sw: if the fly is to be split, then limit its growth in SwFlyFrame::Format()

It seems the first direct cause why flys are not split is because flys
can grow forever, so an inner paragraph's SwContentFrame::MakeAll() will
never hit the nBottomDist < 0 condition, which is necessary to call into
SwFlowFrame::MoveFwd().

With this, at least nBottomDist is negative when a fly with two
paragraphs is at the bottom of a page and only one of them fits the body
frame.

Also add a debug environment variable, so I can debug the "fly split"
case till we don't have import/export filters for this.

Towards an initial layout for multi-page fly frames.

Change-Id: I43114b5795dd42e518a1d776ccd2e7ab607ad859
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/146376
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

2 files changed, 25 insertions, 0 deletions

diff --git a/sw/source/core/attr/formatflysplit.cxx b/sw/source/core/attr/formatflysplit.cxx
index 72816b2ead4e..bcbfcc2d5e96 100644
--- a/sw/source/core/attr/formatflysplit.cxx
+++ b/sw/source/core/attr/formatflysplit.cxx
@@ -21,6 +21,15 @@
 
 #include <libxml/xmlwriter.h>
 
+SwFormatFlySplit::SwFormatFlySplit(bool bSplit)
+    : SfxBoolItem(RES_FLY_SPLIT, bSplit)
+{
+    if (getenv("SW_FORCE_FLY_SPLIT"))
+    {
+        SetValue(true);
+    }
+}
+
 SwFormatFlySplit* SwFormatFlySplit::Clone(SfxItemPool*) const
 {
     return new SwFormatFlySplit(*this);
diff --git a/sw/source/core/layout/fly.cxx b/sw/source/core/layout/fly.cxx
index 4cee6d9e712d..1ece49fb78b5 100644
--- a/sw/source/core/layout/fly.cxx
+++ b/sw/source/core/layout/fly.cxx
@@ -75,6 +75,7 @@
 #include <bodyfrm.hxx>
 #include <FrameControlsManager.hxx>
 #include <ndtxt.hxx>
+#include <formatflysplit.hxx>
 
 using namespace ::com::sun::star;
 
@@ -1303,6 +1304,21 @@ void SwFlyFrame::Format( vcl::RenderContext* /*pRenderContext*/, const SwBorderA
             if ( nRemaining < MINFLY )
                 nRemaining = MINFLY;
 
+            const SwFrame* pAnchor = GetAnchorFrame();
+            const SwFrame* pAnchorUpper = pAnchor ? pAnchor->GetUpper() : nullptr;
+            if (pAnchorUpper && GetFormat()->GetFlySplit().GetValue())
+            {
+                // If the fly is allowed to be split, then limit its size to the upper of the
+                // anchor.
+                SwTwips nDeadline = aRectFnSet.GetPrtBottom(*pAnchorUpper);
+                SwTwips nTop = aRectFnSet.GetTop(getFrameArea());
+                SwTwips nBottom = aRectFnSet.GetTop(getFrameArea()) + nRemaining;
+                if (nBottom > nDeadline)
+                {
+                    nRemaining = nDeadline - nTop;
+                }
+            }
+
             {
                 SwFrameAreaDefinition::FramePrintAreaWriteAccess aPrt(*this);
                 aRectFnSet.SetHeight( aPrt, nRemaining );