Warning, /plasma/kwin/src/scene/shaders/debug_fractional.frag is written in an unsupported language. File is not indexed.

 /*
     SPDX-FileCopyrightText: 2022 Arjen Hiemstra <ahiemstra@heimr.nl>
 
     SPDX-License-Identifier: GPL-2.0-or-later
 */
 
 #version 130 compatibility
 
 uniform float fractionalPrecision;
 uniform vec2 geometrySize;
 
 varying vec2 texcoord0;
 varying float vertexFractional;
 
 // paint every time we query textures at non-integer alignments
 // it implies we're being upscaled in ways that will cause blurryness
 // 2x scaling will go through fine
 void main()
 {
     const float strength = 0.4;
 
     // Calculate an error correction value based on the minimum precision we
     // want to measure.
     float errorCorrection = 1.0 / fractionalPrecision;
 
     // Determine which exact pixel we are reading from the source texture.
     // Texture sampling happens in the middle of a pixel so we need to add 0.5.
     vec2 sourcePixel = texcoord0 * geometrySize + 0.5;
     // Cancel out any precision artifacts below what we actually want to measure.
     sourcePixel = round(sourcePixel * errorCorrection) / errorCorrection;
 
     // The total error is the sum of the fractional parts of the source pixel.
     float error = dot(fract(sourcePixel), vec2(1.0));
 
     vec4 fragColor = vec4(0.0);
 
     if (vertexFractional > 0.5) {
         fragColor = mix(fragColor, vec4(0.0, 0.0, 1.0, 1.0), strength);
     }
 
     if (error > fractionalPrecision) {
         fragColor = mix(fragColor, vec4(1.0, 0.0, 0.0, 1.0), strength);
     }
 
     gl_FragColor = fragColor;
 }