Set an entry in an attachment's /Params dictionary

Writes a string-valued entry in the attachment's embedded-file parameter dictionary (/Params, ISO 32000-1:2008 Table 46). The string-valued standard key is "ModDate" — the modification date as a PDF date string (see pdf_parse_date() for the format); custom keys are allowed too.

Usage

pdf_attachment_set_dict_value(att, key, value)

Arguments

att

A pdfium_attachment from pdf_attachments() or pdf_attachment_new(). Parent doc must be readwrite.

key

The dictionary key as a non-empty character scalar.

value

The string value as a character scalar; UTF-8 accepted.

Value

Invisibly returns the parent pdfium_doc.

Details

The description (/Desc) and the associated-file relationship (/AFRelationship) are not /Params entries: they live on the attachment's file specification dictionary. Set the description with pdf_attachment_set_description() and read both with pdf_attachment_description() / pdf_attachment_af_relationship().

Wraps FPDFAttachment_SetStringValue, which writes into the attachment's /Params subdictionary. Mirrors pdf_attachment_dict_value() on the read side.

Ordering: PDFium's FPDFAttachment_SetStringValue requires the attachment's /Params dictionary to already exist. Call pdf_attachment_set_data() first on any attachment that doesn't have one yet (the file data write auto-creates /Params, populating Size, CreationDate, and CheckSum); only then can you append further keys with this function. On a fresh attachment from pdf_attachment_new() this means the natural sequence is pdf_attachment_new() → pdf_attachment_set_data() → pdf_attachment_set_dict_value().

Not exposed: the file stream's own /Subtype entry (the MIME type returned by pdf_attachment_mime_type()) lives on the attachment's embedded file stream, not on /Params, and PDFium has no public setter for it. Passing key = "Subtype" here writes /Params/Subtype, which won't be picked up by pdf_attachment_mime_type(). See dev/upstream-patches/ for the upstream gap.

Encoding: values are written as PDF text strings, so any Unicode text round-trips through pdf_attachment_dict_value() and a save / reload. (PDFium releases before chromium/8066 stored the raw UTF-8 bytes, which read back garbled for non-ASCII text.)

See also

pdf_attachment_dict_value().