Fix X11 primary-monitor coordinates without changing fullscreen policy

Adapt the geometry fix from PR #12 to the current relative-mouse implementation. Keep display IDs independent of primary-first screen ordering, translate window and pointer coordinates consistently, and invalidate geometry on both RandR event types.

Handle failed RandR snapshots and free EDID data. Add isolated native geometry regression coverage and use the configured SDK when linking the X11 probe.

Validated all 30 component patches, the X11 and CoreGraphics builds, six native geometry groups, and the existing relative-mouse checks. The user confirmed the installed fix works on 2026-10-16.

Co-authored-by: Maka <[email protected]>

docs/TESTING.md

@@ -412,3 +412,34 @@ and exercises 100 cancellations with both retained and early-released caller
 references, without launching or inspecting Riot. A failure prints
 `CFHOST_CANCEL_CHECK fail stage=...`; `unexpected-callback` means a completed
 lookup arrived instead of the cancellation.
+
+## Primary-monitor geometry regression
+
+After preparing the sources and configuring/building Darling, run:
+
+```sh
+python3 scripts/prepare.py --check-only
+python3 tools/check-x11-display-geometry.py
+cc -std=c11 -Wall -Wextra -Werror tools/test-x11-relative-mouse.c -o build/test-x11-relative-mouse
+build/test-x11-relative-mouse
+```
+
+The native probe requires the existing per-user AppKit and CoreGraphics overlays
+and a running X11/Xwayland display. It rebuilds the changed X11 and CoreGraphics
+objects and tests them in a temporary framework overlay, without installing them.
+Six `DISPLAY_GEOMETRY ...=pass` lines are required; full output is saved in
+`build/pr12-display-check.log`.
+
+It checks the live primary screen's origin, synthetic single-monitor and offset
+layouts (including vertically arranged screens and negative Cocoa coordinates),
+unmapped window creation/resizing, display IDs after primary-first ordering,
+CoreGraphics bounds and spatial queries, absolute and relative warp translation,
+relative deltas, both RandR cache-invalidation events, and the root-screen fallback.
+Warps are intercepted: the probe does not move the desktop pointer or send game
+input. Synthetic layouts exercise coordinate conversion and display API behavior;
+they do not simulate physical monitor hotplug or validate League rendering.
+Fullscreen policy is unchanged. Manually verify game launch, window placement,
+click alignment and edge panning on the affected monitor layout before rollout.
+
+After installing the tested X11 and CoreGraphics binaries locally, the user
+reported that everything was working (2026-10-16). Fullscreen policy was unchanged.