Entry 102

Data Drain: DataDrainMenu's frames, its rules answered by the field, and the drops handed out

2026-09-25uibattletest

Filescrates/piney-fieldui/src/menus/drain.rscrates/piney-fieldui/src/ctrl.rscrates/piney-fieldui/src/lib.rscrates/piney-fieldui/src/talk.rscrates/piney-fieldui/src/tables.rscrates/piney-fieldui/src/menus/mod.rscrates/piney-fieldui/src/menus/getitem.rscrates/piney-fieldui/src/menus/trade.rscrates/piney-fieldui/src/menus/hack.rscrates/piney-fieldui/examples/fieldui_probe.rscrates/piney-world/src/combat/mod.rscrates/piney-world/src/field_world.rscrates/piney-game/src/area.rscrates/piney-game/src/world.rscrates/piney-game/src/session.rstools/test_fieldui_rs.pydocs/engine/field-ui.md

Picking Data Drain in a fight opened menu 66, which the port closed at once: nothing was drained. That left no virus cores (they are drain drops), so no gate hack after 96. The rules were already in piney_battle::drain, checked by tools/test_battle_drain_rs.py, but nothing ran them.

What the game does

DataDrainMenu (gcmn 0x00532ae0, 10 KB) runs these steps (the details are on the field UI page):

• 0. Noise and a fade to black, and the movie when drainDemo is on. Then the rules, which the port answers from the runtime: the boss affect, the infection, the drops into drainItem, and ccDeleteCmnd. The targets are cleared, a flash, the tasks woken, three frames.
• 1-3. The side-effect roll, made twice from step 0. Without a side effect: noise, then "Viral infection has spread!".
• 10-12. With one: the effect (dataDrainErosionTbl), noise, a level down at frame 30, and its message. Effect 30, SYSTEM ERROR, ends the game.
• 20. drainCount, the bracelet's growth with its pages, then menu 67 with the drops.

waitCount is zeroed only at step 0's start, so steps 2 and 11 go on from the count step 0's fade left.

The port

• crates/piney-fieldui/src/menus/drain.rs. Step 0's own frames are Resume steps (After::Drain), as the gate hack's are. Steps 1-20 run a frame each.
• The rules are the runtime's. Request::DataDrain and Request::DrainSideEffect need no mid-frame stop, unlike an item's use: the menu reads the drops only at step 20, and step 0's roll reads the save's infection three frames after the rules ran. The runtime answers at the frame's end with FieldUi::drain_drops and drain_side_effect.
• The field world. FieldWorld::data_drain, drain_side_effect and kite_level_down run piney_battle::drain on the combat scene. area.rs handles the requests. WorldHidden, which replaces the gate hack's HackScreen (as MenuNoise replaces HackNoise), blanks the world under the black.
• TalkState::drain_item is now 17 long, the game's +0x1ac-+0x1f0. 67 read only 4, and the trade pages use the first 4.
• The movie is not ported. The port goes on as with drainDemo off.

Checked

• tools/test_fieldui_rs.py. It runs the game's DataDrainMenu natively; 66 is off its unported list.
  • Hooks. The effects and fly fonts are hooked, LevelDown and the game over are logged, and the drain's noise and flashes are logged from its own code.
  • The rules' results. The infection, drops, side effect and the party's HP and SP after it are recorded as the game ran. They are fed to the probe in order, as the runtime's answers.
  • test_data_drain (420 and 520 frames). One run has no side effect: the warning, 20, 67 and the item's window. The other has one: its noise, its window, and the effect's heal on the party's panels.
  • Result. Every frame's state, packets, kanji, message, events and watched save bytes match. The ten random battle-menu runs now go through Drain too.
• Along the way. The side effect's party changes, the target dropped by ccDeleteCmnd (which keeps the sort chain) and several drains in one run were each found by a comparison failing. drainDemo 1 was found the same way: the game waits on its movie.
• The other suites. All six field UI suites (132 tests) pass.
• session::tests::data_drain_in_a_fight. After event 3, Kite is given Data Drain and the bracelet and walks to the east portal. Once the goblin's protect is broken, he drains it through PERSONAL, Skills and the Data Drain page. The area's rules run (data_drain 2), the infection moves, and the drop is handed out through 67 and 29.
• The rest. The workspace's tests, clippy, fmt and the docs check pass.