tdf#86578: sw: fix rendering of legacy documents with fly achored at fly

Resurrect the special hack "lcl_SubtractFlys" that effectively paints
"lower" flys on top of "higher" flys, defying the z-ordering, if the
lower fly is *anchored* in or at the higher fly.

It turns out that this is not obvious to emulate in any other way that it
is currently implemented:

One idea would be to split up painting of the fly background from the
foreground, by creating 2 different view objects per fly as children
of the SdrPage when decomposing it in svx; but the problem is, they will
be ordered in z-order of the flys, and the point would be to paint the
backgrounds first and in a different order, call it "anchoring order".

What that order should be is hard to tell, there is a conflict between
the defined z-order and the flys that are part of one "anchoring
hierarchy" and should have their backgrounds re-ordered, because
entirely unrelated flys that could belong to different "anchoring
hierarchies" but overlap the first ones may result in a cyclic ordering.

Painting one "anchoring hierarchy" recursively would not get
z-order of flys from different anchoring hierarchies right.

Another difficulty is that heaven-layer backgrounds would need to be
painted before hell-layer ones.

Another aspect of the lcl_SubtractFlys is that it entirely ignores
drawing shapes; only Writer's own flys are handled.

Since none of the above makes much sense, we clearly want to
deprecate the lcl_SubtractFlys rendering.

Introduce a new compatibility flag "SubtractFlysAnchoredAtFlys" so that
the legacy rendering is only active for legacy documents, while new ones
remain free from its taint.

(regression from 6e61ecd09679a66060f932835622821d39e92f01)

Change-Id: I710fe79710b89c8f865ebb7162e14713aac6cc4a

1 files changed, 6 insertions, 0 deletions

diff --git a/sw/source/core/doc/DocumentSettingManager.cxx b/sw/source/core/doc/DocumentSettingManager.cxx
index ba6511c44646..83ba90f99e78 100644
--- a/sw/source/core/doc/DocumentSettingManager.cxx
+++ b/sw/source/core/doc/DocumentSettingManager.cxx
@@ -81,6 +81,7 @@ sw::DocumentSettingManager::DocumentSettingManager(SwDoc &rDoc)
     mbTabOverMargin(false),
     mbSurroundTextWrapSmall(false),
     mbPropLineSpacingShrinksFirstLine(true),
+    mbSubtractFlys(false),
     mApplyParagraphMarkFormatToNumbering(false),
     mbLastBrowseMode( false )
 
@@ -156,6 +157,7 @@ bool sw::DocumentSettingManager::get(/*[in]*/ DocumentSettingId id) const
         case DocumentSettingId::TAB_OVER_MARGIN: return mbTabOverMargin;
         case DocumentSettingId::SURROUND_TEXT_WRAP_SMALL: return mbSurroundTextWrapSmall;
         case DocumentSettingId::PROP_LINE_SPACING_SHRINKS_FIRST_LINE: return mbPropLineSpacingShrinksFirstLine;
+        case DocumentSettingId::SUBTRACT_FLYS: return mbSubtractFlys;
 
         case DocumentSettingId::BROWSE_MODE: return mbLastBrowseMode; // Attention: normally the SwViewShell has to be asked!
         case DocumentSettingId::HTML_MODE: return mbHTMLMode;
@@ -322,6 +324,10 @@ void sw::DocumentSettingManager::set(/*[in]*/ DocumentSettingId id, /*[in]*/ boo
             mbPropLineSpacingShrinksFirstLine = value;
             break;
 
+        case DocumentSettingId::SUBTRACT_FLYS:
+            mbSubtractFlys = value;
+            break;
+
         // COMPATIBILITY FLAGS END
 
         case DocumentSettingId::BROWSE_MODE: //can be used temporary (load/save) when no SwViewShell is available