Touchpad settings page missing; users cannot tune tap-to-click, scroll method, or acceleration

[wzzfather]

Touchpad settings page missing in OpenGamepadUI settings

Summary

OpenGamepadUI currently exposes no user-tunable parameters for the laptop/handheld touchpad. On Steam Big Picture / KDE Wayland, when InputPlumber (or directly libinput) feeds touchpad events through OpenGamepadUI and then into Steam, the user can only adjust Steam → Settings → Controller → Touchpad → Cursor Sensitivity. There is no way to set:

• Tap-to-click and tap-to-drag
• Two-finger / edge scroll method
• PointerAcceleration (libinput adaptive / flat profile)
• DisableWhileTyping
• Natural / reverse scrolling
• Click method (clickfinger / buttonareas)

When a non-Steam-Deck device is used (for example a GPD Win Mini 2024 with HTIX5288:00 0911:5288 touchpad), the default InputPlumber composite re-emits the touchpad as a uinput InputPlumber Touchpad device. That virtual device is forwarded by OpenGamepadUI to Steam without any configuration knobs, so users have no recourse to fix drifting cursors or broken two-finger scrolling.

Reproduction steps

1. Boot Bazzite-Deck on a handheld/laptop with an i2c touchpad (HTIX5288 or similar).
2. Open OpenGamepadUI → Settings.
3. Note that there is no Touchpad section in the settings tree (verified on OpenGamepadUI shipped with Bazzite 44.20260908).
4. While the touchpad works in Steam Big Picture, two-finger scrolling behaves erratically and tap-to-click cannot be enabled.

Expected behavior

OpenGamepadUI should expose a "Touchpad Settings" page with at least:

• Tap to click (enable/disable)
• Tap drag / drag lock
• Two-finger scroll / edge scroll toggle
• Scroll factor (low / medium / high)
• Natural scrolling
• Pointer acceleration profile (none / adaptive) and factor
• Disable while typing

These settings should map to either:

• DBus calls to org.shadowblip.InputPlumber (when InputPlumber is feeding the touchpad), or
• A ~/.config/kcminputrc patcher that writes the corresponding [Libinput][...][Touchpad] section so libinput picks them up when the touchpad is passed through.

Implementation notes

• OpenGamepadUI is a Godot app and stores its config in ~/.local/share/opengamepadui/settings.cfg. That config format does not currently contain any [touchpad] section.
• Today, the binary opengamepad-ui.x86_64 contains only a single string match for TapTimer in any touchpad-related code path, confirming that there is no UI for tap/drag/scroll.
• The Touchpad events are loaded as InputPlumberTouchpadEvent (res://core/systems/input/events/touchpad_event.gd).

Suggested fix

Add a new settings page in OpenGamepadUI that:

1. Reads existing InputPlumber device properties (org.shadowblip.Input.Source.EventDevice) to detect touchpad source paths.
2. Exposes a small subset of libinput properties via a TouchpadSettings section, persisted to ~/.local/share/opengamepadui/settings.cfg.
3. Applies changes either by:
   • DBus org.shadowblip.InputPlumber calls (preferred), or
   • Writing ~/.config/kcminputrc entries when OpenGamepadUI's session does not own the touchpad directly.

Environment

• Bazzite 44.20260908 (ghcr.io/ublue-os/bazzite-deck:stable)
• OpenGamepadUI (current packaged)
• InputPlumber 0.79.0
• Steam client 1788652215
• Touchpad: HTIX5288:00 0911:5288 (i2c, 67x48 mm, multitouch)

Workaround

Today the only knob is Steam → Settings → Controller → Touchpad → Cursor Sensitivity. Users have to manually edit ~/.config/kcminputrc and restart Plasma to recover libinput-level control on devices where InputPlumber does not grab the touchpad.