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, 66 insertions, 0 deletions

diff --git a/desktop/modules/appearance/shatter.frag b/desktop/modules/appearance/shatter.frag
new file mode 100644
index 0000000..4c9e40d
--- /dev/null
+++ b/desktop/modules/appearance/shatter.frag
@@ -0,0 +1,66 @@
+// 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 breaking into Voronoi shards that shrink, slide away from
+// where the blow landed and fade, each on its own delay. A shard only moves
+// inside the room its shrinking leaves, so a pixel needs one cell lookup to
+// find it, rather than a search of the neighbours. Compiled with:
+// qsb --qt6 -o shatter.frag.qsb shatter.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;
+    vec2 origin;
+};
+layout(binding = 1) uniform sampler2D source;
+
+vec2 hash2(vec2 p) {
+    return fract(sin(vec2(dot(p, vec2(127.1, 311.7)), dot(p, vec2(269.5, 183.3)))) * 43758.5453);
+}
+
+// The nearest seed to p: its cell in xy, its position in zw.
+vec4 cell(vec2 p) {
+    vec2 i = floor(p), f = fract(p);
+    float best = 9.0;
+    vec4 r = vec4(0.0);
+    for (int y = -1; y <= 1; y++) {
+        for (int x = -1; x <= 1; x++) {
+            vec2 g = vec2(float(x), float(y));
+            vec2 s = g + hash2(i + g);
+            float d = dot(s - f, s - f);
+            if (d < best) { best = d; r = vec4(i + g, i + s); }
+        }
+    }
+    return r;
+}
+
+void main() {
+    const float n = 6.0;
+    vec2 asp = vec2(aspect, 1.0);
+    vec2 p = qt_TexCoord0 * asp * n;
+    vec4 c = cell(p);
+    vec2 seed = c.zw;
+
+    vec2 away = seed / n - origin * asp;
+    float d = clamp(length(away) / length(max(origin, 1.0 - origin) * asp), 0.0, 1.0);
+    float l = clamp((progress - 0.6 * mix(d, hash2(c.xy).x, 0.3)) / 0.4, 0.0, 1.0);
+
+    float s = 1.0 - 0.85 * l;
+    vec2 q = seed + (p - seed - normalize(away + 1e-4) * (1.0 - s) * 0.4) / s;
+    if (cell(q).xy != c.xy) { fragColor = vec4(0.0); return; }
+
+    float a = 1.0 - smoothstep(0.4, 1.0, l);
+    fragColor = vec4(texture(source, q / (asp * n)).rgb * a, a) * qt_Opacity;
+}