/usr/share/kwin/shaders/1.10/vignetting.frag is in kwin-data 4:5.5.5-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | uniform vec2 u_center;
uniform float u_radius;
uniform float u_progress;
void main() {
float d = smoothstep(0, u_radius, distance(gl_FragCoord.xy, u_center));
gl_FragColor = vec4(0.0, 0.0, 0.0, d * u_progress);
}
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