Dolphin preview plugins [Kubuntu Wily 15.10]

[Leonardo Giordani]

Hi all,

first of all many thanks for your work on Kubuntu. I have been using it
exclusively for the last 5 years so it is an important part of my daily
life.

I have some issues with Dolphin and previews, and wanted to ask some
details about the whole system. I will point out some problems (in my
opinion), but I just want to understand and perhaps help improving Kubuntu.

My issue starts with a fresh installation of Kubuntu Wily, where Dolphin
does not previews PDFs. So I went to Control -> Configure Dolphin... ->
General - >Previews and found the following available choices ("#" marks
the active ones):

* Comic Books
# Folders
* Font files
# Images (GIF, PNG, BMP, ...)
# JPEG Images
* SVG Images
* Text Files

First problem: it is incredibly difficult to find updated information on
this matter. Is there an official manual somewhere? How is a new user
supposed to find how to add new choices? All I can find are old blog and
forum posts related to KDE4.

Second thought: I would install the required packages by default, and the
same for video thumbnails.

On some KDE4-related forums this issue is solved by installing the
kdegraphics-thumbnailers package, so I tried investigating it. Installing
it does not change the set of preview choices in Dolphin, however.

This package installs things in /usr/lib/kde4 (e.g.
/usr/lib/kde4/gsthumbnail.so) and /usr/share/kde4/services (e.g.
/usr/share/kde4/services/gsthumbnail.desktop). Looking around in the
system, however I found that KDE5 services are in /usr/share/kservices5.

Where does Dolphin look for thumbnailer plugins? How is this configured?

Moreover, there are two installed jpegthumbnail.so, one coming from
kde-runtime (/usr/lib/kde4/jpegthumbnail.so) and another coming from
kio-extras (/usr/lib/x86_64-linux-gnu/qt5/plugins/jpegthumbnail.so). What's
the difference? The file /usr/share/kservices5/jpegthumbnail.desktop is
then installed by kio-extras-data, while
/usr/share/kde4/services/jpegthumbnail.desktop is installed by
kde-runtime-data. I'm very confused.

A summary of my questions:

* Is it possible to improve UX in adding/removing Dolphin preview plugins?
* Is it possible to consider installing PDF and video thumbnails by default?
* How are PDF previews enabled on Wily?
* Where does Dolphin look for thumbnailer plugins and how to configure it?
* What is the difference between the kde-runtime thumbnailers (e.g.
jpegthumbnail.so)
and the kio-extras ones?
* What is the difference between kio-extras-data .desktop files and
kde-runtime-data
ones?

Thank you very much in advance

Leo



Leonardo Giordani
@tw_lgiordani <http://twitter.com/tw_lgiordani> - lgiordani.com
My profile on About.me <http://about.me/leonardo.giordani> - My GitHub page
<https://github.com/lgiordani>
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