[Libreoffice-bugs] [Bug 132212] Text flow not correct after loading a large document

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=132212

--- Comment #20 from Jan-Marek Glogowski <glogow at fbihome.de> ---
(In reply to Telesto from comment #18)
> @Jan-Marek. 
> 
> Adding again.. this is related to timer/scheduler anyhow.

Maybe, but more likely it's Writer's idle layouter to blame. It's probably not
a problem of the scheduler per-se.

> * The bug doc has 366 pages after bunch of Timer/scheduler changes by Tobias
> Madl. Before 469/471
> * There are cases of text behind images.. which likely correlate with number
> of pages (however didn't notice the issue in some cases; or didn't look good
> enough for them)..

So I opened the attached document. What I see is:

* Generally, on open, the TOC has the last entry as "Release information -
363".
* The TOC changes on TOC update (context menu -> "Update Index/Table").
* LO 4.4.7:
  * On open, LO claims the document has 467 pages
  * After TOC update: 371 pages; last TOC entry is "Release information - 366"
  * The layout will sometimes be updated by scrolling with PgUp / PgDn, if LO
detects a wrong layout
* LO 7.0 / master a few days old:
  * On open, the document instantly shows as 367 pages
  * After TOC update: still 367 pages; last TOC entry is "Release information -
362"

So we have 371 vs 367, which is IMHO still a lot, but currently I would just
claim bug fixes and better layout, eventually from changing to Harfbuzz test
rendering or our own fixes.

Some observation:
* A particular bad page here is 23. In 4.4 it just contains a single line here,
which moves to page 22 in 7.0.
* I also saw some overlapping image problems in 4.4, even after triggering the
TOC update. But generally they are hard to spot here.

So currently my conclusion is that 4.4 is more buggy then current master w.r.t
this document. The initial scheduler rewrite might even have fixed some stuff.
Actually I don't see a problem here with master.

Eventually related bug: there was bug 123257 / bug 119748 / bug 131707, which
is hopefully finally fixed in master since 2020-04-03, which originally looked
like a scheduler bug, but turned out to be a Writer layouter bug. The exact
triggering condition was indeed the flow setting of the images, which was
ignored in some obscure circumstances, I still don't fully understand. The
default setting in the code is flow-through, so that's why the bug manifested
(actually that is good, as these bugs would go unnoticed otherwise, I guess).

BTW: the fix is small, but since 6.4 is almost still and layout changes tend to
regress, no backport was done. 

P.S. it still might be a scheduler bug on Windows, since I've done all this on
Linux.

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