https://bugs.documentfoundation.org/show_bug.cgi?id=174110
Bug ID: 174110
Summary: PDF/UA: an Impress group without alternative text is
tagged as one Figure that holds the text of its
members and takes the /Alt of a member
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 209273
--> https://bugs.documentfoundation.org/attachment.cgi?id=209273&action=edit
Group without alternative text: two text boxes and a picture with Title "Arrow
icon"
In Impress, shapes are often grouped only to move and resize them together. The
PDF export with Universal Accessibility (PDF/UA) tags every group as one
Figure, whether the group has an alternative text or not. A group without a
Title or Description therefore:
- puts the text of its members inside the Figure: the text boxes become P
elements of an image, and the alternate description of a Figure may be used in
place of its content (ISO 32000-1, 14.9.3), so a reader may skip the text;
- gets the /Alt of one of its members: the Title of a picture inside the group
becomes the /Alt of the whole group.
veraPDF does not report it, as the Figure has an /Alt. Adobe Acrobat's Read Out
Loud reads "Arrow icon" and then the text, so the steps are announced as part
of an image described as "Arrow icon".
Steps to reproduce:
1. Open the attached group-without-alt.fodp: a group, without Title and
Description, of two text boxes ("Step one: open the file", "Step two: save it")
and a picture with Title "Arrow icon".
2. File > Export as PDF, with "Universal Accessibility (PDF/UA)" checked.
3. Look at the structure tree, or read the page with a screen reader.
Actual:
/Figure /Alt (Arrow icon)
/P (Step one: open the file)
/P (Step two: save it)
[the picture]
Expected: a group without a Title or Description is a Div, a grouping element
without semantics (ISO 32000-1, 14.8.4.2), and its members are tagged inside it
as if they were not grouped:
/Div
/Div /P (Step one: open the file)
/Div /P (Step two: save it)
/Figure /Alt (Arrow icon)
A group with a Title or Description stays a Figure with that /Alt, as the
author described it as one image; a decorative group stays an artifact.
PowerPoint's PDF export also tags a group without alternative text by its
members only.
ISO 14289-1 (PDF/UA-1) 7.3: a Figure is content that is an image, and its
alternate text replaces it; 7.1: content shall be tagged in its logical
structure. WCAG 2.1 1.3.1 (Info and Relationships).
In svx/source/sdr/contact/viewobjectcontact.cxx,
ViewObjectContact::createStructureTag tags an SdrObjKind::Group as
StructElement::Figure, and tags only top-level objects
(getParentSdrObjectFromSdrObject() == nullptr), so the members of a group never
get their own element; drawinglayer's processObjectInfoPrimitive2D then writes
a member's Title as the alternate text of the current element, the group's
Figure.
The attached group-without-alt.26.8-output.pdf is the output of 26.8.0.3.
Reproduced on 26.8.0.3, macOS.
See also tdf#174106 (decorative member of a group), tdf#174109 (click-action
link).
Referenced Bugs:
https://bugs.documentfoundation.org/show_bug.cgi?id=139007
[Bug 139007] [META] PDF accessibility
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