I was looking through Picard’s options, hoping for an option to choose a darker color scheme. I found the following in Options > User Interface:
I got all excited, but when I clicked on it, the dropdown only included “Default” and “System.” I selected “System,” but this doesn’t follow any theme changes I make in the system (Linux Mint 20.3, Cinnamon desktop).
Is there a way to add additional themes to this list? I haven’t been able to find any.
With “Default” Picard will always use the Qt5 Fusion theme (which is the default theme Qt5 provides), no matter what is otherwise configured on your system. With “System” Picard will use the Qt5 theme as configured on your system. The latter options means you can get a vastly different appearance of all user interface components depending on what you have set locally.
The color palette however might follow your system even in standard mode, but that is highly different between systems. If you are running KDE configuration of this is straight forward in the desktop environment’s settings. On other environments things can be more difficult to configure, e.g. Ubuntu by default does not seem to provide a good configuration for Qt5 applications. Qt5 has the so called platform themes, which are supposed to provide integration with the underlying platform, which in theory can provide color palettes based on your system settings.
I found that using the “gtk2” platform theme (see Uniform look for Qt and GTK applications - ArchWiki) makes Qt5 follow the color palette on my GNOME setup. You can do this with the default “Fusion” theme, it just changes the color palette then. If you choose “System” it will also change the look of the UI elements.
Another option is to use qt5ct and explicitly select one of the dark or light themes your system provides, see Qt - ArchWiki . In this case you have to choose “System”.
Or you install Picard using Flatpak. The Flatpak setup already seems to use a configuration that makes the Qt5 apps follow the color palette (at least on GNOME, don’t know about Cinnamon). I think it uses the “gnome” Qt platform (https://github.com/FedoraQt/QGnomePlatform) theme for this, but this seems not to be available as a package for Ubuntu.
Also of interest for this is the following ticket:
The essence: One of the issues on Linux compared to e.g. Windows was, that there is no easy way to tell if the current system is supposed to run in dark or light UI mode. There is a new DBus interface to change that, so desktops could indicate the configuration in a standardized way. If this exists we could explicitly change the color palette used by Picard. One downside is still that we would need to hardcode a light and dark color palette in Picard to be used (but we already hard code a dark one for Windows).