Dear Maintainer,

Setting Dark Theme in GNOME Shell Settings, does not affect the Theme upon the next start of Vym.
Setting Dark Theme explicitly does change the setting on next startup.
That the Dark Theme can be set at all, is an improvment on the version in Trixie.
I'm not sure what I'd have to do, to test this feature with the upstream version.
It would be great if the the Dark Theme would be honered via the GNOME Shell settings.
Not sure if this should be set ui Severity minor or even wishlist for using a Qt-App with GNOME, but it seems to currently be the only Mind Map GUI available for Debian Desktops and I do find it rather painful to the eyes when switch to the application on an otherwise dark themed desktop.
Thank you very much!

David Ayers

On Tue, Feb 24, 2026 at 05:13:30PM +0100, David Ayers wrote:

Hello David,

since I'm using a wayland + sway setup, and have a personal preference for light themes,
I can not provide a lot of advice without further research and testing.

What I could find with a quick search was that there is
a) qt6-gtk-platformtheme package which might help to have it installed
b) setting env variable QT_QPA_PLATFORMTHEME=gtk3

For a) I would assume an `apt install qt6-gtk-platformtheme` and restart of vym is enough to test.
b) requires starting from a terminal, and to be sure run `export QT_QPA_PLATFORMTHEME=gtk3; vym`.

Sven

Hello Sven,

Am Dienstag, dem 24.02.2026 um 18:40 +0100 schrieb Sven Hoexter:
installation:

Start-Date: 2026-02-24  13:41:23
Commandline: packagekit role='install-packages'
Requested-By: ayers (1000)
...
vym:amd64 (2.9.604-1), zip:amd64 (3.0-15, automatic), qt6-gtk-platformtheme:amd64 (6.9.2+dfsg-4, automatic),
...

(Installing that package on trixie though, does have the effect of new
maps having a dark canvas.  It doesn't make the window, menu or widget
use the Dark Theme and existing maps still have the white background,
but that may be something I can tweak... let's focus in testing.)

Setting "export QT_QPA_PLATFORMTHEME=gtk3" before starting via command
line does not have an effect on honoring the "System setting for dark
theme".


Thank you very much for picking this up so promptly with actionable
advice!

I've got a testing VM running and may find the time to dig into this
further:

sudo apt install dpkg-dev
apt build-dep
dpkg-source -x vym_2.9.604-1.dsc

It may very well be an upstream logic bug here:
src/main.cpp
L424
    // Use dark theme depending on system appearance and preferences
    int text_hsv_value = app.palette().color(QPalette::WindowText).value();
    int bg_hsv_value = app.palette().color(QPalette::Base).value();
    systemSeemsDark = (text_hsv_value > bg_hsv_value);
    QString settingsDarkTheme = settings.value("/system/darkTheme", "system").toString();
    usingDarkTheme = false;
    iconTheme = "bright";
    if (settingsDarkTheme != "never") {
        if (settingsDarkTheme == "always" || (settingsDarkTheme == "system" && systemSeemsDark)) {
            usingDarkTheme = true;
            iconTheme = "dark";
	}
    }

I haven't wrapped my head around it yet but once I find time to figure
out how to actually build and install the package, I hope to be able to
provide a patch that could be submitted upstream.

Thank you very much!
David Ayers

PS: I did find:
https://www.debian.org/doc/manuals/maint-guide/build.en.html
which is actually target for maintainers but now I also found this:
https://wiki.debian.org/BuildingTutorial
so please give me the weekend, to see if I can figure this out...

On Wed, Feb 25, 2026 at 01:22:31PM +0100, David Ayers wrote:

Hello David,

Ok, that's good.

Well the version in trixie is the last stable release which is still using
Qt5. The 2.9.500+ versions in testing/sid are what soon will be vym 3 and
use Qt6. I would prefer to focus on those, because we can't change the
version in trixie anyway.

I could get hold of an Ubuntu 25.10 desktop installation this morning, which
as far as I know uses a customized Gnome installation, and there vym picks up
the system dark theme. Window decoration is an instant change, application menu
and canvas requires a restart. That was tested with vym 2.9.604 using the
default theme setting "System settings for dark theme".
Now the question is what might be the relevant magic Ubuntu applied.
From the perspective of the installed qt6 packages I see that
qt6-gtk-platformtheme is installed and qt6-qpa-plugins, but I'm not sure if
the later is relevant. I do not see any QPlatform reference (https://doc.qt.io/qt-6/qpa.html)
in the vym code.

That variable is also unset on the Ubuntu system I tried.

That should be fine, allowing you to override the system setting or
if the system settings suggest it's dark, it's switching to the dark theme.

Rebuilding should be rather easy if you do it in place on a system with
a deb-src configured to fetch source packages:
apt source vym # grab the source package
apt install build-essential fakeroot # get the general build tools in place
apt build-dep vym # install the build dependencies
cd vym-2.9.604
dpkg-buildpackage -us -uc -rfakeroot # build the package

Though I believe that shouldn't be necessary. At least the current Qt6 based
version should be working fine.

Sven

Am Mittwoch, dem 25.02.2026 um 15:05 +0100 schrieb Sven Hoexter:
the full set up packages installed be the last command:

Start-Date: 2026-02-24  13:41:23
Commandline: packagekit role='install-packages'
Requested-By: ayers (1000)
Install: libb2-1:amd64 (0.98.1-1.1+b3, automatic), qt6-wayland:amd64
(6.9.2-3, automatic), libqt6wlshellintegration6:amd64 (6.9.2-3,
automatic), qt6-svg-plugins:amd64 (6.9.2-5, automatic), libxcb-
image0:amd64 (0.4.0-2+b3, automatic), libxcb-icccm4:amd64 (0.4.2-1+b1,
automatic), libts0t64:amd64 (1.22-1.1+b2, automatic),
libqt6quick6:amd64 (6.9.2+dfsg-5, automatic), xsltproc:amd64 (1.1.43-
0.3, automatic), libqt6network6:amd64 (6.9.2+dfsg-4, automatic),
vym:amd64 (2.9.604-1), zip:amd64 (3.0-15, automatic), qt6-gtk-
platformtheme:amd64 (6.9.2+dfsg-4, automatic), libqt6core6t64:amd64
(6.9.2+dfsg-4, automatic), libqt6qml6:amd64 (6.9.2+dfsg-5, automatic),
libqt6widgets6:amd64 (6.9.2+dfsg-4, automatic), libqt6dbus6:amd64
(6.9.2+dfsg-4, automatic), libdouble-conversion3:amd64 (3.4.0-1,
automatic), libqt6printsupport6:amd64 (6.9.2+dfsg-4, automatic),
libqt6gui6:amd64 (6.9.2+dfsg-4, automatic), gnome-themes-extra-
data:amd64 (3.28-5, automatic), libpcre2-16-0:amd64 (10.46-1+b1,
automatic), qt6-translations-l10n:amd64 (6.9.2-3, automatic), libxcb-
keysyms1:amd64 (0.4.1-1+b1, automatic), libqt6svgwidgets6:amd64 (6.9.2-
5, automatic), libxcb-cursor0:amd64 (0.1.6-1, automatic),
libqt6svg6:amd64 (6.9.2-5, automatic), libqt6waylandcompositor6:amd64
(6.9.2-3, automatic), libqt6qmlmeta6:amd64 (6.9.2+dfsg-5, automatic),
libqt6waylandclient6:amd64 (6.9.2-3, automatic), libqt6qmlmodels6:amd64
(6.9.2+dfsg-5, automatic), libxcb-render-util0:amd64 (0.3.10-1+b1,
automatic), libqt6opengl6:amd64 (6.9.2+dfsg-4, automatic), qt6-qpa-
plugins:amd64 (6.9.2+dfsg-4, automatic), libqt6qmlworkerscript6:amd64
(6.9.2+dfsg-5, automatic), libxcb-xinput0:amd64 (1.17.0-2+b2,
automatic)
End-Date: 2026-02-24  13:43:01

Ack...

Yes, I've got it do build (thank for the fakeroot bits... I actually
uninstalled vym and installed the built package successfully but I'll
use the fakeroot in the future).

But if the same code works for Ubuntu 25.10 and not for testing then I
guess I need to find a different rabbit hole... stay tuned.

Thank you, Sven!
David

On Wed, Feb 25, 2026 at 04:11:39PM +0100, David Ayers wrote:

Hi David,

I made some more tests on the Ubuntu system. What I understand now is that
if vym is believing it's running in a dark themed session it also uses a
dark theme for new maps. But if you have a map which was created
with a light theme, this map stays with the light theme.

I took some screenshots and placed them at https://sven.stormbind.net/debian/vym/theme-ubuntu/

Maybe I get around to install a local vm with a Debian default Gnome setup
for further testing, but that will take some time.

Sven

Hello Sven,

Am Mittwoch, dem 25.02.2026 um 18:53 +0100 schrieb Sven Hoexter:

In your role as Debian Maintainer, I wouldn't worry about the
background color of maps yet.  It is a lot more nuanced than switching
the windows and widgets colors.

If I open a LibreOffice Writer .odt file,  I don't want the white
background paper representation to irritate my eyes, but when I print
document or create a PDF, I don't want a black background either.
There is distinct difference between what I want my screen to show me
and the properties of the document itself.

The fact that currently vym may be conflating these two by changing the
background color in the vym 'document' instead of mapping the standard
(light) colors to dark colors only for the display, should not be part
of this issue.  Solving that will most likely open quite a can of
worms.  Not something that we need so solve here an now.

But thank you very much, Sven, for looking into this!
David