    else wr = 0;

    str_out[len] = '\0';

    lv_bidi_dir_t dir = base_dir;

    /*Empty the bracket stack*/
    br_stack_p = 0;

    /*Process neutral chars in the beginning*/
    while(rd < len) {
        uint32_t letter = lv_txt_encoded_next(str_in, &rd);
        dir = lv_bidi_get_letter_dir(letter);
        if(dir == LV_BIDI_DIR_NEUTRAL)  dir = bracket_process(str_in, rd, len, letter, base_dir);

        if(dir != LV_BIDI_DIR_NEUTRAL && dir != LV_BIDI_DIR_WEAK) break;
    }

    if(rd && str_in[rd] != '\0') lv_txt_encoded_prev(str_in, &rd);

    if(rd) {
        if(base_dir == LV_BIDI_DIR_LTR) {
            memcpy(&str_out[wr], str_in, rd);
            wr += rd;
        } else {
            wr -= rd;
            rtl_reverse(&str_out[wr], str_in, rd);
        }
    }

    /*Get and process the runs*/
    while(rd < len) {
        run_dir = get_next_run(&str_in[rd], base_dir, len - rd, &run_len);

        if(base_dir == LV_BIDI_DIR_LTR) {
            if(run_dir == LV_BIDI_DIR_LTR)  memcpy(&str_out[wr], &str_in[rd], run_len);
            else rtl_reverse(&str_out[wr], &str_in[rd], run_len);
           wr += run_len;
       } else {
           wr -= run_len;
           if(run_dir == LV_BIDI_DIR_LTR)  memcpy(&str_out[wr], &str_in[rd], run_len);
           else rtl_reverse(&str_out[wr], &str_in[rd], run_len);
       }

        rd += run_len;
    }
}

uint32_t lv_bidi_get_next_paragraph(const char * txt)
{
    uint32_t i = 0;

    lv_txt_encoded_next(txt, &i);

    while(txt[i] != '\0' && txt[i] != '\n' && txt[i] != '\r') {
        lv_txt_encoded_next(txt, &i);
    }

    return i;
}

static lv_bidi_dir_t get_next_run(const char * txt, lv_bidi_dir_t base_dir, uint32_t max_len, uint32_t * len)
{
    uint32_t i = 0;
    uint32_t letter;

    letter = lv_txt_encoded_next(txt, NULL);
    lv_bidi_dir_t dir = lv_bidi_get_letter_dir(letter);
    if(dir == LV_BIDI_DIR_NEUTRAL)  dir = bracket_process(txt, 0, *len, letter, base_dir);


    /*Find the first strong char. Skip the neutrals*/
    while(dir == LV_BIDI_DIR_NEUTRAL || dir == LV_BIDI_DIR_WEAK) {
        letter = lv_txt_encoded_next(txt, &i);
        dir = lv_bidi_get_letter_dir(letter);
        if(dir == LV_BIDI_DIR_NEUTRAL)  dir = bracket_process(txt, i, *len, letter, base_dir);

        if(i >= max_len || txt[i] == '\0' || txt[i] == '\n' || txt[i] == '\r') {
            *len = i;
            return base_dir;
        }
    }

    lv_bidi_dir_t run_dir = dir;

    uint32_t i_prev = i;
    uint32_t i_last_strong = i;

    /*Find the next char which has different direction*/
    lv_bidi_dir_t next_dir = base_dir;
    while(i_prev < max_len && txt[i] != '\0' && txt[i] != '\n' && txt[i] != '\r') {
        letter = lv_txt_encoded_next(txt, &i);
        next_dir  = lv_bidi_get_letter_dir(letter);
        if(dir == LV_BIDI_DIR_NEUTRAL)  dir = bracket_process(txt, i, *len, letter, base_dir);

        /*New dir found?*/
        if((next_dir == LV_BIDI_DIR_RTL || next_dir == LV_BIDI_DIR_LTR) && next_dir != run_dir) {
            /*Include neutrals if `run_dir == base_dir` */
            if(run_dir == base_dir) *len = i_prev;
            /*Exclude neutrals if `run_dir != base_dir` */
            else *len = i_last_strong;

            return run_dir;
        }

        if(next_dir != LV_BIDI_DIR_NEUTRAL) i_last_strong = i;

        i_prev = i;
    }


    /*Handle end of of string. Apply `base_dir` on trailing neutrals*/

    /*Include neutrals if `run_dir == base_dir` */
    if(run_dir == base_dir) *len = i_prev;
    /*Exclude neutrals if `run_dir != base_dir` */
    else *len = i_last_strong;

    return run_dir;

}

static void rtl_reverse(char * dest, const char * src, uint32_t len)
{
    uint32_t i = len;
    uint32_t wr = 0;

    while(i) {
        uint32_t letter = lv_txt_encoded_prev(src, &i);

        /*Keep weak letters (numbers) as LTR*/
        if(lv_bidi_letter_is_weak(letter)) {
            uint32_t last_weak = i;
            uint32_t first_weak = i;
            while(i) {
                letter = lv_txt_encoded_prev(src, &i);
                /*No need to call `char_change_to_pair` because there not such chars here*/

                /*Finish on non-weak char */
                /*but treat number and currency related chars as weak*/
                if(lv_bidi_letter_is_weak(letter) == false && letter != '.' && letter != ',' && letter != '$' && letter != '%') {
                    lv_txt_encoded_next(src, &i);   /*Rewind one letter*/
                    first_weak = i;
                    break;
                }
            }
            if(i == 0) first_weak = 0;

            memcpy(&dest[wr], &src[first_weak], last_weak - first_weak + 1);
            wr += last_weak - first_weak + 1;

        }
        /*Simply store in reversed order*/
        else {
            uint32_t letter_size = lv_txt_encoded_size((const char *)&src[i]);
            /*Swap arithmetical symbols*/
            if(letter_size == 1) {
                uint32_t new_letter = letter = char_change_to_pair(letter);
                dest[wr] = (uint8_t)new_letter;
                wr += 1;
            }
            /*Just store the letter*/
            else {
                memcpy(&dest[wr], &src[i], letter_size);
                wr += letter_size;
            }
        }
    }
}

static uint32_t char_change_to_pair(uint32_t letter)
{

    uint8_t i;
    for(i = 0; bracket_left[i] != '\0'; i++) {
        if(letter == bracket_left[i]) return bracket_right[i];
    }

    for(i = 0; bracket_right[i] != '\0'; i++) {
        if(letter == bracket_right[i]) return bracket_left[i];
    }

    return letter;
}

static lv_bidi_dir_t bracket_process(const char * txt, uint32_t next_pos, uint32_t len, uint32_t letter, lv_bidi_dir_t base_dir)
{
    if(br_stack_p >= LV_BIDI_BRACKLET_DEPTH) return LV_BIDI_DIR_NEUTRAL;

    lv_bidi_dir_t bracket_dir = LV_BIDI_DIR_NEUTRAL;

    uint8_t i;
    /*Is the letter an opening bracket?*/
    for(i = 0; bracket_left[i] != '\0'; i++) {
        if(bracket_left[i] == letter) {
            /* If so find it's matching closing bracket.
             * If a char with base dir. direction is found then the brackets will have `base_dir` direction*/
            uint32_t txt_i = next_pos;
            while(txt_i < len) {
                uint32_t letter_next = lv_txt_encoded_next(txt, &txt_i);
                if(letter_next == bracket_right[i]) {
                    /*Closing bracket found*/
                    break;
                } else {
                    /*Save the dir*/
                    lv_bidi_dir_t letter_dir = lv_bidi_get_letter_dir(letter);
                    if(letter_dir == base_dir) {
                        bracket_dir = base_dir;
                    }
                }
            }

            /*There were no matching closing bracket*/
            if(txt_i >= len)  return LV_BIDI_DIR_NEUTRAL;

            /*There where a strong char with base dir in the bracket so the dir is found.*/
            if(bracket_dir != LV_BIDI_DIR_NEUTRAL) break;

            /*If there were no matching strong chars in the brackets then check the previous chars*/
            txt_i = next_pos;
            if(txt_i) lv_txt_encoded_prev(txt, &txt_i);
            if(txt_i) lv_txt_encoded_prev(txt, &txt_i);
            while(txt_i > 0) {
                uint32_t letter_next = lv_txt_encoded_prev(txt, &txt_i);
                lv_bidi_dir_t letter_dir = lv_bidi_get_letter_dir(letter);
                if(letter_dir == LV_BIDI_DIR_LTR || letter_dir == LV_BIDI_DIR_RTL) {
                    bracket_dir = letter_dir;
                    break;
                }
            }


            /*There where a previous strong char which can be used*/
            if(bracket_dir != LV_BIDI_DIR_NEUTRAL) break;

            /*There were no strong chars before the bracket, so use the base dir.*/
            if(txt_i == 0) bracket_dir = base_dir;

            break;
        }
    }


    /*The letter was an opening bracket*/
    if(bracket_left[i] != '\0') {

        if(bracket_dir == LV_BIDI_DIR_NEUTRAL) return bracket_dir;

        br_stack[br_stack_p].bracklet_pos = i;
        br_stack[br_stack_p].dir = bracket_dir;

        br_stack_p++;
        return bracket_dir;
    } else {
        /*Is the letter a closing bracket of the last opening?*/
        if(letter == bracket_right[br_stack[br_stack_p].bracklet_pos]) {
            bracket_dir = br_stack[br_stack_p].dir;
            br_stack_p--;
            return bracket_dir;
        }
    }

    return LV_BIDI_DIR_NEUTRAL;
}


#endif /*LV_USE_BIDI*/