tdf#123636 writerfilter: handle deferred breaks on frames

...similar to handling breaks before shapes in lcl_startShape.

Three different examples found to create/split a paragraph.
Which one to use? (addDummy, m_bIsSplitPara, and
lcl_startCharacterGroup). SplitPara is not good because the
paragraph properties probably should not be copied to the
dummy paragraph (like numbering for example). Slightly
modified the lcl_startChar example to ensure that the dummy
paragraph doesn't steal a part of the properties, but is
only default properties plus page-break.

This doesn't export very well, so roundtripping is very poor.

Research Note: There exists a compat flag showBreaksInFrames
(Display Page/Column Breaks Present in Frames)
"This element specifies whether applications should
honor the presence of page and/or column breaks which are
present within the contents of paragraphs which have been
defined as frames using the framePr element."
--Currently, LO does nothing with this flag. Probably too
exotic and irrelevant (word 2003 era?).

No existing unit tests found that have isSet(pg_brk) frames.

Change-Id: I29f815355401c7af8b347a3ed9d0298bc9b27b93
Reviewed-on: https://gerrit.libreoffice.org/71255
Tested-by: Jenkins
Reviewed-by: Justin Luth <justin_luth@sil.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>

sw/qa/extras/ooxmlexport/ooxmlexport13.cxx

@@ -97,7 +97,8 @@ DECLARE_OOXMLEXPORT_TEST(testTdf123636_newlinePageBreak2, "tdf123636_newlinePage
 {
     //WITHOUT SplitPgBreakAndParaMark: a following anchored shape should force a page break
     //CPPUNIT_ASSERT_EQUAL_MESSAGE( "Number of Paragraphs", 2, getParagraphs() );
-    //CPPUNIT_ASSERT_EQUAL_MESSAGE( "Number of Pages", 2, getPages() );
+    CPPUNIT_ASSERT_EQUAL(OUString(), getProperty<OUString>(getParagraph(2, ""), "NumberingStyleName"));
+    CPPUNIT_ASSERT_EQUAL_MESSAGE( "Number of Pages", 2, getPages() );
 }
 
 DECLARE_OOXMLEXPORT_TEST(testTdf123636_newlinePageBreak3, "tdf123636_newlinePageBreak3.docx")

writerfilter/source/dmapper/DomainMapper.cxx

@@ -1965,6 +1965,22 @@ void DomainMapper::sprmWithProps( Sprm& rSprm, const PropertyMapPtr& rContext )
         PropertyMapPtr pContext = m_pImpl->GetTopContextOfType(CONTEXT_PARAGRAPH);
         if( pContext.get() )
         {
+            // If there is a deferred page break applied to this framed paragraph,
+            // create a dummy paragraph without extra properties,
+            // so that the anchored frame will be on the correct page (similar to shapes).
+            if (pContext->isSet(PROP_BREAK_TYPE))
+            {
+                pContext->Erase(PROP_BREAK_TYPE);
+
+                lcl_startParagraphGroup();
+                m_pImpl->GetTopContext()->Insert(PROP_BREAK_TYPE, uno::makeAny(style::BreakType_PAGE_BEFORE));
+                lcl_startCharacterGroup();
+                sal_uInt8 const sBreak[] = { 0xd };
+                lcl_text(sBreak, 1);
+                lcl_endCharacterGroup();
+                lcl_endParagraphGroup();
+            }
+
             ParagraphPropertyMap* pParaContext = dynamic_cast< ParagraphPropertyMap* >( pContext.get() );
             if (pParaContext)
                 pParaContext->SetFrameMode();