Form fields containing diacritics not displaying correctly

[bretwalker]

Using:
pdfcpu: v0.6.0 dev
commit: e33b502 (2023-12-13T10:22:47Z)
base : go1.21.0

On macOS 13.6 (22G120)

When I populate a form with text containing text with diacritics, it is not rendered properly in Adobe Acrobat Pro 2023.008.20458 when opened. The text does appear as expected once I click on the form field in Acrobat Pro.

If I edit populate the form using either Acrobat or macOS Preview using the same text as is in the JSON, the file opens as expected in Acrobat.

out.json
populated.out.json
template-pl.pdf
template.pdf

[hhrutter]

This may not be obvious but when filling you have to ensure all characters you fill are represented in the fill font which any PDF may set explicitly.

That is the reason for some characters not being displayed.

[hhrutter]

The cause of this is that this PDF form defines the fill font to be a Type 1 core font.
For fill strings containing code points above 0xFF this results in these characters to disappear because they can't be represented by any glyph.

The solutions for this is embedding a font which contains these missing glyphs.

[hhrutter]

This is fixed with latest commit.