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, 43 insertions, 0 deletions

diff --git a/desktop/modules/appearance/ripple.frag b/desktop/modules/appearance/ripple.frag
new file mode 100644
index 0000000..a610537
--- /dev/null
+++ b/desktop/modules/appearance/ripple.frag
@@ -0,0 +1,43 @@
+// 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.
+
+// A ring spreading from a random point, bending both pictures as it passes,
+// the new one behind it. Opaque throughout. Compiled with:
+// qsb --qt6 -o ripple.frag.qsb ripple.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;
+layout(binding = 2) uniform sampler2D target;
+
+void main() {
+    vec2 asp = vec2(aspect, 1.0);
+    vec2 v = (qt_TexCoord0 - origin) * asp;
+    float d = length(v) / length(max(origin, 1.0 - origin) * asp);
+
+    // e runs -1 to 1 across the ring. It starts wholly outside the picture
+    // and ends wholly past it, so neither end is bent.
+    const float w = 0.12;
+    float e = (d - mix(-w, 1.0 + w, progress)) / w;
+    float ring = 1.0 - smoothstep(0.0, 1.0, abs(e));
+    vec2 off = v / max(length(v), 1e-4) / asp * sin(e * 3.14159) * ring * 0.03;
+
+    vec2 uv = qt_TexCoord0 + off;
+    vec3 col = mix(texture(target, uv).rgb, texture(source, uv).rgb, smoothstep(-0.6, 0.6, e));
+    fragColor = vec4(col, 1.0) * qt_Opacity;
+}