https://bugs.documentfoundation.org/show_bug.cgi?id=174184
Bug ID: 174184
Summary: PDF/UA: the /Link annotation of an Impress click
action is not in the structure tree
Product: LibreOffice
Version: 26.8.0.3 release
Hardware: All
OS: All
Status: UNCONFIRMED
Keywords: accessibility, filter:pdf
Severity: normal
Priority: medium
Component: Impress
Assignee: [email protected]
Reporter: [email protected]
Blocks: 139007
Created attachment 209378
--> https://bugs.documentfoundation.org/attachment.cgi?id=209378&action=edit
Picture with alt text and a click action (https://example.org/)
When a shape or picture in Impress has an Interaction (click action), such as
"Go to page or object" or "Go to document" (a URL), the PDF export creates a
/Link annotation over the shape. With Universal Accessibility (PDF/UA), that
annotation is not in the structure tree: no Link element, no /OBJR, no
/StructParent. A screen reader cannot tie the link to the content it is on, and
veraPDF reports it.
Steps to reproduce:
1. Open the attached picture-link.fodp: a picture with Title "Logo",
Description "Company logo, links to example.org", and a click action that opens
https://example.org/.
2. File > Export as PDF, with "Universal Accessibility (PDF/UA)" checked.
3. Look at the structure tree and the page /Annots, or check with veraPDF
(PDF/UA-1).
Actual:
- the /Link annotation has no /StructParent;
- the structure tree has only /Figure /Alt (Logo - Company logo, links to
example.org);
- veraPDF PDF/UA-1 rule 7.18.5-1 fails: "Links shall be tagged according to ISO
32000-1:2008, 14.8.4.4.2, Link Element".
Expected: a Link structure element around the element of the shape, with an
/OBJR to the annotation, as Writer does for a linked image since tdf#154939:
/Link
/Figure /Alt (Logo - Company logo, links to example.org)
OBJR -> the /Link annotation
The same for a text box (the Link around its Div) and for a member of a group.
In a group without alternative text, which is a Div since tdf#174110, the Link
wraps the member inside the Div. A group with alternative text is one Figure,
so the Link of a member goes inside that Figure; its /Alt should then describe
the link too (Matterhorn 13-002).
A link on a decorative shape, or on a shape of the master page, is on content
that is an artifact, with no structure element to attach the Link to; that is
not covered here.
ISO 14289-1 (PDF/UA-1) 7.18.5: links shall be tagged with a Link element; ISO
32000-1 14.8.4.4.2: the Link element refers to its annotation with an /OBJR.
In sd/source/ui/unoidl/unomodel.cxx, ImplPDFExportShapeInteraction creates the
link with CreateLink, but its id is not tied to any structure element. Media
shapes are already handled: their /Screen annotation id is recorded per shape
and svx/source/sdr/contact/viewobjectcontact.cxx attaches it to the shape's
Annot element via GetScreenAnnotIds; the same can be done for click-action
links.
The attached picture-link.26.8-output.pdf is the output of 26.8.1.1; veraPDF
(PDF/UA-1) fails only 7.18.5-1 on it.
Reproduced on 26.8.1.1 (bf6ef2662401) and 26.8.0.3, macOS. The same with a PPTX
a:hlinkClick on a picture.
See also tdf#174109 (the /Contents of the same link), tdf#174110 (groups),
tdf#154939 (linked images in Writer).
Referenced Bugs:
https://bugs.documentfoundation.org/show_bug.cgi?id=139007
[Bug 139007] [META] PDF accessibility
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