# lv_text_ap.h (/api/misc/lv_text_ap_h)
Functions [#functions]
lv_text_ap_strlen [#lv_text_ap_strlen]
Calculate the number of bytes required to store the Arabic/Persian processed version of a UTF-8 string, excluding the null terminator. Analogous to strlen() but accounts for character form substitutions (e.g. initial, medial, final, isolated forms).
```c title=" " lineNumbers=1
size_t lv_text_ap_strlen(const char *txt)
```
Parameters
| Name | Type | Description |
| ----- | -------------- | ----------------------------------------------------- |
| `txt` | `const char *` | Null-terminated UTF-8 input string. Must not be NULL. |
**Returns:** — Number of bytes in the processed output, excluding '\0'. Allocate (lv\_text\_ap\_strlen(txt) + 1) bytes for the output buffer.
lv_text_ap_proc [#lv_text_ap_proc]
Process a UTF-8 string and replace Arabic/Persian characters with their correct contextual forms (isolated, initial, medial, final) based on their position within each word.
The output buffer must be pre-allocated with at least (lv\_text\_ap\_strlen(txt) + 1) bytes.
Returns early if `txt` or `txt_out` are null
```c title=" " lineNumbers=1
void lv_text_ap_proc(const char *txt, char *txt_out)
```
Parameters
| Name | Type | Description |
| --------- | -------------- | ------------------------------------------------------------------------------------ |
| `txt` | `const char *` | Null-terminated UTF-8 input string. |
| `txt_out` | `char *` | Output buffer to write the processed UTF-8 string into. Must not overlap with `txt`. |
Non-Arabic/Persian characters are copied to the output unchanged.
Macros [#macros]
LV_UNDEF_ARABIC_PERSIAN_CHARS [#lv_undef_arabic_persian_chars]
```c title=" " lineNumbers=1
#define LV_UNDEF_ARABIC_PERSIAN_CHARS (UINT32_MAX)
```
LV_AP_ALPHABET_BASE_CODE [#lv_ap_alphabet_base_code]
```c title=" " lineNumbers=1
#define LV_AP_ALPHABET_BASE_CODE 0x0622
```
LV_AP_END_CHARS_LIST [#lv_ap_end_chars_list]
```c title=" " lineNumbers=1
#define LV_AP_END_CHARS_LIST {0,0,0,0,0,{0,0}}
```
Dependencies [#dependencies]