MobileGL/userguide/configuration.md

Configuration

MobileGL is configured with MOBILEGL_* variables. This page lists the ones meant for users. Variables that exist for development, CI and benchmarking (MOBILEGL_PIPE_*, most MOBILEGL_IPC_* tuning knobs, quirk overrides) are left out on purpose. Some of them are negative controls that break rendering by design.

Where settings come from

Settings are read once, when the library initializes in a process. Changing them later has no effect until the process restarts.

Source	Platform	Precedence
debug.mobilegl.backend property	Android	Overrides MOBILEGL_BACKEND_TYPE from every other source
debug.mobilegl.transport property	Android, split builds	Overrides MOBILEGL_TRANSPORT from every other source
Process environment	all	Highest for everything else
/etc/mobilegl/backend (one line: the backend name)	desktop Linux	Below the environment; MOBILEGL_BACKEND_TYPE only
/etc/mobilegl/client.conf (KEY=value lines)	desktop Linux	Below the backend file
debug.mobilegl.env property (KEY=VALUE;KEY=VALUE, at most 91 characters)	Android	Below the environment
Built-in default	all	Lowest

• Only keys starting with MOBILEGL_ or LIBGL_ are accepted from the environment and from client.conf.
• MOBILEGL_CONFIG_FILE and MOBILEGL_BACKEND_FILE name other files instead of the two /etc files; an empty value turns a file off.
• A server process (MOBILEGL_IPC_ROLE=server) reads neither file nor debug.mobilegl.env.
• Settings marked env only below are read straight from the process environment. They ignore the files and debug.mobilegl.env.
• On Android, use adb shell setprop <property> <value> (no root needed). Properties apply to every app on the device that loads MobileGL, and last until reboot.

Value rules:

• Flag: on when set to anything other than empty, 0 or false (case-insensitive).
• Auto/on/off: unset keeps the built-in choice; a flag-true value forces it on; anything else forces it off.
• Integer: a value outside the range is ignored with a warning in the log, and the default is used.

Where a setting takes effect: each process reads its own settings. When you connect to a server that was started separately (the plugin's render server, a Linux server), the backend settings (MOBILEGL_ESPRYT_*, MOBILEGL_MAGMA_*, MOBILEGL_FRAMES_IN_FLIGHT) belong in the server's environment too. The backend itself is the exception: the client asks for it (see MOBILEGL_BACKEND_TYPE).

Backend and general

Variable	Values	Default	Meaning
MOBILEGL_BACKEND_TYPE	DirectGLES, DirectVulkan	DirectGLES	Espryt (GLES) or Magma (Vulkan). Case-sensitive. Any other value leaves MobileGL without a backend. In a split session the client's value is sent to the server, which uses it unless the server pinned a different one.
MOBILEGL_FRAMES_IN_FLIGHT	1-64	3	How many frames may be queued ahead of the GPU. Magma: its frame contexts. Espryt: after presenting frame N it waits for frame N+1-value to finish (1 = full CPU/GPU sync). Split topologies: the client may run max(1, value - 2) presents ahead of the server, so 4 gives one more frame of overlap (and of latency). The old name MOBILEGL_MAGMA_FRAMESINFLIGHT still works but is deprecated.
MOBILEGL_RELAXED_SEMANTICS	flag	off	Apply legacy leniencies (for example drawing with vertex array object 0, reusing texture names after delete) even to contexts that explicitly requested a core profile. Contexts that did not request core get them anyway.
MOBILEGL_ADVERTISE_FP64	flag	off	Advertise GL_ARB_gpu_shader_fp64. double types compile either way but run at 32-bit precision.
MOBILEGL_DISABLE_TIMERQUERY	flag	off	Hide and disable GPU timer queries
MOBILEGL_COHERENT_AS_FLUSH	flag	off	Treat persistent maps with GL_MAP_FLUSH_EXPLICIT_BIT as coherent, for engines that never flush them
MOBILEGL_ASYNC_SHADER_COMPILE	auto/on/off	on	Compile and link shaders on worker threads. Off runs them on the calling thread and withdraws GL_KHR_parallel_shader_compile.
MOBILEGL_ASYNC_SHADER_COMPILE_THREADS	0-64	0	Worker count; 0 = min(4, number of big cores)
MOBILEGL_SHADER_CACHE	auto/on/off	on	In-memory shader translation cache. Turn it off to rule it out when a shader renders wrongly.
MOBILEGL_ES_CONTEXT_IDENTITY	1	off	env only. Contexts created for the OpenGL ES API report themselves as OpenGL ES 3.2 instead of the desktop version

Espryt (DirectGLES)

Variable	Values	Default	Meaning
MOBILEGL_ESPRYT_USE_ANGLE	flag	off	Load libEGL_angle.so / libGLESv2_angle.so instead of the system EGL/GLES. Not used on Windows, where Espryt always loads ANGLE's libEGL.dll / libGLESv2.dll.
MOBILEGL_ESPRYT_AVOID_SAMPLER_MIPMAP_MIN_FILTER	flag	off	Avoid mipmap minification filters in samplers (a workaround for certain driver bugs)
MOBILEGL_YUV_DRIVER_CONVERSION	1	off	env only. Convert YUV images with the driver's external-sampler conversion instead of MobileGL's own

Magma (DirectVulkan)

Variable	Values	Default	Meaning
MOBILEGL_MAGMA_DISABLE_SUBGROUP	flag	off	Do not use Vulkan subgroup operations in shaders
MOBILEGL_MAGMA_R11G11B10F_FALLBACK	flag	off	Use a fallback format for GL_R11F_G11F_B10F
MOBILEGL_MAGMA_MAX_DRAWS_PER_COMMAND_BUFFER	0-16777216	16384	Submit a command buffer mid-frame after this many draws/dispatches (0 = never). Bounds driver memory in huge loading frames.
MOBILEGL_MAGMA_DESCRIPTOR_TRIM_FRAMES	0-1048576	120	Free grown descriptor pools after this many quiet frames (0 = never)
MOBILEGL_MAGMA_EXTRA_SWAPCHAIN_IMAGES	0-16	0	Ask for this many swapchain images beyond the surface's minimum (capped at its maximum). The window buffer the display has just released is then reused later, when its release has usually signaled, so fewer frames wait for it. Each image costs a full-size colour buffer plus a depth/stencil buffer of the same size.
VK_ICD_FILENAMES	path to an ICD JSON	loader default	Standard Vulkan loader variable: picks the Vulkan driver

Logging and diagnostics

Variable	Values	Default	Meaning
MOBILEGL_LOG_FILE_PATH	path	Android: /sdcard/MG/latest.log; elsewhere none	env only. Log file. Split builds write <name>.client<ext> and <name>.server<ext> instead (for example latest.client.log); in a client, .server receives the lines the server forwards. The file is truncated when opened. On Android, logs also go to logcat with tag MobileGL.
MOBILEGL_FPS_LOG	1	off	env only (Android: also debug.mobilegl.fps_log). One line about every two seconds with frame rate and frame time.
MOBILEGL_GPU_HANG_BUDGET_MS	0-600000	2000	env only (Android: also debug.mobilegl.gpu_hang_budget_ms). A GPU submission running longer than this ends its session as hung. 0 turns the watchdog off; do that on slow software rasterizers.

Transport (split builds only)

Variable	Values	Default	Meaning
MOBILEGL_TRANSPORT	monolith, inproc, spawn	monolith	Where the backend runs (README.md). unix:... / pipe:... are rejected (logged, and the run stays monolith); use MOBILEGL_IPC_CONTROL. Ignored in builds without the split layer.
MOBILEGL_IPC_CONTROL	fork, unix:<path>, unix:@<name>, tcp://<host>:<port>	fork	With spawn: fork launches a private server; the others connect to a running one. (fd:<a>,<b> is set by the plugin's external-client helper.)
MOBILEGL_IPC_DATA	auto, shm, stream	auto	Data plane. auto picks shared memory for Unix sockets and fork, and a stream for TCP; TCP accepts only stream, the others only shm.
MOBILEGL_IPC_SURFACE	offscreen, server	offscreen	server: window surfaces are created on the server's own window, and the client's window handle is ignored. Needs a server with a display (the plugin's on-screen server, or an app embedding one). Only meaningful with spawn.
MOBILEGL_IPC_TOKEN	string	none	env only. Shared secret; client and server must agree. A server listening on a non-loopback TCP address requires one of at least 16 bytes.
MOBILEGL_IPC_SERVER_PATH	path	next to libMobileGL.so	Server executable for fork
MOBILEGL_IPC_PROBE_TIMEOUT_MS	0-60000	250	Before starting a session, probe the configured unix:/tcp:// endpoint; if nothing answers, the EGL/GLX/GBM entry points decline so the system's next GL implementation is used. 0 disables the probe.
MOBILEGL_IPC_RECOVER	0, 1	1	After the server dies or the device is lost, let the next eglCreateContext / eglCreate*Surface / eglInitialize start a fresh session. 0 makes the loss final for the process.
MOBILEGL_IPC_CONTROL_TIMEOUT_MS	100-600000	5000	How long the client waits for an answer to a surface operation
MOBILEGL_IPC_COLD_START_MS	100-600000	20000	The same wait while the server brings its backend up (first surface and first make-current)
MOBILEGL_IPC_PRESENT_CREDIT	1-8	derived from MOBILEGL_FRAMES_IN_FLIGHT	Explicit override of how many presents the client may run ahead
MOBILEGL_IPC_REQUIRE_SAME_BUILD	1	off	env only. Refuse a server built from a different revision (by default that is a warning)

Server process

libMobileGLServer.so and embedding apps (see android-plugin.md):

Variable	Meaning
MOBILEGL_IPC_DIAL=no	Required in the server's environment. It stops the server from acting as a client itself.
MOBILEGL_IPC_ROLE=server	Marks the server role. libMobileGLServer.so sets it itself; an embedding app sets it before loading the library.
MOBILEGL_IPC_ENDPOINT	Endpoint, when none is given on the command line
MOBILEGL_BACKEND_TYPE	Optional: pin the server to one backend and refuse clients asking for the other
MOBILEGL_IPC_TOKEN	Token clients must present
MOBILEGL_IPC_INPROC_MAX_SESSIONS	Concurrent sessions of an embedded Unix-socket server (default 16, at most 256)

The server refuses to start (exit code 65) if it inherited MOBILEGL_TRANSPORT, MOBILEGL_IPC_SERVER_PATH, MOBILEGL_IPC_RING_MB or MOBILEGL_IPC_STAGE_MB.

Linux desktop

Variable	Meaning
MOBILEGL_CONFIG_FILE, MOBILEGL_BACKEND_FILE	env only. Other config files (default /etc/mobilegl/client.conf, /etc/mobilegl/backend); empty = none
MOBILEGL_DEVICE_DRM_NODE	Render node reported as MobileGL's EGL device (default /dev/dri/renderD128)
MOBILEGL_WAYLAND_DMABUF	env only. 0 presents Wayland windows through wl_shm instead of dma-bufs
MOBILEGL_GLX_PRESENT	env only. readback, shm or putimage forces a GLX readback path instead of DRI3/Present
MOBILEGL_X11_DIAL	env only. Override whether MobileGL may open an X11 connection
MOBILEGL_GBM_LIBRARY	env only. Where mobilegl_gbm.so loads libMobileGL.so from
__EGL_VENDOR_LIBRARY_FILENAMES, __GLX_VENDOR_LIBRARY_NAME, GBM_BACKEND	glvnd / libgbm variables that select MobileGL; see linux.md