sw: fix unexpected paragraph border inside table cells

The bug document has a table cell, which contains a paragraph with
borders. Its left/right/bottom borders are rendered in Writer, but not
in Word.

The reason for the left/right border is that it's outside the
paragraph's frame area, which is not rendered in Word. Fix this by
clipping the rendered borders so they don't go outside the paragraph's
frame area. (Normally the frame area is the larger rectangle, and then
margins may cause a smaller "print area", but in this case we have a
negative right margin, so clipping the print area to fit into the frame
area actually does something.)

This is quite similar to what commit
1e21902106cbe57658bed03ed24d4d0863685cfd (tdf#117884: intersect border
with paint area of upper frame., 2018-05-26) did for table borders.

The bottom border is a different problem: the cell has a fixed height
and enough content so the paragraph is cut off vertically. This means
that technically the bottom border would be inside the frame area, but
Word cuts it off, because they apply clipping on the not-yet-cut-off
rectangle. Fix this by dropping the bottom margin when the frame is cut
off.

Change-Id: I7f65b68997330b247db65839db8a484e74f78c64
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/128569
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

3 files changed, 57 insertions, 3 deletions

diff --git a/sw/qa/core/layout/data/para-border-in-cell-clip.docx b/sw/qa/core/layout/data/para-border-in-cell-clip.docx
new file mode 100644
index 000000000000..7c516853648c
--- /dev/null
+++ b/sw/qa/core/layout/data/para-border-in-cell-clip.docx
diff --git a/sw/qa/core/layout/layout.cxx b/sw/qa/core/layout/layout.cxx
index c099cd8072ae..8b8174d76941 100644
--- a/sw/qa/core/layout/layout.cxx
+++ b/sw/qa/core/layout/layout.cxx
@@ -674,6 +674,26 @@ CPPUNIT_TEST_FIXTURE(SwCoreLayoutTest, testDoubleBorderHorizontal)
     CPPUNIT_ASSERT_GREATER(aBorderWidthVec[3], aBorderWidthVec[2]);
 }
 
+CPPUNIT_TEST_FIXTURE(SwCoreLayoutTest, testParaBorderInCellClip)
+{
+    // Given a document which has outside-cell borders defined, which should not be visible:
+    SwDoc* pDoc = createSwDoc(DATA_DIRECTORY, "para-border-in-cell-clip.docx");
+    SwDocShell* pShell = pDoc->GetDocShell();
+
+    // When rendering those borders:
+    std::shared_ptr<GDIMetaFile> xMetaFile = pShell->GetPreviewMetaFile();
+
+    // Then make sure that we have clipping setup for both paragraphs inside the table cell:
+    MetafileXmlDump dumper;
+    xmlDocUniquePtr pXmlDoc = dumpAndParse(dumper, *xMetaFile);
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: 2
+    // - Actual  : 0
+    // - XPath '//clipregion/polygon' number of nodes is incorrect
+    // i.e. there was no clipping applied, leading to unexpected left/right borders.
+    assertXPath(pXmlDoc, "//clipregion/polygon", 2);
+}
+
 CPPUNIT_PLUGIN_IMPLEMENT();
 
 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */
diff --git a/sw/source/core/layout/paintfrm.cxx b/sw/source/core/layout/paintfrm.cxx
index 413bec974299..868817ff5147 100644
--- a/sw/source/core/layout/paintfrm.cxx
+++ b/sw/source/core/layout/paintfrm.cxx
@@ -119,6 +119,7 @@
 #include <comphelper/lok.hxx>
 #include <svtools/optionsdrawinglayer.hxx>
 #include <vcl/GraphicLoader.hxx>
+#include <basegfx/polygon/b2dpolygontools.hxx>
 
 using namespace ::editeng;
 using namespace ::com::sun::star;
@@ -5359,6 +5360,25 @@ void SwFrame::PaintSwFrameShadowAndBorder(
             pBottomBorder = aAccess.Get()->GetBox().GetBottom();
         }
 
+        bool bWordTableCell = false;
+        SwViewShell* pShell = getRootFrame()->GetCurrShell();
+        if (pShell)
+        {
+            const IDocumentSettingAccess& rIDSA = pShell->GetDoc()->getIDocumentSettingAccess();
+            bWordTableCell = rIDSA.get(DocumentSettingId::TABLE_ROW_KEEP);
+        }
+        bool bInWordTableCell = IsContentFrame() && GetUpper()->IsCellFrame() && bWordTableCell;
+        if (bInWordTableCell)
+        {
+            // Compat mode: don't paint bottom border if we know the bottom of the content was cut
+            // off.
+            auto pContentFrame = static_cast<const SwContentFrame*>(this);
+            if (pContentFrame->IsUndersized())
+            {
+                pBottomBorder = nullptr;
+            }
+        }
+
         if(nullptr != pLeftBorder || nullptr != pRightBorder || nullptr != pTopBorder || nullptr != pBottomBorder)
         {
             // now we have all SvxBorderLine(s) sorted out, create geometry
@@ -5372,14 +5392,28 @@ void SwFrame::PaintSwFrameShadowAndBorder(
             const svx::frame::Style aStyleLeft(pLeftBorder, 1.0);
             drawinglayer::primitive2d::Primitive2DContainer aBorderLineTarget;
 
-            aBorderLineTarget.append(
-                drawinglayer::primitive2d::Primitive2DReference(
+            drawinglayer::primitive2d::Primitive2DReference aRetval(
                     new drawinglayer::primitive2d::SwBorderRectanglePrimitive2D(
                         aBorderTransform,
                         aStyleTop,
                         aStyleRight,
                         aStyleBottom,
-                        aStyleLeft)));
+                        aStyleLeft));
+
+            if (bInWordTableCell)
+            {
+                // Compat mode: cut off the borders which are outside of our own area.
+                const SwRect& rClip = getFrameArea();
+                basegfx::B2DRectangle aClip(rClip.Left(), rClip.Top(), rClip.Right(),
+                                            rClip.Bottom());
+                const basegfx::B2DPolyPolygon aPolyPolygon(
+                    basegfx::utils::createPolygonFromRect(aClip));
+                const drawinglayer::primitive2d::Primitive2DReference xClipped(
+                    new drawinglayer::primitive2d::MaskPrimitive2D(aPolyPolygon, { aRetval }));
+                aRetval = xClipped;
+            }
+
+            aBorderLineTarget.append(aRetval);
             gProp.pBLines->AddBorderLines(std::move(aBorderLineTarget));
         }
     }