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Join a letter to the base before it however many marks are between them #161

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Merged
jakejackson1 merged 1 commit into from
Sep 16, 2026
+55 −16
Merged

Join a letter to the base before it however many marks are between them #161

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19 changes: 3 additions & 16 deletions src/Shaper/Arabic.php
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Original file line number Diff line number Diff line change
Expand Up @@ -174,27 +174,14 @@ public static function shape(&$info, $arabGlyphs, $glyphClassMarks, $usetags, $s
$chars[] = $info[$i]['hex'];
}

$crntChar = null;
$prevChar = null;
$nextChar = null;
$output = [];
$max = count($chars);
for ($i = $max - 1; $i >= 0; $i--) {
$crntChar = $chars[$i];
if ($i > 0) {
$prevChar = hexdec($chars[$i - 1]);
} else {
$prevChar = null;
}
if ($prevChar && isset($transparentJoin[$prevChar]) && isset($chars[$i - 2])) {
$prevChar = hexdec($chars[$i - 2]);
if ($prevChar && isset($transparentJoin[$prevChar]) && isset($chars[$i - 3])) {
$prevChar = hexdec($chars[$i - 3]);
if ($prevChar && isset($transparentJoin[$prevChar]) && isset($chars[$i - 4])) {
$prevChar = hexdec($chars[$i - 4]);
}
}
}
// joining sees the base a mark is written on, however many marks the base carries
$n = self::skipTransparent($chars, $i, -1, $transparentJoin);
$prevChar = isset($chars[$n]) ? hexdec($chars[$n]) : null;
if ($crntChar && isset($transparentJoin[hexdec($crntChar)])) {
// If next_char = RightJoining && prev_char = LeftJoining:
if (isset($chars[$i + 1]) && $chars[$i + 1] && isset(self::$rightJoining[hexdec($chars[$i + 1])]) && $prevChar && isset(self::$leftJoining[$prevChar])) {
Expand Down
52 changes: 52 additions & 0 deletions tests/Mpdf/Shaper/ArabicTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,9 @@ class ArabicTest extends \Yoast\PHPUnitPolyfills\TestCases\TestCase
/** U+073A SYRIAC HBASA ABOVE */
const HBASA = '0073A';

/** U+073B SYRIAC HBASA BELOW */
const HBASA_BELOW = '0073B';

/** U+0712 SYRIAC LETTER BETH, dual-joining */
const BETH = '00712';

Expand Down Expand Up @@ -117,6 +120,40 @@ public function testAMarkBetweenTwoLettersDoesNotBreakTheirJoin()
$this->assertSame([['B_INIT', 2], [self::FATHA, 0], ['B_FINA', 1]], $forms);
}

/**
* Nothing limits how many marks a base carries, and the lookback stepped over at most three of
* them: a fourth left the following letter reading a mark as the character behind it, and a mark
* joins nothing. GravityPDF/mpdf#154.
*
* The first letter is asserted alongside the last because the two directions are found
* differently - forwards is the last letter the backwards walk over the run passed, which never
* had a limit - and it is the pair that says the marks are invisible to joining from either side.
*/
public function testALetterJoinsToTheBaseBeforeItHoweverManyMarksAreBetweenThem()
{
$four = [self::BETH, self::PTHAHA, self::ZQAPHA, self::RBASA, self::HBASA, self::BETH];
$five = [self::BETH, self::PTHAHA, self::ZQAPHA, self::RBASA, self::HBASA, self::HBASA_BELOW, self::BETH];

$forms = $this->shape($four, self::ALL_FORMS, 'syrc');

$this->assertSame(['BE_INIT', 2], $forms[0]);
$this->assertSame(['BE_FINA', 1], $forms[5]);
$this->assertSame(['BE_FINA', 1], $this->shape($five, self::ALL_FORMS, 'syrc')[6]);
}

/**
* The marks counted are the Transparent-Joining table together with GDEF's mark class, so a mark
* only the font declares takes up a place in the walk like any other.
*/
public function testAMarkOnlyGdefDeclaresIsSteppedOverWithTheRest()
{
$run = [self::BETH, self::PTHAHA, self::ZQAPHA, self::RBASA, self::COMBINING_GRAVE, self::BETH];

$forms = $this->shape($run, self::ALL_FORMS, 'syrc', self::COMBINING_GRAVE);

$this->assertSame(['BE_FINA', 1], $forms[5]);
}

/**
* The four form features can be switched off through OTLtags, in which case the character is left
* as it came in rather than substituted
Expand Down Expand Up @@ -300,6 +337,21 @@ public function testAPointedWordDrawsTheSameAlaphAsTheUnpointedWord()
}
}

/**
* Through a real font: the marks are drawn where they were written and the letters either side
* read as though they were not there, so a heavily pointed word has to draw the same two BETHs as
* the unpointed one. Estrangelo Edessa states no isolated BETH either, so the second letter losing
* its final form left the nominal U+0712 behind.
*/
public function testAHeavilyPointedWordDrawsTheSameLettersAsTheUnpointedWord()
{
$unpointed = $this->render([self::BETH, self::BETH]);
$pointed = $this->render([self::BETH, self::PTHAHA, self::ZQAPHA, self::RBASA, self::HBASA, self::BETH]);

$this->assertSame($unpointed[0], $pointed[0]);
$this->assertSame($unpointed[1], $pointed[5]);
}

/**
* The same character through a real font, which is where the wrong entry showed: Estrangelo Edessa
* carries a BETH for each of the four forms, and the form the shaper asks for is the glyph that
Expand Down
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