Add opt-in auto-orientation support

[ThalesC]

Summary

Adds opt-in internal display auto-orientation support using iio-sensor-proxy.

This can be enabled with either:

• --auto-orientation
• AUTO_ORIENTATION=1

When enabled, Gamescope listens for accelerometer orientation changes, applies the matching orientation to the internal display, refreshes Xwayland output metadata, and updates the patched EDID/output mode state. It also adds Super + R as a shortcut to toggle auto-orientation at runtime.

This is opt-in only. No devices are enabled automatically by this patch.

Build

This adds an optional Meson feature, auto_orientation, backed by gio-2.0 (pkgconfig(gio-2.0)).

If the dependency is unavailable and the feature is left on auto, Gamescope builds normally without auto-orientation support.

Testing

Tested on a GPD Pocket 3 running Bazzite Game Mode.

Verified:

• Steam UI rotates across all four orientations
• Super + R toggles auto-orientation on/off
• Melvor Idle rotates correctly
• Ale & Tale Tavern rotates correctly while running a 3D scene with object physics
• Repeated orientation changes continue working without freezing
• Repeatedly toggling auto-orientation during gameplay continues working correctly

Known behavior from testing:

• The first orientation change may briefly show a black screen for around 3-5 seconds
• Later orientation changes are instantaneous

Authorship / Disclosure

This patch was developed with assistance from OpenAI Codex.

I designed the feature, guided the implementation, built and tested the branch locally, and validated it on real hardware.