Hello,
This looks to me like missing icons.
I would try to get some breeze icon set, or check how the icons are configured for Qt programs.

Hi,

I installed the following breeze-related non-dev, non-gtk, non-xfce and non-Gnome icon packages from the Debian repositories for Debian 12:

- breeze-icon-theme-rcc
- qml-module-org-kde-qqc2breezestyle

After each installation of one of these packages I logged out from KDE and logged again into KDE, then each time I started Falkon - but each time the buttons which are subject to this bug report here were not displayed.

When I search for all packages which are installed or are available in/for my Debian 12 installation using the command "apt list *icon*", this command returns 172 installed or installable packages.

Viewing the names of these 172 packages I know about some packages that they are not used by Falkon, like packages related to gtk or Gnome. But there are too many package names left where I do not (exaktly) know if Falkon could make use of them to display the missing buttons as described in this bug report.

And I do not know how to search the source code of Falkon which I cloned from github for information about the name(s) of Debian package(s) that could be necessary to let Falkon display the buttons mentioned in this bug report.

Do you have any suggestions how I could search the Falkon source code for possibly missing Debian packages on my machine?

> or check how the icons are configured for Qt programs.

I do not know how to do that.

And could it be possible that I would need to install one or more certain *-dev packages to use them for re-compilation of Falkon against these unknown *-dev packages?

This behaviour still exists in Falkon 24.07.90 (e86f7038a), compiled and installed in my Tuxedo OS 3 installation.

I tried the following to resolve this issue in Falkon 24.07.90 - I installed the following packages:

breeze-dev kf6-breeze-icon-theme-dev kf6-frameworkintegration-dev libkf6iconthemes libkf6iconthemes-dev plasma-theme-oxygen kf6-oxygen-icon-theme

This did not resolve the issue reported in this bug report.

I noticed that in the Edit menu > Preferences > Appearance > on the "Themes" tab the big rectangular field that should show information about installed themes is completely empty, as it was the case in former versions of Falkon which I compiled so far. 

So on that tab I downloaded the "Linux Glass - Falkon Glass Theme" which is a zip file. I unzipped this zip file locally, so I noticed that it contains a directory called "themes" which itself contains the following subdirectories, which must be each individual themes:

linux_dark_glass_00
linux_dark_glass_50
linux_dark_glass_80
linux_light_glass_00
linux_light_glass_50
linux_light_glass_80

I copied all these directories to the following location in my Falkon installation: 

/opt/falkon/falkon/bin/falkon/share/falkon/themes/

After that I ensured that all sub directories starting from /opt/falkon recursively are owned by the user and his user group with limited privileges ("normal" user with no root privileges) who starts and uses Falkon in KDE.

I also noticed that the directory

/opt/falkon/falkon/bin/falkon/share/falkon/themes/linux/images/

contains the following image files which have file names which indicate that they should get displayed in the Falkon GUI, like in the Navigation bar (but they are not, as reported in this bug report):

arrow-down.svg
exit-fullscreen.svg
goto.svg
library-bg.png
menu.svg
semi-transp.png
star-a.svg
star.svg
tab-left-arrow.svg
tab-right-arrow.svg
tools-rtl.svg
tools.svg
transp.png
user.sv

I then restarted Falkon, and it appeared that in the Edit menu > Preferences > Appearance > no information about any theme is still displayed on the "Themes" tab.

It seems as if Falkon either does not "know" the correct standard location of the default themes including their respective icons, or maybe Falkon does not know anything at all about default themes.

When I start Falkon from within a console, the console generates among others the following information:

'Cannot load theme  "linux"'

Hello,
> When I start Falkon from within a console, the console generates among others the following information:
> 'Cannot load theme  "linux"'

This looks like an issue with incorrect search path in Falkon.
This issue happens (to me) when it is installed in nonstandard path or when it was compiled from sources (and run from non standard path).
To solve it, I set few environment variables in the shell.
Try to check the "falkon:config" (Menu, Help, Configuration Information) page to see in which path Falkon searches for the themes, plugins, etc.

An example from prefix.sh script from kdesrcbuild:

export PATH=/home/juraj/kde6/usr/bin:$PATH

# LD_LIBRARY_PATH only needed if you are building without rpath
# export LD_LIBRARY_PATH=/home/juraj/kde6/usr/lib:$LD_LIBRARY_PATH

export XDG_DATA_DIRS=/home/juraj/kde6/usr/share:${XDG_DATA_DIRS:-/usr/local/share:/usr/share}
export XDG_CONFIG_DIRS=/home/juraj/kde6/usr/etc/xdg:${XDG_CONFIG_DIRS:-/etc/xdg}

export QT_PLUGIN_PATH=/home/juraj/kde6/usr/lib/plugins:$QT_PLUGIN_PATH
export QML2_IMPORT_PATH=/home/juraj/kde6/usr/lib/qml:$QML2_IMPORT_PATH

export QT_QUICK_CONTROLS_STYLE_PATH=/home/juraj/kde6/usr/lib/qml/QtQuick/Controls.2/:$QT_QUICK_CONTROLS_STYLE_PATH

export MANPATH=/home/juraj/kde6/usr/share/man:${MANPATH:-/usr/local/share/man:/usr/share/man}

Hi Juraj,

Thanks for your information. 

When I saw the $XDG_DATA_DIRS environment variable in your comment, I immediately knew that this variable must be the cause for the behavior described in this bug report here. 

The $XDG_DATA_DIRS environment variable is not set by default by Tuxedo OS 3 (it has no value assigned), so I manually had set it in a *.sh file in the /etc/profile.d/ directory, letting $XDG_DATA_DIRS point to a sub directory in the installation directory of my Falkon compilation in /opt. But this environment variable definition caused a black screen after each login into KDE, so I left the  $XDG_DATA_DIRS environment variable commented until I read your last comment in this bug report.

So I just have defined $XDG_DATA_DIRS in my *.sh file in /etc/profile.d/ directory this way:

export FALKON_PATH_IN_OPT=/opt/falkon/falkon/bin/falkon
[...]
export XDG_DATA_DIRS=$FALKON_PATH_IN_OPT/share:/usr/share

And now Falkon displays all icons in its Navigation bar and all available themes (included the ones which I downloaded from the KDE store) in the Edit menu > Preferences > Appearance > on the "Themes" tab.

You can close this but report.