---
title: HTPC — magic4pc (LG Magic Remote)
created: '2026-05-28'
updated: '2026-05-28'
type: tech
namespace: family
tags: [htpc, how-to, pitfalls]
sources: [family/how-to/htpc-magic4pc.md]
confidence: medium
related:
  - "[[htpc-bazzite-proton]]"
  - "[[tech/htpc-steam-emulators]]"
---

# HTPC — magic4pc (LG Magic Remote)

Go-client for using the LG Magic Remote (webOS TV app) as HTPC
mouse/keyboard input. Fork: `mallexxx/magic4pc_altclient` branch
`bazzite-linux`.

LG TV: `192.168.1.75`, HTPC: `192.168.1.86`.

## Architecture

- **TV server**: webOS app on LG TV → sends UDP to fixed source
  port **9106**
- **HTPC client**: `/usr/local/bin/magic4pc`, UDP listener
- **xdotool**: single persistent process via stdin pipe (mouse +
  keyboard)
- **ydotool**: gamescope-specific keys (Ctrl+1, Ctrl+2) via
  `/run/user/1000/.ydotool_socket`

Session detection:
- `isGamescopeSession()` — scans `/proc/*/cmdline` for `kwin_wayland`;
  if absent → gamescope (Steam Big Picture mode)
- `activeDisplay()` — KDE uses Xwayland display from kwin args; gamescope
  uses `:1` (game) if visible windows present, else `:0` (Steam BP)

## Button Mapping

| Button | Keycode | Gamescope | KDE Desktop |
|--------|---------|-----------|-------------|
| Red | 403 | Ctrl+1 (Steam menu) | Super |
| Green | 404 | Escape | Escape |
| Yellow | 405 | Ctrl+2 (Steam QAM) | Middle click |
| Blue | 406 | Right click | Right click |
| Back | 461 | Mouse X1 | Mouse X1 |
| D-pad | 37-40 | Arrow keys | Arrow keys |
| Ch+/Ch- | 33/34 | PageUp/Down | PageUp/Down |
| Play/Stop/Pause | 415/413/19 | XF86Audio* | XF86Audio* |
| Touch (swipe) | — | mousemove (scaled) | mousemove |
| Tap | — | Left click | Left click |

## Mouse Coordinate Mapping

TV sends coordinates in 0–1920 × 0–1080 space.

**In gamescope:** uses letterbox algorithm.
1. Find active window: (a) under cursor via `getmouselocation`, or
   (b) largest bounding-box window (non-popup, highest ID)
2. Compute 16:9 letterbox viewport from window width:
   `lb_h = win_w * 9/16`
3. Compute offset: `off_y = -(lb_h - win_h) / 2`
4. Map: `x11_x = tv_x * scale + off_x`; clip negatives to 0

**In KDE:** `getdisplaygeometry` → scale = display / 1920×1080.

## Key Pitfalls

| Problem | Fix |
|---------|-----|
| TV "service error" / won't reconnect | Fixed source UDP port 9106 |
| TV stuck "waiting for client" | Server keepalive timeout 10s |
| KDE XTest prompt on every click | Single persistent xdotool process |
| KDE XTest prompt after xdotool restart | `XwaylandEisNoPrompt=true` in kwinrc |
| Wrong mouse coordinates | Dynamic scale via `xdotool getdisplaygeometry` |
| Binary lost after `rpm-ostree upgrade` | Rebuild and redeploy |

## Deploy

```bash
# Build on Mac
cd ~/Developer/magic4pc_altclient
GOOS=linux GOARCH=amd64 go build -o magic4pc .

# Copy + restart on HTPC
scp magic4pc htpc:/home/bazzite/magic4pc/magic4pc
echo bazzite | sudo -S systemctl stop magic4pc.service
echo bazzite | sudo -S cp /home/bazzite/magic4pc/magic4pc \
  /usr/local/bin/magic4pc
echo bazzite | sudo -S systemctl start magic4pc.service
```

Sudoers rule (no-password systemctl):
```
bazzite ALL=(ALL) NOPASSWD: /usr/bin/systemctl
```

## See Also

- [[htpc-bazzite-proton]] — Proton game compatibility on this HTPC
- [[tech/htpc-steam-emulators]] — Steam, emulators, gamepad config