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, 44 insertions, 0 deletions

diff --git a/desktop/modules/appearance/melt.frag b/desktop/modules/appearance/melt.frag
new file mode 100644
index 0000000..86ef369
--- /dev/null
+++ b/desktop/modules/appearance/melt.frag
@@ -0,0 +1,44 @@
+// 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 running down the screen like wet paint, each column
+// starting late by its noise and accelerating. Compiled with:
+// qsb --qt6 -o melt.frag.qsb melt.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);
+}
+
+void main() {
+    float x = qt_TexCoord0.x * aspect;
+    float delay = 0.25 * (noise(vec2(x * 40.0, 0.0)) + noise(vec2(x * 9.0, 3.0)));
+    float l = clamp((progress - delay) / 0.5, 0.0, 1.0);
+
+    // Past 1, so the bottom row clears the screen.
+    vec2 uv = vec2(qt_TexCoord0.x, qt_TexCoord0.y - l * l * 1.02);
+    float a = smoothstep(-0.004, 0.0, uv.y);
+    fragColor = vec4(texture(source, uv).rgb * a, a) * qt_Opacity;
+}