# Shift Scroll Horizontal

## Symptom

Shift+scroll no longer produced horizontal scrolling on the controlled Mac.

## Root Cause

The hidden event-capture page only sent `{ deltaY }` for wheel events. The receiver already supported horizontal wheel frames with `robot.scrollMouse(frame.x || 0, frame.y || 0)`, but `app.js` forwarded only `{ y: data.deltaY }`, so horizontal scroll data was dropped.

## Fix

`event-capture/event-capture.html` now sends `deltaX`, `deltaY`, and `shiftKey`. `app.js` normalizes wheel data into `{ x, y }`, mapping Shift+vertical wheel to horizontal scroll when Electron did not already emit `deltaX`.

## Evidence

Verification run:

```text
node --check app.js
node --check app-ui/renderer.js
git diff --check
npm run package:mac
```

The rebuilt app bundle contains the updated event-capture and app code.

## Status

DONE_WITH_CONCERNS: statically verified and packaged, but not live-tested across two Macs in a remote control session.
