MilkDrop: a preset generator of our own (#579, part 1)

[CaYatur]

The first half of #579: a MilkDrop preset generator of our own. Mash-ups come in a second PR.

What it does

Studio → MilkDrop Preset Generator: four sliders (energy, warmth, density, motion) and a seed write an original .milk.

• Six motion patterns, six wave patterns and four shape patterns.
• Four composite and two warp shaders.
• All of it written in this repository, in MilkDrop 2's file format. Version lines only when there is a shader.

Preview, save and code

• Preview. Generate loads the preset without saving it, through the MilkDrop panel's own selection path (layer stack, history, every window). For an unsaved preset:
  • rating, favorite and tags stay off;
  • ◀ skips it;
  • Next continues from the top of the list.
• Save. Save to Library saves the generator's last result, not the screen: auto-advance may have moved on.
• Id. md_gen1_<code>, so saving twice leaves one file.
• Code. energy-warmth-density-motion-seed brings a preset back.
  • Spaces, capitals and leading zeros read as the same code.
  • An axis above 100 makes the code invalid instead of clamping it.
• Sliders. A slider keeps the seed. Every part draws from its own random stream, so warmth changes only colours and density adds elements without re-rolling the palette.
• Platforms. The same code gives the same file on every platform. Only arithmetic and rounding reach the written numbers, and 7 golden hashes pin it.

Safety

• Invert, solarize, brighten and darken stay off.
• No above, below, if or rand.
• Colours and alphas stay in [0, 1] at any volume. MilkDrop wraps an overflowing colour rather than clamping it, so an overflow would flicker with the beat.

Measured

Scripts outside the repo, the engine in Electron, flash limiter and reduced motion off.

• Render probe. 200 presets (every 0/100 corner twice and 168 random points) × silence, demo and loud bass, 5 s at 320×180.
  • No shader fell back to the fixed pipeline, and all 200 were clean in all three runs.
  • At least 4% of the screen lit in silence and 9% with sound.
  • At most 33% near white.
  • At most 2 flashes/s in any sixteenth of the screen (2 of 600 runs).
  • At least 4.7% of pixels visibly changing within a second.
• 960×720. 40 presets, all clean.
• Originality. Of 73,405 fragments longer than 30 characters in 2,000 presets, none appears in the 10,332-preset corpus.
• Isolated copy. Generate → the visualizer window drew it; slider kept the seed; typed code worked; saving twice left one file; favorite worked after saving; English UI has no Turkish.

The probe found four defects, and the generator changed for each:

• Near-black sparse presets. A sparse preset now always gets a custom wave, and the left-vs-right wave modes are used only with at least two elements.
• White-out at decay 0.99. Decay now tops out at 0.98, and the main wave's alpha follows it.
• Rotating rings frozen in silence. They now wobble.
• Edge-sharpening shader flashing 3/s. Its gains are lower.

Tests

37 new tests: 24 for the generator and 13 for the panel with a fake DOM. The i18n coverage test also scans the new panel. 26 of 26 mutations are caught. npm test passes 2147/2147; smoke passes, and the user-data checksums were unchanged.

Not done: mash-ups (next PR), and MIDI/OSC or web-remote actions that generate.

Refs #579