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XFA: `measure.pushFont is not a function` — rich text containing <b> or <i> breaks layout

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
84/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
javascript
Domain
frontend

Research direction

Start in src/core/xfa/text.js, comparing TextMeasure with the pushFont callers in src/core/xfa/xhtml.js. Reproduce with enableXfa and rich text containing or , then verify that layout completes and pages are built without the missing-method error.

Written by the indexing model from the issue text.

Description

src/core/xfa/xhtml.js calls measure.pushFont(...) in two places:

// class B, line ~375
[$pushGlyphs](measure) {
  measure.pushFont({ weight: "bold" });
  super[$pushGlyphs](measure);
  measure.popFont();
}

// class I, line ~466
[$pushGlyphs](measure) {
  measure.pushFont({ posture: "italic" });
  super[$pushGlyphs](measure);
  measure.popFont();
}

TextMeasure in src/core/xfa/text.js defines pushData, popFont, addPara, addString and compute. There is no pushFont on it, nor on FontSelector.

So any XFA document whose rich text contains <b> or <i> throws TypeError: measure.pushFont is not a function during layout.

Why it is hard to recognise

XFAFactory._createPages catches the error and only warns, so no pages are built and getDocument rejects with:

UnknownErrorException: Cannot read properties of undefined (reading 'length')

which names neither bold text nor the missing method. A document differing from a working one by a single <b> fails with a message that points nowhere near the cause.

Reproduction

Load any dynamic XFA document (enableXfa: true) whose rich text contains a <b> or <i> element, for example an exData of contentType="text/html" holding:

<body xmlns="http://www.w3.org/1999/xhtml"><p><b>Important:</b> text</p></body>

Confirmed on master today; originally found on 4.6.82.

Suggested fix

Add to TextMeasure:

pushFont(xfaFont) {
  this.fontSelector.pushData(
    xfaFont,
    { top: NaN, bottom: NaN, left: NaN, right: NaN },
    null
  );
}

The margin has to be an object of NaNs rather than null, because FontSelector.pushData tests isNaN(margin[side]). That is exactly what XhtmlObject[$pushGlyphs] already passes on the path that works.

Dominant language
JavaScript
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Merged PRs (30d)
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