Package: diffpdf
Version: 2.1.3.1-2
Control: affects -1 gnome
After upgrading Debian 11 to Debian 12, changes to the Zoom field stopped taking immediate effect. Reproduce:
1) Start a gnome session.
2) diffpdf any two different files (it suffices that the first page differs visibly, character-wise, and word-wise), e.g.,
LC_ALL=C diffpdf /usr/share/texmf/doc/bibtex/biber/biber.pdf /usr/share/texmf/doc/latex/preview/preview.pdf &
3) Observe the following printed to the console:
QSocketNotifier: Can only be used with threads started with QThread QObject::connect: Cannot queue arguments of type 'QTextBlock' (Make sure 'QTextBlock' is registered using qRegisterMetaType().) QObject::connect: Cannot queue arguments of type 'QTextCursor' (Make sure 'QTextCursor' is registered using qRegisterMetaType().)
4) Alter the “Zoom:” field (in our example, from 154 % to 800 %) and Press [Enter].
5) Observe no change to the view (screenshot attached).
We expect that at last step, the view also changes (in our example, we'd expect enlarged contents). This was the case in diffpdf in Debian 11. The new, erroneous behavior occurs in both X.Org and Wayland. Now in order to observe the page in a new zoom, we have to click “← Previous” and then “→ Next” or close diffpdf and re-open it.
A bugfix is needed.
Gratefully,
AlMa

In my recollection of Debian 11, even changing a single digit in the Zoom field led to an immediate redraw, i.e., even before pressing ⏎.  So the current situation is double worse.
As of how it _should_ be, I think that whenever a keyboard is attached, only hitting [Enter] or moving the cursor (or, perhaps, the focus) elsewhere should incur a change in the view. If no real or virtual keyboard is attached (which is hard to imagine, but the world is huge), also changing a single digit should incur a change in the view.
Gratefully,
AlMa

retitle 1041494 diffpdf: changes to zoom for small documents (⩽ 19 pages in at least one file) don't take effect on ↩
thanks
You have to take small documents to reproduce this CLEANLY.  Presumably at least one of the two compared PDF files must have at most 19 pages to reproduce this cleanly.  E.g., run pdflatex on one file containing
\documentclass[ngerman]{article} \usepackage{babel} \usepackage[bible]{blindtext} \begin{document} \Blindtext[87] \end{document}
and then run pdflatex on another file containing
\documentclass[ngerman]{article} \usepackage{babel} \usepackage[random]{blindtext} \begin{document} \Blindtext[49] \end{document}
and diffpdf the results.
If each of the compared PDF files has at least 20 pages, another bug kicks in, namely, http://bugs.debian.org/1051422 http://bugs.debian.org/1051422. In short, the function of the zoom field is very broken; please repair this.
Gratefully,
Alma