🔧 Tweak glitch effect

src/Glitch.js

@@ -43,6 +43,7 @@ var Glitch = class {
       const Clutter = imports.gi.Clutter;
 
       // Store uniform locations of newly created shaders.
+      shader._uSeed     = shader.get_uniform_location('uSeed');
       shader._uColor    = shader.get_uniform_location('uColor');
       shader._uScale    = shader.get_uniform_location('uScale');
       shader._uStrength = shader.get_uniform_location('uStrength');
@@ -52,7 +53,11 @@ var Glitch = class {
       shader.connect('begin-animation', (shader, settings) => {
         const c = Clutter.Color.from_string(settings.get_string('glitch-color'))[1];
 
+        // If we are performing an integration tests, we use a fixed seed.
+        const testMode = settings.get_boolean('test-mode');
+
         // clang-format off
+        shader.set_uniform_float(shader._uSeed,  1, [testMode ? 0 : Math.random()]);
         shader.set_uniform_float(shader._uColor, 3, [c.red / 255, c.green / 255, c.blue / 255]);
         shader.set_uniform_float(shader._uScale, 1, [settings.get_double('glitch-scale')]);
         shader.set_uniform_float(shader._uStrength, 1, [settings.get_double('glitch-strength')]);