Symptom

The LogicGate editor showed the gate type twice: once in a GateTypeSelector dropdown row above the truth table, and again as a highlighted column inside the truth table. Picking a gate from the dropdown updated the highlight in the table; the table couldn’t be used as input. Two controls, one piece of state — confusing, and the dropdown row took up a full row of vertical space for no reason.

Root cause

composeApp/.../EditLogicGate.kt had grown two views over the same meta.gateType field. The LogicGateTruthTable already rendered every gate as a column with a primary-container highlight, which is itself a strong visual affordance for “this is the selected gate.” But the columns were not clickable, so the user had to reach for the dropdown. The dropdown stayed because nobody had wired the columns up to set the gate type.

Fix

• composeApp/.../EditLogicGate.kt —
  • Removed the GateTypeSelector(...) call from EditLogicGateForNode and the entire private fun GateTypeSelector(...) composable.
  • Threaded an onGateSelected: (LogicGate) -> Unit parameter into LogicGateTruthTable, plus an optional onClick: (() -> Unit)? on TruthTableColumn. Each gate result column now calls onGateSelected(gate). The A and B input columns stay non-clickable (they don’t represent a selectable choice).
  • Updated the table card title from "Truth Table" to "Truth Table — tap a column to select gate type" so the affordance is discoverable without onboarding text. The selected column still uses primaryContainer background — that visual convention (highlight = selected) carries through.
• composeApp/src/desktopTest/.../screenshot/Fixtures.kt — added logicGateSwarm() (an AND gate with two boolean DataPoint sources and a target) so the editor renders against realistic state.
• composeApp/src/desktopTest/.../screenshot/Scenarios.kt — new editorLogicGate Roborazzi scenario that captures the editor in its default AND state.
• composeApp/src/desktopTest/.../screenshot/ScreenshotCatalog.kt — added editor__logic-gate to docsCanonical so the PNG is part of the published docs asset set.
• docs/assets/screenshots/editor__logic-gate.png — the recorded screenshot, committed alongside the code so a future regression produces a visible diff.

Prevention

• One control per piece of state. When you find two UI elements that both read and write the same field, one of them is redundant. Pick the more discoverable / more compact one and delete the other. Don’t leave both “to be safe” — duplication is itself a usability cost (the user has to figure out which to trust).
• Highlighted-row tables are already pickers — wire the click. Any table that highlights a “selected” row/column is implicitly promising the user that the table is interactive. If it isn’t, you have a debt: either remove the highlight or make it clickable. Almost always the answer is the latter.
• Re-record screenshots when removing UI. A removal-of-UI commit with no screenshot diff is invisible in review. The new editor__logic-gate PNG is the artifact that makes the dropdown’s removal visually verifiable in the PR — no need to spin up the app to confirm.