wallpaper: six more transitions

Ink, shatter, ripple, melt, blinds and cross-warp. Each draws the old
picture exactly at progress 0 and the new one at 1, or the cover would
pop as it comes and goes: rendered under Xvfb with llvmpipe against the
plain pictures, all seven differ by 0 at both ends. Ripple and cross-warp
sample the new picture, the rest are transparent over it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/desktop/modules/appearance/ink.frag b/desktop/modules/appearance/ink.frag
new file mode 100644
index 0000000..8a6f655
--- /dev/null
+++ b/desktop/modules/appearance/ink.frag
@@ -0,0 +1,52 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// The old wallpaper dissolving like ink in water: a soft edge through noise
+// warped by more noise, the picture smearing as it goes. Compiled with:
+// qsb --qt6 -o ink.frag.qsb ink.frag
+#version 440
+layout(location = 0) in vec2 qt_TexCoord0;
+layout(location = 0) out vec4 fragColor;
+layout(std140, binding = 0) uniform buf {
+    mat4 qt_Matrix;
+    float qt_Opacity;
+    float progress;
+    float aspect;
+};
+layout(binding = 1) uniform sampler2D source;
+
+float hash(vec2 p) { return fract(sin(dot(p, vec2(12.9898, 78.233))) * 43758.5453); }
+
+float noise(vec2 p) {
+    vec2 i = floor(p), f = fract(p);
+    vec2 u = f * f * (3.0 - 2.0 * f);
+    return mix(mix(hash(i), hash(i + vec2(1, 0)), u.x),
+               mix(hash(i + vec2(0, 1)), hash(i + vec2(1, 1)), u.x), u.y);
+}
+
+float fbm(vec2 p) {
+    float v = 0.0, a = 0.5;
+    for (int i = 0; i < 5; i++) { v += a * noise(p); p *= 2.03; a *= 0.5; }
+    return v;
+}
+
+void main() {
+    vec2 p = qt_TexCoord0 * vec2(aspect, 1.0);
+    vec2 warp = vec2(fbm(p * 3.0 + progress), fbm(p * 3.0 + 7.3 - progress));
+    // fbm sits around 0.2 to 0.8; stretched and clamped, so the edge below
+    // sweeps past every pixel.
+    float t = clamp((fbm(p * 2.0 + warp * 1.5) - 0.2) / 0.6, 0.0, 1.0);
+
+    const float w = 0.15;
+    float a = smoothstep(0.0, w, t - mix(-w, 1.0, progress));
+    vec2 uv = qt_TexCoord0 + (warp - 0.5) * 0.04 * (1.0 - a);
+    fragColor = vec4(texture(source, uv).rgb * a, a) * qt_Opacity;
+}