[dolphin] [Bug 413648] New: Dolphin File-Manager Doesn't Create Thumbnails when Using the 'gtk2' Style of 'qtstyleplugins'

[Jamie Michelle]

https://bugs.kde.org/show_bug.cgi?id=413648

            Bug ID: 413648
           Summary: Dolphin File-Manager Doesn't Create Thumbnails when
                    Using the 'gtk2' Style of 'qtstyleplugins'
           Product: dolphin
           Version: unspecified
          Platform: Archlinux Packages
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: dolphin-bugs-null at kde.org
          Reporter: ladyjamie at yahoo.com
                CC: kfm-devel at kde.org
  Target Milestone: ---

Hi, everyone. When the Arch Linux-based package 'qt5-styleplugins' is used and
the environment variable QT_QPA_PLATFORMTHEME= is set on "gtk2", or "qt5ct"
with its interface set on Appearance > Style: gtk2, the Dolphin file-manager
will not create new thumbnails, although thumbnails that were previously
created (such as with Thunar, or Dolphin not using "gtk2") will be shown. This
problem doesn't occur with the other styles of 'qtstyleplugins'.

I traced this problem back to GLib. The problem was introduced with the
following package, and remains in later versions:

glib2-2.62.1-1-x86_64.pkg.tar.xz

The following version and previous versions work properly:

glib2-2.60.6-1-x86_64.pkg.tar.xz

However, using this previous version breaks some (but not all) GTK+ 3 programs.

How I tracked the problem to GLib was that I replaced (using 'downgrade') with
previous known working versions any package that I thought might be connected
to Dolphin's thumbnailing or its theming (including Dolphin itself), yet
nothing had any effect. Then I thought to start Dolphin in a 'uxterm' in order
to see the output. That's when I saw that GLib was outputting errors that were
causing '/usr/lib/qt/plugins/kf5/kio/thumbnail.so' to crash. Upon seeing that,
when I replaced the GLib package as related above, thumbnailing worked.

What I take the GLib error messages (involving 'platform_get_argv0' in the
output) to mean is that GLib doesn't recognize the platform "gtk2", and that
then causes 'thumbnail.so' to crash. Thus, in order for 'thumbnail.so' to work,
apparently it requires GLib not to exit with error messages like that upon not
recognizing the platform.

I here provide links to three PNGs of 'uxterm' output when Dolphin is started
in it. 'Dolphin-thumbnailing-working-Windows-style-via-qt5ct.png' is when the
'qt5ct' program is set on the "Windows" style, and thumbnailing works.
'Dolphin-thumbnailing-failing-gtk2-style-via-qt5ct.png' is when the 'qt5ct'
program is set on the "gtk2" style, and thumbnailing doesn't work.
'Dolphin-thumbnailing-failing-gtk2-style-direct.png' is when
QT_QPA_PLATFORMTHEME= is directly set on "gtk2", and thumbnailing doesn't work.

* Dolphin-thumbnailing-working-Windows-style-via-qt5ct.png ,
https://ibb.co/TWBqj4f , https://archive.is/VTMQO .

* Dolphin-thumbnailing-failing-gtk2-style-via-qt5ct.png ,
https://ibb.co/VYd1145 , https://archive.is/5As1p .

* Dolphin-thumbnailing-failing-gtk2-style-direct.png , https://ibb.co/7ypN042 ,
https://archive.is/lPQkw .

Whether the style is set via the 'qt5ct' program or is directly set with
QT_QPA_PLATFORMTHEME= doesn't matter to this problem. If "gtk2" is the style,
thumbnailing fails either way, yet every other style works.

This problem is quite unfortunate because I use the "gtk2" style for Qt 5
programs, and Dolphin is my primary file-manager. Further, this breaks my
Computing Machine desktop-environment theme ( https://www.pling.com/p/1315191/
).

Can this problem please be fixed? Thank you for your time on this matter!

-- 
You are receiving this mail because:
You are on the CC list for the bug.