diff --git a/src/font/charset-arabic.c b/src/font/charset-arabic.c
index da7c44e6..16985153 100644
--- a/src/font/charset-arabic.c
+++ b/src/font/charset-arabic.c
@@ -15,7 +15,7 @@
  *   and Graphics User Interface (GUI) support system for embedded systems
  *   and smart IoT devices.
  *
- *   Copyright (C) 2002~2018, Beijing FMSoft Technologies Co., Ltd.
+ *   Copyright (C) 2002~2023, Beijing FMSoft Technologies Co., Ltd.
  *   Copyright (C) 1998~2002, WEI Yongming
  *
  *   This program is free software: you can redistribute it and/or modify
@@ -868,6 +868,7 @@ static CHARSETOPS CharsetOps_iso8859_6 = {
     3,
     FONT_CHARSET_ISO8859_6,
     0,
+    1,
     iso8859_6_len_first_char,
     iso8859_6_get_char_value,
     iso8859_6_get_shaped_char_value,
diff --git a/src/font/charset-unicode.c b/src/font/charset-unicode.c
index d9591b34..d93219ff 100644
--- a/src/font/charset-unicode.c
+++ b/src/font/charset-unicode.c
@@ -15,7 +15,7 @@
  *   and Graphics User Interface (GUI) support system for embedded systems
  *   and smart IoT devices.
  *
- *   Copyright (C) 2002~2018, Beijing FMSoft Technologies Co., Ltd.
+ *   Copyright (C) 2002~2023, Beijing FMSoft Technologies Co., Ltd.
  *   Copyright (C) 1998~2002, WEI Yongming
  *
  *   This program is free software: you can redistribute it and/or modify
@@ -239,10 +239,36 @@ static const BidiType linear_enum_to_bidi_type[] = {
 #undef _UNIBIDI_ADD_TYPE
 };
 
+/* Since 5.0.13: this function only returns BidiType which
+   is recognizable by the legacy BIDI algorithm. */
 static BidiType unicode_bidi_char_type(Achar32 ch)
 {
     ch = REAL_ACHAR(ch);
-    return linear_enum_to_bidi_type[UNIBIDI_GET_BIDI_TYPE(ch)];
+    BidiType bt = linear_enum_to_bidi_type[UNIBIDI_GET_BIDI_TYPE(ch)];
+
+    switch (bt) {
+        case BIDI_TYPE_LTR:
+        case BIDI_TYPE_RTL:
+        case BIDI_TYPE_AL:
+        case BIDI_TYPE_EN:
+        case BIDI_TYPE_AN:
+        case BIDI_TYPE_ET:
+        case BIDI_TYPE_CS:
+        case BIDI_TYPE_NSM:
+        case BIDI_TYPE_BN:
+        case BIDI_TYPE_BS:
+        case BIDI_TYPE_SS:
+        case BIDI_TYPE_WS:
+        case BIDI_TYPE_ON:
+        case BIDI_TYPE_SOT:
+        case BIDI_TYPE_EOT:
+            return bt;
+        default:
+            _DBG_PRINTF("Not recognizable for char (0x%04x): %u\n", ch, bt);
+            break;
+    }
+
+    return BIDI_TYPE_WS;
 }
 
 BidiType GUIAPI UCharGetBidiType(Uchar32 uc)
@@ -628,6 +654,7 @@ CHARSETOPS __mg_CharsetOps_utf8 = {
     6,
     FONT_CHARSET_UTF8,
     0,
+    0,
     utf8_len_first_char,
     utf8_get_char_value,
     NULL,
@@ -854,6 +881,7 @@ CHARSETOPS __mg_CharsetOps_utf16le = {
     4,
     FONT_CHARSET_UTF16LE,
     0,
+    0,
     utf16le_len_first_char,
     utf16le_get_char_value,
     NULL,
@@ -1080,6 +1108,7 @@ CHARSETOPS __mg_CharsetOps_utf16be = {
     4,
     FONT_CHARSET_UTF16BE,
     0,
+    0,
     utf16be_len_first_char,
     utf16be_get_char_value,
     NULL,
diff --git a/src/font/charset.c b/src/font/charset.c
index a09da79d..d6ed2649 100644
--- a/src/font/charset.c
+++ b/src/font/charset.c
@@ -15,7 +15,7 @@
  *   and Graphics User Interface (GUI) support system for embedded systems
  *   and smart IoT devices.
  *
- *   Copyright (C) 2002~2018, Beijing FMSoft Technologies Co., Ltd.
+ *   Copyright (C) 2002~2023, Beijing FMSoft Technologies Co., Ltd.
  *   Copyright (C) 1998~2002, WEI Yongming
  *
  *   This program is free software: you can redistribute it and/or modify
@@ -235,6 +235,7 @@ static CHARSETOPS CharsetOps_ascii = {
     1,
     FONT_CHARSET_US_ASCII,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -298,6 +299,7 @@ static CHARSETOPS CharsetOps_iso8859_1 = {
     1,
     FONT_CHARSET_ISO8859_1,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -409,6 +411,7 @@ static CHARSETOPS CharsetOps_iso8859_2 = {
     1,
     FONT_CHARSET_ISO8859_2,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -521,6 +524,7 @@ static CHARSETOPS CharsetOps_iso8859_3 = {
     1,
     FONT_CHARSET_ISO8859_3,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -634,6 +638,7 @@ static CHARSETOPS CharsetOps_iso8859_4 = {
     1,
     FONT_CHARSET_ISO8859_4,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -728,6 +733,7 @@ static CHARSETOPS CharsetOps_iso8859_5 = {
     1,
     FONT_CHARSET_ISO8859_5,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -886,6 +892,7 @@ static CHARSETOPS CharsetOps_iso8859_7 = {
     1,
     FONT_CHARSET_ISO8859_7,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1159,6 +1166,7 @@ static CHARSETOPS CharsetOps_iso8859_8 = {
     2, // This is a trick for bidi reorder only implemented for MBC.
     FONT_CHARSET_ISO8859_8,
     0,
+    1,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1260,6 +1268,7 @@ static CHARSETOPS CharsetOps_iso8859_9 = {
     1,
     FONT_CHARSET_ISO8859_9,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1373,6 +1382,7 @@ static CHARSETOPS CharsetOps_iso8859_10 = {
     1,
     FONT_CHARSET_ISO8859_10,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1485,6 +1495,7 @@ static CHARSETOPS CharsetOps_iso8859_11 = {
     1,
     FONT_CHARSET_ISO8859_11,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1597,6 +1608,7 @@ static CHARSETOPS CharsetOps_iso8859_13 = {
     1,
     FONT_CHARSET_ISO8859_13,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1709,6 +1721,7 @@ static CHARSETOPS CharsetOps_iso8859_14 = {
     1,
     FONT_CHARSET_ISO8859_14,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1820,6 +1833,7 @@ static CHARSETOPS CharsetOps_iso8859_15 = {
     1,
     FONT_CHARSET_ISO8859_15,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -1970,6 +1984,7 @@ static CHARSETOPS CharsetOps_iso8859_16 = {
     1,
     FONT_CHARSET_ISO8859_16,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -2167,6 +2182,7 @@ static CHARSETOPS CharsetOps_gb2312_0 = {
     2,
     FONT_CHARSET_GB2312_0,
     0,
+    0,
     gb2312_0_len_first_char,
     gb2312_0_get_char_value,
     NULL,
@@ -2324,6 +2340,7 @@ static CHARSETOPS CharsetOps_gbk = {
     2,
     FONT_CHARSET_GBK,
     0,
+    0,
     gbk_len_first_char,
     gbk_get_char_value,
     NULL,
@@ -2592,6 +2609,7 @@ static CHARSETOPS CharsetOps_gb18030_0 = {
     4,
     FONT_CHARSET_GB18030_0,
     0,
+    0,
     gb18030_0_len_first_char,
     gb18030_0_get_char_value,
     NULL,
@@ -2749,6 +2767,7 @@ static CHARSETOPS CharsetOps_big5 = {
     2,
     FONT_CHARSET_BIG5,
     0,
+    0,
     big5_len_first_char,
     big5_get_char_value,
     NULL,
@@ -2895,6 +2914,7 @@ static CHARSETOPS CharsetOps_ksc5601_0 = {
     2,
     FONT_CHARSET_EUCKR,
     0,
+    0,
     ksc5601_0_len_first_char,
     ksc5601_0_get_char_value,
     NULL,
@@ -3019,6 +3039,7 @@ static CHARSETOPS CharsetOps_jisx0201_0 = {
     1,
     FONT_CHARSET_JISX0201_0,
     0,
+    0,
     jisx0201_0_len_first_char,
     jisx0201_0_get_char_value,
     NULL,
@@ -3162,6 +3183,7 @@ static CHARSETOPS CharsetOps_jisx0208_0 = {
     2,
     FONT_CHARSET_JISX0208_0,
     0,
+    0,
     jisx0208_0_len_first_char,
     jisx0208_0_get_char_value,
     NULL,
@@ -3247,6 +3269,7 @@ static CHARSETOPS CharsetOps_jisx0201_1 = {
     1,
     FONT_CHARSET_JISX0201_1,
     0,
+    0,
     sb_len_first_char,
     sb_get_char_value,
     NULL,
@@ -3418,6 +3441,7 @@ static CHARSETOPS CharsetOps_jisx0208_1 = {
     2,
     FONT_CHARSET_JISX0208_1,
     0,
+    0,
     jisx0208_1_len_first_char,
     jisx0208_1_get_char_value,
     NULL,
diff --git a/src/include/devfont.h b/src/include/devfont.h
index 017c23b4..a25d7001 100644
--- a/src/include/devfont.h
+++ b/src/include/devfont.h
@@ -15,7 +15,7 @@
  *   and Graphics User Interface (GUI) support system for embedded systems
  *   and smart IoT devices.
  *
- *   Copyright (C) 2002~2018, Beijing FMSoft Technologies Co., Ltd.
+ *   Copyright (C) 2002~2023, Beijing FMSoft Technologies Co., Ltd.
  *   Copyright (C) 1998~2002, WEI Yongming
  *
  *   This program is free software: you can redistribute it and/or modify
@@ -209,6 +209,9 @@ struct _CHARSETOPS
     /** Default character. */
     Achar32 def_char_value;
 
+    /** Whether use legacy BIDI algorithm (Since 5.0.13). */
+    unsigned legacy_bidi:1;
+
     /** The method to get the length of the first character. */
     int (*len_first_char) (const unsigned char* mstr, int mstrlen);