POC: "Import from file" panel — place a local .kicad_sym / .kicad_mod on the canvas

[matejcsok-pcb]

What

Proof of concept for plugin-style item ingress in the standalone editor: a floating Import from file panel (session menu → Import from file) that takes a .kicad_sym or .kicad_mod from the user's machine and places it on the open eeschema / pcbnew canvas.

• File picker or drag-and-drop onto the panel.
• A multi-symbol library shows a symbol dropdown (top-level symbols only, units hidden).
• Add to canvas arms a click catcher over the drawing area; the next click is the drop point, grid-snapped. Esc cancels. Viewport centre is the fallback if the canvas rect can't be found.

How (no C++)

The blob goes through the editors' existing collab items-apply bridge, Module.kicadCollabApplyItems, i.e. the clipboard-paste parsers:

• pcbnew accepts a bare (footprint …); the panel adds (at x y) and caps the format version.
• eeschema takes the clipboard dialect (lib_symbols (symbol "Nick:Name" …)) (symbol (lib_id "Nick:Name") …) — the definition travels with the instance, so a library the editor has never seen still works.

Click → position: CSS px → canvas px (rect ratio, HiDPI-safe) → world IU via kicadCollabGetViewport, the same mapping the comment pins use.

Files

• wasm/import-item.ts — blob builders + click/viewport mapping (pure, unit-tested: 12 tests).
• components/ImportItemPanel.tsx — the panel.
• WasmTool.tsx, wasm-tool/SessionMenu.tsx — wiring + menu toggle.

Verified

• Demo schematic: Device R and C placed; the stored (at …) equals the mapped click exactly.
• Demo board: R_0603_1608Metric placed with pads / courtyard / REF**.
• vitest 492 green, tsc --noEmit clean, no console errors from the feature.

Known POC limits (documented in wasm/import-item.ts)

• The apply commits with SKIP_UNDO and is folded into the collab baseline: not undoable, not broadcast to peers / the Y.Doc. Fine in api doc mode (File→Save writes it), wrong for ydoc mode.
• The symbol lands unannotated (R?) without instance data; Annotate fixes it.
• Placement is a commit at a point, not an interactive drag.

Follow-up route for the real feature

One embind export per editor feeding a pre-built item to SCH_ACTIONS::placeSymbol / PCB_ACTIONS::placeFootprint (both take an item and go interactive at the cursor, with normal undo), plus registering the file as a runtime lib via localFileLibsSource + kicadLibsAddEntry so the stock chooser lists it. The wx-side browser→canvas file DnD hook (registerDragDropHandlers / Module._OnFileDropped) exists but has no JS half yet.

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