sw: fix moving of at-page anchored flys to different page

The problem is that some flys are anchored at a page with Y pos 35k and
are moved to a page with Y pos 17k, while retaining
mbFrameAreaPositionValid=true and their existing Y position.

The flys will never be painted or even invalidated again because their
position is off-page.

This is somehow a regression from commit
0b53f794ffb2550288610b9488f11fd21ab85aae - without the new mutation of
an empty-page to a normal page due to at-page flys by resetting
m_bEmptyPage in SwPageFrame::UpdateAttr_() on it the problem didn't
happen.

Due to the above commit, the page 3 is not an empty-page any more as it
has 2 flys anchored on it; previously those flys were moved (only in the
layout, not in the model!) to page 4 by some funny code in
SwRootFrame::AssertPageFlys(), which at first glance seems like an
improvement.

Change-Id: Ia071931b26e64245f90233232dd2ac0d64365ce6
Reviewed-on: https://gerrit.libreoffice.org/75009
Tested-by: Jenkins
Reviewed-by: Michael Stahl <Michael.Stahl@cib.de>

0 files changed, 0 insertions, 0 deletions