For all completness, here his screenshot:

Hi Hans,

It seems like GTK3 is not alpha anymore for Lazarus Pascal ;-)

Interesting! Will give it a try today or tomorrow. 👍 
Seems they didn't update the widget status Wiki page yet.
will have to rebuild Lazarus from trunk though so it will take a minute 😉 

Been at it most of the morning, and so far have not even been able to get an application to even start with the GTK3 widget set ...

Crashes instantly. Looking into it though, could be just an issue with the latest trunk version. Still testing 😉 

Note: Since Qt5 is even worse (do you have screenshots?), I do wonder about the theme you're using. Could you try another theme? Just to see if it makes a difference.

As for your other post:

Just quoting the comment so we have all together here:

The interesting detail is that some of the buttons ([Cannot Rename], [Episode Details] and [Remove]), from the above linked screenshot, are visible in the dark mode. The icon [Toggle cleanup filter for search results On/Off] from the [TV Shows] section is visible as well.

There should be some difference between those and the rest of the buttons. I hope that will help you to identify at least that part of the issue.

Some of the buttons in the [Settings] menu as visible as well. Please, let me know if you want those details!

The KDE is allowing to set per application env variable that will specify the theme only for that application:

• QT example: Exec=env QT_STYLE_OVERRIDE=Kvantum YourGTKAppExecutableName
• GTK+ example: Exec=env GTK_THEME=Adwaita:dark YourGTKAppExecutableName
• GTK2 example: Exec=env GTK2_RC_FILES=/path/to/your/theme/gtkrc YourGTKAppExecutableName

The themes’ names for GTK+ (that’s covering GTK3) can be found in:

System Settings > Appearance & Style > Colors & Themes > Application Style > Configure GNOME/GTK Applications Style…

The application, supporting the themes, should respect the variable, but it seems like this is not working as well.
Besides those cosmetic issues, it seems like a great application that can easily replace FileBot or the one I’m currently using – Advanced Renamer.

The buttons that -are- visible (Cannot Rename, Remove, Episode Details) are actually in a disabled state. For reference:

As for the theme support etc - I'm totally relying on the implementation done by the Lazarus team, which in general serves me best since my in-depth knowledge of (for example) GTK is about zero haha.
I'm actually developing completely under macOS, then recompile (and do some minor adjustments) under Linux and/or Windows so I can test there as well.
As far as I can see, under Manjaro,  the theme settings are being honored (see my screenshots). Can you test another theme?

After some more testing with GTK3, I would say GTK3's implementation in Lazarus Pascal should probably should move back to alpha stage or at least say "beta" stage.

I run into the weirdest problems.
For example:

Resize window just instantly crashes the application.

Control anchoring/alignment does not seem to work (see screenshot - verlap)), etc.

GTK2:

GTK3:

Some controls just fall outside of the window view:

GTK2:

GTK3:

Etc.

Naturally this could be caused by other factors, for example the Manjaro distro itself - I wouldn't know.

Did notice that the buttons look the same as with GTK2 though.

Note: I already made a minor tweak to get the font color of the headers for example, to be better visible in darkmode (eg. white font instead of the previously darker font color).

Doing a full update of Manjaro right (the GNOME desktop manager explicitly states its using GTK3) just to make sure, but I would not want to distribute an application depending on a very recent update. Would be better to have the most common setup, right? 😉 

Just for more testing: can you give me a link to the exact Linux distro you're using right now? I may want to spin up a virtual machine matching your settings in case choosing a different theme is not making a change for you.

Hi Hans,

Thank you for the time spend on the problem, man!

Most of my home workstations are on Nobara - to have most of the Linux multimedia HW features - all of those are on Breeze Dark theme.

Desktop 1

Laptop 1

Theme info

I just figured that I never tested this on the travel laptop - it's running Mint. I'll test it today and let you know the result.

Greets!

I forgot to tell you that with the QT (for Nobara/Fedora the library is qt5pas) the window is going crazy with error

qt.qpa.wayland: Wayland does not support QWindow::requestActivate()
QPainter::begin: A paint device can only be painted by one painter at a time.
QPainter::setCompositionMode: Painter not active
QWidget::repaint: Recursive repaint detected
QBackingStore::endPaint() called with active painter; did you forget to destroy it or call QPainter::end() on it?

I'll do the Mint test when that laptop is back with my daughter ;-)

Under Mint everything looks fine for both Light and Dark themes.

I always try to make my applications available for the 3 major operating systems (macOS, Windows and Linux), but I'm just a Mac user and the occasional Windows gamer.

Linux, from a developers perspective, has caused me more pain and suffering than the other 2 combined and I've had more than once that I wanted to give up on Linux ... 
(thanks to the help from other forum users I didn't give up yet)

If only the Linux distro teams would team up and make things consistent, man Linux would then be unbeatable.
Unfortunately, up to now its been a mess. 😪 
Having tinkered with Linux for over 30 years now, on and off, I really keep wanting to like Linux but always get disappointed.

Also not a fan of the qt5pass mess either - depending on the package manager on your Linux distro, this is properly updated or not.
I think this is why you're experiencing weird errors. Maybe? I've encountered this as well with other distros.
Makes me wonder why the involved Lazarus developers even chose that path - why not embed it right away into the executable?
But having said that: my knowledge on that topic is very limited, so I blame myself for not understanding why this is done the way it is.

Good find that it looks correct under Mint (which makes me think most Debian based Linux distros will work correct). 👍 
Works correct under Manjaro (Arch Linux based) as well.

Feels like this may be an issue in Fedora related distros?
That's why I was wondering if a different dark theme would show the same problems.

I'm not a "low level" developer when it comes to GTK or Qt, so I'm not sure how to fix this issue. 😞 
Any ideas or suggestions are most welcome of course.

What edition of Nobara should I grab to do some testing in a Virtual Machine?
Looks like you have the KDE Plasma edition? 

I'll give this one a try:

(I'll do a recompile on that VM to see what happens)

@hans , that one or Nobara-43-Official-2026-01-25.iso should be fine

I'm using the Nvidia one, but it doesn't make sense for VM to go in that way.

Well, my Mac wouldn't have anything Nvidia anyway 🤣 
I'll give it a try in the next few days! 😉