Make slog-stdlog into an optional dependency

slog-stdlog has a significant dependency tree and is basically unsued if
the downstream crate of Smithay always provides a logger (like anvil),
so it is not really needed.

Cargo.toml

@@ -24,7 +24,7 @@ libc = "0.2.70"
 libloading = "0.6.0"
 nix = "0.17"
 slog = "2"
-slog-stdlog = "4"
+slog-stdlog = { version = "4", optional = true }
 tempfile = "3.0"
 thiserror = "1"
 udev = { version = "0.4", optional = true }
@@ -46,7 +46,7 @@ gl_generator = { version = "0.14", optional = true }
 pkg-config = { version = "0.3.17", optional = true }
 
 [features]
-default = ["backend_winit", "backend_drm_legacy", "backend_drm_atomic", "backend_drm_gbm", "backend_drm_eglstream", "backend_drm_egl", "backend_libinput", "backend_udev", "backend_session_logind", "renderer_glium", "xwayland", "wayland_frontend"]
+default = ["backend_winit", "backend_drm_legacy", "backend_drm_atomic", "backend_drm_gbm", "backend_drm_eglstream", "backend_drm_egl", "backend_libinput", "backend_udev", "backend_session_logind", "renderer_glium", "xwayland", "wayland_frontend", "slog-stdlog"]
 backend_winit = ["winit", "wayland-server/dlopen", "backend_egl", "wayland-egl", "renderer_gl", "use_system_lib"]
 backend_drm = ["drm", "failure"]
 backend_drm_atomic = ["backend_drm"]

src/backend/drm/atomic/mod.rs

@@ -220,7 +220,7 @@ impl<A: AsRawFd + 'static> AtomicDrmDevice<A> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm"));
         info!(log, "AtomicDrmDevice initializing");
 
         let dev_id = fstat(fd.as_raw_fd()).map_err(Error::UnableToGetDeviceId)?.st_rdev;

src/backend/drm/common/fallback.rs

@@ -181,7 +181,7 @@ impl<A: AsRawFd + Clone + 'static> FallbackDevice<AtomicDrmDevice<A>, LegacyDrmD
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm_fallback"));
         info!(log, "Trying to initialize AtomicDrmDevice");
 
         let force_legacy = env::var("SMITHAY_USE_LEGACY")
@@ -246,7 +246,7 @@ where
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm_fallback"));
 
         let driver = crate::backend::udev::driver(dev.device_id()).expect("Failed to query device");
         info!(log, "Drm device driver: {:?}", driver);
@@ -299,7 +299,7 @@ where
         D2: NativeDisplay<B2, Arguments = EglDeviceArguments>,
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm_fallback"));
         match dev {
             FallbackDevice::Preference(gbm) => match EglDevice::new(gbm, log) {
                 Ok(dev) => Ok(FallbackDevice::Preference(dev)),
@@ -335,7 +335,7 @@ where
         D2: NativeDisplay<B2, Arguments = EglDeviceArguments>,
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm_fallback"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm_fallback"));
         match dev {
             FallbackDevice::Preference(gbm) => {
                 match EglDevice::new_with_defaults(gbm, default_attributes, default_requirements, log) {

src/backend/drm/egl/mod.rs

@@ -123,7 +123,7 @@ where
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_egl"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_egl"));
 
         dev.clear_handler();
 

src/backend/drm/eglstream/mod.rs

@@ -98,7 +98,7 @@ impl<D: RawDevice + ControlDevice + 'static> EglStreamDevice<D> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_eglstream"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_eglstream"));
 
         raw.clear_handler();
 

src/backend/drm/gbm/mod.rs

@@ -106,7 +106,7 @@ impl<D: RawDevice + ControlDevice + 'static> GbmDevice<D> {
             );
         });
 
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_gbm"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_gbm"));
 
         dev.clear_handler();
 

src/backend/drm/legacy/mod.rs

@@ -119,7 +119,7 @@ impl<A: AsRawFd + 'static> LegacyDrmDevice<A> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_drm"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_drm"));
         info!(log, "LegacyDrmDevice initializing");
 
         let dev_id = fstat(dev.as_raw_fd())

src/backend/egl/context.rs

@@ -33,7 +33,7 @@ impl EGLContext {
         B: native::Backend,
         N: native::NativeDisplay<B>,
     {
-        let log = crate::slog_or_stdlog(log.into()).new(o!("smithay_module" => "renderer_egl"));
+        let log = crate::slog_or_fallback(log.into()).new(o!("smithay_module" => "renderer_egl"));
 
         // If no version is given, try OpenGLES 3.0, if available,
         // fallback to 2.0 otherwise

src/backend/egl/display.rs

@@ -69,7 +69,7 @@ impl<B: native::Backend, N: native::NativeDisplay<B>> EGLDisplay<B, N> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger.into()).new(o!("smithay_module" => "renderer_egl"));
+        let log = crate::slog_or_fallback(logger.into()).new(o!("smithay_module" => "renderer_egl"));
         let ptr = native.ptr()?;
         let egl_attribs = native.attributes();
 

src/backend/egl/surface.rs

@@ -50,7 +50,7 @@ impl<N: native::NativeSurface> EGLSurface<N> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(log.into()).new(o!("smithay_module" => "renderer_egl"));
+        let log = crate::slog_or_fallback(log.into()).new(o!("smithay_module" => "renderer_egl"));
 
         let surface_attributes = {
             let mut out: Vec<c_int> = Vec::with_capacity(3);

src/backend/libinput/mod.rs

@@ -47,7 +47,7 @@ impl LibinputInputBackend {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_libinput"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_libinput"));
         info!(log, "Initializing a libinput backend");
         LibinputInputBackend {
             context,

src/backend/session/auto.rs

@@ -69,7 +69,7 @@ impl AutoSession {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let logger = crate::slog_or_stdlog(logger)
+        let logger = crate::slog_or_fallback(logger)
             .new(o!("smithay_module" => "backend_session_auto", "session_type" => "auto"));
 
         info!(logger, "Trying to create logind session");

src/backend/session/dbus/logind.rs

@@ -89,7 +89,7 @@ impl LogindSession {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let logger = crate::slog_or_stdlog(logger)
+        let logger = crate::slog_or_fallback(logger)
             .new(o!("smithay_module" => "backend_session", "session_type" => "logind"));
 
         // Acquire session_id, seat and vt (if any) via libsystemd

src/backend/session/direct.rs

@@ -168,7 +168,7 @@ impl DirectSession {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let logger = crate::slog_or_stdlog(logger)
+        let logger = crate::slog_or_fallback(logger)
             .new(o!("smithay_module" => "backend_session", "session_type" => "direct/vt"));
 
         let fd = tty

src/backend/udev.rs

@@ -78,7 +78,7 @@ impl UdevBackend {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_udev"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_udev"));
 
         let devices = all_gpus(seat)?
             .into_iter()

src/backend/winit.rs

@@ -152,7 +152,7 @@ pub fn init_from_builder_with_gl_attr<L>(
 where
     L: Into<Option<::slog::Logger>>,
 {
-    let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "backend_winit"));
+    let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "backend_winit"));
     info!(log, "Initializing a winit backend");
 
     let events_loop = EventLoop::new();

src/lib.rs

@@ -2,7 +2,10 @@
 //! **Smithay: the Wayland compositor smithy**
 //!
 //! Most entry points in the modules can take an optional [`slog::Logger`](::slog::Logger) as argument
-//! that will be used as a drain for logging. If `None` is provided, they'll log to `slog-stdlog`.
+//! that will be used as a drain for logging. If `None` is provided, the behavior depends on
+//! whether the `slog-stdlog` is enabled. If yes, the module will log to the global logger of the
+//! `log` crate. If not, the logs will discarded. This cargo feature is part of the default set of
+//! features of Smithay.
 
 // `error_chain!` can recurse deeply
 #![recursion_limit = "1024"]
@@ -29,7 +32,8 @@ pub mod xwayland;
 
 pub mod reexports;
 
-fn slog_or_stdlog<L>(logger: L) -> ::slog::Logger
+#[cfg(feature = "slog-stdlog")]
+fn slog_or_fallback<L>(logger: L) -> ::slog::Logger
 where
     L: Into<Option<::slog::Logger>>,
 {
@@ -38,3 +42,13 @@ where
         .into()
         .unwrap_or_else(|| ::slog::Logger::root(::slog_stdlog::StdLog.fuse(), o!()))
 }
+
+#[cfg(not(feature = "slog-stdlog"))]
+fn slog_or_fallback<L>(logger: L) -> ::slog::Logger
+where
+    L: Into<Option<::slog::Logger>>,
+{
+    logger
+        .into()
+        .unwrap_or_else(|| ::slog::Logger::root(::slog::Discard, o!()))
+}

src/wayland/compositor/mod.rs

@@ -491,7 +491,7 @@ where
     R: Default + RoleType + Role<SubsurfaceRole> + Send + 'static,
     Impl: FnMut(SurfaceEvent, WlSurface, CompositorToken<R>) + 'static,
 {
-    let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "compositor_handler"));
+    let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "compositor_handler"));
     let implem = Rc::new(RefCell::new(implem));
 
     let compositor = display.create_global(

src/wayland/data_device/mod.rs

@@ -286,7 +286,7 @@ where
     R: Role<DnDIconRole> + 'static,
     L: Into<Option<::slog::Logger>>,
 {
-    let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "data_device_mgr"));
+    let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "data_device_mgr"));
     let action_choice = Rc::new(RefCell::new(action_choice));
     let callback = Rc::new(RefCell::new(callback));
     display.create_global(

src/wayland/dmabuf/mod.rs

@@ -183,7 +183,7 @@ where
     L: Into<Option<::slog::Logger>>,
     H: DmabufHandler + 'static,
 {
-    let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "dmabuf_handler"));
+    let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "dmabuf_handler"));
 
     let max_planes = formats.iter().map(|f| f.plane_count).max().unwrap_or(0);
     let formats = Rc::new(formats);

src/wayland/explicit_synchronization/mod.rs

@@ -206,7 +206,8 @@ where
     L: Into<Option<::slog::Logger>>,
     R: 'static,
 {
-    let _log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "wayland_explicit_synchronization"));
+    let _log =
+        crate::slog_or_fallback(logger).new(o!("smithay_module" => "wayland_explicit_synchronization"));
 
     display.create_global::<ZwpLinuxExplicitSynchronizationV1, _>(
         2,

src/wayland/output/mod.rs

@@ -174,7 +174,7 @@ impl Output {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger).new(o!("smithay_module" => "output_handler"));
+        let log = crate::slog_or_fallback(logger).new(o!("smithay_module" => "output_handler"));
 
         info!(log, "Creating new wl_output"; "name" => &name);
 

src/wayland/seat/mod.rs

@@ -127,7 +127,7 @@ impl Seat {
         R: Role<CursorImageRole> + 'static,
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger);
+        let log = crate::slog_or_fallback(logger);
         let arc = Rc::new(SeatRc {
             inner: RefCell::new(Inner {
                 pointer: None,

src/wayland/shell/legacy/mod.rs

@@ -305,7 +305,7 @@ where
     L: Into<Option<::slog::Logger>>,
     Impl: FnMut(ShellRequest<R>) + 'static,
 {
-    let _log = crate::slog_or_stdlog(logger);
+    let _log = crate::slog_or_fallback(logger);
 
     let implementation = Rc::new(RefCell::new(implementation));
 

src/wayland/shell/xdg/mod.rs

@@ -289,7 +289,7 @@ where
     L: Into<Option<::slog::Logger>>,
     Impl: FnMut(XdgRequest<R>) + 'static,
 {
-    let log = crate::slog_or_stdlog(logger);
+    let log = crate::slog_or_fallback(logger);
     let shell_state = Arc::new(Mutex::new(ShellState {
         known_toplevels: Vec::new(),
         known_popups: Vec::new(),

src/wayland/shm/mod.rs

@@ -109,7 +109,7 @@ pub fn init_shm_global<L>(
 where
     L: Into<Option<::slog::Logger>>,
 {
-    let log = crate::slog_or_stdlog(logger);
+    let log = crate::slog_or_fallback(logger);
 
     // always add the mandatory formats
     formats.push(wl_shm::Format::Argb8888);

src/xwayland/xserver.rs

@@ -88,7 +88,7 @@ impl<WM: XWindowManager + 'static> XWayland<WM> {
     where
         L: Into<Option<::slog::Logger>>,
     {
-        let log = crate::slog_or_stdlog(logger);
+        let log = crate::slog_or_fallback(logger);
         let inner = Rc::new(RefCell::new(Inner {
             wm,
             kill_source: {