CRT - KWin Desktop Effect

A fullscreen CRT post-processing effect for KDE Plasma 6 / KWin 6 (Wayland). It runs the whole desktop through a shader that emulates a cathode-ray tube: phosphor mask, scanlines, glow and curvature. The pipeline is gamma-correct and the masks are luminance-preserving, so text stays readable and the image is not darkened.

Features

• Three mask types: aperture grille (Trinitron), shadow mask, slot mask
• Four phosphor schemes: RGB, green (P1), amber (P3), white (B/W)
• Gaussian-beam scanlines
• Glow, curvature with bezel, vignette
• Brightness, contrast, gamma, saturation
• Everything is adjustable live from the effect's settings page

Requirements

KDE Plasma 6 / KWin 6 on Wayland with OpenGL compositing.

Build dependencies (Fedora):

sudo dnf install extra-cmake-modules kwin-devel qt6-qtbase-devel \
  qt6-qtbase-private-devel qt6-qtdeclarative-devel kf6-kcoreaddons-devel \
  kf6-kconfig-devel kf6-kconfigwidgets-devel kf6-kcmutils-devel kf6-ki18n-devel \
  kf6-kwindowsystem-devel libdrm-devel libepoxy-devel mesa-libgbm-devel \
  vulkan-loader-devel vulkan-headers wayland-protocols-devel

Install on Fedora (COPR)

sudo dnf copr enable maxib0n/kwin-effect-crt
sudo dnf install kwin-effect-crt

Then log out and back in, and enable it in System Settings > Desktop Effects > CRT.

Build and install from source

./build-and-install.sh

This builds the plugin and installs it to /usr (sudo is used only for the install step). KWin keeps a loaded plugin in memory, so after installing, log out and back in to load the new binary.

Usage

Enable it in System Settings > Desktop Effects > CRT, then open the settings button next to it to choose the mask type, phosphor and the rest. Settings are stored under kwinrc [CRT].

To toggle it from a terminal:

./toggle.sh

Develop and test

A nested KWin session lets you try the effect in a window without touching your real session, using the local build:

cmake -B build -S . && cmake --build build --parallel
./scripts/test-nested.sh
MASK=2 COLOR=2 GLOW=0.25 ./scripts/test-nested.sh

Quick parameters are passed via environment variables (MASK, COLOR, MS, SS, GLOW, CURV, VIG, SCALE).

How it works

A KWin::Effect that runs first in the chain. In paintScreen() it renders the composited scene into a per-output offscreen texture, then draws one fullscreen quad sampling that texture through the CRT fragment shader. The shader is embedded in the binary. See src/Effect.cpp.

Uninstall

./uninstall.sh

License

GPL-3.0-or-later.