tdf#57423 drawinglayer: PDF/UA export: more Alt texts for SdrObjects

Currently /Alt texts are generated from ObjectInfoPrimitive2D, but this
is only evaluated in VclMetafileProcessor2D::processGraphicPrimitive2D()
so while it's created for every SdrObject, it's ignored in most cases.

There doesn't appear to be a reason why this is done in
processGraphicPrimitive2D() and not a more generic location, the special
conditions that are checked there don't have anything to do with Alt
texts, they effectively guard some optimisation done to bitmaps in
PageSyncData::PlaySyncPageAct().

There is another issue in that not every SdrObject gets a
StructureTagPrimitive2D, and even if there is a StructureTagPrimitive2D
it may be ignored if it's in the background.

The Alt text must only be produced if there is a structure element for
the same SdrObject, else it would end up on some unrelated structure
element.

Fix all this by moving processing to a new function which checks that
there is a current StructureTagPrimitive2D for a SdrObject in effect.

The only problem with this is that previously Writer images produced Alt
text, and now they don't - but Writer needs some fixing anyway.

Change-Id: I2a362e8a9cd93e5bc817c6eed546c46b46e14980
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143189
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/drawinglayer/primitive2d/structuretagprimitive2d.hxx b/include/drawinglayer/primitive2d/structuretagprimitive2d.hxx
index bf8a48f98748..40ad422c2b9a 100644
--- a/include/drawinglayer/primitive2d/structuretagprimitive2d.hxx
+++ b/include/drawinglayer/primitive2d/structuretagprimitive2d.hxx
@@ -65,6 +65,7 @@ namespace drawinglayer::primitive2d
             const vcl::PDFWriter::StructElement& getStructureElement() const { return maStructureElement; }
             bool isBackground() const { return mbBackground; }
             bool isImage() const { return mbIsImage; }
+            bool isTaggedSdrObject() const;
             sal_Int32 GetAnchorStructureElementId() const { return m_nAnchorStructureElementId; }
 
             /// compare operator