103 lines
3.3 KiB
Markdown
103 lines
3.3 KiB
Markdown
---
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title: HTPC — magic4pc (LG Magic Remote)
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created: '2026-05-28'
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updated: '2026-05-28'
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type: tech
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namespace: family
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tags: [htpc, how-to, pitfalls]
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sources: [family/how-to/htpc-magic4pc.md]
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confidence: medium
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related:
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- "[[htpc-bazzite-proton]]"
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- "[[tech/htpc-steam-emulators]]"
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---
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# HTPC — magic4pc (LG Magic Remote)
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Go-client for using the LG Magic Remote (webOS TV app) as HTPC
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mouse/keyboard input. Fork: `mallexxx/magic4pc_altclient` branch
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`bazzite-linux`.
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LG TV: `192.168.1.75`, HTPC: `192.168.1.86`.
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## Architecture
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- **TV server**: webOS app on LG TV → sends UDP to fixed source
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port **9106**
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- **HTPC client**: `/usr/local/bin/magic4pc`, UDP listener
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- **xdotool**: single persistent process via stdin pipe (mouse +
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keyboard)
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- **ydotool**: gamescope-specific keys (Ctrl+1, Ctrl+2) via
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`/run/user/1000/.ydotool_socket`
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Session detection:
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- `isGamescopeSession()` — scans `/proc/*/cmdline` for `kwin_wayland`;
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if absent → gamescope (Steam Big Picture mode)
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- `activeDisplay()` — KDE uses Xwayland display from kwin args; gamescope
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uses `:1` (game) if visible windows present, else `:0` (Steam BP)
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## Button Mapping
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| Button | Keycode | Gamescope | KDE Desktop |
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|--------|---------|-----------|-------------|
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| Red | 403 | Ctrl+1 (Steam menu) | Super |
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| Green | 404 | Escape | Escape |
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| Yellow | 405 | Ctrl+2 (Steam QAM) | Middle click |
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| Blue | 406 | Right click | Right click |
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| Back | 461 | Mouse X1 | Mouse X1 |
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| D-pad | 37-40 | Arrow keys | Arrow keys |
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| Ch+/Ch- | 33/34 | PageUp/Down | PageUp/Down |
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| Play/Stop/Pause | 415/413/19 | XF86Audio* | XF86Audio* |
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| Touch (swipe) | — | mousemove (scaled) | mousemove |
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| Tap | — | Left click | Left click |
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## Mouse Coordinate Mapping
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TV sends coordinates in 0–1920 × 0–1080 space.
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**In gamescope:** uses letterbox algorithm.
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1. Find active window: (a) under cursor via `getmouselocation`, or
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(b) largest bounding-box window (non-popup, highest ID)
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2. Compute 16:9 letterbox viewport from window width:
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`lb_h = win_w * 9/16`
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3. Compute offset: `off_y = -(lb_h - win_h) / 2`
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4. Map: `x11_x = tv_x * scale + off_x`; clip negatives to 0
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**In KDE:** `getdisplaygeometry` → scale = display / 1920×1080.
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## Key Pitfalls
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| Problem | Fix |
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|---------|-----|
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| TV "service error" / won't reconnect | Fixed source UDP port 9106 |
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| TV stuck "waiting for client" | Server keepalive timeout 10s |
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| KDE XTest prompt on every click | Single persistent xdotool process |
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| KDE XTest prompt after xdotool restart | `XwaylandEisNoPrompt=true` in kwinrc |
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| Wrong mouse coordinates | Dynamic scale via `xdotool getdisplaygeometry` |
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| Binary lost after `rpm-ostree upgrade` | Rebuild and redeploy |
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## Deploy
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```bash
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# Build on Mac
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cd ~/Developer/magic4pc_altclient
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GOOS=linux GOARCH=amd64 go build -o magic4pc .
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# Copy + restart on HTPC
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scp magic4pc htpc:/home/bazzite/magic4pc/magic4pc
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echo bazzite | sudo -S systemctl stop magic4pc.service
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echo bazzite | sudo -S cp /home/bazzite/magic4pc/magic4pc \
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/usr/local/bin/magic4pc
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echo bazzite | sudo -S systemctl start magic4pc.service
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```
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Sudoers rule (no-password systemctl):
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```
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bazzite ALL=(ALL) NOPASSWD: /usr/bin/systemctl
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```
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## See Also
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- [[htpc-bazzite-proton]] — Proton game compatibility on this HTPC
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- [[tech/htpc-steam-emulators]] — Steam, emulators, gamepad config
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