I rather the dark version of breeze since is easy to my eyes, specially to read, when on oxygen, I liked how the window shadow was a glow, this in the dark themes is essential to distinguish the end of the window when a few are open and overlapping in the same screen, I like the "flatness" of breeze but it becomes a challenge to quickly find the title-bar and or the tool-toolbar, I had to really focus on that specific window to pick it up.

I always thought the glow in oxygen to be an asset more than just eye-candy, would be great to have something similar.

Would you be able to provide a screenshot for what you want to propose?

The shadow's color is determined by the window decoration, which in turn can pick up colors from the color scheme.
It might make sense to pick a color from the scheme (one which is supposed to contrast with the window's main color) to use for the shadow, then. That would ensure that there is always a clear destinction between windows.

That said, wouldn't it maybe make more sense to use a bright color for the window border instead of the frame?

Some precision about window decoration colors in the *current* breeze decoration code (which can be changed of course)

1/ The shadow comes from QPalette::Shadow role, which unfortunatly
- is _not_ configurable in our color configuration module
- has no distinction between active and inactive windows
- is used in many other parts of the widget style (such as buttons shadow).

This is for instance quite different from oxygen, where the decoration shadow colors could be configured independently, in its own (custom) config module, with different settings for active and inactive windows, and disrigarding what color scheme (oxygen, oxygen-dark, ...) you use, which in turn was causing other issues (the fact that you had to go to two differnt places to change colors)

As for now I have no clean solution that would take the best of both cases (breeze and oxygen) and suggestions are welcome. (I guess ideally we'd like to extend the colors kcm to active/inactive window decoration shadow color, alongside with titlbar foreground and background colors).

2/ as far as I know (but Martin/Thomas, etc. might know better), the window decoration "frame" color (in contrast to the titlebar color) is by default picked from the QPalette::Background color (the default background for everything), and is not configurable in the KCM either.
The 'custom' color roles (ColorRole::ActiveFrame, ColorRole::InactiveFrame) already exist though, so making it configurable should be only a matter of configuring the KCM.

Best,

Hugo

Thank you for providing us with the necessary background, Hugo!

I am really all for exposing as many of the color roles as possible for configuration. Yes, this makes the config UI more complicated, but it allows color schemes to take everything into consideration in order to provide a perfectly polished experience.

I'd like to put in a vote for this as well. The blue glow, like it was in Plasma 4 Oxygen, is helpful for identifying the active window and it is also aesthetically pleasing. It would be nice to have a configuration option for Breeze Dark and any other themes for Plasma 5 to be able to set the glow / shadow colors.