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Add support for Arabic reshaping

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This code can probably be polished a bit more, but the hard part is
over!

This part was written with guidance of this code:
https://github.com/TerryCavanagh/hx_arabic_shaper
This commit is contained in:
Dav999 2024-01-03 00:11:51 +01:00 committed by Misa Elizabeth Kai
parent e011273eb3
commit ef712f9f0c
1 changed files with 78 additions and 2 deletions
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80
desktop_version/src/FontBidi.cpp
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@ -271,6 +271,84 @@ const char* bidi_transform(const char* text)
for (SBUInteger i = 0; i < n_runs; i++)
{
bool is_ltr = runs[i].level % 2 == 0;
if (!is_ltr)
{
// Time for reshaping!
enum arabic_form { NONE, ISOLATED, INITIAL, MEDIAL, FINAL };
arabic_form forms[1024];
uint32_t replacements[1024];
const ArabicLetter* letter;
const ArabicLetter* previous_letter = NULL;
arabic_form previous_form = NONE;
for (size_t c = 0; c < runs[i].length; c++)
{
uintptr_t letter_ptr;
bool found = hashmap_get(arabic_letters_map, &utf32_in[runs[i].offset + c], sizeof(uint32_t), &letter_ptr);
if (!found)
{
forms[c] = NONE;
replacements[c] = 0;
previous_form = NONE;
previous_letter = NULL;
continue;
}
letter = (const ArabicLetter*) letter_ptr;
if (previous_form == NONE)
{
// Maybe the first letter, or the one after an unknown one
forms[c] = ISOLATED;
replacements[c] = 0;
}
else if (letter->final == 0 && letter->medial == 0)
{
// letter doesn't connect with the one before
forms[c] = ISOLATED;
replacements[c] = 0;
}
else if (previous_letter->initial == 0 && previous_letter->medial == 0)
{
// previous_letter doesn't connect with the one after
forms[c] = ISOLATED;
replacements[c] = 0;
}
else if (previous_form == FINAL && previous_letter->medial == 0)
{
// previous_letter doesn't connect with the ones before and after
forms[c] = ISOLATED;
replacements[c] = 0;
}
else if (previous_form == ISOLATED)
{
forms[c-1] = INITIAL;
forms[c] = FINAL;
replacements[c-1] = previous_letter->initial;
replacements[c] = letter->final;
}
else
{
/* Otherwise, we will change the previous letter
* to connect to the current letter */
forms[c-1] = MEDIAL;
forms[c] = FINAL;
replacements[c-1] = previous_letter->medial;
replacements[c] = letter->final;
}
previous_form = forms[c];
previous_letter = (const ArabicLetter*) letter;
}
// Now that we have all the forms, time to change the codepoints!
for (size_t c = 0; c < runs[i].length; c++)
{
if (replacements[c] != 0)
{
utf32_in[runs[i].offset + c] = replacements[c];
}
}
}
for (size_t c = 0; c < runs[i].length; c++)
{
size_t ix;
@ -289,8 +367,6 @@ const char* bidi_transform(const char* text)
goto no_more_runs;
}
// TODO prolly do something with reshaping here
UTF8_encoding enc = UTF8_encode(utf32_in[ix]);
size_t n_copy = SDL_min(enc.nbytes, (size_t) out_room_left);
SDL_memcpy(