The upcoming KDE Plasma 6.8 release, scheduled for mid-October, will introduce a KWin feature enabling the window manager to add server-side drop shadows to applications that lack their own.
Window shadows can generally be drawn either by the compositor or by the application itself. Many GTK applications use client-side decorations and render their own shadows, while Qt applications commonly ask the compositor to draw both the window decoration and its shadow.
However, some applications do neither, resulting in windows with square corners, no shadow, and a visually inconsistent appearance compared to the rest of the Plasma desktop.
This new functionality, recently merged into KWin for Plasma 6.8, fixes this issue. According to KWin developer Vlad Zahorodnii, it lets users force compositor-drawn shadows on these windows, helping third-party applications integrate more fluently with Plasma.
Users can already achieve a similar result in Plasma 6.7, but the process requires several manual steps. They must create a KWin window rule to force server-side decoration and configure a window-specific override in the Breeze decoration settings to hide the titlebar.
Plasma 6.8 automates this workaround with a new window rule, “Window manager draws titlebar, frame, and shadows,” which replaces the older “No titlebar and frame” option and delivers a more direct way to request compositor-side decorations or shadows for individual applications.
This feature, however, will not work immediately with all third-party window decorations. Decoration themes must explicitly support a new shadow-only style in addition to standard titled decorations. They must also adjust their appearance based on the selected style, such as hiding the titlebar while retaining the border and shadow.
KWin will automatically add shadows to suitable X11 windows when it detects neither server-side decoration nor client-side shadows. Many affected X11 applications will benefit without additional configuration.
The situation is more complicated under Wayland. KWin is unable to reliably determine whether a Wayland application uses subsurfaces to draw its own shadow or other surrounding visual elements. Automatically adding another shadow could therefore produce incorrect results.
For this reason, KWin will not automatically apply the new behavior to Wayland windows. Users will need to create window rules manually. Zahorodnii noted that a future Wayland protocol could let applications explicitly indicate whether compositor-side shadows should be used.
For additional details, see the post on Zahorodnii’s blog.
