Fix missing fields in acroform #134
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jimmoffet
commented
May 16, 2024
jimmoffet
commented
May 16, 2024
| type: 'not-supported', | ||
| name: 'CHARACTER IMAGE', | ||
| name: 'CHARACTER IMAGE.undefined', |
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edge case, looking into it
jimmoffet
commented
May 16, 2024
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| const pdfDoc = await PDFDocument.load(pdfBytes); | ||
| const widgets = await getWidgets(pdfDoc); | ||
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| pdfDoc.catalog.set( | ||
| PDFName.of('AcroForm'), | ||
| pdfDoc.context.obj({ | ||
| Fields: widgets.map(widget => pdfDoc.context.getObjectRef(widget)), // array of widget refs | ||
| }) | ||
| ); | ||
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|
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This is where we add all of the widgets to the acroform, which will now get pulled into form via pdfDoc.getForm() below
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Interesting, so this is backfilling poorly annotated fields into the source PDF? That seems like an interesting approach. I like that it gives us a clear picture of the "error" of the source PDF, that we could perhaps inform the user about.
jimmoffet
commented
May 16, 2024
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| // TODO: copied from pdf-lib acrofield internals, check if it's already exposed outside of acroform somewhere | ||
| export const getWidgets = async (pdfDoc: PDFDocument): Promise<PDFDict[]> => { | ||
| return pdfDoc.context | ||
| .enumerateIndirectObjects() | ||
| .map(([, obj]) => obj) | ||
| .filter( | ||
| obj => | ||
| obj instanceof PDFDict && | ||
| obj.get(PDFName.of('Type')) === PDFName.of('Annot') && | ||
| obj.get(PDFName.of('Subtype')) === PDFName.of('Widget') | ||
| ) | ||
| .map(obj => obj as PDFDict); | ||
| }; | ||
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|
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Seems useful, so I'm exporting, but I don't feel strongly about it. It's ripped straight from pdf-lib, but seems to be only exposed on the acrofield object, which isn't useful in our case...
danielnaab
approved these changes
May 16, 2024
danielnaab
approved these changes
May 21, 2024
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Working with low level objects isn't super fun in pdf-lib, haha, but I got there.
Ultimately, the offending pdf was poorly-authored (surprise) and some, but not all, widgets were added to the acroform catalog object. I'm guessing the author just gave up at the prospect of adding all those checkboxes to the acroform. Unfortunately, pdf-lib does not check for loose widgets that weren't added to the acroform object.
PDFFormis essentially a 1:1 wrapper on acroform.The solution was to iterate over all of the annotations with the widget type and add them to the doc's acroform manually. After that, we can grab the
PDFFormand call.getFields()and get back those nicePDFFieldobjects just like we did before.This solution should generically capture any widgets missing from the acroform. I'm not sure if there will be a situation where there are widgets that the author intentionally kept outside of the acroform that we don't want in the acroform, but I can't think of one...