feat(logging): enable lightweight env_logger automatically

Cargo.toml

@@ -12,6 +12,7 @@ include = ["src/**/*.rs", "data/*", "Cargo.toml", "AUTHORS", "COPYING", "NEWS"]
 [dependencies]
 cdb2 = "0.7.0"
 directories = "5.0.0"
+env_logger = { version = "0.11.3", default-features = false, optional = true }
 log = "0.4.21"
 riff = "2.0.0"
 rusqlite = { version = "0.30.0", optional = true }
@@ -24,7 +25,7 @@ crate-type = ["rlib", "staticlib"]
 
 [features]
 default = []
-capi = []
+capi = ["dep:env_logger"]
 sqlite = ["dep:rusqlite"]
 
 [dev-dependencies]

src/capi/logger.rs

@@ -16,16 +16,22 @@ type ExternLoggerFn =
     unsafe extern "C" fn(data: *mut c_void, level: c_int, fmt: *const c_char, arg: ...);
 
 pub(crate) struct ChewingLogger {
+    env_logger: Mutex<Option<env_logger::Logger>>,
     logger: Mutex<Option<(ExternLoggerFn, AtomicPtr<c_void>)>>,
 }
 
 impl ChewingLogger {
     pub(crate) const fn new() -> ChewingLogger {
         ChewingLogger {
+            env_logger: Mutex::new(None),
             logger: Mutex::new(None),
         }
     }
-    pub(crate) fn init(&self) {}
+    pub(crate) fn init(&self) {
+        if let Ok(mut prev) = self.env_logger.lock() {
+            *prev = Some(env_logger::Logger::from_default_env());
+        }
+    }
     pub(crate) fn set(&self, logger: Option<(ExternLoggerFn, *mut c_void)>) {
         if let Ok(mut prev) = self.logger.lock() {
             *prev = logger.map(|(l, d)| (l, d.into()));
@@ -60,6 +66,11 @@ impl Log for ChewingLogger {
                 return;
             }
         }
+        if let Ok(logger) = self.env_logger.lock() {
+            if let Some(el) = logger.as_ref() {
+                el.log(record);
+            }
+        }
     }
 
     fn flush(&self) {}