implement Visual Studio logs

ports/libsimpleservo/capi/src/lib.rs

@@ -5,6 +5,10 @@
 #[macro_use]
 extern crate log;
 
+#[cfg(target_os = "windows")]
+mod vslogger;
+
+#[cfg(not(target_os = "windows"))]
 use env_logger;
 use simpleservo::{self, gl_glue, ServoGlue, SERVO};
 use simpleservo::{Coordinates, EventLoopWaker, HostTrait, InitOptions, VRInitOptions};
@@ -66,13 +70,33 @@ pub extern "C" fn servo_version() -> *const c_char {
     ptr
 }
 
+#[cfg(target_os = "windows")]
+fn init_logger() {
+    use log::LevelFilter;
+    use std::sync::Once;
+    use vslogger::VSLogger;
+
+    static LOGGER: VSLogger = VSLogger;
+    static LOGGER_INIT: Once = Once::new();
+    LOGGER_INIT.call_once(|| {
+        log::set_logger(&LOGGER)
+            .map(|_| log::set_max_level(LevelFilter::Debug))
+            .unwrap();
+    });
+}
+
+#[cfg(not(target_os = "windows"))]
+fn init_logger() {
+    crate::env_logger::init();
+}
+
 fn init(
     opts: CInitOptions,
     gl: gl_glue::ServoGl,
     wakeup: extern "C" fn(),
     callbacks: CHostCallbacks,
 ) {
-    crate::env_logger::init();
+    init_logger();
 
     let args = if !opts.args.is_null() {
         let args = unsafe { CStr::from_ptr(opts.args) };
@@ -116,6 +140,7 @@ pub extern "C" fn init_with_egl(
     wakeup: extern "C" fn(),
     callbacks: CHostCallbacks,
 ) {
+    init_logger();
     let gl = gl_glue::egl::init().unwrap();
     init(opts, gl, wakeup, callbacks)
 }
@@ -127,6 +152,7 @@ pub extern "C" fn init_with_gl(
     wakeup: extern "C" fn(),
     callbacks: CHostCallbacks,
 ) {
+    init_logger();
     let gl = gl_glue::gl::init().unwrap();
     init(opts, gl, wakeup, callbacks)
 }

ports/libsimpleservo/capi/src/vslogger.rs

@@ -0,0 +1,24 @@
+use log::{self, Level, Metadata, Record};
+
+extern "C" {
+    fn OutputDebugStringA(s: *const u8);
+}
+
+pub struct VSLogger;
+
+impl log::Log for VSLogger {
+    fn enabled(&self, metadata: &Metadata) -> bool {
+        metadata.level() <= Level::Warn
+    }
+
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            let log = format!("RUST: {} - {}\r\n\0", record.level(), record.args());
+            unsafe {
+                OutputDebugStringA(log.as_ptr());
+            };
+        }
+    }
+
+    fn flush(&self) {}
+}