tdf#119875 sw: fix invalid pos of frame after 0-sized section with laycache

The interesting part of the layout of page 2 is:

- frame #40 is a section frame with a text frame which is in a list
  ("A")
- frame #48 is a section frame after that, with the same top=19213

Given that frame #40 has height > 0, they overlap when the page is
rendered. What happens is:

- frame #40 grows
- there are other section frames between #40 and #48 in-between, but
  they don't have an SwSection
- these frames are skipped
- then the position of #48 is invalidated

So the next time we calculate the position of #48, we look the last
skipped (previous) section frame (which still has top=19213, since its
position was not invalidated above), and since its height is 0, we
conclude that our current top=19213 is valid after all.

This is like this since commit 84a3db80b4fd66c6854b3135b5f69b61fd828e62
(initial import, 2000-09-18), so leave the code there that invalidates
not only the next frame, but all the way down to the first
non-SwSection-less-SwSectionFrame. But instead of just invalidating the
last frame, invalidate the in-between SwSection-less-SwSectionFrames as
well.

In practice this did not cause a problem in case the document has no
layout cache. If it does, then the frames are created on pages hinted by
the cache, then later moved to their final place. In practice this bug
was visible only in this later case. (I.e. such a layout cache can be
only created if the machine that saved the document last time does not
have the fonts needed by the document installed; and then the document
is opened on an other machine which has those fonts.)

(cherry picked from commit b5937112d4035fb9ffb472e1bf36567d9c78c820)

Conflicts:
	sw/qa/extras/layout/layout.cxx

Reviewed-on: https://gerrit.libreoffice.org/60658
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>
(cherry picked from commit e850b5a1283485273b91135df15cae7faaac3861)

Change-Id: I02ae9f63d0b4b5e9d014df53ed2cf21a04b15090

3 files changed, 39 insertions, 4 deletions

diff --git a/sw/qa/extras/layout/data/tdf119875.odt b/sw/qa/extras/layout/data/tdf119875.odt
new file mode 100644
index 000000000000..6f579546e312
--- /dev/null
+++ b/sw/qa/extras/layout/data/tdf119875.odt
diff --git a/sw/qa/extras/layout/layout.cxx b/sw/qa/extras/layout/layout.cxx
index 8c9740b7e2ae..5dee5c580402 100644
--- a/sw/qa/extras/layout/layout.cxx
+++ b/sw/qa/extras/layout/layout.cxx
@@ -23,6 +23,7 @@ public:
     void testTdf117923();
     void testTdf118058();
     void testTdf117188();
+    void testTdf119875();
 
     CPPUNIT_TEST_SUITE(SwLayoutWriter);
     CPPUNIT_TEST(testTdf116830);
@@ -31,6 +32,7 @@ public:
     CPPUNIT_TEST(testTdf117923);
     CPPUNIT_TEST(testTdf118058);
     CPPUNIT_TEST(testTdf117188);
+    CPPUNIT_TEST(testTdf119875);
     CPPUNIT_TEST_SUITE_END();
 
 private:
@@ -156,6 +158,19 @@ void SwLayoutWriter::testTdf117188()
     assertXPath(pXmlDoc, "/root/page/body/txt/anchored/fly/infos/prtBounds", "height", sHeight);
 }
 
+void SwLayoutWriter::testTdf119875()
+{
+    createDoc("tdf119875.odt");
+    xmlDocPtr pXmlDoc = parseLayoutDump();
+    sal_Int32 nFirstTop
+        = getXPath(pXmlDoc, "/root/page[2]/body/section[1]/infos/bounds", "top").toInt32();
+    sal_Int32 nSecondTop
+        = getXPath(pXmlDoc, "/root/page[2]/body/section[2]/infos/bounds", "top").toInt32();
+    // The first section had the same top value as the second one, so they
+    // overlapped.
+    CPPUNIT_ASSERT_LESS(nSecondTop, nFirstTop);
+}
+
 CPPUNIT_TEST_SUITE_REGISTRATION(SwLayoutWriter);
 CPPUNIT_PLUGIN_IMPLEMENT();
 
diff --git a/sw/source/core/layout/sectfrm.cxx b/sw/source/core/layout/sectfrm.cxx
index 3790c92a199d..f456da19b54d 100644
--- a/sw/source/core/layout/sectfrm.cxx
+++ b/sw/source/core/layout/sectfrm.cxx
@@ -44,6 +44,21 @@
 #include <flyfrms.hxx>
 #include <sortedobjs.hxx>
 
+namespace
+{
+/**
+ * Performs the correct type of position invalidation depending on if we're in
+ * CalcContent().
+ */
+void InvalidateFramePos(SwFrame* pFrame, bool bInCalcContent)
+{
+    if (bInCalcContent)
+        pFrame->InvalidatePos_();
+    else
+        pFrame->InvalidatePos();
+}
+}
+
 SwSectionFrame::SwSectionFrame( SwSection &rSect, SwFrame* pSib )
     : SwLayoutFrame( rSect.GetFormat(), pSib )
     , SwFlowFrame( static_cast<SwFrame&>(*this) )
@@ -2121,15 +2136,20 @@ SwTwips SwSectionFrame::Grow_( SwTwips nDist, bool bTst )
                 }
                 if( GetNext() )
                 {
+                    // Own height changed, need to invalidate the position of
+                    // next frames.
                     SwFrame *pFrame = GetNext();
                     while( pFrame && pFrame->IsSctFrame() && !static_cast<SwSectionFrame*>(pFrame)->GetSection() )
+                    {
+                        // Invalidate all in-between frames, otherwise position
+                        // calculation (which only looks back to one relative
+                        // frame) will have an incorrect result.
+                        InvalidateFramePos(pFrame, bInCalcContent);
                         pFrame = pFrame->GetNext();
+                    }
                     if( pFrame )
                     {
-                        if( bInCalcContent )
-                            pFrame->InvalidatePos_();
-                        else
-                            pFrame->InvalidatePos();
+                        InvalidateFramePos(pFrame, bInCalcContent);
                     }
                 }
                 // #i28701# - Due to the new object positioning