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, 5 insertions, 0 deletions

diff --git a/drawinglayer/source/processor2d/vclmetafileprocessor2d.hxx b/drawinglayer/source/processor2d/vclmetafileprocessor2d.hxx
index 0393039f4455..730b7aac11f2 100644
--- a/drawinglayer/source/processor2d/vclmetafileprocessor2d.hxx
+++ b/drawinglayer/source/processor2d/vclmetafileprocessor2d.hxx
@@ -63,6 +63,7 @@ class PolyPolygonColorPrimitive2D;
 class MaskPrimitive2D;
 class UnifiedTransparencePrimitive2D;
 class TransparencePrimitive2D;
+class ObjectInfoPrimitive2D;
 class StructureTagPrimitive2D;
 }
 
@@ -142,6 +143,8 @@ private:
         const primitive2d::UnifiedTransparencePrimitive2D& rUniTransparenceCandidate);
     void processTransparencePrimitive2D(
         const primitive2d::TransparencePrimitive2D& rTransparenceCandidate);
+    void
+    processObjectInfoPrimitive2D(const primitive2d::ObjectInfoPrimitive2D& rObjectInfoPrimitive2D);
     void processStructureTagPrimitive2D(
         const primitive2d::StructureTagPrimitive2D& rStructureTagCandidate);
 
@@ -191,6 +194,8 @@ private:
 
     std::stack<vcl::PDFWriter::StructElement> maListElements;
 
+    primitive2d::StructureTagPrimitive2D const* mpCurrentStructureTag = nullptr;
+
 protected:
     /*  the local processor for BasePrimitive2D-Implementation based primitives,
         called from the common process()-implementation