Ubuntu – “’gtk2′ Qt style” in Lubuntu 19.10

accessibilitylubuntuqt5themes

OS: Lubuntu 19.10

I have a need for my applications to be entirely dark-themed. Lubuntu 19.10 comes with Adwaita-dark (and Adwaita) for GTK2/3 applications. I've also added the materia-gtk-theme package so that I can choose Materia-dark instead of Adwaita-dark.

If I open Preferences > LXQt settings > Appearance, simply selecting a dark theme for GTK2 and GTK3 does the job for GTK2/3 applications (not shown).

The issue arises with making Qt applications look dark as well. None of the three default Qt styles, Breeze, Fusion, or Windows, provide dark-themed Qt applications.

Image showing pcmanfm-qt, kcalc, featherpad, qterminal all in the background and LXQt Appearance on top.

Lubuntu 19.10 LXQt Appearance window

However, there is this:

To attempt uniform theming, either select similar style/theme (if available) across all lists, or select 'gtk2' Qt style (if available) to mimic GTK themes.

As the dropdown next to Qt Style shows, there's no 'gtk2' Qt style.

How do I install this 'gtk2' Qt style? Which package, preferably from the standard repositories, provides it?

Best Answer

One solution is to install qt5-style-plugins.

The following additional packages will be installed:
  qt5-gtk2-platformtheme qt5-style-plugin-cleanlooks qt5-style-plugin-motif
  qt5-style-plugin-plastique
The following NEW packages will be installed:
  qt5-gtk2-platformtheme qt5-style-plugin-cleanlooks qt5-style-plugin-motif
  qt5-style-plugin-plastique qt5-style-plugins

Once installed, open LXQt Appearance again. The gtk2 style is now available.

(A log out and log in seems needed to make pcmanfm-qt use the dark theme.)

The image shows various Qt applications (featherpad, konsole, pcmanfm-qt, and LXQt Appearance) themed dark.

Qt Applications are now dark-themed

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