tdf#112118: DOCX: properly import/export border distance

https://wiki.openoffice.org/wiki/Writer/MSInteroperability/PageBorder
discusses implementation differences between ODF model and MS formats
wrt dealing with page margins and distances to borders.

This patch corrects import from DOCX, so that the border distance and
width doesn't add to the margin size imported from file anymore. It
takes care to preserve size from page edge to text (the most important
size that affects document layout). When borders go outside of range
valid for ODF, the margin is set to keep text area intact, and the
border is placed as close to intended position as possible.

Export code now also properly handles border width. Also, an improved
heuristic implemented to better export cases unsupported by Word, so
that the result would look closer to ODF original. We still write
correct sizes to OOXML, so that when reopened by LO, the borders will
be in correct places; but as Word cannot handle sizes more than 31 pt,
it will show borders shifted.

This prevents from adding border widths and distances to page margins
at each opening of DOCX, saving back the changed value, increasing
the margins each time.

Change-Id: Ia978ab119dd661949d6c321aea91397f28d205b0
Reviewed-on: https://gerrit.libreoffice.org/51267
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

2 files changed, 117 insertions, 66 deletions

diff --git a/sw/source/filter/ww8/docxattributeoutput.cxx b/sw/source/filter/ww8/docxattributeoutput.cxx
index 1cde1640af0b..21b4d57d4321 100644
--- a/sw/source/filter/ww8/docxattributeoutput.cxx
+++ b/sw/source/filter/ww8/docxattributeoutput.cxx
@@ -3036,8 +3036,6 @@ static OutputBorderOptions lcl_getTableDefaultBorderOptions(bool bEcma)
     rOptions.bWriteTag = true;
     rOptions.bWriteInsideHV = true;
     rOptions.bWriteDistance = false;
-    rOptions.aShadowLocation = SvxShadowLocation::NONE;
-    rOptions.bCheckDistanceSize = false;
 
     return rOptions;
 }
@@ -3051,8 +3049,6 @@ static OutputBorderOptions lcl_getTableCellBorderOptions(bool bEcma)
     rOptions.bWriteTag = true;
     rOptions.bWriteInsideHV = true;
     rOptions.bWriteDistance = false;
-    rOptions.aShadowLocation = SvxShadowLocation::NONE;
-    rOptions.bCheckDistanceSize = false;
 
     return rOptions;
 }
@@ -3066,23 +3062,103 @@ static OutputBorderOptions lcl_getBoxBorderOptions()
     rOptions.bWriteTag = false;
     rOptions.bWriteInsideHV = false;
     rOptions.bWriteDistance = true;
-    rOptions.aShadowLocation = SvxShadowLocation::NONE;
-    rOptions.bCheckDistanceSize = false;
 
     return rOptions;
 }
 
-static bool boxHasLineLargerThan31(const SvxBoxItem& rBox)
+struct BorderDistances
 {
-    return  (
-                ( rBox.GetDistance( SvxBoxItemLine::TOP ) / 20 ) > 31 ||
-                ( rBox.GetDistance( SvxBoxItemLine::LEFT ) / 20 ) > 31 ||
-                ( rBox.GetDistance( SvxBoxItemLine::BOTTOM ) / 20 ) > 31 ||
-                ( rBox.GetDistance( SvxBoxItemLine::RIGHT ) / 20 ) > 31
-            );
+    bool bFromEdge = false;
+    sal_uInt16 nTop = 0;
+    sal_uInt16 nLeft = 0;
+    sal_uInt16 nBottom = 0;
+    sal_uInt16 nRight = 0;
+};
+
+// Heuristics to decide if we need to use "from edge" offset of borders
+//
+// There are two cases when we can safely use "from text" or "from edge" offset without distorting
+// border position (modulo rounding errors):
+// 1. When distance of all borders from text is no greater than 31 pt, we use "from text"
+// 2. Otherwise, if distance of all borders from edge is no greater than 31 pt, we use "from edge"
+// In all other cases, the position of borders would be distirted on export, because Word doesn't
+// support the offset of >31 pts (https://msdn.microsoft.com/en-us/library/ff533820), and we need
+// to decide which type of offset would provide less wrong result (i.e., the result would look
+// closer to original). Here, we just check sum of distances from text to borders, and if it is
+// less than sum of distances from borders to edges. The alternative would be to compare total areas
+// between text-and-borders and between borders-and-edges (taking into account different lengths of
+// borders, and visual impact of that).
+static void CalculateExportDistances(const SvxBoxItem& rBox, const PageMargins& rMargins,
+                                     OutputBorderOptions& rOptions)
+{
+    rOptions.pDistances = std::make_shared<BorderDistances>();
+
+    const sal_uInt16 nT = rBox.GetDistance(SvxBoxItemLine::TOP);
+    const sal_uInt16 nL = rBox.GetDistance(SvxBoxItemLine::LEFT);
+    const sal_uInt16 nB = rBox.GetDistance(SvxBoxItemLine::BOTTOM);
+    const sal_uInt16 nR = rBox.GetDistance(SvxBoxItemLine::RIGHT);
+
+    // Only take into account existing borders
+    const SvxBorderLine* pLnT = rBox.GetLine(SvxBoxItemLine::TOP);
+    const SvxBorderLine* pLnL = rBox.GetLine(SvxBoxItemLine::LEFT);
+    const SvxBorderLine* pLnB = rBox.GetLine(SvxBoxItemLine::BOTTOM);
+    const SvxBorderLine* pLnR = rBox.GetLine(SvxBoxItemLine::RIGHT);
+
+    // We need to take border widths into account
+    const sal_uInt16 nWidthT = pLnT ? pLnT->GetWidth() : 0;
+    const sal_uInt16 nWidthL = pLnL ? pLnL->GetWidth() : 0;
+    const sal_uInt16 nWidthB = pLnB ? pLnB->GetWidth() : 0;
+    const sal_uInt16 nWidthR = pLnR ? pLnR->GetWidth() : 0;
+
+    // Resulting distances from text to borders
+    const sal_uInt16 nT2BT = pLnT ? nT : 0;
+    const sal_uInt16 nT2BL = pLnL ? nL : 0;
+    const sal_uInt16 nT2BB = pLnB ? nB : 0;
+    const sal_uInt16 nT2BR = pLnR ? nR : 0;
+
+    // Resulting distances from edge to borders
+    const sal_uInt16 nE2BT = pLnT ? rMargins.nPageMarginTop - nT - nWidthT : 0;
+    const sal_uInt16 nE2BL = pLnL ? rMargins.nPageMarginLeft - nL - nWidthL : 0;
+    const sal_uInt16 nE2BB = pLnB ? rMargins.nPageMarginBottom - nB - nWidthB : 0;
+    const sal_uInt16 nE2BR = pLnR ? rMargins.nPageMarginRight - nR - nWidthR : 0;
+
+    // 1. If all borders are in range of 31 pts from text
+    if ((nT2BT / 20) <= 31 && (nT2BL / 20) <= 31 && (nT2BB / 20) <= 31 && (nT2BR / 20) <= 31)
+    {
+        rOptions.pDistances->bFromEdge = false;
+    }
+    else
+    {
+        // 2. If all borders are in range of 31 pts from edge
+        if ((nE2BT / 20) <= 31 && (nE2BL / 20) <= 31 && (nE2BB / 20) <= 31 && (nE2BR / 20) <= 31)
+        {
+            rOptions.pDistances->bFromEdge = true;
+        }
+        else
+        {
+            // Let's try to guess which would be the best approximation
+            rOptions.pDistances->bFromEdge =
+                (nT2BT + nT2BL + nT2BB + nT2BR) > (nE2BT + nE2BL + nE2BB + nE2BR);
+        }
+    }
+
+    if (rOptions.pDistances->bFromEdge)
+    {
+        rOptions.pDistances->nTop = nE2BT;
+        rOptions.pDistances->nLeft = nE2BL;
+        rOptions.pDistances->nBottom = nE2BB;
+        rOptions.pDistances->nRight = nE2BR;
+    }
+    else
+    {
+        rOptions.pDistances->nTop = nT2BT;
+        rOptions.pDistances->nLeft = nT2BL;
+        rOptions.pDistances->nBottom = nT2BB;
+        rOptions.pDistances->nRight = nT2BR;
+    }
 }
 
-static void impl_borders( FSHelperPtr const & pSerializer, const SvxBoxItem& rBox, const OutputBorderOptions& rOptions, PageMargins const * pageMargins,
+static void impl_borders( FSHelperPtr const & pSerializer, const SvxBoxItem& rBox, const OutputBorderOptions& rOptions,
                           std::map<SvxBoxItemLine, css::table::BorderLine2> &rTableStyleConf )
 {
     static const SvxBoxItemLine aBorders[] =
@@ -3100,16 +3176,6 @@ static void impl_borders( FSHelperPtr const & pSerializer, const SvxBoxItem& rBo
     bool tagWritten = false;
     const SvxBoxItemLine* pBrd = aBorders;
 
-    bool bExportDistanceFromPageEdge = false;
-    if ( rOptions.bCheckDistanceSize && boxHasLineLargerThan31(rBox) )
-    {
-        // The distance is larger than '31'. This cannot be exported as 'distance from text'.
-        // Instead - it should be exported as 'distance from page edge'.
-        // This is based on http://wiki.openoffice.org/wiki/Writer/MSInteroperability/PageBorder
-        // Specifically 'export case #2'
-        bExportDistanceFromPageEdge = true;
-    }
-
     bool bWriteInsideH = false;
     bool bWriteInsideV = false;
     for( int i = 0; i < 4; ++i, ++pBrd )
@@ -3158,22 +3224,20 @@ static void impl_borders( FSHelperPtr const & pSerializer, const SvxBoxItem& rBo
         sal_uInt16 nDist = 0;
         if (rOptions.bWriteDistance)
         {
-            if (bExportDistanceFromPageEdge)
+            if (rOptions.pDistances)
             {
-                // Export 'Distance from Page Edge'
                 if ( *pBrd == SvxBoxItemLine::TOP)
-                    nDist = pageMargins->nPageMarginTop - rBox.GetDistance( *pBrd );
+                    nDist = rOptions.pDistances->nTop;
                 else if ( *pBrd == SvxBoxItemLine::LEFT)
-                    nDist = pageMargins->nPageMarginLeft - rBox.GetDistance( *pBrd );
+                    nDist = rOptions.pDistances->nLeft;
                 else if ( *pBrd == SvxBoxItemLine::BOTTOM)
-                    nDist = pageMargins->nPageMarginBottom - rBox.GetDistance( *pBrd );
+                    nDist = rOptions.pDistances->nBottom;
                 else if ( *pBrd == SvxBoxItemLine::RIGHT)
-                    nDist = pageMargins->nPageMarginRight - rBox.GetDistance( *pBrd );
+                    nDist = rOptions.pDistances->nRight;
             }
             else
             {
-                // Export 'Distance from text'
-                nDist = rBox.GetDistance( *pBrd );
+                nDist = rBox.GetDistance(*pBrd);
             }
         }
 
@@ -3322,7 +3386,7 @@ void DocxAttributeOutput::TableCellProperties( ww8::WW8TableNodeInfoInner::Point
     const SvxBoxItem& rDefaultBox = (*tableFirstCells.rbegin())->getTableBox( )->GetFrameFormat( )->GetBox( );
     {
         // The cell borders
-        impl_borders( m_pSerializer, rBox, lcl_getTableCellBorderOptions(bEcma), nullptr, m_aTableStyleConf );
+        impl_borders( m_pSerializer, rBox, lcl_getTableCellBorderOptions(bEcma), m_aTableStyleConf );
     }
 
     TableBackgrounds( pTableTextNodeInfoInner );
@@ -3826,7 +3890,7 @@ void DocxAttributeOutput::TableDefaultBorders( ww8::WW8TableNodeInfoInner::Point
     if (m_aTableStyleConf.empty())
     {
         // the defaults of the table are taken from the top-left cell
-        impl_borders(m_pSerializer, pFrameFormat->GetBox(), lcl_getTableDefaultBorderOptions(bEcma), nullptr, m_aTableStyleConf);
+        impl_borders(m_pSerializer, pFrameFormat->GetBox(), lcl_getTableDefaultBorderOptions(bEcma), m_aTableStyleConf);
     }
 }
 
@@ -6068,27 +6132,8 @@ void DocxAttributeOutput::SectionPageBorders( const SwFrameFormat* pFormat, cons
     if ( !(pBottom || pTop || pLeft || pRight) )
         return;
 
-    bool bExportDistanceFromPageEdge = false;
-    if ( boxHasLineLargerThan31(rBox) )
-    {
-        // The distance is larger than '31'. This cannot be exported as 'distance from text'.
-        // Instead - it should be exported as 'distance from page edge'.
-        // This is based on http://wiki.openoffice.org/wiki/Writer/MSInteroperability/PageBorder
-        // Specifically 'export case #2'
-        bExportDistanceFromPageEdge = true;
-    }
-
-    // All distances are relative to the text margins
-    m_pSerializer->startElementNS( XML_w, XML_pgBorders,
-           FSNS( XML_w, XML_display ), "allPages",
-           FSNS( XML_w, XML_offsetFrom ), bExportDistanceFromPageEdge ? "page" : "text",
-           FSEND );
-
     OutputBorderOptions aOutputBorderOptions = lcl_getBoxBorderOptions();
 
-    // Check if the distance is larger than 31 points
-    aOutputBorderOptions.bCheckDistanceSize = true;
-
     // Check if there is a shadow item
     const SfxPoolItem* pItem = GetExport().HasItem( RES_SHADOW );
     if ( pItem )
@@ -6106,9 +6151,16 @@ void DocxAttributeOutput::SectionPageBorders( const SwFrameFormat* pFormat, cons
     if (aGlue.HasFooter())
         aMargins.nPageMarginBottom = aGlue.dyaHdrBottom;
 
+    CalculateExportDistances(rBox, aMargins, aOutputBorderOptions);
+
+    // All distances are relative to the text margins
+    m_pSerializer->startElementNS(XML_w, XML_pgBorders,
+        FSNS(XML_w, XML_display), "allPages",
+        FSNS(XML_w, XML_offsetFrom), aOutputBorderOptions.pDistances->bFromEdge ? "page" : "text",
+        FSEND);
+
     std::map<SvxBoxItemLine, css::table::BorderLine2> aEmptyMap; // empty styles map
-    impl_borders( m_pSerializer, rBox, aOutputBorderOptions, &aMargins,
-                  aEmptyMap );
+    impl_borders( m_pSerializer, rBox, aOutputBorderOptions, aEmptyMap );
 
     m_pSerializer->endElementNS( XML_w, XML_pgBorders );
 
@@ -8570,8 +8622,7 @@ void DocxAttributeOutput::FormatBox( const SvxBoxItem& rBox )
         m_pSerializer->startElementNS( XML_w, XML_pBdr, FSEND );
 
         std::map<SvxBoxItemLine, css::table::BorderLine2> aEmptyMap; // empty styles map
-        impl_borders( m_pSerializer, rBox, aOutputBorderOptions, &m_pageMargins,
-                      aEmptyMap );
+        impl_borders( m_pSerializer, rBox, aOutputBorderOptions, aEmptyMap );
 
         // Close the paragraph's borders tag
         m_pSerializer->endElementNS( XML_w, XML_pBdr );
diff --git a/sw/source/filter/ww8/docxattributeoutput.hxx b/sw/source/filter/ww8/docxattributeoutput.hxx
index edc9688d858f..887976a53931 100644
--- a/sw/source/filter/ww8/docxattributeoutput.hxx
+++ b/sw/source/filter/ww8/docxattributeoutput.hxx
@@ -68,6 +68,8 @@ enum DocxColBreakStatus
     COLBRK_WRITE
 };
 
+struct BorderDistances;
+
 /**
  * A structure that holds information about the options selected
  * when outputting a border to DOCX.
@@ -80,15 +82,13 @@ enum DocxColBreakStatus
  */
 struct OutputBorderOptions
 {
-    sal_Int32           tag;
-    bool                bUseStartEnd;
-    bool                bWriteTag;
-    bool                bWriteInsideHV;
-    bool                bWriteDistance;
-    SvxShadowLocation   aShadowLocation;
-    bool                bCheckDistanceSize;
-
-    OutputBorderOptions() : tag(0), bUseStartEnd(false), bWriteTag(true), bWriteInsideHV(false), bWriteDistance(false), aShadowLocation(SvxShadowLocation::NONE), bCheckDistanceSize(false) {}
+    sal_Int32           tag = 0;
+    bool                bUseStartEnd = false;
+    bool                bWriteTag = true;
+    bool                bWriteInsideHV = false;
+    bool                bWriteDistance = false;
+    SvxShadowLocation   aShadowLocation = SvxShadowLocation::NONE;
+    std::shared_ptr<BorderDistances> pDistances;
 };
 
 /**