sw: fix layout loop due to a keep-with-next vs 100% image height conflict

The document in question has a landscape page, the last paragraph has an
image where the width is 100% and the height is set to keep the ratio
(which 1:1). This means that SwFlyFreeFrame::CheckClip() will scale the
image down, so the image fits the page (and give up that 100% width was
requested).

The next problem is that this image has a wrap type set to none, so not
only the total height of the page is taken, but also no content is
allowed on the left/right side, effectively taking the entire body
frame. Combine this with a previous paragraph, which is a heading, so
keep-with-next is set for it. Layout loops because keep-with-next and
take-the-entire-page are conflicting requirements and we used to have no
explicit code to relax one of them when both are present:

SwFlowFrame::MoveBwd: frame is 4, old upper is 10, new upper is 2
SwFlowFrame::MoveFwd: frame is 4, old upper is 2, new upper is 10
SwFlowFrame::MoveBwd: frame is 4, old upper is 10, new upper is 2
SwFlowFrame::MoveFwd: frame is 4, old upper is 2, new upper is 10
SwFlowFrame::MoveBwd: loop control, frame is 4, old upper is 10, new upper would be 2, but not moving there

Fix the problem by giving up keep-with-next to stop the loop, mostly
because we have to give up one of the requirements and Word resolves the
conflict this way.

Change-Id: I7da1ebcff9302cd144887f63efb94e0b2b2be8fd
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/108119
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

1 files changed, 57 insertions, 1 deletions

diff --git a/sw/source/core/layout/flowfrm.cxx b/sw/source/core/layout/flowfrm.cxx
index 7b91a1bc74cc..aeeb9df158cf 100644
--- a/sw/source/core/layout/flowfrm.cxx
+++ b/sw/source/core/layout/flowfrm.cxx
@@ -176,6 +176,61 @@ void SwFlowFrame::CheckKeep()
         pPre->InvalidatePos();
 }
 
+namespace
+{
+/**
+ * Determines if the next content frame after rThis will require the full area of the parent body
+ * frame.
+ */
+bool IsNextContentFullPage(const SwFrame& rThis)
+{
+    const SwFrame* pNext = rThis.FindNextCnt();
+    if (!pNext)
+    {
+        return false;
+    }
+
+    const SwSortedObjs* pNextDrawObjs = pNext->GetDrawObjs();
+    if (!pNextDrawObjs || !pNextDrawObjs->size())
+    {
+        return false;
+    }
+
+    for (const auto& pDrawObj : *pNextDrawObjs)
+    {
+        if (!pDrawObj)
+        {
+            continue;
+        }
+
+        SwTwips nDrawObjHeight = pDrawObj->GetObjRectWithSpaces().Height();
+        const SwPageFrame* pPageFrame = pDrawObj->GetPageFrame();
+        if (!pPageFrame)
+        {
+            continue;
+        }
+
+        SwTwips nBodyHeight = pPageFrame->GetLower()->getFrameArea().Height();
+        if (nDrawObjHeight < nBodyHeight)
+        {
+            continue;
+        }
+
+        const SwFormatSurround& rSurround = pDrawObj->GetFrameFormat().GetSurround();
+        if (rSurround.GetSurround() != text::WrapTextMode_NONE)
+        {
+            continue;
+        }
+
+        // At this point the height of the draw object will use all the vertical available space,
+        // and also no wrapping will be performed, so all horizontal space will be taken as well.
+        return true;
+    }
+
+    return false;
+}
+}
+
 bool SwFlowFrame::IsKeep(SvxFormatKeepItem const& rKeep,
         SvxFormatBreakItem const& rBreak,
         bool const bCheckIfLastRowShouldKeep) const
@@ -186,10 +241,11 @@ bool SwFlowFrame::IsKeep(SvxFormatKeepItem const& rKeep,
     // 3. If bBreakCheck is set to true, this function only checks
     //    if there are any break after attributes set at rAttrs
     //    or break before attributes set for the next content (or next table)
+    // 4. Keep is ignored if the next frame will require its own page.
     bool bKeep = bCheckIfLastRowShouldKeep ||
                  (  !m_rThis.IsInFootnote() &&
                     ( !m_rThis.IsInTab() || m_rThis.IsTabFrame() ) &&
-                    rKeep.GetValue() );
+                    rKeep.GetValue() && !IsNextContentFullPage(m_rThis));
 
     OSL_ENSURE( !bCheckIfLastRowShouldKeep || m_rThis.IsTabFrame(),
             "IsKeep with bCheckIfLastRowShouldKeep should only be used for tabfrms" );