Hi everybory,
I'm using KDevelop 5.0.3 downloaded as AppImage in an XFCE 4.10 environment od Debian Jessie. I would like to use a dark theme across all applications. So far I have set up dark themes using following ways:
* GTK applications using XFCE Settings -> Appearance
* KDE4 applications (konsole, kwrite) using systemsettings -> Application appearance
* Kate editor through Kdevelop -> Settings -> Editor -> Appearance

So far, result looks like this, everything except KDevelop window is dark already: Full resolution screenshot here


I have also built a QT5 Configuration tool (qt5ct), however it does not seem to affect KDevelop's appearance. My question is, where KDevelop (AppImage version) takes appearance settings from? As far as I know, it is QT5 based, so it ignores KDE4 appearance settings. Can the qt5ct tool be used in order to make KDevelop dark? Or is there any way to provide it some files somewhere to use another appearance settings?

Edit: I have found that I can force appearance style used with QT_STYLE_OVERRIDE environment variable, however I have not made it dark already
# QT_STYLE_OVERRIDE=gtk2 ./KDevelop-5.0.3-x86_64.AppImage

Edit2: I have downloaded KDevelop 5.1 beta 1 and realized that it has Setting -> Color Theme option, however it lists no themes available. Using a beta release would be an acceptable solution for me - maybe I just need to install such themes somewhere?

I have found a working solution:

A QT application can be given a style sheet using -stylesheet option.

I have downloaded a style sheet linked in this post:
http://tech-artists.org/forum/showthread.php?2359-Release-Qt-dark-orange-stylesheet

And ran KDevelop as:
# QT_STYLE_OVERRIDE=Fusion ./KDevelop-5.0.3-x86_64.AppImage -stylesheet ./darkorange.stylesheet

To be honest (as the packager of the AppImage) I haven't completely understood it either.

The problem goes something like this, by setting your QT_QPA_PLATFORMTHEME environment variable to qt5ct, you tell Qt applications to load the qt5ct theme plugin, which then decides about things like colour scheme, widget style, and file picker dialog to use. However, from the AppImage we cannot load the qt5ct plugin from your system: it might not be compiled against a version of Qt which is binary-compatible to what we ship. Thus the style does not apply.

Why it does not load colour schemes (or how loading colour schemes works at all) from your system, I don't know, I'll have to look into that.
You might be able to extract the AppImage and copy them to the right location in there, but I'm surprised it doesn't take them from your system.

Greetings,
Sven