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Output characters in reading order even if the PDF has them reversed #436

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Output characters in reading order even if the PDF has them reversed #436

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47 changes: 39 additions & 8 deletions base/core/evaluator.js
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Original file line number Diff line number Diff line change
Expand Up @@ -895,21 +895,52 @@ var PartialEvaluator = (function PartialEvaluatorClosure() {
args[3], args[4], args[5]);
break;
case 'TJ':
// PDF 32000-1 §9.4.3: each numeric element is subtracted from the
// current horizontal coordinate (thousandths of a text-space unit).
// Positive number → cursor moves LEFT, negative → cursor moves RIGHT.
// Some generators lay glyphs out right-to-left using large positive
// jumps between strings; track each string's x position in text
// space and emit them in left-to-right reading order.
var items = args[0];
var tjX = 0;
var pieces = [];
for (var j = 0, jj = items.length; j < jj; j++) {
if (typeof items[j] === 'string') {
chunk += fontCharsToUnicode(items[j], font);
} else if (items[j] < 0 && font.spaceWidth > 0) {
var fakeSpaces = -items[j] / font.spaceWidth;
if (fakeSpaces > MULTI_SPACE_FACTOR) {
fakeSpaces = Math.round(fakeSpaces);
while (fakeSpaces--) {
var pieceText = fontCharsToUnicode(items[j], font);
var pieceWidth = 0;
var pieceGlyphs = font.charsToGlyphs(items[j]);
for (var k = 0, kk = pieceGlyphs.length; k < kk; k++) {
var pg = pieceGlyphs[k];
pieceWidth += (pg && pg.width) || font.defaultWidth || 0;
}
pieces.push({ text: pieceText, x: tjX, width: pieceWidth });
tjX += pieceWidth;
} else {
tjX -= items[j];
}

@modesty modesty Sep 12, 2026

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ln 912-919: Summing glyph widths alone ignores character and word spacing and can cause regression. Example: Courier, 10pt, 10 Tc [(A) 700 (B)] TJ. :

Tc adds 10 units of character spacing. After drawing A, the actual cursor advances 6 + 10 = 16 units. The 700 adjustment then moves it back 7 units, so B starts at x = 9, to the right of A.

With this change, it counts only the glyph width: 6 − 7 = −1, results in changing extraction from AB to BA.

}
// Stable sort by x so reverse-laid runs come out in reading order
// while same-x or already-forward pieces keep their original order.
pieces.sort(function (a, b) { return a.x - b.x; });
var prevEnd = null;

@modesty modesty Sep 12, 2026

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spatially reordering RTL test should be avoided before bidi processing. For a reverse-positioned Hebrew run, this sort puts the characters into left-to-right visual order, but the subsequent PDFJS.bidi(chunk, -1, font.vertical) reorders them again.

spatial reconstruction should be made direction-aware and coordinate with the existing bidi conversion.

for (var p = 0, pp = pieces.length; p < pp; p++) {
var piece = pieces[p];
if (prevEnd !== null && font.spaceWidth > 0) {
var gap = piece.x - prevEnd;
if (gap > 0) {
var fakeSpaces = gap / font.spaceWidth;
if (fakeSpaces > MULTI_SPACE_FACTOR) {
fakeSpaces = Math.round(fakeSpaces);
while (fakeSpaces--) {
chunk += ' ';
}
} else if (fakeSpaces > SPACE_FACTOR) {
chunk += ' ';
}
} else if (fakeSpaces > SPACE_FACTOR) {
chunk += ' ';
}
}
chunk += piece.text;
prevEnd = piece.x + piece.width;
}
break;
case 'Tj':
Expand Down