Based on the discussion, the user wants to toggle the Shift key (tap once for "on," tap again for "off") instead of holding it down. Here's how to solve this on Linux:
### Recommended Solution: Use `keyd` (Works on X11/Wayland)
1. **Install `keyd`**:
bash
git clone
https://github.com/rvaiya/keyd
cd keyd
make && sudo make install
sudo systemctl enable --now keyd
2. **Configure**:
Edit `/etc/keyd/default.conf`:
ini
[ids]
*
[main]
# Make left Shift a toggle key
leftshift = toggle(shift)
# Optional: Disable right Shift or leave as normal
rightshift = overload(shift, rshift)
3. **Reload**:
bash
sudo systemctl restart keyd
### Alternative Solutions
- **For X11 (Older Systems)**:
Use `xmodmap` to remap keys, but this requires scripting to emulate toggle behavior.
- **Python/`evdev`** (Advanced):
Create a script to intercept Shift key events and toggle state (complex, not recommended for beginners).
### Why This Works
- `keyd` handles key remapping at the kernel level, working reliably across desktop environments (GNOME, KDE, etc.) and display servers (X11/Wayland).
- The `toggle(shift)` function converts the key into a sticky/latching key (like Caps Lock but for Shift).
### Notes
- **Caps Lock vs. Shift**: The user specifically wants Shift toggled (not Caps Lock), likely for gaming or accessibility.
- **Windows Comparison**: Windows has native APIs for this (e.g., `SetKeyboardState`), but Linux requires tools like `keyd` for similar flexibility.
Test immediately after configuring. If issues occur, check logs with `journalctl -u keyd -f`.
