tdf#148934 PDF/UA export: add Contents entry to Link annotations

* Specification: ISO 14289-1:2014, Clause: 7.18.5, Test number: 2
Links shall contain an alternate description via their Contents key as described in ISO 32000-1:2008, 14.9.3.

These links are created all over the code, in some cases it's a bit
dubious what the content/alt-text should be, but let's try to use the
most suitable looking bit of text in whatever the context is.

* Specification: ISO 14289-1:2014, Clause: 7.18.3, Test number: 1
Every page on which there is an annotation shall contain in its page dictionary the key Tabs, and its value shall be S.

Change-Id: I7b63feb759f0c75047f854ed9997918f829a537e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/141826
Tested-by: Jenkins
Reviewed-by: Michael Stahl <michael.stahl@allotropia.de>

5 files changed, 29 insertions, 8 deletions

diff --git a/vcl/inc/pdf/pdfwriter_impl.hxx b/vcl/inc/pdf/pdfwriter_impl.hxx
index f415475e5441..6102b64a8956 100644
--- a/vcl/inc/pdf/pdfwriter_impl.hxx
+++ b/vcl/inc/pdf/pdfwriter_impl.hxx
@@ -422,10 +422,12 @@ struct PDFLink : public PDFAnnotation
     sal_Int32                   m_nDest; // set to -1 for URL, to a dest else
     OUString               m_aURL;
     sal_Int32                   m_nStructParent; // struct parent entry
+    OUString m_AltText;
 
-    PDFLink()
+    PDFLink(OUString const& rAltText)
             : m_nDest( -1 ),
               m_nStructParent( -1 )
+            , m_AltText(rAltText)
     {}
 };
 
@@ -1273,7 +1275,7 @@ public:
     sal_Int32   emitDocumentMetadata();
 
     // links
-    sal_Int32 createLink( const tools::Rectangle& rRect, sal_Int32 nPageNr );
+    sal_Int32 createLink(const tools::Rectangle& rRect, sal_Int32 nPageNr, OUString const& rAltText);
     sal_Int32 createDest( const tools::Rectangle& rRect, sal_Int32 nPageNr, PDFWriter::DestAreaType eType );
     sal_Int32 registerDestReference( sal_Int32 nDestId, const tools::Rectangle& rRect, sal_Int32 nPageNr, PDFWriter::DestAreaType eType );
     void      setLinkDest( sal_Int32 nLinkId, sal_Int32 nDestId );
diff --git a/vcl/qa/cppunit/pdfexport/pdfexport.cxx b/vcl/qa/cppunit/pdfexport/pdfexport.cxx
index 7c5ee9f67952..0e8c4fb05407 100644
--- a/vcl/qa/cppunit/pdfexport/pdfexport.cxx
+++ b/vcl/qa/cppunit/pdfexport/pdfexport.cxx
@@ -3596,6 +3596,9 @@ CPPUNIT_TEST_FIXTURE(PdfExportTest, testURIs)
         CPPUNIT_ASSERT_EQUAL(
             OString("Annot"),
             static_cast<vcl::filter::PDFNameElement*>(pAnnot->Lookup("Type"))->GetValue());
+        CPPUNIT_ASSERT_EQUAL(
+            OString("Link"),
+            static_cast<vcl::filter::PDFNameElement*>(pAnnot->Lookup("Subtype"))->GetValue());
         auto pAction = dynamic_cast<vcl::filter::PDFDictionaryElement*>(pAnnot->Lookup("A"));
         CPPUNIT_ASSERT(pAction);
         auto pURIElem
@@ -3603,6 +3606,11 @@ CPPUNIT_TEST_FIXTURE(PdfExportTest, testURIs)
         CPPUNIT_ASSERT(pURIElem);
         // Check it matches
         CPPUNIT_ASSERT_EQUAL(URIs[i].out, pURIElem->GetValue());
+        // tdf#148934 check a11y
+        CPPUNIT_ASSERT_EQUAL(
+            OUString("Test pdf"),
+            ::vcl::filter::PDFDocument::DecodeHexStringUTF16BE(
+                *dynamic_cast<vcl::filter::PDFHexStringElement*>(pAnnot->Lookup("Contents"))));
     }
 }
 
diff --git a/vcl/source/gdi/pdfextoutdevdata.cxx b/vcl/source/gdi/pdfextoutdevdata.cxx
index 96a77a15d94d..00e4f4a9c1bd 100644
--- a/vcl/source/gdi/pdfextoutdevdata.cxx
+++ b/vcl/source/gdi/pdfextoutdevdata.cxx
@@ -181,11 +181,12 @@ void GlobalSyncData::PlayGlobalActions( PDFWriter& rWriter )
                 rWriter.Push( PushFlags::MAPMODE );
                 rWriter.SetMapMode( mParaMapModes.front() );
                 mParaMapModes.pop_front();
-                mParaIds.push_back( rWriter.CreateLink( mParaRects.front(), mParaInts.front() ) );
+                mParaIds.push_back( rWriter.CreateLink(mParaRects.front(), mParaInts.front(), mParaOUStrings.front()) );
                 // resolve LinkAnnotation structural attribute
                 rWriter.SetLinkPropertyID( mParaIds.back(), sal_Int32(mParaIds.size()-1) );
                 mParaRects.pop_front();
                 mParaInts.pop_front();
+                mParaOUStrings.pop_front();
                 rWriter.Pop();
             }
             break;
@@ -659,12 +660,13 @@ sal_Int32 PDFExtOutDevData::CreateDest( const tools::Rectangle& rRect, sal_Int32
     mpGlobalSyncData->mParaDestAreaTypes.push_back( eType );
     return mpGlobalSyncData->mCurId++;
 }
-sal_Int32 PDFExtOutDevData::CreateLink( const tools::Rectangle& rRect, sal_Int32 nPageNr )
+sal_Int32 PDFExtOutDevData::CreateLink(const tools::Rectangle& rRect, OUString const& rAltText, sal_Int32 nPageNr)
 {
     mpGlobalSyncData->mActions.push_back( PDFExtOutDevDataSync::CreateLink );
     mpGlobalSyncData->mParaRects.push_back( rRect );
     mpGlobalSyncData->mParaMapModes.push_back( mrOutDev.GetMapMode() );
     mpGlobalSyncData->mParaInts.push_back( nPageNr == -1 ? mnPage : nPageNr );
+    mpGlobalSyncData->mParaOUStrings.push_back(rAltText);
     return mpGlobalSyncData->mCurId++;
 }
 
diff --git a/vcl/source/gdi/pdfwriter.cxx b/vcl/source/gdi/pdfwriter.cxx
index ca9fb352eb74..efea6a987f5b 100644
--- a/vcl/source/gdi/pdfwriter.cxx
+++ b/vcl/source/gdi/pdfwriter.cxx
@@ -330,9 +330,9 @@ void PDFWriter::DrawJPGBitmap( SvStream& rStreamData, bool bIsTrueColor, const S
     xImplementation->drawJPGBitmap( rStreamData, bIsTrueColor, rSrcSizePixel, rTargetArea, rAlphaMask, rGraphic );
 }
 
-sal_Int32 PDFWriter::CreateLink( const tools::Rectangle& rRect, sal_Int32 nPageNr )
+sal_Int32 PDFWriter::CreateLink(const tools::Rectangle& rRect, sal_Int32 nPageNr, OUString const& rAltText)
 {
-    return xImplementation->createLink( rRect, nPageNr );
+    return xImplementation->createLink(rRect, nPageNr, rAltText);
 }
 
 sal_Int32 PDFWriter::CreateScreen(const tools::Rectangle& rRect, sal_Int32 nPageNr)
diff --git a/vcl/source/gdi/pdfwriter_impl.cxx b/vcl/source/gdi/pdfwriter_impl.cxx
index 8fbbea859f2b..6214489203b3 100644
--- a/vcl/source/gdi/pdfwriter_impl.cxx
+++ b/vcl/source/gdi/pdfwriter_impl.cxx
@@ -737,6 +737,12 @@ bool PDFPage::emit(sal_Int32 nParentObject )
             aLine.append( ((i+1)%15) ? " " : "\n" );
         }
         aLine.append( "]\n" );
+        if (m_pWriter->m_aContext.Version != PDFWriter::PDFVersion::PDF_A_1
+            && PDFWriter::PDFVersion::PDF_1_5 <= m_pWriter->m_aContext.Version)
+        {
+            // ISO 14289-1:2014, Clause: 7.18.3
+            aLine.append( "/Tabs(S)\n" );
+        }
     }
     if( !m_aMCIDParents.empty() )
     {
@@ -3520,6 +3526,9 @@ bool PDFWriterImpl::emitLinkAnnotations()
         aLine.append( ' ' );
         appendFixedInt( rLink.m_aRect.Bottom(), aLine );
         aLine.append( "]" );
+        // ISO 14289-1:2014, Clause: 7.18.5
+        aLine.append("/Contents");
+        appendUnicodeTextStringEncrypt(rLink.m_AltText, rLink.m_nObject, aLine);
         if( rLink.m_nDest >= 0 )
         {
             aLine.append( "/Dest" );
@@ -10158,7 +10167,7 @@ void PDFWriterImpl::createNote( const tools::Rectangle& rRect, const PDFNote& rN
     m_aPages[nPageNr].m_aAnnotations.push_back(rNoteEntry.m_aPopUpAnnotation.m_nObject);
 }
 
-sal_Int32 PDFWriterImpl::createLink( const tools::Rectangle& rRect, sal_Int32 nPageNr )
+sal_Int32 PDFWriterImpl::createLink(const tools::Rectangle& rRect, sal_Int32 nPageNr, OUString const& rAltText)
 {
     if( nPageNr < 0 )
         nPageNr = m_nCurrentPage;
@@ -10168,7 +10177,7 @@ sal_Int32 PDFWriterImpl::createLink( const tools::Rectangle& rRect, sal_Int32 nP
 
     sal_Int32 nRet = m_aLinks.size();
 
-    m_aLinks.emplace_back( );
+    m_aLinks.emplace_back(rAltText);
     m_aLinks.back().m_nObject   = createObject();
     m_aLinks.back().m_nPage     = nPageNr;
     m_aLinks.back().m_aRect     = rRect;