darling-lol/docs/TROUBLESHOOTING.md

Troubleshooting

NixOS launcher fails before Riot opens

A message saying Darling must be setuid root is not fixed by running sudo inside buildFHSEnv: bubblewrap enables no_new_privs, so setuid elevation is ignored there. Use the package's rootless launcher with subordinate UID/GID mapping enabled. Never make a mutable workspace executable host-setuid-root.

If a newly installed client aborts with Cannot load libavformat.so.62 (ELF), check the FHS runtime dependencies. The generated Darling wrappers use FFmpeg 8 SONAMEs, so an unversioned nixpkgs ffmpeg dependency can break them when its major changes. The package pins ffmpeg_8; do not create fake ABI symlinks.

Older packages used cp -n and never refreshed already-copied tools. The current launcher replaces packaged source files while retaining compiled/runtime data. An incomplete prefix can be backed up by renaming it with Darling stopped; never delete a populated Riot/game prefix just to repair the launcher.

Use the setup instructions from the repository root as your ordinary user. Exit the game and both clients manually before a full installation or Darling restart. Incremental server/memory installers can replace files without interrupting processes, but their changes need a later full restart to activate.

Memory installer: permission denied

An earlier sudo server installation can create root-owned build/backups. The old memory installer tried to create build/backups/memory-runtime there and failed at backup_folder.mkdir(...). The corrected default is a separate user-owned build/memory-runtime-backups directory:

python3 tools/install-riot-memory-runtime.py

For an explicitly chosen backup location:

python3 tools/install-riot-memory-runtime.py --backup-dir "$HOME/darling-memory-backups"

If the destination library itself is root-owned, inspect the named path and its ownership before retrying with sudo. Do not run all setup/build steps as root or recursively change ownership of the system SDK. Backups and binaries are ignored by Git and must stay local.

Updated library or server still behaves like the old version

Atomic replacement preserves active process mappings. Darling also uses an overlay filesystem; updating its backing prefix from the host can leave an old file visible inside the active namespace. A fresh standalone guest check continued to report the old memory behavior despite the host path having the new checksum. Reopening only Riot does not replace this namespace.

After exiting the game and both clients manually:

darling shutdown
sh scripts/run.sh

Do not run these commands during a match. Use the independent reclamation probe in testing to verify the new guest behavior after activation. An installer result with installed: true and restart_performed: false confirms the disk update, not activation.

Around 5 GB of RAM with just the clients open

The observed proportional resident footprint was roughly 4.3 GiB across Riot, League and Darling, including 50 crash-handler processes. Roughly 3 GiB came from private anonymous mappings/native heaps; graphics mappings accounted for about 238 MiB. Large virtual address reservations are not equivalent to resident RAM, and summed RSS double-counts shared pages. Use proportional set size (PSS), swap and host memory pressure to assess the actual footprint.

The old kernel library returned success for Darwin allocator free/reuse hints without making any pages reclaimable. The replacement maps free/reusable hints to Linux MADV_FREE, and reuse to MADV_POPULATE_WRITE. The standalone 4 MiB buffer becomes reclaimable and returns to normal on reuse while preserving surviving data. This fixes a demonstrated runtime behavior, but does not explain all client allocations or prove a specific RAM reduction. Linux may retain lazily reclaimable pages in RSS while RAM is available. A five-minute idle observation did not show rapid client memory growth.

Build/install the kernel library using the incremental update steps, then perform the manual restart when finished playing. Linux 5.14+ is required. Do not kill client helpers as an attempted memory optimization during play.

Installer exits, cannot write temporary files, or Install appears idle

Use sh scripts/installer.sh euw (or your supported region). The first-time launcher must omit the installed client's --app-root and pass --skip-to-install; the normal wrapper now does this. It also selects league_of_legends so the product installation UI appears after login.

The installer window closing on its own, followed by subprocess exit, is usually a successful install: Riot's installer puts the client in /Users/Shared/Riot Games/Riot Client.app and exits, and its LaunchServices hand-off to that client does not start it under Darling. scripts/installer.sh now launches the installed client itself, and the runner links it to /Applications/Riot Client.app when that link is missing. If the client was not installed, the wrapper prints the installer's log directory; check the end of the newest Launcher log there.

If logs report guest /private/tmp permission errors, the default prefix needs its own temporary directory. The corrected full runtime installer creates it. To repair just this default-prefix directory as your ordinary user:

mkdir -p "$HOME/.darling/private/tmp"
chmod 1777 "$HOME/.darling/private/tmp"

The installer fetcher no longer treats a missing archive Info.plist or the informational unzip | head listing as a fatal download failure. Download and extraction errors still fail. The wrapper invokes this fetcher with Bash, since its pipefail setting is unsupported by some /bin/sh implementations.

There is also a separate known compatibility gap: native LaunchAgent watch registration can return HTTP 409 after the League install path is accepted, leaving the download idle. A historical inspector hook handles this and interrupted pending_verify states in 28 mock cases, but that hook is disabled in normal launches and excluded from the manual workflow. There is no verified runtime-only replacement for that handoff in this snapshot. Do not assume the native permission and launcher fixes resolve every idle Install case, or enable debugger/API automation to work around it.

Riot exits and League reports that it lost its connection

Check the launcher stderr or build/desktop-launch.log when launched through the generated application-menu entry. The following Objective-C exceptions were observed immediately before RiotClientServices aborted:

-[NSURLSessionDataTask initWithRequest:completionHandler:]: unrecognized selector
-[NSURLSession finishTasksAndInvalidate]: unrecognized selector

League then reports localhost connection refusal and loses its external-client authorization. Restarting temporarily clears the broken session, but does not implement the missing methods. The CFNetwork patch now supplies a minimal completion-handler data-task implementation, uses the existing NSURLConnection transport on a worker, and tracks outstanding tasks while a session finishes or cancels. Session factories create the concrete CFNetwork session so its delegate-queue storage is not confused with the public class's synthesized properties. The URL convenience method also preserves GET rather than forcing POST.

Rebuild and install the base and paired runtime with both clients and the game closed. Run the standalone NSURLSession regression in testing. This is partial NSURLSession compatibility: in-flight cancellation reports the cancellation once but does not interrupt the synchronous transport already in progress. Completion handlers use a global worker queue rather than the session's delegate queue. Delegate-only data tasks, suspension, background sessions, downloads and uploads are not established by these tests.

Client remains running without a window

New launches can exit with Client already running, exiting when a stale Riot session has no visible window. After exiting the game and clients, darling shutdown followed by scripts/run.sh recovers this case without deleting game files. For a dedicated Riot installation in the default prefix, Hyprland users can opt in to automatic recovery:

RCLOL_RECOVER_HIDDEN_CLIENT=1 ./scripts/run.sh

The helper requires an owned Riot process in the default prefix and a successful Hyprland window query. It preserves a running game, any visible Riot/League window, foreign-owned processes and custom prefixes, and takes no action when ownership or window information cannot be read. A hidden background client or download is restarted when recovery is enabled. Other desktop environments are not supported by this helper; recovery is off by default.

Client window stays black after a match

The League client keeps its Chromium/CEF UI (LeagueClientUx and its helpers) alive during a match. Riot's own "Close client during game" option closes that UI on Windows, but under Darling the pre-match instance keeps running: the client the backend starts when the match ends is a second CEF instance on the same --user-data-dir, and its window never paints. Its DOM and audio work and the window stays black. Closing the client by hand during the match leaves the same state for the same reason.

An opt-in helper closes that UI itself, from the host, and only while a match runs, so the client that appears afterwards is the only instance:

RCLOL_CLOSE_CLIENT_IN_GAME=1 ./scripts/run.sh

This is not a memory measure: the UI is closed because it competes with the game for CPU during the match. Measured on a four-core host with a Radeon RX 550, a practice match reported roughly 120 FPS with the client UI running and roughly 180 FPS with it closed. On that host a local supervisor using the same detection closed 13 client processes (2027 MiB resident) when a practice match started, and the client came back as one instance with a painted window when it ended; the helper described here has not been through a live match yet. Riot's own option is the equivalent on Windows, so leave either one disabled if the in-client chat is wanted during a match.

The helper is off by default and fails closed: it attributes both the game and the client to the launcher's prefix through the loader's __mldr_sockpath (guest processes do not carry DPREFIX), never closes a client younger than 60 seconds (the one the backend starts after a match), leaves the Riot client, the League backend and the game untouched, and takes no action when ownership, the environment or the stat fields cannot be read. The client UI is recognised by the name of its executable, not by the command line: LeagueCrashHandler processes carry the client UI name in their arguments only, so they are left alone. It leaves by itself after ten minutes without a client or a match. Diagnose it in one observation, without waiting for a match:

python3 tools/close-league-client-in-game.py --once --dry-run

Downloads repeatedly fail with an IPv6 CONNECT_TO error

The bundled downloader was observed retrying CDN chunks with:

Use of IPv6 in *_CONNECT_TO without IPv6 support built-in

The launcher now defaults RCLOL_CDN_IPV4_ONLY=1. The Libinfo resolver suppresses AAAA queries only for subdomains of riotcdn.net, retaining IPv4 DNS rotation, TLS and the normal resolver for all other names. It does not pin CDN addresses or disable IPv6 on the Linux host. Opt out with:

RCLOL_CDN_IPV4_ONLY=0 ./scripts/run.sh

The resolver change requires a rebuilt/installed base runtime. The environment flag alone cannot alter an older Libinfo binary.

Riot closes after a network lookup is cancelled

Two local crashes were traced to CFNetwork::_HostCancel calling CFRetain(NULL). CFHostCancelInfoResolution scheduled its cancellation callback with an empty context, so processing that source triggered SIGTRAP in CoreFoundation and terminated RiotClientServices. The UI helpers then exited as a consequence.

The CFNetwork patch supplies the host and retains it until the cancellation source is invalidated. The standalone riot-cfhost-cancel-check reproduces the old trap and passes 100 cancellations with the fix, including releasing the caller's host reference before callback delivery. This establishes the cancellation fix; a long Riot session still needs confirmation. With both clients and the game closed, run ./scripts/update.sh to install it, then sh scripts/run.sh.

UI crashes after a button opens an external link

LaunchServices dereferenced a nullable error-output pointer in six paths. The patch checks the pointer itself and populates supplied outputs; the standalone regression covers missing handlers and null outputs. Electron opens LaunchServices through an absolute CoreServices subframework path, so the paired installer also replaces that binary in the stopped guest prefix. Updating only RuntimeFrameworks/LaunchServices.framework can leave the crash unfixed.

LaunchServices now opens http, https and mailto links on the Linux desktop itself. It loads the host's libsystemd.so.0 and asks xdg-desktop-portal (org.freedesktop.portal.OpenURI) on the user session bus to open the link, so your default browser starts outside Darling and survives darling shutdown. Without a portal, it starts xdg-open in a transient systemd user unit instead. It also reports a handler for these schemes, since Electron checks for one before opening a link. Other schemes, control characters and URLs over 4096 bytes are rejected. If a link still does nothing, check the client's stderr for a LaunchServices: line and that busctl --user status org.freedesktop.portal.Desktop works on the host. Both LaunchServices and AppKit must be rebuilt. The hand-off passed the host-side D-Bus regression and opened the host browser from a guest through both open(1) and NSWorkspace; a link clicked in the Riot client is not yet confirmed. The null-pointer fix does not explain every unrelated button crash.

Riot client shows "Not Found" instead of its UI

On affected setups, including the reported NixOS installation, the client window opens but only shows Not Found, and its log has ENOENT, dist/renderer/index.html not found in …/app.asar although the archive contains that file. Electron's asynchronous file opening can copy an archive entry to a temporary file first (copyFileOut), and a failed copy can be reported as "not found". Chromium checks MAC_CHROMIUM_TMPDIR before falling back to NSTemporaryDirectory(); an unusable default temporary directory can therefore produce this symptom even while synchronous archive reads work.

The launcher defaults MAC_CHROMIUM_TMPDIR to /private/tmp, preserving a non-empty override. scripts/install-runtime.sh creates that guest directory with mode 1777. Verify directory creation and temporary-file writes with a standalone guest probe, then launch the client normally and check whether its UI loads. Do not run diagnostic scripts through Riot's executable. This workaround addresses temporary-file failures; an actually missing or damaged archive needs separate investigation.

Language dropdown closes Riot, or client resize leaves a clipped UI

The report in issue #1 contains an Electron renderer abort with Symbol not found: _CTFontDescriptorCreateMatchingFontDescriptors. CoreText now exports font-descriptor matching and localized-attribute lookup, and enumerates installed font families through fontconfig instead of returning a null stub. Localized lookup currently falls back to canonical font names. The standalone font-list check exercises Chromium's sequence, including mandatory family matching and retained results.

AppKit also left backing-layer geometry at the old size until a coordinate conversion occurred. It now updates that geometry during frame/bounds changes, and invalidates parent transforms before child resize callbacks. Native parent geometry is updated before resizing child windows, whose Y positions depend on the parent's current height. Standalone regressions reproduce both stale-size defects and pass with the corrections. A follow-up test confirmed that the language dropdown is fixed, but League still displays a 1280×720 image inside a 1600×900 window. The geometry regressions alone do not establish a fix for that remaining resize failure.

Rebuild and install the runtime using the update instructions, with the game and both clients closed. CoreText is now included in the GPU/runtime installer alongside AppKit; existing installations need this new override too. Until then, a locale can be selected at launch, for example RCLOL_REGION=BR RCLOL_LOCALE=pt_BR ./scripts/run.sh.

Live inspection subsequently confirmed a 1600×900 outer League window with both its CoreAnimation child and presentation target still at 1280×720. NSThemeFrame selected the last non-menu/toolbar child as the content view. A standalone reproduction showed that an overlay added after the real content received the resize instead. Frame layout now identifies the window's actual content owner (including a containing wrapper), and applies ordinary autoresizing masks to other decorations. A hidden-window regression reproduces the old behavior with an overlay sibling and passes after the fix. The user retested with this build loaded; League still failed to resize. This correction therefore does not resolve the remaining client failure.

The subsequent file trace showed the browser view reaching the new frame size without a renderer resize, and a later shrink left RenderWidgetHostViewCocoa at 1600×900 inside 1280×720 parents. Darling's NSView setFrame: directly updated geometry without dispatching setFrameSize:. Chromium's Cocoa implementation explicitly relies on this dispatch to notify the renderer. AppKit now calls the component setters for changed origins/sizes, with a private geometry updater to avoid recursion. A standalone subclass regression failed before this correction (one callback from four size changes) and passes after it (four callbacks, including parent autoresizing in both directions). The user retested with this AppKit build loaded and still saw clipping. Passive inspection then showed the native CoreAnimation child and a published frame at 1600×900, with the presentation target remaining at 1280×720.

The X11 presentation selector also retained a software publisher across popup updates even after the window outgrew its old presentation target. If that publisher switched to a small popup and a different publisher supplied the resized main frame, the selector kept following the popup slot and never resized the presentation child. It now retains that owner only while the old presentation dimensions still match a native target. A two-publisher standalone pixel regression reproduces the black enlarged area on the old backend; the new backend passes 1280×720 → 1600×900 → 1024×576 → 1280×720 with and without the shared-memory transport. After installing this backend locally, the user confirmed that League window resizing works (2026-10-15).

For the AppKit and X11 corrections, exit the game and both clients manually, then use the small update instead of rebuilding the entire runtime:

python3 scripts/configure.py
python3 build/runtime/tools/build-riot-appkit-runtime.py
python3 build/runtime/tools/build-riot-x11-runtime.py
darling shutdown
sh build/runtime/tools/install-riot-appkit-runtime.sh
sh scripts/run.sh

The installer requires the existing per-user AppKit overlay, saves a checksum-named backup under build/appkit-runtime-backups, and atomically replaces each binary, including the paired X11 backend. It does not stop processes or change the system SDK. After launch, change League between 1280×720 and 1600×900 and verify both the rendered extent and click alignment.

The installer previously preferred an existing build/riot-QuartzCore over its newly built build/m336-QuartzCore. It now installs the artifact it just rebuilt, and that builder recompiles all patched compositor and Metal presentation objects. This avoids silently installing an older optional probe build.

If resize clipping recurs, launch with size-only runtime tracing and resize the client manually:

mkdir -p build
env DARLING_UI_GEOMETRY_TRACE=1 sh scripts/run.sh 2>&1 \
  | rg --line-buffered '^UI_GEOMETRY ' | tee build/ui-geometry.log

Change from 1280×720 to 1600×900 and leave the client open at the broken size. AppKit also writes a bounded window/view hierarchy to the guest /tmp/darling-ui-geometry.log (host ~/.darling/private/tmp/darling-ui-geometry.log). Read that file as well as build/ui-geometry.log: League redirects stderr, so the terminal capture alone can omit all of its resize events. The traces record window/view classes, identities, dimensions and autoresizing masks, layer scale and IOSurface dimensions at size changes. Tracing is disabled on ordinary launches. It uses the runtime's own geometry setters and surface publisher, with no debugger, client API access or input automation.

The practice-tool exit in the same report remains unresolved: the supplied League client log records the game starting and exiting about two seconds later, but contains no game-process crash reason. These font and resize fixes do not establish a fix for that exit. Further diagnosis needs the game's own log/crash report or stderr from the affected machine.

Client reports macOS 10.10 and VAN -101

The legacy CarbonCore Gestalt implementation read a Darwin kernel release as though it were a macOS product version, then fell through into gestaltSysArchitecture, overwriting every result with gestaltIntel (10). The standalone probe reproduced gestalt=10.10.10 even though kern.osproductversion was already 14.7. Version selectors now read that existing product version, return before the architecture case, initialize missing patch versions to zero and implement the documented packed-BCD limits. Null outputs and unknown selectors return errors.

After installing this correction and restarting locally, the client reported macOS 14.7 and the user confirmed that Play became available. Later launches failed again, including a launch without DARLING_UI_GEOMETRY_TRACE. The running client was verified to have the corrected CarbonCore binary loaded. Both successful and failed sessions reported macOS 14.7; successful sessions logged MvgState: 0, while failed sessions logged MvgState: 5, despite MvgInit and MvgRegisterLogin returning zero in both. These state values are observations, not a diagnosis of their undocumented meaning. The version correction is therefore insufficient to resolve VAN -101, and tracing is not required to reproduce the failure. Entering a match remains unverified. Riot describes VAN -101 as an unsupported system configuration and recommends a supported operating system or a support ticket with logs. No verified Darling compatibility fix for this failure is available in this snapshot. A temporary test rollback of commit ac4a832 restores proc_listpids returning ENOTSUP; it was followed by both a successful launch and another VAN failure, so it has not established that commit as the cause. Tracing was enabled on the latter launch; its contribution remains unproven.

Build the small update with python3 build/runtime/tools/build-riot-carboncore-runtime.py. After manually exiting the game and both clients:

darling shutdown
sh build/runtime/tools/install-riot-carboncore-runtime.sh
sh scripts/run.sh

The installer adds a CarbonCore framework override and the matching absolute CoreServices subframework binary in the guest prefix, with checksum-named backups in build/carboncore-runtime-backups. It does not modify the SDK or restart processes. Both forms are needed because framework lookup and explicit subframework loading can take different paths. Ordinary full runtime installation includes this update too.

LOLSIGFAIL … addr=0x143 every 10 seconds

iokitd crashed in host glibc's pthread_mutex_lock and launchd restarted it every 10 seconds. It called eglGetDisplay() with an Xlib display, so Mesa picked the platform from EGL_PLATFORM. Wayland sessions often set that to wayland, and the first darling command passes its environment to every guest service, including iokitd. scripts/run.sh sets EGL_PLATFORM=x11 and was unaffected, but darling shell from a Wayland terminal (including the one in scripts/install-runtime.sh) started the loop. iokitd now requests the X11 platform explicitly. The fix is part of the base install (sudo cmake --install); until then, start Darling with EGL_PLATFORM=x11.

Blocky video or flickering startup logo

The first dynamically resolved GL call could lose floating-point arguments during ELF symbol lookup. Chromium's linear sampler request then failed and left nearest sampling. The generated resolver now preserves those registers. Install both the rebuilt native libGL.dylib in RuntimeLibraries and the OpenGL framework's library copy using the paired runtime installer; the framework alone is insufficient.

A separate multi-window path stopped the active async presenter when another differently sized surface was drawn in the same context. Such surfaces now use readback without stopping it. Native regressions cover both fixes; user confirmation of the startup splash remains pending. See testing for the first-call sampler and interleaved-window probes.

Build fails on a new compiler or runs out of memory

• objc4 debug macro mismatch: use the empty build type from scripts/build.sh, rather than Release/NDEBUG.
• OpenDirectory 32-bit ivar errors: keep TARGET_i386=OFF; the supported client is x86-64.
• Undefined empty Objective-C collection symbols: retain the patched macOS 10.15 Objective-C runtime code generation.
• LLVM branch opcode errors: retain the Indium LLVM 22/23 compatibility patch; do not replace its branch handling with an unconditional version-specific opcode.
• Scalar float errors or opcode 71 after updating: Unsupported LLVM value: float 0.000000e+00 (also 1.000000e+00) and Unhandled instruction opcode: 71 can result from compiling Iridium with LLVM 22 headers and loading LLVM 23. The LLVM C API changed enum values between those majors. The build now selects headers and the shared library together; initialization rejects a mismatched major with Iridium LLVM version mismatch. Close the game and both clients, then run git pull and ./scripts/update.sh to rebuild and reinstall both the base runtime and per-user overrides. If the same errors persist, include the update's Iridium LLVM headers: line and a newly generated metal-errors.log with the report.
• Every game shader fails to compile on LLVM 23 (r3dlog full of Failed to compile shader, then Material Missing Pipeline and a crash before the loading screen; /tmp/metal-errors.log shows Unsupported LLVM value: <3 x float> zeroinitializer): LLVM 23 represents vector splats as vector-typed ConstantFP/ConstantInt, which Iridium did not translate. Indium now splats them itself. Rebuild and reinstall the Metal/Indium pair (setup). The offline check python3 tools/build-riot-air-check.py --native translates shader libraries without the game.
• Build process killed: lower parallelism, for example JOBS=2 ./scripts/build.sh or --parallel 1 for an incremental component build.
• Incremental helper cannot find flags.make or link.txt: use Unix Makefiles, not Ninja.
• Prebuilt Swift file contains Git LFS pointer text: install Git LFS and fetch the original upstream assets; pointer text is not a usable library.
• Submodule fetch stops with no output right after src/external/sqlite: the next submodule is src/external/swift, whose pinned .lfsconfig points at the retired git-lfs.darlinghq.org. The checkout is blocked on that host, not on sqlite. prepare.py redirects that submodule's LFS requests to GitHub. To finish a fetch that was interrupted before any patches were applied, run git -C build/darling-src -c lfs.url=https://github.com/darlinghq/darling-swift.git/info/lfs submodule update --init --recursive --progress, then re-run ./scripts/build.sh. Do not run that submodule update once prepare.py has applied patches: it resets every submodule working tree to the pinned revision and discards the patches.

launchd crashes at boot after changing compiler flags

darling shell fails with Error connecting to shellspawn and /tmp/lolsig.log shows LOLSIGFAIL pid=1 sig=11 code=1 addr=0x0 in memmove, called from snprintf in libkqueue's epoll_event_dump. The binaries were tuned for AMD Zen: clang 23 with -mtune=znver* (also selected by -march=native or -mtune=native on Zen) loads a thread-local variable's descriptor into a register other than %rdi, but dyld's tlv_get_addr reads %rdi, so every __thread and thread_local access returns NULL. Rebuild with -mtune=generic (the default in scripts/build.sh and the overlay builders), and check any binary with:

python3 tools/check-darwin-tlv-calls.py <binary>...

It prints each thread-local access that calls its thunk without the descriptor in %rdi and exits 1. A plain darling shell boot does not load the RuntimeLibraries overlays; to boot the way the launcher does, run env DYLD_LIBRARY_PATH=/Users/<user>/RuntimeLibraries DYLD_FRAMEWORK_PATH=/Users/<user>/RuntimeFrameworks darling shell /usr/bin/true.

Base install refuses to continue while Darling is not running

sudo cmake --install prints Darling currently running for <user>, shutting it down... several times and then Darling launchd PID … remains alive after shutdown. A guest launchd outlived its darlingserver, so darling shutdown sees no container to stop. python3 build/runtime/tools/ensure-darling-runtime.py stops such a launchd (your own, only when no darlingserver runs); scripts/run.sh and scripts/install-runtime.sh run it too.

Lower fight FPS than Windows

The game code itself runs natively under Darling: the x86-64 slice of the universal binary executes unchanged, picks its instruction-set paths with cpuid on the real CPU, and sizes its worker pool from the real logical CPU count. What differs from Windows is the path around it. Every Metal call goes through Objective-C, the Metal wrapper, Indium and Vulkan instead of a native Direct3D driver, and kernel services go through the emulation and darlingserver. In an ARAM fight the game's own code now takes most of a frame; see status for measurements.

If FPS drops back towards the 10-13 morning numbers (75–85 on Hexgate):

1. Make sure the current kernel library, Metal and Indium overlays are installed and active: exit the game and both clients, then darling shutdown and sh scripts/run.sh (setup).
2. Check the game's line in /tmp/rclol-game-decisions.log: it should read local_semaphores=1 and core_isolation=0. No /tmp/rclol-no-local-* file should exist unless you created it on purpose.
3. A server wait above about 0.5 ms per frame means one of the local paths is off. A runqueue wait above a few percent on the main thread means the CPU is oversubscribed, for example by /tmp/rclol-core-isolation or background load.

Compare matches on the same map: Bilgewater runs a few percent below Hexgate.

On Hyprland, also check that direct scanout is off (hyprctl getoption render:direct_scanout prints int: 0). The first match with it off ran about 16 FPS faster than the previous one on the same build; see the next section.

On the NVIDIA proprietary driver, check the submit worker's kernel time: a thread of the game process spending most of its time in the kernel (/proc/<pid>/task/<tid>/stat system time, or perf trace -s -p <pid>) points at driver calls. Each vkQueueSubmit2 and each CPU-side vkSignalSemaphore is an RM control ioctl (command 0xc020462a) that queues on a driver-wide lock. Before 2026-10-18 every command buffer signalled the event loop's wake-up semaphore, ~25 times per frame; with lazy wake-ups (default) and a 5 ms batch window (/tmp/metal-submit-batch-us = 5000, /tmp/metal-submit-batch-max = 64) an RTX 4090 ran at 206–552 FPS against 91–147 FPS with /tmp/metal-no-lazy-wakeup, in alternating 20 s phases of one match (the later phases with wake-ups on were capped at 240 FPS) (see setup).

The NVIDIA performance figures above were reported on an earlier runtime base; they have not been remeasured after integration with current main.

Hybrid graphics laptops (AMD/Intel iGPU + NVIDIA)

Metal renders with Vulkan, and each finished frame is handed to an OpenGL (EGL) context that presents it. The hand-off uses opaque file descriptors, which only work when Vulkan and OpenGL run on the same GPU. Indium takes the first Vulkan device the loader lists, and on a hybrid laptop both that device and the EGL context are normally the integrated GPU, so the discrete GPU stays idle. A report in issue #3 (Ryzen 9 5900HS, RTX 3060 Laptop) measured 60-70 FPS in ARAM on the integrated GPU; on the NVIDIA GPU the game showed a black screen. Running on an NVIDIA GPU is not validated.

Run on the discrete GPU

Start the launcher with PRIME render offload so that both Vulkan and OpenGL move to the NVIDIA GPU:

prime-run sh scripts/run.sh

prime-run sets __NV_PRIME_RENDER_OFFLOAD=1, __VK_LAYER_NV_optimus=NVIDIA_only and __GLX_VENDOR_LIBRARY_NAME=nvidia. darling copies the caller's environment into the guest, and guest processes inherit it; whether the Riot client passes all of it to the game has not been checked; the log below shows the result. Darling's OpenGL uses EGL, so if the log below still shows the integrated GPU as the presenting renderer, also set __EGL_VENDOR_LIBRARY_FILENAMES=/usr/share/glvnd/egl_vendor.d/10_nvidia.json. On two Mesa GPUs, DRI_PRIME=1 does the same.

The guest file /tmp/metal-gpu (a device index or part of its name, for example nvidia) moves only the Vulkan side. Use it for diagnosis: on its own it splits the two sides across GPUs, and frames cannot be presented.

Check which GPU rendered

Each process that uses Metal appends to guest /tmp/metal-device.log (host ~/.darling/private/tmp/metal-device.log): every Vulkan device the loader reported, the selected one and why, and the renderer of the presenting OpenGL context with both device UUIDs:

[MetalDevice] pid=… physical name="NVIDIA GeForce RTX 3060 Laptop GPU" type=discrete vendorID=0x10de … supported=yes
[MetalDevice] pid=… selected name="NVIDIA GeForce RTX 3060 Laptop GPU" type=discrete … reason=loader-first
[MetalDevice] pid=… created VkDevice for 1 of 1 supported device(s) (selected only)
[MetalDevice] pid=… presenting GL renderer="…" vendor="NVIDIA Corporation" … match=yes

MISMATCH on the presenting line means Vulkan and OpenGL are on different GPUs. match=unknown means the OpenGL driver reports no device UUID. Include this file with performance reports.

The log also lists the selected device's memory heaps and types, and one line the first time each kind of resource (buffer, texture, drawable, drawable-internal) gets a storage mode and memory type:

[MetalDevice] pid=… memory heap=0 size=6144MiB deviceLocal=yes
[MetalDevice] pid=… memory type=0 flags=0x0(none) heap=1
[MetalDevice] pid=… memory alloc kind=texture storage=private typeBits=0x… type=1 flags=0x1(DEVICE_LOCAL) heap=0 heapDeviceLocal=yes firstFit=0 flags=0x0(none) heap=1 heapDeviceLocal=no changed=yes

Resources only the GPU uses (private, memoryless, and drawables, including League's framebufferOnly-off ones unless /tmp/metal-no-drawable-vram exists) take the first allowed DEVICE_LOCAL type. Before 2026-10-16 they took the first allowed type (firstFit), which on NVIDIA can be system RAM; changed=yes marks where the two differ. shared and managed resources keep the first host-visible type. On the RX 6600 (RADV) type 0 is DEVICE_LOCAL, so nothing changes there.

The first import of a drawable into the presenting OpenGL context, and the first semaphore import, are logged too; later ones only when they fail (at most five):

[MetalDevice] pid=… drawable GL import (first) dedicated=yes size=… 1920x1080 memoryType=1 vkTiling=linear glTiling=linear dedicated_error=0x0 import_error=0x0 setup_error=0x0 storage_error=0x0 query_error=0x0 ok
[MetalDevice] pid=… drawable GL semaphore (first) import_error=0x0 wait_error=0x0 ok (checked for the first 600 imports)

A non-zero error or FAILED means the frames cannot reach the window. Before 2026-10-16 the import did not mark the memory as dedicated, which the extension requires; Mesa ignores it, and it is the suspected cause of the NVIDIA black screen (not yet confirmed). An NVIDIA log of 2026-10-16 showed glTiling=optimal with setup_error=0x501 storage_error=0x501 FAILED: NVIDIA's GL rejects GL_LINEAR_TILING_EXT, so the linear Vulkan image could not be imported. Since then the internal image and the GL texture use optimal tiling when GL_VENDOR contains NVIDIA (vkTiling=optimal glTiling=optimal ok is the expected line); everything else keeps linear. If the game shows a black screen on NVIDIA, report it with this file.

An additional NVIDIA report on 68f816d showed successful optimal-tiling import but repeated Metal Device timed out giving us a Drawable to present messages. Its presentation trace shows all three drawables queued and all three main-thread presentation callbacks running, followed by timeouts with three frames still queued. The compositor only prepared a Metal layer when it was the root layer, skipping nested Metal layers. It now prepares Metal layers throughout the tree. A standalone nested-layer reproduction exhausts the pool before this correction and passes ten presentations with pixel readback after it; the root-layer probe also passes. Confirmation on the reporter's NVIDIA system is still needed.

NVIDIA resize signals, CPU readback and completion latency

The EGL-compatible window visual, compositor back buffer and collision-safe RPC socket allocation fixes are already part of the runtime. The remaining NVIDIA work covers these independent paths:

• A terminal resize can deliver SIGWINCH to a native driver thread without a Darling RPC socket. The runtime forwards that resize notification to the guest main thread; it keeps the existing handling for other signals and faults.
• With RCLOL_GPU_DIRECT_PRESENT=0, Chromium frames arrive through CPU readback. The local compositor skips non-Metal trees to avoid covering the live client with stale cached textures. Mixed trees still prepare and present Metal layers.
• NVIDIA timeline waits can wake late after GPU completion. Each device now polls briefly while completions are pending before blocking: 2000 microseconds by default on NVIDIA and zero on other vendors. An idle device blocks immediately. The guest file /tmp/metal-wait-spin-us overrides the budget when the device is created; 0 disables polling. Values are capped at 10000 microseconds and malformed values use the vendor default. Restart Darling to change the budget.

The contributor reported custom matches on a single-GPU RTX 3060, driver 615.71, with sway/Xwayland using CPU readback. The initial polling change improved their reported rate from about 20 to 27 FPS. Those observations predate the narrowed integration; they do not establish hybrid-GPU or general NVIDIA support.

NVIDIA 580 (Pascal and older): black game window

Driver 580 is the last branch for Pascal (GTX 10-series) and older GPUs. With __GL_THREADED_OPTIMIZATIONS=1, this driver with egl-x11 1.0.6 rejects the X11 EGLDisplay with EGL_BAD_DISPLAY on every thread that has a context current. The display stays valid on other threads, and eglReleaseThread() makes it work again on the failing one. A small native EGL program outside Darling shows the same: eglQueryString(display, EGL_VENDOR) after eglMakeCurrent returns NVIDIA without the variable and fails with EGL_BAD_DISPLAY with it.

In the Riot client the main thread loses EGL right after its first window frame; CGLCreateContext then fails with CGL error 10004 and, if another display is opened, glvnd hands it to Mesa's software renderer, which cannot present the game's NVIDIA Vulkan frames. The launcher therefore leaves threaded optimizations off (__GL_THREADED_OPTIMIZATIONS=0). Setting the variable to 1 before launch restores the old behaviour.

Tested on a GTX 1060 6GB with driver 580.178.04 on NixOS, Hyprland and Xwayland: the client and the tutorial match render on the NVIDIA GPU. Newer drivers were not retested with the option off.

Metal device name and memory budget

MTLDevice reports the host GPU: its Vulkan name in macOS style (for example AMD Radeon RX 6800 XT (RADV NAVI21) becomes AMD Radeon RX 6800 XT) and a working set (recommendedMaxWorkingSetSize) from the GPU's Vulkan memory heaps. Apps size their GPU allocations from the working set, so only override it to match the card's real memory. Both can be overridden per launch:

DARLING_METAL_GPU_NAME='AMD Radeon Pro 5500M' DARLING_METAL_VRAM_MB=4096 ./scripts/run.sh

The Riot launcher sets DARLING_METAL_MAC_GPU_NAME=1: the name becomes the GPU that the MacBookPro16,1 IOKit reports shipped with, from the host's vendor: AMD Radeon Pro 5500M on AMD and Intel UHD Graphics 630 on Intel. NVIDIA GPUs keep their own name, so the game never takes AMD or Intel driver paths on an NVIDIA card. The working set is still the host's. DARLING_METAL_MAC_GPU_NAME=0 ./scripts/run.sh reports the host name instead; other Darling apps report it unless they set the variable. DARLING_METAL_GPU_NAME wins over both.

registryID is a fixed non-zero value, as on a real Mac.

Host-side checks

These are host settings, not game settings. Run on AC power, and use a performance power profile (powerprofilesctl set performance, or asusctl profile -P Performance on ASUS laptops). On the tested desktop the game is limited mostly by its own main thread on the CPU, not by the GPU (see status), so laptop CPU power limits matter as much as the GPU choice.

Mouse latency despite good FPS

Issue #10 reports mouse latency with FPS comparable to Windows. FPS alone does not measure input-to-display latency, and the report does not yet identify which stage adds the delay.

The X11 backend previously called XSync after every cursor-shape update, waiting for an X server reply on the input thread. It now uses XFlush to send the change immediately without waiting. This removes an avoidable round trip during cursor updates. A local manual retest on 2026-10-16 found that the mouse problem no longer occurred with VSync enabled. Input-to-display latency has not been measured, and confirmation from the original reporter is still pending. Rebuild and install with ./scripts/update.sh after exiting the game and both clients.

A later input trace showed League setting the cursor about 190 times and unhiding it about 100 times per second, each time sending the same cursor to the X server. The backend now skips the update when the window already has that cursor. The effect on latency has not been measured.

The backend's relative mouse mode (CGAssociateMouseAndMouseCursorPosition(false)) previously warped the pointer to the window center, treated the game's own cursor warps as motion and reported deltaY upside down. It now follows macOS: the cursor stays where it is, events carry the physical motion as deltas (positive deltaY downwards, also for ordinary motion), the game's warps move the cursor without a delta, and +[NSEvent mouseLocation] returns that cursor. On Xwayland a warp takes effect only while the cursor is hidden, so with a visible cursor the pointer is not held in place. python3 tools/riot-input-offline-check.py checks the shipped patch on the host without fetching Darling. Add --xvfb /path/to/Xvfb to exercise real Xorg protocol on an isolated virtual display; it never uses your desktop display. For Xorg/XLibre (issue #17), relative capture now starts from a fresh XQueryPointer snapshot and ignores older queued motion. Warp echoes match both their X request serial and position, so a real motion crossing the anchor cannot be mistaken for an echo. Application warp targets are clipped to the grabbed window in root coordinates, including on a secondary monitor; events, mouseLocation, and rewarps share that target. Queued motion before a pending warp does not generate another rewarp. A failed pointer query leaves relative capture suspended, and focus loss releases the grab until the window receives keyboard focus again. Host regression tests cover these paths, but League on the tested Hyprland setup never enters this mode; in-game confirmation on XLibre is still required.

For a manual comparison, keep the scene, FPS cap, display refresh and compositor settings the same. Record whether the delay affects the cursor itself, camera movement, or actions after clicking, and compare the in-game VSync setting on and off. Include the desktop/compositor, X11 or Xwayland session, GPU/driver, monitor refresh and fullscreen/windowed mode in the report. Do not automate game input. The fullscreen cursor-shape problem below is a separate known symptom.

Click offset grows towards the bottom of the screen

A growing vertical offset has been reported on KDE Plasma/Wayland with Xwayland. The cause is unconfirmed, including whether it is related to commit 426fb75. The borderless fullscreen request has been restored separately; retest alignment once the game covers the panel.

If it persists, enable the passive input trace before the next manual game launch:

darling shell touch /tmp/rclol-input-trace

The flag is checked once per process, so enable it before launching the game. During a short manual test, compare clicks near the top, middle and bottom, and note the direction and approximate size of the error. Include the in-game resolution and window mode, Plasma's scale setting for each monitor, and the host output of xrandr --listmonitors. Collect the guest log with:

darling shell cat /tmp/rclol-input-trace.log > rclol-input-trace.log
darling shell rm -f /tmp/rclol-input-trace

Removing the flag disables tracing for subsequently started processes. The log records motion, warps, pointer-position queries and relative-mode transitions; it can establish whether the relative path is active, but cannot by itself establish where the game rendered a clicked target. If practical, compare the same resolution in a smaller window and in borderless fullscreen.

Cursor stops changing shape in fullscreen

On Hyprland the game's cursor can keep its first shape (for example, it never switches to the attack cursor) until you leave and re-enter fullscreen. Darling sends every change to the X server; what freezes the shape on screen is Hyprland's direct scanout of the fullscreen Xwayland window. Turn it off in hyprland.conf:

render {
    direct_scanout = 0
}

hyprctl keyword render:direct_scanout 0 applies it until Hyprland restarts.

Black layer over a running Metal game

The X11 Chromium presenter searches shared Core Animation frame slots by surface size. Native League game windows now bypass that presenter, so a same-size client frame cannot create a presentation child over the game's Metal drawable. This also disables the remote-frame polling timer for the game while preserving Chromium client presentation.

tools/riot-remote-frame-ownership-check.m exercises the cached-frame path without creating a display or window. tools/build-riot-x11-runtime.py builds this probe. For an unidentified overlay, python3 tools/trace-riot-windows.py --output build/riot-window-trace.jsonl passively records Riot/League windows, including unmanaged windows and child stacking, for one hour. It requires the host python-xlib package and does not send input.

If a black fullscreen game has only its normal Metal child and becomes visible after removing and restoring fullscreen, inspect the initial fullscreen transition. Automatic fullscreen now requires the window to cover an active monitor, so temporary 1x1 startup windows and ordinary windowed sizes are not promoted. Explicit Cocoa fullscreen requests are preserved. riot-fullscreen-geometry-check (built by the X11 builder) checks the policy against active XRandR monitor geometry using only read requests; the next game launch is still required to validate the startup sequence.

Visible cursor while relative on Xwayland (PR #18)

When Xwayland does not honour warps, the virtual cursor follows real pointer motion and application warps leave it in place. Expected warp echoes are still discarded using their request serial and coordinates. This keeps clicks and camera edge panning aligned with the visible cursor on GNOME/gamescope. The contributor confirmed this path in a gamescope practice-tool session; plain GNOME and NVIDIA still require manual verification.

Recovery requires every matching client to be at least 60 seconds old and a complete Hyprland window record (class, title, mapped, hidden). A second process scan after window inspection must find the same client identities and no game. Missing information or shutdown failure leaves normal launch in charge.