MilkDrop: mash-ups from the library (#579, part 2)

[CaYatur]

The second half of #579: mash-ups of the presets in the user's library. The generator came in #609.

What it does

The generator card gets a Mash-up from Your Library block. A preset is built out of six parts of others, each taken whole from one preset:

Part	What it holds
Look	Decay, gamma, echo, the four flags, main wave, borders, motion vectors
Motion	The equations, plus zoom/rot/cx/cy/dx/dy/warp/sx/sy and the warp animation
Waves	The custom waves
Shapes	The custom shapes
Warp	The warp shader
Composite	The composite shader, plus the blur ranges b1n…b1ed, which set GetBlur's scale

• Line mapping. Every key belongs to exactly one part; the list was counted from the corpus (86 header keys). Lines are copied as they are, numbers included. Version lines are rewritten from the presets that give the shaders.
• Choosing donors. New Mash-up draws each part from the presets the MilkDrop panel's list shows, so its search and filter apply, and only from presets with that part.
• "None". Warp and composite come out "none" 12% of the time, so the look's fixed pipeline still gets a turn.
• Editing. One part can be drawn again, or all six can start from the preset on screen. An unsaved preview is never in the list and never gives a part.
• History and id. ◀ ▶ step through a recipe history and skip a recipe whose preset was deleted. The id comes from the recipe (md_mix1_…), so saving twice leaves one file.

Clean room: the behaviour was described in our own words first, and MilkDrop 2's mash-up code was not opened.

Measured on the whole 10,332-preset corpus

Scripts outside the repo.

• Part tests. They agree with the parser for every preset and part, at 13.5 µs a test.
• One-preset round trip. A mash-up of one preset is that preset again for all 10,332. Only 5 files get different version lines, all malformed or old headers.
• Mixed donors. In 5,000 random mash-ups every part equals its donor's, parameters split by part, and the version lines match the shaders.
• Engine. 300 random mash-ups ran in the engine (214 with a warp shader, 221 with a composite one) with no new shader or equation failure.
• Isolated copy with 40 corpus presets.
  • A search left 20 presets in the list; 6 mash-ups drew 14 of them and nothing outside.
  • The visualizer drew the mash-up.
  • Drawing one part again changed only that part, and ◀ went back.
  • Saving twice left one file.
  • The English UI has no Turkish.

Found on the way:

• Blur keys mistaken for a shader. The composite part's blur ranges were first counted as shader lines, which gave 308 MilkDrop 1 presets version lines for a composite shader they don't have. Fixed before this PR.
• A duplicated key. One corpus file writes the same key twice. Our parser keeps the last value, and the part test follows it. Which value MilkDrop 2 keeps is left to MilkDrop: fidelity follow-ups after #560 #580.
• Names that didn't stay names in English. The interface splits text at " · " and translates the pieces.
  • A mash-up saved as "Karışım · …" would read "Blend · …".
  • One generated word pair ("Dingin Halkalar") is a builtin preset's name ("Still Rings").
  • Mash-up names now use ": ", and the ring nouns changed. A test runs every generated word pair and a mash-up name through the English translation.

Tests

20 new tests: 10 for the module, 9 for the panel with a fake DOM (the search is typed into the MilkDrop panel's real search box), and 1 that runs generated and mash-up names through the English translation. 23 of 23 mutations are caught; a 24th was equivalent, and its branch was removed. npm test passes 2167/2167. Smoke passes, and the user-data checksums were unchanged.

Not done: MIDI/OSC or web-remote actions that generate or mix.

Refs #579