Created attachment 165100 [details] Master doc Step to reproduce : 1 Open Master doc 2 Export as PDF 3 Open Child doc 4 Export as PDF PDF should be the same Works fine with AOO (even if the rendering is not the same, both PDF are the same
Created attachment 165101 [details] Child doc
Created attachment 165102 [details] PDF of master doc with LO
Created attachment 165103 [details] PDF of child doc with LO
Created attachment 165104 [details] PDF of master doc with AOO
Created attachment 165105 [details] PDF of child doc with AOO
No need to go through the whole rigmarole of comparing PDFs. It can easily be seen just by loading up the document and seeing a gap above the gray title shading. Bibisected to LO 5.3 author Justin Luth on 2016-11-03 19:02:41 +0000 commit 5d9d0f3c979732ade57b9c4c4960dd030ffdc9f9 there is a function for that: CalcLineSpace(xx, bEvenIfNoLine) which is a dud commit that really points to bug 41542, which is about using the border spacing even when border lines are not enabled - as per ODF specs. It looks to me like the master document is copying the border padding from the first paragraph of the child document. So you will likely see the same thing in AOO if you add a border to child.odt's title. (I see that in LO 3.5 - as far back as I can test.) So for this particular document, you can "fix" it by removing the paragraph's borderless padding of .44cm. It seems strange to me that the border padding would be copied, because it doesn't seem to copy the borders themselves. I'll make this bug report NEW to investigate that question.
So I found the source of the problem. It is a layout issue. Yuck. In calcmove.cxx's SwLayoutFrame::MakeAll the sectionfrm somehow acquires the border padding from what seems to be a random cache, with pAccess = std::make_unique<SwBorderAttrAccess>(SwFrame::GetCache(), this); This looks like a really generic piece of code, so I don't have high hopes of being able to fix it.
repro 7.6+ Steps to reproduce: -download both files -open Doc maitre 01.odm -edit the link (in the popup navigator) to point to Titre...odt -update: now you should see the contents of Titre in Doc maitre 01. -and it looks fine now. -save and reload -now you see the gap at the top of the page.